GUIDE No.

DIE-CUTTING

QUESTIONNAIRE

Basic objectives of die cutting:

a. To shape solid materials, and especially for cold stamping of metals. this
shape can be pierced, (punched), bent, stamped, etc.

b. Do not use chip removal as a manufacturing process.

c. Minimize manufacturing time and costs of a piece.

d. The maximum use of the material to be used.

e. Being able to manufacture parts in series.

f. Working with complex geometries that are difficult to achieve through any type of machining.

2. Differences between a slow stroke press and a fast stroke press

Slow Race Press Quick Race Press

|

Used in cutting processes of large areas, where it is needed | Cutting processes

simple or with few areas, and low

a greater torque or cutting force. thicknesses, where a greater is sought

performance and greater speed
| of production. |

To generate folds of significant or complex surfaces. It can be used in

small surfaces, since in larger areas

| it can lead to deformities and wrinkles in the

|

| materials. |

Deep or complex geometry embedding, ensuring the Simple sausages or

small ones to ensure the movement

influence of the material. quick from the strip according to the race of the
press. |

It can be used on both thin and thick pieces, since it is generally applied in
low thickness parts, placed

that this type of press can better withstand the loads that with thicker pieces the
material may suffer

elevated. tears instead of flowing as it should, moreover the

type of press

| fast may not support very high loads due to the

|

| work speed. |

The dies and accessories must be designed. The dies and other parts.
must be designed to withstand

to support heavy loads. loads and also withstand friction from

repetitive work at |

| at high speed. |

3. Operating principle of the eccentric press.

Eccentric drive ones are used only where a single hammer blow is needed.
short. The energy from the flywheel can be transmitted to the main shaft, either directly or to
through a gear train. The articulated joint press adjusts ideally to the
minting, pressing or forging operations. They have a short stroke and are capable of printing a
extreme force. There is a tree of the eccentric driven by a motor through a flywheel
with a clutch and braking device on the eccentric of this shaft, there is arranged a
eccentric bushing that can be rotated and is fixed to the shaft by means of a ring with claws. If it
Loosen the claw ring; the eccentric sleeve can rotate relative to the eccentric shaft.
This allows for the adjustment of the press slider; the run can be varied according to the size.
from the press from 0 to a maximum career. The alternative movement is transmitted to the
slider from the head of the connecting rod by means of a ball screw. This screw can rotate
and thus screw or unscrew itself in the head of the connecting rod, through this adjustment of the
height and of the race, the eccentric part is operated by a crankshaft that in turn is
driven by an electric motor.

4. Classification of presses according to their means of actuation.

Aries Power Application Methods To

| Aries |

Simple effect vertical Crank |

Double effect vertical Leva |

In four slides Eccentric |

Special configuration Power screw |

| Rack and pinion |

| Articulated board |

| Hydraulics |

| Elbow lever |

| Pneumatics |

5. Existing stamping processes

TYPE OF PROCESS APPLICATIONS |

Shearing, Cutting, It is a cutting process for sheets and plates. It can reach |

Guillotined to define themselves as cuts without specific geometries. |

Buried Mortajado is a fine cutting process for sheet and plate.

| It differs from shearing in that the blade is at a certain angle.

Niblado The sheet cutting (Nibbling) includes making successive cutouts

| until a larger or cropped shape is produced. |

Drilling To cut out a shaped hole in a sheet or plates |

| metallic. Applications include drilling washers.

| holes for rivets through structural steel elements,

| openings in panels that are to be finished with other processes to

| to be able to set up instruments or equipment and in operations |

| similar. |

Punching A cutting operation of sheets or plates, generally cold,

| through a mechanical device formed by two tools |

brother-in-law It is almost a cold work with small parts. It is moved the

| material for the pressure and impact towards the cavities of the

| matrix. Its main application for manufacturing coins medals and

| similar pieces. |

Musked, Cut. Removal of pieces (or different forms) from the edges. |

| Also called destijerado. |

Lanced Leave an ear without removing any material. |

Folded Fold a sheet according to the measurements. |

cured meat Surface and deep pieces with relatively simple shapes.

INDEPENDENT WORK

1. procedure for mounting dies in a press.

[pic]

As we can see in the figure, the die is mounted on the bench or table of the
respective table which will have channels in t to provide for brackets or fastening screws
Which ones are going to anchor to the bench to our respective die, we need to take into account
It tells of a perfect alignment between the matrix and the punch of our die.
In the press head, the upper part of our die is held which will perform the
load the respective plate or sheet of material to be die-cut, obviously it is held to the head
it can be like in this example with a tightening screw that will hold the part in place
superior.

2. parts of a press and their respective functions

a. transmission: it is the fundamental part of the press that transmits the force to
Any of the actuating elements can be mechanical, pneumatic, or hydraulic.

b. fixed press bench or table: Foundation and main support of the structure on
the ones that mount and guide the operational parts of the machine.

c. frame: part that protects the internal elements of the press.

d. wheel: Main device located on the crown of the mechanical press, which is
it is connected to the power source and regulates the corresponding movement of the piston.

e. Embolo: Main upper portion of the press that moves up and down
inside the frame. The upper matrix door is connected to the plunger.

f. Crown: Upper part of the press that contains the driving mechanisms or cylinders,
that guide the corresponding movement of the piston.

g. Frame: Structure of the press that supports the piston on the base and guides it.
corresponding movement of the piston.

h. Crankshaft: Device that in some mechanical presses connects the piston to the flywheel.
 i. Cylinder: Main driver of a hydraulic or pneumatic press that uses fluid to
force the movement of the piston enclosed within the device.

pic

3. working principle of the presses

The operation of motor-operated presses is based on the following principle:

The engine spins a flywheel of the press that is connected to its crankshaft.
directly or through gears or belts, operating with the help of a clutch of
friction; This clutch is operated by means of a pedal or a button station.

The clutch automatically disconnects after each revolution, unless the

operator keep the pedal pressed, in which case the press repeats the work.

After the clutch disconnects from the flywheel, a brake stops the movement of the
own crankshaft. A connecting rod transmits the movement of the crankshaft to a moving part of the press
the ram, sliding on some guides.

When the presses do not require mechanical drive, one or more are used.
hydraulic cylinders which will execute the process of the piston that is responsible for performing the
respective pressing, the load varies depending on the respective pressure supplied to the
system.

GUIDE No. 2

TECHNOLOGY IN DIE MANUFACTURING

QUESTIONNAIRE

1. Differences between wire erosion and penetration erosion

BY THREAD FOR PENETRATION |

To erode, use a minimum wire of 0.3mm, which is installed

electrode, which may be made of

on a reel and transported to another at the other end. electrolytic copper or in

graphite. |

Rapid wear of the eroding material in this case the thread, due to the wear being less, a
electrode can be used several times

In general, it can only be used once, except in the case to execute the same.
erosion function. |

from the tungsten wire. | |

It is a rather time-consuming process. Even more than penetration. It takes time to

carry out the respective erosion. |

Their costs are even higher than that of penetration. It represents high costs.
|

The movement is carried out by the table, on the three axes, while during the erosion only
work at the table while it is not

the thread moves on the spools. he is moving, the movement is carried out by him
penetrator. |

2. Steps for the development of a die

a. Cost evaluation

b. Typology of the piece

Size

2. Material and characteristics

3. Dimensions
 4. Tolerances

5. Obtaining process

6. Technical specifications

c. Die design

Progressive

2. Axial or coaxial or composite

3. Materials

4. Manufacturing process

5. Provision

6. Parts

7. Load and stress calculations

8. Type of press to be used

9. Size
d. Machinery to be used

Lathes

2. Milling machines

3. Files

4. Boring machines

5. Rectifiers

6. Drills

7. Erosion Processes

8. Heat treatments

e. Work plan

1. Schedule

2. Work routes

3. Calculations

f. Project Execution
 g. Startup

3. Importance of costs in the development of tooling

The costs of tooling are of vital importance because through an analysis regarding
to the manufacturing cost of our die, adding production cost it can be seen if it is
the manufacturing of the die for the expected production is viable. We have to take into account
indirect and direct costs for both the manufacturing of the die and the production of
that piece with the specific requirements.

4. Main differences between final machining and primary machining

PRIMARY MECHANIZED FINAL MACHINED

|

Rough finishes, pieces with certain roughnesses, depending on | Better finishes,

pieces with very low uniform surfaces

of the tool, machine, and man. roughnesses.

|

To verify the project Tolerances according to the part drawings

|

Assemblies and adjustments for proper functioning. Production test of the

piece and final quality control. |

Parts verification. Final adjustments and startup of the

production of the piece.

5. Main steels that make up each classification mentioned in the chapter

STEEL FUNCTION FOR THE DIE

|

|F-1110, 1.1141, XC-15, 1370 Good welding material

|
|F-1140, 1.1191, XC-45, 1650 Tempering by induction
|

|F-1250, 1.7220, 35 CD 4, 2234 Bonify hardness max. 35 HRc.

|

|F-1280, 1.6511, 35 NCD 4 Parts for friction resistance

|

F-5211, 1.2379, Z160CDV12, 2310 High wear resistance

|

F-5220, 1.2510, 90MCV5, 2140 Parts that operate at voltage

|

F-5229, 1.2842, 90MV8 Tenacity and elasticity

|

BLUE CHIP, 1.1248, XC-70, 1774, F-114 Manufacturing of drip trays

|

|F-522,F-524 | |

CARMO, 2249 Pre-tensioned steel at 46Hrc

|

|GG-25, FGL215HB,0215-00 Gray cast iron for bases

|

|GGG-60, FGS600-3, 0732-03 Steel foundry. Pusher cars

|

Independent work

1. Outline regarding the planning of the assigned project.

The scheme to be followed and the plan for the realization of the assigned project for the area of
the following is toolmaking:

a. Die design and creation of drawings

b. Planning of the material to be used, types of machining to be followed.

c. Job planning, measurements, and specifications.

d. Machining of parts.

e. Metrology

f. Tests

g. Adjustments

h. Startup

2. Research CAD-CAM methods and their application in the subject

In the field of Toolmaking, especially in the manufacture of molds, programming a

CNC machine for obtaining complex geometries can be a very laborious task, and
therefore susceptible to errors if it is necessary to produce pieces of small or unique batches.
Therefore, it is increasingly common for a CNC machine tool to work together with a
machining software. The methods used for the process are of vital importance
for the design of dies and molds: computer tools are usually used such as
AutoCAD, Autodesk Inventor, Autosketch, programs from the company AutoDesk, CATIA, Tekla
Structures, Pro/Engineer, Microstation, IntelliCAD, QCad, Rhinoceros, 3D, Solid Edge
SolidWorks, Unigraphics, NX4, ArchiCAD for CAD modeling and the programs used
in CAM; PowerMill, Tebis, WorkNC, MaterCAM, Machining Strategist Cimatron, HyperMill,
Procam, Surfcam, Edge Cam, Esprit CAD-CAM, Bob CAD-CAM.

LABORATORY GUIDE N°3

Preparation of the strip and feeding of a die

QUESTIONNAIRE

1. Calculate the step assuming that your project is developed as a progressive matrix.

Deep embedding project, according to the calculations, the following results are obtained.

