Exercise no:- 5 Date:-
AIM: Study and Design of Press Tool
General Concept of Press Tool:
Press making techniques utilize economical tooling
equipment design have greatly opened. They may for mass
production of articles such that most of necessaries like
automobile refrigerator furnace & domestic wears of stainless
steel have comes within the cost reach of common for many
operation to be performed on sheet metal for further fabrication
the relation of press tool is prime problem. Another problem in
design of tool of press tooling equipment is a man of
experience. Specification and types of press are known to him
on whom the tooling can be mounted. In fact the design of
press tool is accomplished keeping the specification of the
press in mind to give the idle of the range of press that can
hardened for mass production on them. Briefly known idea of
press becomes very important.
Classification of Press:
Press can be classified in the following manner.
1. By the power reservoir.
2. By the intended purpose.
3. By method of transmitting power.
4. By frame design.
5. By no. of independently moving items.
6. By rated tonnage capacity.
By the power source:
According to this classification of this press may be named
as manual driven press, hydraulic press & pneumatic press.
Intended Purpose:
A power press may be used for punching, Bending,
coining, and embossing etc. depend upon the operation. The
press may be named as punching press, bending press,
coining press, and Embossing press etc.
Method of transmitting power:
There exist large variety of frame style & size in which
process are available press area of vertical & inclined design.
Frame design:
It may be of double frame & size single frame, they may
be open at back both double & single frame press the work for
scrap to drop through the gap under gravity.
Number of rams:
Design depending upon the no. of rams of press may be
single action, double action or triple action press.
Capacity of the press:
The tonnage capacity of press indicates the maximum
pressure which the pressure in design & safety accommodate.
Shut height:
It’s a distance between RAM bottom to top of BOLSTER
PLAT. It is an important dimension of press. The tooling
equipment designer most of the press because of the punch &
die along with the holder are to be designed for a particular
shut light of the press available. Such height determines the
height and opening of die for effective working.
Max. Shut height – Max. Opening capacity of press
Min. Shut height – Thickness of Die
Centre of pressure:
In case of irregular shaped punch the summation of
irregular shearing forces. On the side on the centre of ram may
be greatly exceeded the force on the other side.
These results in bending movement in press ram,
undesirable deflection & misalignment. It is thus necessary in
case of irregular shaped punches to find out exact centre of
pressure & layout the punch position in punch in such a way
that centre of line of shank are in the same straight line
summation of shearing forces must be symmetrical about
centre of pressure. It is centre of gravity of line i.e. the
parameter of blank centre. It is not centre of gravity of area.
It can be find out by
1) Graphical method
2) Analytical method
3) Wire method
Principle of metal cutting:
The shearing action in die cutting operation is explain in
fig. The cutting operation done in die is called shearing as it is
done in between two cutting edges (punch & die). In this
operation chip is not produced & it is mainly used for the cutting
of standard sheet strip or coiled strip.
In shearing operation mechanically heavy pressure is
applied on the block stock material. This pressure is applied by
means of a press.
In short metal cutting by shearing action can be arranged
in three stages as under:
I. Plastic deformation
II. Reduction in thickness or area
III. Fracture of sheet metal
Nomenclature of die:
There are various components of mentioned as below.
I. Die block
II. Blanking punch
III. Knock out device
IV. Punch holder
V. Pilot
VI. Die sets
VII. Stock stop
VIII. Die shoes
IX. Spring stripper
Classification of die:
There are many dies which are designed to perform only
one operation with stroke of ram. They are simple design but
several operation to be complete in one stroke of the ram. The
design becomes little complicated dies of the first class are
simple operation dies & dies of the second class are called
multiple operation dies.
Single action press:
1) Single operation:
Cutting die
Forming die
2) Multiple operation:
Progressive die
Transfer die
Combination die
Compound die
Double action press:
1)Single operated
2)Multiple operated
Progressive die:
In a progressive die 2 or more operation are performed
simultaneously at a single stroke of the press by mounting
separate set of dies and punches at two or more different
station. The metal is progressed from one station to other till
the complete part is obtained. The progressive punching and
the blanking die is illustrated in the fig.
Compound die:
In a compound die two or more cutting operation are
accomplished at one station of the press in every stroke of the
ram fig. illustrates the compound blanking and piercing die.
Combinations die:
In combination die both cutting and non-cutting operation are
accomplished at one station of the press in every stroke of ram
fig. illustrate a combination blanking and drawing die. Showing
different stage of the operation. The upper die block serves as
a blanking punch and houses a drawing punch as its centre. As
the punch descends the metal is first sheared and the required
size of the blank is obtained.