Development diameter is 35.79 mm

The thickness of the sheet is 0.75 mm... Gauge 22

Space between piece and piece = 3 x (e) = 3 x 0.75 mm = 2.25 mm

Step = Development diameter + space between pieces

Step = 35.79 mm + 2.25 mm = 38.04 mm

2. What would be the ideal strip distribution according to the previous item?

[pic]

3. How is the cutting material calculated for pieces with irregular shapes and that have
deep cold cuts?

It is calculated using the development diameter of the piece, (in case it is a piece
circular), in the case of irregularly shaped pieces, the development that it should have must be calculated.
this piece, that is to say, to carry the area of the embedded figure, which is equal to the sum of the area of the
background of the piece, and the one of the faces; it is clear that the pieces, due to being irregular, are never completed
to have a completely accurate calculation, for this reason a tolerance should be left above the
estimated area and then trim the excess surface.
4. What are the factors that influence the preparation of the strip?

The factors that influence the distribution and preparation of the strip are:

a. The complexity of the pieces (complex geometry).

b. Margins of separation between piece and piece.

c. The passage of the die.

d. Blade pitch margin, (if it is one, or if it needs two pitch blades)

e. Thickness and width of the sheet.

f. Type of feeding of the die

g. Press specifications. (type of stroke, capacity, etc.)

advantages

| ADVANTAGES DISADVANTAGES |

Cut, shearing A fast forward can be made in the step of | If it is very large,
it is possible that the die

| he pulls it, and the cut pieces come out I need wedges; and besides, it
must remove

| |easily from the back side of the die |the pieces that remain
below, somehow.

Cured meat If the stuffing is shallow, it can be

deep, it becomes difficult the |
| have a good progress of the strip, and have feeding operation, and
they must |

| quick operations. install additional elements,

as |

| | strip elevators, pins. |

| | Some cured meats must be made in several

|

| | hits, which causes the strip to advance

| | be slow. |

| | Generally, it should be fed in a way

| | manual. |

Folded If the bending of the strip is not very complex, not all pieces
that can be folded |

| one can have a good distribution of the | they can have a system
of feeding. |

| strip, a rather quick advance, and several |

| bending operations in a single stroke of

|

| the press. | |

FREELANCE WORK

1. Different behaviors of materials in each pressing process

Shearing: In this process, both the strip and the finished piece tend to stick.
from the matrix or the punch; depending on the dimensions of the die, the thickness of the sheet,
the tolerances, the strip of material heats up, and sometimes begins to tear in the
edges of the piece.

Embossed and Bent: the material tends to lift due to the load applied to it.
center, to avoid this a tread or sheet press is installed; when the tolerances of the
Die cuts are not correct, the material tends to wrinkle at the edges, or it starts to scratch.
on its outer surface.

2. Different parts of a feeder and their operation

A feeding system aims to replace the operator and make the process more efficient.
of the die-cutting of the pieces; The most common drive system of the entire device
feeding, is provided by a cam arranged on the crankshaft of the press, so that
with each rotation of its axis, the feeder performs a new work cycle. Automatically, the
two other devices must provision and flatten the material beforehand so that the
the feeder introduces it into the matrix; these devices are the unwinder and the straightener
of material.

The unrolling and flattening of the sheet is carried out each time an automatic probe
installed on the unwinder or winder detects that the material curve is in a loop shape
what must exist between the straightener and the feeder is below the minimum point
marked.

For example; when the curve arrow of the material between the unwinder and the
the straightener is high, the device does not act, on the contrary, when the arrow is small the
the paver acts and supplies materials again.

To ensure the precise advancement of the material strip, the feeder is equipped with a
sheet progress pusher.

LABORATORY GUIDE 4

EVALUATION ACTIVITY

No text provided for translation.

∑Mo = (15 Ton)(6 in) + (45 Ton)(2 in) – (75 Ton)(4 in) = -120 Ton in
∑F = (15+45+75) = 135 Tons

If we move the die with respect to the reference axis of the press, one inch towards the
to the right we will have to:

∑Mo = (15 Ton)(7 in) + (45 Ton)(3 in) –(75 Ton)(3 in) = 240 Ton - 225 Ton = 15 Ton . in

QUESTIONNAIRE

1. How are dies classified according to their operation?

Operation performed by the die

• Cutting: where there is separation of the material by shearing or punching

Bending: where a flat or cylindrical piece is taken and modified by bending it.
longitudinally.

• From embedding: when pieces of different geometry are manufactured, and with some depth
according to the volume.

• From printing and minting: when the die seeks to engrave logos, texts, references, or
shapes either in high or low relief.

2. What do you understand by off-centered force in the dies?

I understand by off-centered load in the design of dies when they are being used.
progressive dies in which multiple operations are performed, and where there is also the
high-speed die cutting concept in production processes; The off-center load
it occurs when the net force of the press is not in the central position with respect to the
press during the blow, which leads to a tilt in the die when it is performed
At the moment of the strike, the punch deteriorates the die matrix, burrs are generated, and even
They can split the components of the die.

3. List different differences between a rotary die and a progressive die

Axial Progressive |

Manual feeding or by piece to be obtained Feeding can occur from

automatic form. |

|It does not have a power strip or is difficult to supply due|It has a power strip
for the die-cutting process, the

to the operation performed inside the die the process is much faster.
|

A single process is carried out, meaning it performs in a single |Multiple processes for
obtaining a product, that is, in

hit the entire piece to be manufactured a single die run, several

operations to arrive at |

| a final product. |

A basic die (punch and die) Multiple punches and dies,

depending on the operations to

| execute. |

4. What is the function of the plate press sheet in a stamping die?

The function of the press plate is to hold the sheet or plate that is going to be processed.
respective process of stamping; since the punch tends to lift the sheet at its edges
and this causes problems in the process, it can generate wrinkles, ruptures, tears in the
piece; the press sheet seeks to hold it and allow it to flow into the filling, without the sheet
get up.

5. What is the difference between a deep drawing die and a stamping die?

sausage
 The stuffing is done for the manufacturing of hollow or deeply shaped elements from
from sheet plates. The material is stretched and flows into the mold and is achieved the
expected figure.

The stamping die has sheet metal press in most cases, it has radii through which
the sheet flows more easily, the punch is inserted the sufficient amount into the die
to achieve the required figure.

PRINTED

The stamping consists of engraving by means of pressure and/or impact a series of

figures or shapes to a previously selected piece.

The stamping die does not require a sheet press; the material will not flow from any.
In this way, the punch has a relief corresponding to the letters, figures, or shapes that are being sought.
engrave on the piece, the punch only strikes the piece to engrave the required shape and does not need
not to get involved in any matrix.

INDEPENDENT WORK

Extra-deep punched die

It is a type of sausage that must be made in several blows of the punch, in order to carry out
Properly position the sheet inside the cavity of the die, generally some of these
dies are variables, and as the press runs the race, they go down and
carrying out step by step the desired form.

The characteristics of the sheet or plate are that it must be very ductile, so that it flows in a way
correct within the matrix, and must not break or tear; it must have good plasticity, in order to
that its deformation is easy to achieve; the less thickness of the sheet, the easier it will be
easier to deform; being a deep filling, it is best to have a piece
previously that it is the area of development of the part to be stamped.
Die Cutting Design
Bend

It is the simplest operation after cutting; it consists of a transformation.

in cold or hot of plastically deformable materials around a straight axis, where the
formation occurs without loss of material, it is worth noting that this formation is without
chip starting with a small variation in the cross-section of the semi- piece
finished, according to the conditions of the process, no separations occur and it is preserved the
integrity of the material.

Bending is used to transform sheets, wires, bars, profiles, and tubes, and in it,
external forces act on the part in such a way that internal forces cannot
to oppose a permanent plastic deformation.

From the bending axis, the material is compressed (compression) on the inside and stretched.
on the outside, and that transitional area between both zones is called neutral fiber.

The bending stress decreases towards the neutral fiber and in its vicinity, the material becomes
it only deforms elastically. Like all plastic deformation, it is accompanied by a
elastic deformation, after all bending occurs an elastic recovery that must
take into account, and this depends on the material. The bending stress increases with increasing
distance of the neutral fiber, also increasing the tension as the bending radius decreases.
For example, annealed soft copper bends better than steels; this is because it has
less mechanical resistance.

For sheet bending, bending machines or various types of presses are used,
equipped with appropriate molds or stamps formed of male and female that works in
in a manner similar to how the punch and die work.

Before the bending operation, the stretched length of the piece must be determined.
equal to that of the neutral fiber, because it does not undergo reshaping or stretching and only
experiences a modification of its shape.

For bending operations in general, it is necessary to take into account the following
factors: the radius of curvature and the elasticity of the material, if possible, should be avoided.
live chants; for this purpose it is advised to set the inner radii of curvature, equal or
greater than the thickness of the sheet to be bent in order to avoid excessively stretching the fiber
exterior and to ensure a bending without breaking. These curvature radii are considered
normally: 1 to 2 times the thickness, for soft materials and 3 to 4 times the thickness,
for hard materials.
In plastic transformation, the elastic limit of the material is exceeded and when they are displaced
many atoms, decreases the cohesion at the grain boundaries. In the area of maximum stress
a stricture occurs with subsequent cracking.

P = Punch

M= Matrix

Types of Bending

V-bending: The metal sheet is bent between a punch and a V-shaped die.
The included angles, which range from very obtuse to very acute, can be
make with V-shaped dice. V-bending is generally used for low operations
production and the corresponding dies are frequently made in a curtain press
in V are relatively simple and low cost.

Edge bending: It involves a cantilever load over the metal sheet. It is used to
pressure plate that applies a clamping force to hold the base of the part against the
given, while the punch forces the overhanging part to bend over the edge of a die.
Due to the pressure from the bra, the sliding dice are more complicated and more expensive.
that the dice are in V and are generally used for high production work.

Bending with a press: Used for bending sheets cold to achieve different
angles its application is quite good when special and non-manufactured parts are required
in series, since the costs justify it.

Pipe bending: This process allows bending bars and tubes cold or in
hot for structural elements, machines, furniture, rails, or handles. With this
the process also allows bending of profiles or non-tubular elements such as angles, for which
the same techniques are followed.

Bending by compression: Usually done by hand to bend tubes and some

rods and thick wall profiles. For piping, the minimum radius must be 4 times the diameter.
The tube and the bending angle can reach up to 170°.
 Dragged bending: Where the die is rotated by pulling the piece through a die,
this process is suitable for thin-walled tubes and small radii and can
bends of up to 180° can be achieved.

Bending by pressing: The workpiece is placed between two supports and pressed.
against the die, it is a process used for thick tubes or profiling

Tensile bending: Stretches the piece longitudinally to an elastic limit and.

wraps around the die, it is widely used for non-tubular profiles.

Description of a folding print.

The bending of sheet metal pieces is done using special tools called
bending stamps. These stamps, depending on their construction, can also be suitable for
curved.

It consists of two essential parts: an upper part called the punch and a lower part called
matrix. They complete the print of two side squares, which carry two pieces or two bolts.
of position, necessary to insert the previously cut sheet metal element into its point

Engineering analysis of bending

The metal, whose thickness is = t, is bent through an angle, called the bending angle A. The
The result is a metal sheet with an included angle A', such that A + A' = 180°. The radius of the
The R bend is typically specified on the inner part, rather than on the neutral axis.
This radius of the angle is determined by the radius of the tool that is used to execute the
operation. The bending is done over the width of the workpiece w.

Bending tolerance If the bending radius is small relative to the material, the metal
it tends to stretch during bending. It is important to be able to estimate the magnitude of the stretching.
what happens, so that the length of the final part can match the dimension
specified. The problem is to determine the length of the neutral axis before bending, to
take into account the stretching of the final bent section. This length is called tolerance
folded and can estimate as follows:

BA=2n-(R + Kbat)
Where BA = bending tolerance in inches (mm); A = bending angle in degrees: R =
bent, inch (mm); t = thickness of the material, inch (mm); Kba which is a factor for estimating the
stretched.

Elastic recovery

When the bending pressure is released at the end of the deformation operation, the energy
the elastic remains in the bent part causing it to partially regain its shape
This elastic recovery is called elastic recovery and is defined as the
increase of the angle formed by the bent part in relation to the angle
understood by the training tool after it has been withdrawn.

SB = A' - A'b / A'b

Where SB = elastic recovery; A' = angle formed by the metal sheet in degrees,
A'b = angle encompassed by the bending tool in degrees.

Bending force

The force required to perform the bending depends on the geometry of the punch and the
given, as well as the resistance, thickness, and width of the metal sheet that is being bent. The force
The maximum bending can be estimated by means of the following equation, based on the
bending of a simple beam:

F = KbfTSwt2

Where F = bending force, Ib (N); TS = tensile strength of the sheet metal, lb/inch2
(MPa); w = width of the part in the bending axis direction, inch (mm); t = thickness of the
material or the part, inch (mm); and D = dimension of the open die in inch (mm).
Effort for bending.

It is the force necessary to perform the bending action. It is calculated for

determine the appropriate press to carry out the work. The bending effort is determined.
in V by the following formula:

ED = bending effort in Kg.

C= Coefficient according to distance in h.

R = tensile strength of the material in Kg. / mm².

L= Width of folding.

e = Thickness of the material.

h = Distance from edge to edge.

To obtain a good bending, three factors must be taken into account:

The piece must not undergo any abnormal movement during bending.

The inner bending radii shall be at least equal to the thickness of the sheet.

The surfaces of the punch and die in contact with the sheet will be as smooth as possible.
possible polished.

The process is carried out as follows:

1st Phase. The punch and the movable part of the die remain static at the dead point.
superior, while at the bottom a flat plate is positioned ready to be bent.

2nd Phase. The punch starts the downward stroke until it makes contact with the sheet and initiates the
folded in the same way.

3rd Phase. At the end of the descent race, the punch reaches the lower dead center, and the
the piece is bent.

4th Phase. After the bending, the top or moving part of the die retracts until it reaches
the upper dead point, while the lower extractor pulls the piece out of the mouth of the
the matrix is ready to fold a new piece.

From the bending axis, the material becomes compressed (compression) on the inside and
stretched on the outside, and that transitional area between both zones is called fiber
neutral.

The bending stress decreases towards the neutral axis and in its vicinity the
the material deforms only elastically. Like all plastic deformation, it is accompanied by
due to elastic deformation, after all bending there is an elastic recovery that
It must be taken into account, and this depends on the material.

The bending tension increases as the distance from the neutral fiber increases,
also increasing the tension by decreasing the bending radius. For example, copper
Soft cooked bends better than steels, this is because it has less resistance.
mechanics.

Description of a print to fold

The bending of sheet metal pieces is done using special tools called
bending stamps. These stamps, depending on their construction, can also be suitable for
curved.

It consists of two essential parts: an upper part called punch and a lower part called
matrix. Two lateral squares complete the print, which have two pieces or two bolts.
of position, necessary to introduce the sheet metal element at its point previously
cut.

Lubricants for bending and stamping

During bending and other stamping operations, it is necessary for the surfaces to
contact between the sheet and the stamp should slide easily with minimal friction.
Clearly, the main objective is to facilitate the operation of shaping and reducing the
wear of the stamps. With proper lubrication, any issue can also be overcome.
small defect in the project or construction of the prints and remedy any eventual ones
deficiencies of the material to be printed; waste can also be eliminated or reduced
production.

Lubricants can be classified as follows:

Fats and soaps:

Magnus N. 421.

Magnus N. 448.

Chlorinated oils:
 Magnus DO-2A.

Magnus CC2.

Magnus DO-29.

Emulsifiable oils:

Magnus Clean Cut.

Magnus Sulfa-Cool.

Fatty Acids:

Magnus DO-5th.

Sulfurated fats:

Magnus Cutting Base No. 66.

Magnus DO-6A.

Soaps Products:

Magnus DC-5.

Magnus DC-K.

Magnus DO-17.

Bending operation

The same concepts and considerations presented for bending are valid for the
curved. This operation is distinguished from bending by its different characteristic function.
By using special and different stamps, both a thread can be bent
steel that a strip of sheet to obtain, respectively, a hook or a tube.

One of the bends is performed using a stamping process with a movable die.

In this case, the bending stamp must perform the function of transforming an element of
flat sheet in another hollow cylindrical shape (tube).

In this, it can be seen how the section of the sheet metal piece is made up of a segment.
straight ended in two curved pieces; these two pieces have been made expressly
to facilitate the curvature of the sheet in the stamping and, at the same time, to obtain the joint
in V that facilitates the welding of the two ends of the piece. The two terminal curves are
they are obtained simultaneously with the cut if the sheet does not exceed a thickness of 1 mm, adopting
the method of constructing the convex punch according to the profile to be obtained. To build the tube, are
two stamps are necessary; however, in the case that the sheet exceeds a thickness of 1 mm,
Another stamp will be needed to perform the two rounded actions following the operation.
of cutting. With a more refined method, the manufacturing of the tube can be carried out by
a single print; logically, this will be more complicated but partly it will compensate, with a
superior production, to the expense incurred to build it. Figure 45 presents schematically
the three bending phases carried out with a single stamp: in the first phase, the sheet metal undergoes
the cut and the beginning of the bending; in a second it undergoes the first bend, and in a
third, the complete bending.

In any case, these phases occur in a single time, that is, in a single race.
vertical of the stamp or punch fixed to the press rod. These two methods are
employees particularly in the large-scale production of short tubes.

Elastic recovery of bending

Due to the elastic nature of the material, the curved piece partially regains its shape.
initial, slightly decreasing its final curved angle (from a1 to a2).

Elastic recovery from point a1 to a2

Bending moment

A machine will be able to successfully bend a specific piece when its moment
the Mf (bending moment) should be greater than the material's resistance moment. To determine
which machine is the most suitable for each product, the resistant modulus w can be calculated.
from the same and select a machine with a higher module. As the voltage is unknown
applied at every moment to each piece, its maximum resistance to stress is taken as the value.
traction Rt:

Resilient module
The resistant module depends on the geometry of each piece and its axis of rotation. For tubes of
circular section, external diameter D and thickness e, the resistant module is calculated using the
next equation:

There are different bending techniques, among which one can highlight as one of the
most common is:

The bending with a rotating arm and mandrel: It is currently the most accurate technology.
versatile. It allows the production of very complex pieces with strict quality and great capacity of
automation.

Multi-radio machines

The most sophisticated rotating arm bending machines incorporate various heights of
curved, so that each one has tools for different bending radii. From this
Various radii can be produced in their design automatically.

Variable radio machines

It is also common to use one of the heights to curve with a variable radius.
called variable-radius bending can generate any radius
of curvature (R > 8 D) and works by pushing the tube axially against some rollers of
variable position, depending on a previous calibration.

Curved to the right and left

Certain complex designs cannot be made with bending machines that rotate in
a single direction, due to their design requiring right and left turns within
from the same bending sequence.
Bidirectional bending machines

To achieve this purpose, special double rotating arm machines can be used.
-one arm for each sense-. The tubes of smaller diameters can also curve in
both directions with machines having a movable head and a symmetrical arm with two jaws
opposing. Another simpler possibility is to manually change the support.
side of the machine before each sequence.

sausage

Stamping is an operation for forming metal sheets that are used to make parts.
in a couplable manner, of boxes and other more complex hollow shapes. It is done by placing a
metal sheet over the cavity of a die and pushing the metal into the cavity of it
with a punch.

It is one of the most complex operations in sheet metal stamping and is applied for
transform the flat sheet metal scraps into caps or into the internal reduction of their
diameter with the simultaneous increase of the depth of the cap cavity. These
operations are fulfilled in embedding matrices.. The large radius of chamfer R of the edge of
Matrix work 1 ensures the smooth transformation of the sheet metal (of thickness s) into
cap.

The operation of the sausage consists of the following: the male 2, compressing on the part
the middle of the disc of metal, it sinks into the hole of matrix 1. The middle part of the disc of
chapa, sinking into the matrix hole, drags down the rest of its annular part.

To avoid the formation of folds, pressure sleeves 3 are used, with a

A cap can be obtained that is 1.5 to 2 times the smaller diameter than that of the disk.
the initial cap. The further reduction in the dimensions of the cap is achieved with the
following sausages.

According to the configuration of the part that is embedded and the thickness of the disc of
There are multiple special matrices, for example, for the distribution of the sheet metal.
through the interior; by means of rubber, movable bodies, liquid, compressed air and even
explosive processes. The rubber stamping process consists of the sheet 3,
lodged in block 1 is compressed by the male of the upper slider onto the layer of
rubber 2 and gives the sheet the shape of the mold block. The advantages of this procedure
they consist of the low cost of the device, as well as the possibility of printing several discs
of the sheet simultaneously.
 The common parts made by stamping are beverage cans, case heads of
ammunition, sinks, kitchen utensils, and parts for automobile bodies.

Mechanics of molding.

The stamping of cylindrical parts is the basic operation of stamping. With the dimensions and
parameters, we will examine the parameters of the operation and the execution mechanics of the
It is embedded in a disc with a diameter Db within a die using a punch.
of diameter Dp. The punch and the die must have a radius at the corners determined by Rp.
and Rd. If the punch and die have sharp corners (RP and Rd = 0), an operation will be performed
punched from a hole instead of a deep drawing operation. The sides of the punch and the
given are separated by a clear c. This clear is approximately 10% larger than the
thickness of the material in stamping:

C = 1 * 1t

The punch applies a downward force f to deform the metal and the fastener.
From parts or forms, a downward holding force Fh.C is applied. (See in the figure).

Measures of the sausage.

A measure of the severity of a deep drawing operation is the ratio of

embodied DR. It is more easily defined for a cylindrical shape as the relationship between the
disk diameter Db and punch diameter Dp. In equation form, DR = Db / DP

The sausage relationship provides an indicative, albeit crude, measure of the severity of
a certain sausage operation. The greater the relationship, the greater the severity of the operation.
An approximate upper limit of the drawing ratio is a value of 2.0. The limiting value
The real for an operation depends on the corner radius on the punch and the die (Rp and Rd), of
the friction conditions, the depth of stamping, and the characteristics of the sheet
of metal (for example, ductility and degree of directionality of resistance properties
in the metal).

Another way to characterize a given molding operation is by the reduction r, where: r =

Db - Dp

Db

It is closely linked to the relationship with sausage. Consistent with the

previous limit of DR, the value of the reduction r must be less than 0.50.
Determination of the shape size.

To achieve a satisfactory dimension of a cylindrical stamped part, it is necessary to

correct diameter of the initial shape. It must be large enough to supply
the metal necessary to complete the part. If there is too much material, there will be waste
unnecessary. For non-cylindrical shapes, there is the same problem of estimating the size of the
initial shape, alone that this will not be round.

A reasonable method for estimating the diameter of the disk is described below.
initial in a deep stuffing operation in which a round part is produced (by
example, cylindrical glasses and larger complex shapes with axial symmetry). As the
the volume of the final product is the same as that of the initial metal piece, the diameter of the
initial disk can be calculated if we establish that the initial volume of the disk is equal to the
final volume of the product, and we solve for the diameter Db. To facilitate the calculations,
It is generally assumed that the thinning of the walls is nil.

Embutting process.