Introduction to die cutting operation such as.
Blanking:
Its operation of cutting a flat sheet to the desired shape.
The metal punch out is the required product and the plate with
the hole left on the die goes waste. Size of blank is governed
by the size of the die and clearance is left on the punch.
Punching:
Its operation of producing a hole in sheet metal by the punch
and the die. The material punched out to form the hole
constitute the waste. The punch govern the size of hole and
clearance is left on the die.
Types of Dies:
According to bending:
Required shape is obtained from the material by bending.
The blank is in bent position due to bending of its axial at an
angle. The metal is pulled by bending even though the
continuity of metal thickness is maintained. There are two
methods of bending as under:
V- bending:
V- Type die block & same type of punch is used in v-
bending. The force applied in bending within the limit of plastic
deformation. The opening of 6 to 10 times the thickness of
sheet metal is kept. The v-block angle is taken as per the
bending need. The soft metal can be bent easily as shown in
fig. & hard material can be done after heat treatment.
Edge bending
When steel metal is to be bend at an angle from its edge
then the process is called edge bending. The 90 bent is
obtained by exerting pressure from the side & top with proper
arrangement of die block & punch.
According to drawing die:
Single action drawing die:
The simple type of this die consist punch & die, comes in
direct contact. Each pair is produced in integrated piece & has
no die shoe. As the punch comes down, it slowly comes in
contact of previously cut blank. Further movements of punch
will press the blank & finally give the design shape. It demands
uniform pulling of metallic blank so the cavity is formed. Any
geometrical defect prevented by primary checking of material,
punch & die. Its aim is to arrange the lattice structure slowly at
the surfaces under applied pressure, so at plastic deformation,
structure cannot regain its structural form on removal of the
applied pressure & desired shape can be obtained. The almost
uniform thickness remains on whole surface in this operation.
The thickness at the base is kept more in deep drawing
because the area of the base surface does not pulled to that
extent. Drawing work is carried out in different stages, demands
more thickness.
Double action drawing die:
The different motion of both the rams is simultaneously.
Hence it called double action drawing die. The blank holder
come down first with the outer ram held the blank after
establishing contact with it. Therefore the punch fixed on inner
ram come down. The proper full stoke length & chamber to
draw the component are used, therefore hollow component of
desire regular shape is successfully produced by the punch in
its final position. The component is taken out from the die using
knockout mechanism. Both rams operates under the action of
different pressure. So pressure pad is not required & therefore
the plane axis should be unique. To achieve that pressure in
both the cylinders is regulated by packing & relief valve. The
ram movement is slow gives shock & impact less performance.
Utensil, automobile parts, cans & plastic component can be
produced by double action drawing die.
According to forging die:
Drop forging die:
In drop forging die, repeated blows of power hammer is
used to cause flow of metal to fill the die cavity & the final
shape of product is obtained as the shape of the die
impression.
As the shown in fig. the drop forging die is made in two
pieces for producing connecting rod by drop forging die.
Therefore some portion of thickness is kept in upper half &
remaining thickness in the lower half of the die. When these
two pieces of die come together left an impression of parting
line all around the product considering suitability of the parting
line forging die is made up to two pieces having less thickness
of die cavity. If parting is horizontal than drop forging becomes
easy. If parting lines are in all direction, the forging work
sometime become less expensive.
Upset forging die:
As shown in fig. special type of bolt head, clamping devices
for fixture & 2 to 5 kilogram weight of product is forged by upset
forging. The possibility of shrinkage wear & mismatch is less in
this type of die. If they occur than their effect is less because
the work of forming heads is only done in this die. Therefore the
concession or freedom in observation dimension can be taken.
This operation is exactly opposite to the drawing operation. The
rod is held in die after heating & head of bolt, pin etc. is forged
by repeated blow of drop hammer. The success of upset
forging die design is dependent on condition like,
I. Keep length of rod three times its diameter in blank so that
its forging can be done by single blow without causing
buckling.
II. If length of blank is more than three times the diameter of
rod then forged diameter can only be obtain 1.5 times the
rod dia.
III. If the length of the blank is three times the rod diameter,
then after gripping the free end of the blank, upset forging
should be started.
ELEMENTS OF PRESS TOOL
https://youtu.be/kb2gXM7JVUU
PRESS OPERATION
https://youtu.be/J_d8IRT9r7E
PROGRESSIVE DIE
https://youtu.be/8LmwXRpsH7s
COMPOUND DIE
https://youtu.be/U37hWgxS3tg