The cut pieces or discs to be used are placed in the seat or centering ring, secured
to the stamping die, in order to center the disk in the stamping process. A
the stamping device presses the disc against the die in order to prevent it from
They produce folds. The stamping die, as it descends, stretches the material over the edges.
bordered from the matrix, so that a hollow piece is produced. The displacement of
all the crystals that make up the material to be embedded are radical in their
magnitude. Each of the crystals of the material shifts, to the extent that this
slide into the opening between the punch and the die.

The displacement of the material at that moment is similar to the flow of water through the
spillway of a dam. When it is intended that the thickness of the material does not change during
the stamping process, the area of the original piece (cut disk) must be equal to the area of
the surface of the stamped part.

Friction is a factor that must be taken into account as the material slides.
in the gap between the punch and the die. Therefore, this area must be polished and lapped.
This reduces the necessary load for the development of the stuffing. The beveling of the edges of
the matrix helps the plate to slide through the wall of the hole, facilitating the operation of
embossing. Proper lubrication of the trimmed disk and the embossing process is also facilitated.
tool as a whole. The gap that remains between the punch and the stamping die has
that is greater than the thickness of the sheet. They have been accredited as suitable for the case
of steel sheets, clearances from 1.12 to 1.30 times the thickness of the sheet, for sheets of
brass, clearances of 1.08 to 1.20 times the thickness, for aluminum sheets the clearance is from 1.04 to
1.10 times the thickness.

Prior stamping: It is the transformation of a flat sheet into a hollow body.

the tool is called die first. This method of work was formerly called stretching
previous or also pre-stretched.

Intermediate forging: It is the transformation of a hollow body to decrease or

modify your section. This work method was previously called stretched in
pulled or stretched posterior.

Turned-up inverted stamping: It is an intermediate stamping in the opposite direction to

the preceding molding. The tool used is the cuffing die.

Finishing drawing: It is the transformation of a hollow body to achieve that

special attitude or edges with rounding. It is done with the so-called die of
finished.

Stretch forming: It is the transformation of a hollow body to reduce its

wall thickness by means of die and punch for deep drawing. Tool: die of
restriction.

Interior stamping: It is done with a die and a punch; it is the transformation of

edge of an existing hole in a piece so that a neck is formed at the edge
from the perforation due to the impact of the pressing pressure. Tool: piercing die.

Stretch forming: It is the transformation of the edge of an existing perforation.

in one piece to form a neck with simultaneous reduction of the neck thickness or
to transform a neck to reduce its wall thickness, for which there is the die of
simultaneous work, restriction and crossed.

Stuffing Operations
 Reimbursed

If the change in shape required by the design is too severe or the relationship of
the embedding is considerably high, the complete shaping of the part may require more than
a step of stuffing. At the second step of stuffing and any subsequent one, if it
It needs, it is called Reembutido.

Molded from a cup: (1) start of the molding (2) end of the run.

Inverse Embedding

A related operation is reverse embedding, in which an embedded part is placed.

downward in the die and a second molding operation produces a configuration like
that is shown in figure 11. In reverse stamping, the metal sheet is bent in the
same direction on the outer and inner corners of the die, while in the
the metal being rebent bends in opposite directions at the two corners. Due to this
difference, the metal experiences less work hardening during deep drawing
inverse y, therefore, the strength of the embedding is lesser.

Reverse embedding: (1) start and (2) end.

Stuffed without a bra

The main function of the bra is to prevent the wrinkling of the flange while
The part is embedded. The tendency to wrinkle is reduced by increasing the relationship between the
thickness and the diameter of the initial shape. If the ratio t/Db is sufficiently large, it
You can reach the stuffing without the need for a bra, as shown in figure 12.

The sausage stuffer must be funnel or cone-shaped to allow for the

the material to be stamped fits into the cavity of the die. The advantage of stamping without a fastener,
when this is possible, it is a lower cost of the tools and the use of a press more
simple because it avoids the need for a separate control of the movements of the holder and
of the punch.

Sausages without a bra: (1) start of the process and (2) end of the race.
 Cone piece stamping

The execution of these pieces requires, first, a cylindrical cascading formation, and
second, the use of a shaping press. The reduction of the diameter must be more
weak that in cylindrical stuffing, so as not to overload the material. The height of the
Different cylindrical parts are determined by tracing or by calculation, applying the formula.

h=Hxc/a-c

These cylindrical parts are joined to each other by 45-degree bevels.

rounded. The rounding height, at any stage, is calculated using the formula
normal, but taking into account the different chamfers and straight parts to leave on the
embossing.

Dimpling Tools

The putting tools can be classified into:

Simple effect tool:

The tool consists of a die P made of hardened steel equipped with

Air escape drills to prevent deformation of the die during separation and a die.
Hardened steel.

The tool is called "pass-through" if it is designed to expel the piece through

below. In this case, the matrix-shaped hole ends at the bottom with a
sharp edge alive. When the punch rises again, the stamped piece is held by this edge and
is expelled from the mold. For the stamping of thin sheet metal, stems must be provided
retention, in order to avoid any deformation. If the stamping cannot pass through, it
It provides an expeller to raise it to the surface of the matrix.

Simple Effect Embedding Tool

Dual-action tool:

The tool is made up of the same previous elements, but additionally

it involves an SF hard tempered steel support. In the case where the stamping has to
It will be carried out after several stages (steps), the top part of the punch will be beveled.
The area that remains flat will have the corresponding dimensions for the next step.
Double Effect Embossing Tool.

Extraction of the stamped part.

As a consequence of the pulling effort, the stamped material tends to remain

stuck to the punch and if a system is not foreseen to facilitate the extraction of the piece from the punch
it can mean later problems, a suitable method is extraction with a ring and
spring. It is common to use split rings connected by a spring that act as an extractor,
the inner diameter of the ring must have an appropriate rounding that allows passage
from the punch and the material, stretching the spring during its descent, during the
The punch rises, the spring compresses, and the ring acts as a extractor.

Extraction of a stamped part

Defects of the Sausage

The stamping is a more complex operation than cutting or bending sheet metal, because
there are many more things that can go wrong. Numerous defects can arise in a
processed meat products, such as those shown in the figure.

Common defects in stamped parts (a) wrinkling may occur on the flange or (b) in
the wall, (c) tears, (d) torn and (e) superficial scratches.

Wrinkling at the flange or tab. Wrinkling in an embossed part consists of

in a series of folds that form radially in the non-embossed flange of the part of
work, due to compression wrinkling.

Wrinkling on the wall. If the wrinkled flange is embedded in the cylinder, these folds
they appear on the vertical wall of the cylinder.

Torn. This defect consists of a crack that opens in the vertical wall,
usually near the base of the embedded cup, due to high stress on the tension that
cause thinning and breaking of the metal in this region. This type of failure can also
happen when the metal stretches over a sharp corner of the punch.

Eared. This is the formation of irregularities (called ears) on the edge.

superior of the stamped part, caused by anisotropy in the metal sheet. If the material is
perfectly isotropic no ears are formed.

Superficial scratching. Scratches can occur on the surface of the stamped part if the
the punch and the die are not smooth or if the lubrication is insufficient.

Difference between bending and curving

Folding is the simplest operation after cutting; it consists of a

cold or hot transformation of plastically deformable materials around an axis
recto, where the shaping occurs without loss of material, it is worth noting that this
conformation is without chip removal with a small variation in the cross-section of
the semi-finished piece, according to the conditions of the process, no separations occur and it
maintain the integrity of the material.

The same concepts and considerations presented for bending are valid for the
curved. This operation is distinguished from bending by its different characteristic function.
By using special and different stamps, a thread can be curved just as well.
steel that a sheet strip to obtain, respectively, a hook or a tube.

In bending, the piece has a given angle to change the direction of the sheet or
give it any desired shape.

In bending, curved pieces generally have a large part shaped like an arc,
For the realization of this, it is necessary to build molds of several pieces in the punch and the
matrix.

Springs

The springs used in tooling are elements that are employed to facilitate the
cutting, bending, stamping operations are part of the retention systems and
expulsion. They are formed by assembled sheets (of leaf spring) or by a rolled strip in
spiral form around an axis.
 The springs are made of silicon steel wires and come in various types, but the most
used and available on the market are the helical ones. In matrices where it is necessary to
to withstand large efforts, springs are used placed one between another, and the sum of the
efforts are equal to or greater than a thick wire spring that occupies more space.

The maximum or admissible load of the springs must be equal to or greater than the required effort and
when a spring is placed inside another, the direction of the coils must be reversed to
prevent them from intertwining. The resistance of the spring increases to the maximum bending limit and
the increase of turns in the number of useful turns is necessary for the support of the
ends of the spring.

Springs are designed to deliver a force, to push, to pull, to twist or to store.

energy.

Types of Springs

Tension springs: These springs exclusively support tensile forces and are
they are characterized by having a hook at each of their ends, in different styles: English,
German, Catalan, rotating, open, closed or double spiral. These hooks allow for mounting
the tension springs in all imaginable positions.

Compression springs: These springs are specially designed to support

compression forces. They can be cylindrical, conical, biconical, with a fixed or variable pitch.

Torsion springs: They are the springs subjected to torsion forces (moments).

Docks

Springs are mechanical elements capable of withstanding the application of certain

loads deforming significantly, but regaining their initial configuration upon cessation of that
application. The main feature of any material used for manufacturing
springs must have an elastic behavior for a field of tensions as much as possible
as wide as possible. The most commonly used types are steel composites with additions of silicon, which
they considerably increase the breaking limit.

The mechanical springs serve in machines as flexible elements. Perceiving

the work of external forces, these elements transform them into deformation energy
elasticity of the material from which they are made. The constructive form of mechanical springs
it allows perceiving the action of external forces on large sections of road, that is,
to obtain considerable deformations without losing flexible properties.

Springs are commonly used in machines and devices as a force element that
ensures the action of efforts in a given sector of the shock absorber path. Perceiving the
instant energy from a hit, this spring returns it in the form of oscillation energy
elastic.
There are different types of springs for different applications:

The bending springs, also known as bow springs, which have a

configuration of a series of sheets with the same thickness and width, but of different lengths;
widely used in the automotive and railway industries.

The torsion springs, where we find the straight axis type and the helical type.
cylindrical; they achieve in suspension systems, their natural market.

The helical conical springs, whose main characteristic is that their strength
it increases when a greater effort is applied, commonly used in railway vehicles and in the
presses

Rubber docks, which although not made of steel, are increasingly accepted.
they act as buffers and with low elastic displacements, used in
bumpers, vibrating devices, etc.

We will focus on the study of spring steels, the suitability of each type of
steel, according to its chemical composition, for each application; its manufacturing processes,
thermal treatments and finally, the calculations for applications will be introduced
helical springs.

Disc springs: Disc and washer springs consist of a set of elements that
they have the shape of a truncated cone, made of steel sheet of 1 to 20 mm thick. These
springs work like compression springs. They belong to the group of rigid springs with
capacity to bear large loads. For this reason, it is sometimes used in construction.
construction for the vibration isolation of the coatings of the works
industrial.

Flat springs: They are widely used in precision devices, in machines

agricultural, etc. The docks of this type are commonly used for the efforts that act on the
limits of a small race. Flat springs can be held at both ends,
supporting the load from the middle or fixed at one end and supporting the load at the other.

Annular springs: It consists of a set of rings with a special profile. If the rings are loaded
extremes by their perimeter, the outer rings move over the inner ones, whereby
the perimeters, the outer rings move over the inner ones, with which the former
they widen and the seconds compress. In this case, the total height of the spring decreases.

Block springs: These springs operate under compression, with elastic rubber elements.
They are used in the form of blocks of different shapes, mainly as shock absorbers.
to soften the impacts and reduce the vibrations.

Characteristics of spring steels

1. It is essential for steels to have a high yield strength, that is, for the coefficient of
work does not exceed the elastic limit.

In industrial practice, the tensile yield limit usually ranges between 8.83 x 10^8 Pa and
y 1.77.109Pa, depending on the use and the characteristics of dimension, composition, etc.

For a spring to function normally, the value of the elastic limit must be very
high and close to the figures previously mentioned, and as the resistance to breaking tends to fluctuate from
10 to 40% above the yield limit, that is, from 9.81 x 10^8 Pa to 2.35 x 10^8 Pa.

4. It is important for the springs to have fatigue resistance, as many of the springs,
During their useful life, they experience stresses in a cyclical and repetitive manner.

5. It is necessary to avoid the decarburization of the springs in their thermal processes and of
manufacturing, as this catalyzes the fatigue process, because decarburization occurs
initially at the periphery, and it is at the periphery where the dock tends to start its failure.
Similarly, one must take care of the presence of cracks, defects that the spring may have.

Expellers

The ejection systems in the matrices are the devices that adapt to them to
expel the produced pieces as their construction shape adheres to the mold and
the scrap to the punch. For ease of construction and operation,

The expeller can be operated by springs or forcibly.

Elastic expellers keep the cut parts against the cutting strip from which they are left.
then easily separate again. The cut parts are removed from the tool
with the cutting strip. Large surface pieces made from thin sheets do not hold.
with safety to the strip; it can remain inside the tool and be destroyed then in the
next press blow. For this reason, elastic ejectors are not suitable for
this kind of piece.

In the case of forced ejectors, the parts remain first on the plate.
cutting and is expelled just before the upper dead center of the press slider. In
In the case of inclined presses, the pieces fall into containers arranged for that purpose. If a press does not...
It has the device to adopt the oblique position, which is done by removing the pieces that
They fall into the shear plate with compressed air so that they end up in a collecting container.

The cut pieces when they are made of thin sheet metal often remain at
expeller. For this reason, a separating pin provided with a spring is arranged in the expeller that
Tilt the piece so that it falls easily.

Spring Launchers

These are devices that adapt to double effect matrices to expel the
produced parts, since due to the construction method they remain attached to the mold and the
retail of the hybrid punch. For ease of construction and operation, it is advisable that
cylindrical shells.

With a high-power spring at the bottom of the matrix that operates the plate
expulsor through another and the limiting screws. The spring is guided by a threaded tube.
at the ends with a nut and a washer to adjust the pressure. The tube allows for the
output of the waste cut by the upper punch.

Depending on the diameter of the expeller, these can be constructed in two ways: with
spring operation and with ejector bar.

Spring Ejector

Rubber Tacos

Also known as polyurethane tubular springs, these offer designers and

tool manufacturers a good alternative to steel springs in situations
that involve limited space, high support pressure, and proper partitioning,
They are generally able to store more energy than steel. Their characteristics provide
an unusual combination of load resistance, rolling capacity, hardness and
abrasion resistance, retains its flexibility at low temperatures and a full range of
dynamic properties above 140

They are resistant to oil, water, oxygen, ozone, and most chemical solvents, they have
an infinite lifespan when stored without affecting its properties. Its cylindrical body
provides high pressures, shorter distance between center, positive partition, resistance to the
traction, installation and simple delay, do not mark the material and do not break and are more
silent in its operation.

Rubber tacos are incomprehensible, given that their volume remains constant, these
grow in their central section in direct relation to their deflection. Therefore, if a block is
It will deflect by 20%, its diameter in the central section will increase by 20%. It should be anticipated.
this expansion to avoid interference.

Rubber Tacos

Rod Ejectors

They are the guide screws that limit the stroke, these screws hold the ejector plate and these.
are accompanied by a spring and a screw.

Hydraulic Pushers

These are devices that are mostly used in stuffing matrices, in order to
get the part when it is pressed, when it is activated it makes the part rise so that
make its removal easier.

Bump stops

They aim to limit the progress of the band with each press strike.

Side Action Stops

 The side stops, commonly mounted on the side guides of the material,
their mission is to take advantage of the beginnings of the strip, avoiding losses from it
material. They apply to high-production tools, regardless of the retention system
adopted (from pin, rocking or shear). It can be divided into:

First case: In the following, the stop is placed on the thickness of the rule that is constructed
so that, by pressing on the riveted head, the stopper moves easily. There is
to pay attention to the fact that the edge is well rounded, to avoid the spring that makes
retract the hook limit. On the other hand, the neckline of the slider, when colliding with the
The guide rail acts as a limiter for the top travel.

Second case: When special rules are not needed, but the passage for the strip
it brushes on the own guide plate, the shape of the following stop has given very good results.

The groove is carved into the guide perpendicular to the strip's passage groove. The stop is
provided with a collet-type hole, whose ends upon colliding with the pin fixed in the guide,
they limit their career, it is also that there is a light spring that pushes the stop outward.

Side auxiliary bumpers

These are actuated in such a way that the machine itself can control its effect or
functioning in the process.

To make the auxiliary stops work, simply press the stop, and the strip of material.
he will stumble before with the same one than with the final tensioner. The press is activated and this will not do
More than a single operation, this can be repeated as many times as in successive auxiliary limits.
as the matrix requires it, until reaching the final retensioning, where, already disregarding the
prior operations, the side stops cease to act and work can be done by the
normal procedures.

The described system is the one that is normally applied in the final retention matrices.
but in matrices with lateral shear, the material utilization system offers a
variant. The button is concealed by the action of a spring, it can be made to come out
compress the button, forcing it to slide over the inclined plane of the rod
button. When the action on the button ceases, the reaction of the springs causes the return of the
pieces to their original position. This stop, instead of being applied when the strip starts to be
cut, it is used when one reaches the end of it, and due to the cuts of the shear, it is no longer
It is possible to retain her.
 When the side stops are multiple and the matrix, due to its structure, allows it, one can
become automatic, adding one more punch to the matrix, they are all then
less one, the first which must necessarily be operated manually.

This will be easily understood when seeing the side punch, which creates a small
notch on the edge of the tape, where the automatic stop is housed in the form of
tackle, which prevents the strap from retracting. With this combination it is possible to reduce the
number of side stops with three elements. The auxiliary normal stop, the punch, and the stop
automatic helper.

With a similar setup, working in reverse it is possible to cancel the final tensioner.
however, it is not advisable to make this determination, in order not to decrease performance
in production

Automatic Stops (Auto-Stop)

On the anvil of the punch are:

P height adjustment that can be locked by

a nut.

On the guide it is mounted:

A Stop of tempered hard steel, which pivots with play in a milled housing in the
guide and provided with a heel that rests on the matrix.

E -hard steel stop.

R coil spring type, helical spring attached to a rod fixed at the base or spring leaf
that produces the same effect.

Operation

When pushing the band against the stop sign, it rests on the front surface of
its accommodation; when descending, the punch, after having pressed the plate, forces the auto-
stop A from getting up by means of the pusher.

Once again turned back by its spring, the hitchhike A does not fall back in front of
the strip, but on this one when the pusher P goes back up. When pushing the band that no longer
It is subject; the hitchhiking A is going to fall into the hole that has just been drilled and the edge of this
it will serve as a stop again, then starting the cycle over.

Varilla Stops
It consists of a tipping stop and is activated by the movement of the press. This system
allows for greater production than the previous one, it is generally used in matrices in the
The feeding of the strip is done automatically.

Strap Centering Device

The assembly of center pilot pins in the molds has its reason for being in the fact that
guarantee a correct displacement between each of the jumps made by the band. If not
in this way, the common reference points that these would have could be lost
transformations and with it generate displacements in the sheet that would cause
irregularities or defects in the processed parts.

The centrators, with their conical tip, aim to fit into the holes.
from the sheet and center it before the rest of the punches do it, as illustrated in the, of
this shape keeps the steel strip aligned before its transformation. To achieve this,
two or more holes must be made at the beginning of the strip that will later serve for
pilot it along the matrix.

Centering device

Generally, these center pilots are mounted on the punch holder and
they must necessarily protrude more than the bottom face of the pressing plate, this last part is
essential to ensure that the sheet is centered before the punches act.
If the centering devices do not operate, the belt will not go to its place and the pilot and the belt will break.

Fracture of the centering device

If the previously made reference holes in the sheet are very small and in
consequently, very small centering devices are also required, it will be necessary to weigh the
possibility of making the pilots slightly blended, or retractable through
springs. In this way, it will be possible to avoid their breakage and any collateral damage that may occur.
cause. In figure 24 (A, B, and C) we see the correct process of band centering using
punches or centering pilots.

Correct centering process

Bibliography
 Study guide, 'die design.'

Maria Herminia Pereira. 1998

López Navarro. Die cutting and stamping with applications of punching, bending,
embossing and extrusion. Second Edition

J. Koninck. D. Gutter. Manual of the Die Maker Technician: die-cutting-Stamping-

Metal sheet stamping.

Herman W. Pollack. Machine Tools and Material Handling

MIKELL P. GROOVER. Fundamentals of Modern Manufacturing 1st Ed.

The provided text is a URL and does not contain translatable content.

http://en.wikipedia.org/wiki/Elastic_winch

Die-cutting Design

Bowed

It is the simplest operation after the cutting, it consists of a transformation.

in cold or hot of plastically deformable materials around a straight axis, where the
formation occurs without material loss, it is noteworthy that this formation is without
chip removal with a small variation in the cross-section of the semi-
finished, according to the conditions of the process, no separations occur and it is preserved the
integrity of the material.
Bending is used to transform sheets, wires, bars, profiles, and tubes, and in it, the
external forces act on the piece in such a way that internal forces cannot
to oppose a permanent plastic deformation.

From the bending axis, the material becomes compressed (compression) on the inside and stretched.
on the outside, and that transitional area between both zones is called neutral fiber.

Bending stress decreases towards the neutral fiber and in its proximity the material is
it only deforms elastically. Like all plastic deformation, this is accompanied by a
elastic deformation, after all bending there is an elastic recovery that needs to
take into account, and this depends on the material. The bending stress increases as the
distance from the neutral fiber, also increasing the tension by decreasing the bending radius.
For example, annealed soft copper bends better than steels, this is because it has
less mechanical resistance.

For sheet metal bending, bending machines or various types of presses are used.
equipped with appropriate molds or stamps formed of male and female that work in
in a manner analogous to how the punch and die do.

Before the bending operation, the stretched length of the piece must be determined, which is
similar to that of neutral fiber, because it does not undergo reconditioning or stretching and only
it undergoes a modification of its shape.

For bending operations in general, it is necessary to take into account the following
factors: the radius of curvature and the elasticity of the material, if possible, must be avoided the
living chants; for this purpose, it is advisable to set the inner radii of curvature, equal or
greater than the thickness of the sheet to be bent in order not to excessively stretch the fiber
exterior and to ensure bending without breakage. These radii of curvature are considered
normally: 1 to 2 times the thickness for soft materials and 3 to 4 times the thickness,
for hard materials.

In plastic deformation, the elastic limit of the material is exceeded and when they are displaced
many atoms, decreases the cohesion at the grain boundaries. In the area of maximum stress
a constriction occurs with subsequent cracking.

P= Punch

M= Matrix

Types of Bending

V-Bending: The metal sheet is bent between a punch and a V-shaped die.
The included angles, ranging from very obtuse to very acute, can be
make with V-shaped dice. V-bending is generally used for low operations.
production and are frequently carried out in a curtain press, the corresponding dies
in V are relatively simple and low cost.

Edge folding: Involves a cantilever load on the metal sheet. It is used to a

pressure plate that applies a clamping force to hold the base of the part against the
die, while the punch forces the overhanging part to bend over the edge of a die.
Due to the pressure from the bra, the sliding dice are more complicated and more expensive.
that the V dies are generally used for high production work.

Bent with a press: Used to bend sheets in cold, to achieve different

The application of angles is quite good when special and non-manufactured parts are required.
in series, since the costs justify it.

Pipe bending: This process allows for bending bars and tubes cold or in
hot for structural elements, machines, furniture, rails or handles. With this
the process also allows for bending profiles or non-tubular elements such as angles, for which
the same techniques are followed.

Bending by compression: Commonly done by hand to bend tubes and some

rods and thick wall profiles. For piping, the minimum radius must be 4 times the diameter
the tube and the bending angle can reach up to 170°.

Drawn by dragging: Where the die is rotated by pulling the piece through a die,
this process is suitable for thin-walled tubes and small radii and can
to achieve bends of up to 180°.

Bending by pressing: The workpiece is placed between two supports and pressed.
against the die, it is a process used for thick tubes or profiling

Bending by traction: Stretch the piece longitudinally to an elastic limit and it

It wraps around the die, it is widely used for non-tubular profiles.

Description of a print to fold.

The bending of sheet metal pieces is done using special tools called
bending stamps. These stamps, depending on their construction, can also be suitable for
curved.

It consists of two essential parts: an upper part called punch and a lower part called
matrix. They complete the print of two side squares, which have two pieces or two bolts.
of position, necessary to introduce the previously cut sheet metal element at its point

Engineering analysis of bending

The metal, whose thickness is = t, is bent through an angle, called the bending angle A. The
The result is a metal sheet with an included angle A', such that A + A' = 180°. The radius of the
The R bend is normally specified on the inner part, rather than on the neutral axis.
This angle radius is determined by the radius of the tool used to perform the
operation. The bending is done on the width of the workpiece w.

Bending tolerance If the bending radius is small compared to the material, the metal
it tends to stretch during bending. It is important to be able to estimate the magnitude of the stretching.
what happens, so that the length of the final part can match the dimension
specified. The problem is to determine the length of the neutral axis before bending, to
take into account the stretching of the final bent section. This length is called tolerance of
doubled and can be estimated as follows:

BA=2n-(R + Kbat)

Where BA = bending tolerance in inches (mm); A = bending angle in degrees: R =

bent, inch (mm); t = thickness of the material, inch (mm); Kba which is a factor for estimating the
stretched.

Elastic recovery

When the bending pressure is removed at the end of the deformation operation, the energy
the elastic stays in the bent part causing it to partially regain its shape
This elastic recovery is called elastic recovery and is defined as the
increase of the angle formed by the bent part in relation to the angle
understood by the training tool after it is withdrawn.
SB = A' - A'b / A'b

Where SB = elastic recovery; A' = angle encompassed by the metal sheet in degrees,
A'b = angle included by the bending tool in degrees.

Bending force

The force required to perform the bending depends on the geometry of the punch and the
given, as well as the resistance, thickness, and width of the metal sheet being bent. The force
maximum bending can be estimated using the following equation, based on the
bending of a simple beam:

F = KbfTSwt2

Where F = bending force, Ib (N); TS = tensile strength of the sheet metal, lb/in2
(MPa); w = width of the part in the bending axis direction, inch (mm); t = thickness of the
material or the part, inch (mm); and D = dimension of the open die in inch (mm).

Effort for bending.

It is the force necessary to perform the bending action. This is calculated for
determine the appropriate press to carry out the work. The bending force is determined.
in V by the following formula:

ED = bending effort in Kg.

C= Coefficient according to distance in h.

R = tensile strength of the material in Kg. / mm².

L = Width of folding.

e = Thickness of the material.

h = Distance from edge to edge.

To achieve a good bend, three factors must be taken into account:

 The piece must not undergo any abnormal movement during bending.

The inner bending radii shall be at least equal to the thickness of the sheet.

The surfaces of the punch and die in contact with the sheet will be as smooth as possible.
possible polished.

The process is carried out as follows:

1st Phase. The punch and the moving part of the die remain static at the dead point.
superior, while at the bottom a flat plate is positioned ready to be bent.

2nd Phase. The punch begins the descent, until it makes contact with the sheet and initiates the
folded in the same way.

3rd Phase. At the end of the descent race, the punch reaches the lower dead point, and the
the piece remains bent.

4th Phase. After folding, the upper or movable part of the die retracts until it reaches
the upper dead point, while the lower extractor pulls the piece out of the mouth of the
The matrix is ready to fold a new piece.

From the bending axis, the material becomes repressed (compression) from the inside and
stretched on the outside, and that transitional place between both areas is called fiber
neutral.

The bending tension decreases towards the neutral fiber and in its proximity.
the material deforms only elastically. Like all plastic deformation, it is accompanied
due to elastic deformation, after all bending there is an elastic recovery that
it must be taken into account, and this depends on the material.

The bending stress increases as the distance from the neutral fiber increases,
also increasing the tension by reducing the bending radius. For example, copper
Softly cooked material bends better than steels because it has less resistance.
mechanics.

Description of a foldable print

The bending of sheet metal parts is done using special tools called
bending dies. These dies, depending on their construction, can also be suitable for
curved.
It consists of two essential parts: an upper part called the punch and a lower part called
Matrix. They complete the print with two lateral squares, which have two pieces or two bolts.
of position, necessary to insert the sheet metal element into its point beforehand
cut.

Lubricants for bending and stamping

During bending operations and other stamping processes, it is necessary for the surfaces to be
contact between the sheet and the stamp slides easily with minimal friction.
Clearly, the main object is to facilitate the operation of shaping and reducing the
wear of the stamps. With proper lubrication, any can also be overcome
small defect in the project or construction of the prints and remedy any eventual issues
deficiencies of the material to be printed; waste can also be eliminated or reduced
production.

Lubricants can be classified as follows:

Greases and soaps:

Magnus N. 421.

Magnus N. 448.

Chlorinated oils:

Magnus DO-2A.

Magnus CC2.

Magnus DO-29.

Emulsifiable oils:

Magnus Clean Cut.

Magnus Sulfa-Cool.

Fatty Acids:

Magnus DO-5th.

Sulfurized fats:

Magnus Cutting Base No. 66.

Magnus DO-6A.

Soapy Products:
 Magnus DC-5.

Magnus DC-K.

Magnus DO-17.

Bending operation

The same concepts and considerations presented for bending are valid for the
curved. This operation is distinguished from bending by its different characteristic function.
By using special and different stamps, a thread can be curved just as well.
steel that a strip of sheet metal to obtain, respectively, a hook or a tube.

One of the curvings is done using a stamp with a movable matrix.

In this case, the bending stamp must serve the function of transforming an element of
flat sheet in another hollow cylindrical shape (tube).

In this, it can be seen how the section of the sheet metal piece is constituted by a segment.
straight line ending in two curved pieces; these two pieces have been made expressly
to facilitate the curvature of the sheet in the stamp and, at the same time, to obtain the joint
in V that facilitates the welding of both ends of the piece. The two terminal curves are
they are obtained simultaneously with the cut if the sheet does not exceed a thickness of 1 mm, adopting
the method of constructing the convex punch according to the profile to be obtained. To build the tube, they are
two stamps are necessary; however, in the case that the sheet exceeds a thickness of 1 mm,
Another stamp will be needed to execute the two rounded figures following the operation.
of cutting. With a more refined method, the manufacturing of the tube can be carried out through
a single print; logically, this will be more complicated but it will partly compensate, with a
superior production, to the expenditure incurred for its construction. Figure 45 schematically presents
the three bending phases carried out with a single stamping: in the first phase, the metal piece undergoes
the cut and the beginning of the bending; in a second it undergoes the first bending, and in a
third, the complete bending.

In any case, these phases occur in a single time, that is, in a single race.
vertical of the stamp or punch fixed to the press shaft. These two methods are
employees particularly in the mass production of short tubes.

Elastic recovery of bending

Due to the elastic nature of the material, the curved piece partially regains its shape.
initial, slightly decreasing its final curvature angle (from a1 to a2).
Elastic recovery from point a1 to a2

Bending moment

A machine will be able to successfully bend a certain piece when its moment
the bending moment (curvature pair) should be greater than the material's resistant moment. To determine
What machine is the most suitable for each product, the resistant module w can be calculated.
of the same and select a machine with a higher module. As the voltage is unknown
applied at every moment to each piece, its maximum value is taken as its resistance to the
traction Rt:

Resistant module

The moment of resistance depends on the geometry of each piece and its axis of rotation. For tubes of
circular section, outer diameter D and thickness e, the resistant modulus is calculated using the
next equation:

There are different bending techniques, among which one can highlight as one of the
most common is:

The bending with a rotating arm and mandrel: It is currently the most precise technology.
versatile. It allows the production of very complex parts with strict quality and great capacity of
automation.

Multi-radio machines
The most sophisticated rotary arm bending machines incorporate various heights of
curved, so that each one has tools for different bending radii. From this
In this way, pieces with various radii in their design can be produced automatically.

Variable radio machines

It is also common to use one of the heights to bend with a variable radius (also
called variable radius bending). Variable radius bending can generate any radius
of curvature (R > 8 D) and works by pushing the tube axially against some rollers of
variable position, based on prior calibration.

Curved to the right and left

Certain complex designs cannot be made with bending machines that rotate in
a single direction, because due to their design they require right and left curves inside
from the same bending sequence.

Double-bending machines

To achieve this purpose, special double-arm rotating machines can be used.

-an arm for each sense-. The smaller diameter tubes can also bend in
both directions with a movable head machine and a symmetrical arm with two jaws
opposed. Another simpler possibility is to manually change the support
side of the machine before each sequence.

Cold cuts

The stamping is a process of forming metal sheets that are used to make parts
in a fitted manner, of boxes and other more complex hollow shapes. It is done by placing a
metal sheet over the cavity of a die and pushing the metal into the cavity of it
with a punch.

It is one of the most complex operations in sheet stamping and applies to

transform the flat sheet metal scraps into caps or in the interior reduction of its
diameter with the simultaneous increase in the depth of the cavity of the cap. These
operations are carried out in embedding matrices.. The large chamfer radius R of the edge of
matrix work 1 ensures the smooth transformation of the sheet metal (of thickness s) into
cap.

The operation of sausage stuffing consists of the following: male 2, compressing on the part
the middle of the metal disc, sinks it into the hole of matrix 1. The middle part of the disc of
plunging into the matrix hole, drags along the rest of its annular part.

To prevent the formation of creases, pressure sleeves 3 are used, with a

In the past, a cap can be obtained that is 1.5 to 2 times the diameter smaller than that of the disk.
the initial cap. The further reduction in the dimensions of the cap is achieved with the
following sausages.

According to the configuration of the part that is embedded and the thickness of the disc of
There are multiple special matrices, for example, for the distribution of the sheet metal disk.
through the interior; by means of rubber, moving bodies, liquid, compressed air and even
explosive processes. The rubber stamping process consists of the sheet 3,
housed in block 1 is compressed by the male of the upper slider onto the layer of
rubber 2 and gives the sheet the shape of the mold block. The advantages of this procedure
They consist of the affordability of the device, as well as the possibility of printing several discs.
simultaneously sheet.

The common parts made by stamping are beverage cans, casings of

ammunition, sinks, kitchen utensils and parts for automobile bodies.

Mechanics of molding.

The stamping of cylindrical parts is the basic operation of stamping. With the dimensions and
parameters, we will examine the operation parameters and the execution mechanics of the
stuffed. It is embedded in a disk of diameter Db inside a die by means of a punch.
of diameter Dp. The punch and the die must have a radius at the corners determined by Rp
and Rd. If the punch and die have sharp corners (RP and Rd = 0), an operation will be performed
punched from a hole instead of a stamping operation. The sides of the punch and the
The beams are separated by a clear c. This clear is approximately 10% larger than the
thickness of the material in stamping:

C = 1 * 1t

The punch applies a downward force f to deform the metal and the fastener.
from parts or from shapes applies a downward holding force Fh.C (See in the figure).
Measurements of the sausage.

A measure of the severity of a deep drawing operation is the ratio of

embedded DR. This is more easily defined for a cylindrical shape as the relationship between the
disk diameter Db and punch diameter Dp. In equation form, DR = Db / DP

The relationship of sausage provides an indicator, albeit crude, of the severity of

a certain sausage-making operation. The greater the ratio, the greater the severity of the operation.
An approximate upper limit of the filling ratio is a value of 2.0. The limiting value
The real for an operation depends on the corner radius of the punch and the die (Rp and Rd), of
the friction conditions, the depth of drawing, and the characteristics of the sheet
of metal (for example, ductility and degree of directionality of the strength properties
in the metal)

Another way to characterize a given stuffing operation is by the reduction r, where: r =

Db - Dp

Db

It is closely linked to the relationship of sausage. Consistent with the

Previous limit of DR, the value of the reduction r must be less than 0.50.

Determination of shape size.

To achieve a satisfactory dimension of a cylindrical stamped part, the following is needed:

correct diameter of the initial shape. This must be large enough to supply
the necessary metal that completes the part. If there is too much material, there will be waste
unnecessary. For non-cylindrical shapes, there is the same problem of estimating the size of the
initial shape, alone that this will not be round.

The following describes a reasonable method to estimate the diameter of the disk.
initial in a deep embedding operation in which a round part is produced (by
example, cylindrical glasses and larger complex shapes with axial symmetry). As the
the volume of the final product is the same as that of the initial metal piece, the diameter of the
initial disk can be calculated if we establish that the initial volume of the disk is equal to
final volume of the product, and we solve for the diameter Db. To facilitate the calculations,
It is generally assumed that the thinning of the walls is negligible.

DIE FORMING PROCESS.

 The cut pieces or disks to be used are placed in the seat or centering ring, fixed.
to the embedding matrix, with the aim of centering the disk in the stamping process. A
The pressing device squeezes the disc against the stamping die in order to prevent it from
They produce folds. The punching die stretches the material over the edges as it descends.
Bordered from the matrix, so that a hollow piece is produced. The displacement of
All the crystals that constitute the material to be embedded are radical in all its
magnitude. Each of the crystals of the material shifts, to the extent that it
Slide into the opening between the punch and the die.

The displacement of the material at that moment is similar to the flow of water through the
spillway of a dam. When it is intended that the thickness of the material does not change during
in the molding process, the area of the original piece (cut disc) must be equal to the area of
the surface of stamped piece.

Friction is a factor that must be taken into account as the material slides.
in the gap between the punch and the die. Therefore, this area must be polished and lapped.
This reduces the necessary workload for the development of the sausage. The beveling of the edges of
the matrix helps the latch to slide along the wall of the hole, facilitating the operation of
embossing. Proper lubrication of the trimmed disk and of the embossing also facilitates the embossing.
tool as a whole. The gap that remains between the punch and the die has
that it should be greater than the thickness of the sheet. They have been deemed appropriate for the case.
of steel sheets, clearances of 1.12 to 1.30 times the thickness of the sheet, for sheets of
brass, clearances from 1.08 to 1.20 times the thickness, for aluminum sheets the clearance is from 1.04 to
1.10 times the thickness.

Preforming: It is the transformation of a flat sheet into a hollow body.

The tool is called a die first. This method of work was formerly called stretching.
previous or also pre-stretched.

Intermediate forging: It is the transformation of a hollow body to reduce or

modify your section. This working method was previously called stretched in
pulled or stretched posterior.

Cuffed inverted embutition: It is an intermediate embutition in the opposite direction to

the previous embossing. As a tool, there is the rolled edge die.
 Finishing injection: It is the transformation of a hollow body to achieve that.
special attitude or edges with rounding. It is carried out with the so-called die of
finished.

Stretch forming: It is the transformation of a hollow body to reduce its

wall thickness by means of die and punch for stamping. Tool: die of
restriction.

Internal stamping: It is done with a die and male die, it is the transformation of
edge of an existing drilling in a piece so that a neck is formed at the edge
from the drilling due to the effect of stamping pressure. Tool: punching die.

Stretch embossing: It is the transformation of the edge of an existing hole.

in one piece to form a neck with simultaneous reduction of the neck thickness or
to transform a neck to decrease its wall thickness, for which there is the die of
simultaneous work, stricture and crosswise.

Sausage Operations

Refunded

If the change in form required by the design is too severe or that the relationship of
the embedding is considerably high, the complete forming of the part may require more than
a step of stuffing. To the second step of stuffing and to any subsequent one, if it
needs, is called Reembutido.

Reembossing of a cup: (1) start of the reembossing (2) end of the race.

Inverse Embedding

A related operation is reverse molding, in which an inserted part is placed.

downwards on the die and a second die-casting operation produces a configuration like
the one shown in figure 11. In reverse stamping, the metal sheet is bent in the
same direction at the outer and inner corners of the die, while in the
The bent metal is folded in opposite directions at the two corners. Due to this
difference, the metal experiences less work hardening during deep drawing
inverse y, therefore, the strength of the sausage is lower.
Reverse embedding: (1) beginning and (2) end.

Stuffed without a bra

The main function of the bra is to prevent the wrinkling of the lace while
the part is embedded. The tendency to wrinkle is reduced by increasing the relationship between the
thickness and diameter of the initial shape. If the t/Db ratio is large enough, it
You can achieve the stuffing without the need for a bra, as shown in figure 12.

The sausage stuffer must have the shape of a funnel or cone to allow for the
the material to be stamped fits into the cavity of the die. The advantage of stamping without a fastener,
when this is possible, it is a lower cost of the tools and the use of a press more
simple because it avoids the need for a separate control of the movements of the holder and
of the punch.

Processed meats without a bra: (1) start of the process and (2) end of the race.

Coining of conical parts

The execution of these pieces requires, first, a cascading cylindrical formation, and
second, the use of a forming stamper. The diameter reduction must be greater
weak that in the cylindrical stuffing, so as not to overload the material. The height of the
Different cylindrical parts are determined by tracing or by calculation, applying the formula.

h=Hxc/a-c

These cylindrical parts are joined together by 45-degree chamfers.

rounded. The rounding height, at any given stage, is calculated by the formula
normal, but taking into account the different chamfers and straight parts to leave on the
embossing.

Punching Tools

The stamping tools can be classified into:

Simple effect tool:

 The tool consists of a punch P made of hardened steel provided with
air escape drills to prevent the deformation of the die in the separation and a matrix
Made of hardened steel.

The tool is called "pass-through" if it is designed to expel the piece by

below. In this case, the hole in the shape of the matrix ends at the bottom with a
viva edge. When the punch rises again, the stamped piece is held by this edge and
it is expelled from the mold. For the stamping of thin sheet metal, stems must be provided for
retention, in order to avoid any deformation. If the piece cannot pass through, it
it provides a blower to bring it up to the surface of the matrix.

Simple Effect Embossing Tool

Double effect tool:

The tool is made up of the same previous elements, but additionally

It involves a hard-tempered steel SF support. In the event that the stamping has to
after several stages (steps), the top part of the punch will be chamfered. The
The surface that remains flat will have the corresponding dimensions for the next step.

Double Effect Embossing Tool.

Extraction of the stamped piece.

As a consequence of the tensile force, the stamped material tends to remain

stuck to the punch and if a system is not foreseen to facilitate the extraction of the piece from the punch
it can mean later problems, a suitable method is ring extraction and
spring. It is common to use split rings joined by a spring that act as an extractor,
the inner diameter of the ring must have an adequate rounding that allows passage
from the punch and the material, stretching the spring during its descent, during the
the punch's ascent compresses the spring and the ring acts as an extractor.

Extraction of a stamped part

Defects of the sausage

The stamping is a more complex operation than cutting or bending sheet metal,
there are many more things that can go wrong. Numerous defects can arise in a
processed meat product, such as those shown in the figure

Common defects in stamped parts (a) wrinkling can occur on the tab or (b) in
the wall, (c) tears, (d) flapped and (e) superficial scratches.

Wrinkling in the flange or tab. The wrinkling in an embossed part consists of

in a series of folds that form radially in the non-embossed flange of the part of
work, due to compression wrinkling.

Wrinkling on the wall. If the wrinkled flange is embedded in the cylinder, these folds
they appear on the vertical wall of the cylinder.

Torn. This defect consists of a crack that opens in the vertical wall,
usually near the base of the embedded cup, due to high tensile stress
cause thinning and breakage of the metal in this region. This type of failure can also
occur when the metal stretches over a sharp corner of the punch.

Eared. This is the formation of irregularities (called ears) on the edge.

superior of the pressed part, caused by anisotropy in the metal sheet. If the material is
perfectly isotropic no ears are formed.

Superficial scratching. Scratches can occur on the surface of the stamped part if the
the punch and the die are not smooth or if the lubrication is insufficient.

Difference between bending and curving

Bending is the simplest operation after cutting; it consists of a

cold or hot transformation of plastically deformable materials around an axis
recto, where the shaping occurs without material loss, it is worth noting that this
formation is without chip removal with a small variation of the cross section of
 The piece must not undergo any abnormal movement during bending.

The inner bending radii shall be at least equal to the thickness of the sheet.

The surfaces of the punch and die in contact with the sheet will be as smooth as possible.
possible polished.

The process is carried out as follows:

1st Phase. The punch and the moving part of the die remain static at the dead point.
superior, while at the bottom a flat plate is positioned ready to be bent.

2nd Phase. The punch begins the descent, until it makes contact with the sheet and initiates the
folded in the same way.

3rd Phase. At the end of the descent race, the punch reaches the lower dead point, and the
the piece remains bent.

4th Phase. After folding, the upper or movable part of the die retracts until it reaches
the upper dead point, while the lower extractor pulls the piece out of the mouth of the
The matrix is ready to fold a new piece.

From the bending axis, the material becomes repressed (compression) from the inside and
stretched on the outside, and that transitional place between both areas is called fiber
neutral.

The bending tension decreases towards the neutral fiber and in its proximity.
the material deforms only elastically. Like all plastic deformation, it is accompanied
due to elastic deformation, after all bending there is an elastic recovery that
it must be taken into account, and this depends on the material.

The bending stress increases as the distance from the neutral fiber increases,
also increasing the tension by reducing the bending radius. For example, copper
Softly cooked material bends better than steels because it has less resistance.
mechanics.

Description of a foldable print

The bending of sheet metal parts is done using special tools called
bending dies. These dies, depending on their construction, can also be suitable for
curved.
 Compression springs: These springs are specially designed to withstand
compression forces. They can be cylindrical, conical, biconical, fixed pitch or variable pitch.

Torsion springs: These are the springs subjected to torsion forces (moments).

Wharfs

Springs are mechanical elements capable of withstanding the application of certain

loads deforming noticeably, but recovering their initial configuration upon cessation of that
application. The main feature of any material used for manufacturing
springs must exhibit elastic behavior for a stress field as much as possible
as widely as possible. The most commonly used types are steel alloys with silicon additions, which
they considerably extend the breaking limit.

Mechanical springs serve the purpose of flexible elements in machines. Perceiving

the work of external forces, these elements transform it into deformation energy
elasticity of the material from which they are made. The constructive shape of mechanical springs
it allows to perceive the action of external forces on large sections of the road, that is,
achieve considerable deformations without losing flexible properties.

Springs are often used in machines and devices as a force element that
ensures the action of efforts in a given sector of shock absorber path. Perceiving the
instant energy from a blow, this spring returns it in the form of oscillation energy
elastic.

There are different types of springs for different applications:

The bending springs, also known as leaf springs, that have a

configuration of a series of sheets with equal thickness and width, but of different lengths;
widely used in the automotive and railway industries.

The torsion springs, where we find the straight axis type and the helical type.
cylindrical; they achieve in suspension systems, their natural market.

The helical conical springs, whose main characteristic is their resistance

increases when a greater effort is applied, widely used in railway vehicles and in the
presses
Rubber bumpers, which although they are not made of steel, are increasingly accepted.
they act as buffers and with low elastic displacements, used in
bumpers, vibrating devices, etc.

We will focus on the study of spring steels, the suitability of each type of
steel, according to its chemical composition, for each application; its manufacturing processes,
thermal treatments and to conclude, calculations will be introduced as an application for
helical springs.

Disc springs: Disc and washer springs consist of a set of elements that
they have the shape of a truncated cone, made of steel in sheet of 1 to 20 mm thick. These
Springs work like compression springs. They belong to the group of rigid springs with
capacity to withstand heavy loads. For this reason, it is sometimes used in construction projects.
construction for the vibration isolation of the coatings of the works
industrial

Flat springs: They are commonly used in precision instruments, in machines.

agricultural, etc. Springs of this type are usually used for the forces acting on the
limits of a small race. Flat springs can be held at both ends,
supporting the load from the middle or fixed at one end and supported by the other end.

Annular springs: It consists of a set of rings with a special profile. If the rings are loaded
extremities around its perimeter, the outer rings move over the inner ones, which
the perimeters, the outer rings move over the inner ones, which means the former
they widen and the seconds compress. In this case, the total height of the spring decreases.

Block spring: These springs work under compression, with elastic rubber elements.
In the form of blocks of different shapes, they are mainly used as shock absorbers.
to smooth out the shocks and reduce vibrations.

Characteristics of spring steels

It is essential that steels have a high yield strength, that is, that the coefficient of
work does not exceed the elastic limit.

In industrial practice, the tensile yield limit usually ranges between 8.83 x 10^8 Pa and
y 1.77.109Pa, depending on the usage and the characteristics of dimension, composition, etc.
3. For a spring to function normally, the value of the elasticity limit must be very
high and close to the previously mentioned figures, and since the resistance to breaking tends to fluctuate from
10 to 40% above the yield limit, that is, from 9.81 x 10^8 Pa and 2.35 x 10^8 Pa.

4. It is important that the springs have fatigue resistance, as many of the springs,
During their useful life, they receive loads in a cyclical and repetitive manner.

5. It is necessary to avoid the decarburization of the springs in their thermal processes and of
manufacturing, as this catalyzes the fatigue process, because decarburization occurs
initially on the periphery, and it is on the periphery where the dock tends to begin its failure.
It is also necessary to monitor the presence of cracks, defects that the spring may have.

Expellers

The ejection systems in the matrices are the devices that adapt to them to
expel the produced pieces since their construction method causes them to stick to the mold and
the scrap to the punch. For ease of construction and operation,

The expeller can be actuated by springs, or forcibly.

elastic expulsers keep the cut parts against the cutting strip from which they are left
then separate again easily. The cut parts are taken out of the tool.
with the cutting strip. Large surface pieces made with thin sheets do not grip.
with safety to the strip; it can remain inside the tool and then be destroyed in the
next press stroke. For this reason, elastic ejectors are not suitable for
this kind of piece.

In the case of forced ejectors, the pieces initially remain on the plate.
cutting and is expelled just before the top dead center of the press slide. In
in the case of tilting presses, the pieces fall into containers arranged for that purpose. If a press does not
It has the device to adopt the oblique position, which involves removing the pieces that
They fall onto the shear plate with compressed air so that they go into a collection container.

The cut pieces when they are made of thin sheet metal often remain at
expeller. For this purpose, a separating pin equipped with a spring is provided in the expeller that
tilt the piece so that it falls easily.
Spring Dischargers

These are devices that adapt to double effect matrices to expel the
produced parts, as due to the construction method they remain attached to the mold and the
retail of the hybrid punch. For ease of construction and operation, it is advisable that
cylindrical sheets.

With a high power spring at the bottom of the matrix that drives the plate.
expeller through another and the limiting screws. The spring is guided by a threaded tube
at the ends with a nut and a washer to adjust the pressure. The tube allows for the
output of the waste cut by the upper punch.

According to the diameter of the expeller, these can be constructed in two ways: with
operation by spring and with expulsion bar.

Spring Expeller

Rubber Tacos

Also known as polyurethane tubular springs, these offer designers and

tool manufacturers a good alternative to steel springs in situations
that involve limited space, high support pressure, and adequate partitioning,
they are generally able to store more energy than steel. Their characteristics provide
an unusual combination of load resistance, rolling capacity, hardness and
abrasion resistance, retains its flexibility at low temperature and a full range of
dynamic properties above 140

They are resistant to oil, water, oxygen, ozone, and most chemical solvents, they have
an infinite lifespan when stored without affecting its properties. Its cylindrical body
provides high pressures, shorter distance between center, positive partition, resistance to the
traction, installation and simple delay, do not mark the material and do not fracture and are more
silent in its operation.

Rubber tacos are incomprehensible, given that their volume remains constant, these
they grow in their central section in direct relation to their deflection. Therefore, if a block is
It will deflect by 20%, its diameter in the central section will increase by 20%. It must be anticipated.
this expansion to avoid interference.
Rubber Tacos

Rod Ejectors

They are the guide screws that limit the stroke; these screws hold the ejector plate and these
are accompanied by a spring and a screw.

Hydraulic Pushers

These are devices that are mostly used in stuffing matrices, in order to
obtain the part when it is inserted, when it is activated it makes the part rise so that
make its removal easier.

Bumpers

They aim to limit the advance of the band with each press stroke.

Side Action Stops

The side stops, usually mounted on the side guides of the material,
they have as a mission the utilization of the beginnings of the strip, avoiding losses of
material. They apply to high-production tools, regardless of the retention system.
adopted (from pin, rocker or shear). It can be divided into:

First case: In the following, the stop is placed on the thickness of the strip it is built with.
in such a way that by pressing on the riveted head, the stop moves easily. There is
to pay attention to ensuring that the edge is well rounded, to avoid the spring that makes
recess the hook limit. On the other hand, the neckline of the slider, when colliding with the
the guide acts as a limiter for the stop's stroke.

Second case: When no special rules are required, but the passage for the strip
It brushes on the own guide plate, the shape of the following stop has yielded very good results.

The groove is carved in the guide perpendicular to the passage slot of the strip. The stop is
provided with a collet-type hole, whose ends, when they collide with the pin fixed in the guide,
they limit their career, there is also a light spring that pushes the stop outward.
Side auxiliary stops

These are actuated in such a way that the same machine can control its effect or
functioning in the process.

For the auxiliary stops to work, simply press the stop, and the strip of material
it will stumble before the same one than with the final tensioner. The press is made to act and it will not do so
More than a single operation, this can be repeated as many times as needed on successive auxiliary limits.
as the matrix requires, until reaching the final retension, where, disregarding already of the
preliminary operations, lateral stops cease to act and work can be done through the
normal procedures.

The described system is the one normally applied in the final retention matrices.
but in the shear-edge matrices the material utilization system offers a
variant. The button is hidden by the action of a spring, it can be made to come out by
compress the button, forcing it to slide over the inclined plane of the rod
button. When the action on the button ceases, the reaction of the springs causes the return of the
pieces to their original position. This stop, instead of being applied when the strip begins to be
cut off, it is used when one reaches the end of it, and due to the cuts of the shears, it is no longer
It is possible to retain it.

When there are several side stops and the matrix allows it due to its structure, it can
become automatic, adding one more punch to the matrix, then they are all
minus one, the first which must inevitably be activated by hand.

This will be easily understood when looking at the side punch, which makes a small
notch on the edge of the tape, in that notch the automatic stopper is housed in the shape of
trunk, which prevents the strip from retracting. With this combination, it is possible to reduce the
number of lateral stops with three elements. The auxiliary normal stop, the punch, and the stop
automatic assistant.

With a similar setup, working in reverse it is possible to eliminate the final tensioner.
however, it is not advisable to make this decision, in order not to decrease performance
in production

Automatic Stops (Auto-Stop)

On the punch holder, there are:

S
P the height adjustment that can be locked by
a nut.

On the guide is mounted:

A Hardened steel stop that pivots with play in a milled housing.

guide and provided with a heel that rests on the matrix.

E hard steel auto-stop.

R coil spring attached to a rod fixed at the base or leaf-spring

that produces the same effect.

Operation

When pushing the band against the stop sign, it rests on the front surface of
its accommodation; upon descending, the punch, after having pressed the plate, forces the auto-
Stop A from getting up using the pusher.

Once again turned back by its spring, hitchhiking A does not fall in front of
the strip, but about this when the pusher P rises again. When pushing the band that is no longer
the hitchhiking A is going to fall into the hole that has just been drilled and the edge of this
it will serve again as a stopper, then starting the cycle again.

Varilla Stops

It consists of a tilting stop and is activated by the movement of the press. This system
it allows for greater production than the previous one, it is generally used in matrices in the
The feeding of the strip is done automatically.

Strap Centering Device

The assembly of center pilot pins in the molds has its reason for being in the fact that
ensure a correct movement between each of the jumps that the band makes. Otherwise
In this way, the common reference points that they would have could be lost.
transformations and with that generate displacements in the sheet that would cause
irregularities or defects in the processed parts.

The centers, with their conical tip, aim to fit into the holes.
of the sheet and center it before the rest of the punches do, as illustrated in the, of
this form keeps the strip of sheet metal aligned before its transformation. To achieve this,
Two or more holes must be made at the start of the strip that will later serve for
pilot it along the matrix.
Centering

Generally, these center pilots are mounted on the punch holder and
they must necessarily stick out more than the bottom face of the tread plate, the latter is
essential to ensure that the sheet is centered before the punches act.
If the centerpieces do not act, the belt will not go to its place and the pilot and the belt will break.

Fracture of the centering device

If the reference holes previously made in the sheet are very small and in
consequence requires some very small spacers, it will be necessary to weigh the
possibility of making the pilots slightly streaked, or retractable through
springs. This way, their breakage and any collateral damage that could occur can be avoided.
cause. In figure 24 (A, B, and C) we see the correct process of band centering through
punches or central pilots.

Correct centering process

Bibliography

Study guide, 'die design.'

María Herminia Pereira. 1998

López Navarro. Die-cutting and stamping with applications of punching, folding,

embossing and extrusion. Second Edition

J. Koninck. D. Gutter. Manual of the Die Technician: die-cutting - Stamping -

Metal sheet stamping.

Herman W. Pollack. Machine Tools and Material Handling

MIKELL P. GROOVER. Fundamentals of Modern Manufacturing 1st Ed.

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http://es.wikipedia.org/wiki/Muelle_elástico