INTRODUCTION TO MECHANICAL ENGINEERING (22ME1ESIME/22ME2ESIME)

MODULE - 2 FUNDAMENTALS OF MACHINE TOOLS AND OPERATIONS

Fundamentals of Machine Tools and its operations

A device which consumes energy in some available form and converts it into useful work is called
“Machine”
Machines that perform the metal cutting operations or machining operations are called “Machine
tool” Eg: Lathe, Drilling, Milling, Grinding, etc.

Lathe Machine

A general-purpose machine tool used for producing circular objects is called “Lathe.”
Different operations which are performed on lathe machine are: Turning, Facing, Thread cutting,
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Knurling, Facing, Drilling, etc.

B. M. S. C. E. Bengaluru
Sangamesh. C. Godi
Asst. Professor

Types of Lathe (NOT IN SYLLABUS - Only for your information)

Depending on the characteristic functions, the lathe machine is of following types:

1. Engine Lathe - General purpose

2. Speed Lathe - Woodcutting and polishing

3. Turret Lathe - Turret sequencing

4. Capstan Lathe - Extra accessories

5. Automatic Lathe - Automatic control

6. Computer Numerically Controlled (CNC) Lathe

Engine Lathe

Lathes driven by engines (electric motor) which are required to perform a wide variety of operations are
called “Engine Lathe”.
Machining: The process of removing the excess material from the workpiece in the form of chips by
forcing a cutting tool with one or more edges.

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 GAP IN THE
BED
Principal of working of lathe machine

A lathe, basically a turning machine, works on the principle that a cutting tool can remove material in
the form of chips from the rotating workpieces to produce circular objects.
Figure 1 shows a workpiece held rigidly in one of the works holding devices, known as “CHUCK,”
and rotated. A V-shaped cutting tool moved parallel to the axis of the workpiece by holding against it.
Where the workpiece is revolving in the opposite direction of rotation produces circular surfaces.

Work holding device (Chuck)

Round surface
Work piece produced by
machining
Dept. of Mechanical Engg.
B. M. S. C. E. Bengaluru
Sangamesh. C. Godi

Tool
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Figure 1: Principal of working of a Lathe

Major parts of lathe (NOT IN SYLLABUS - Only for your information)

1. Bed (a) Saddle

2. Main drive (b) Cross slide

(c) Compound rest

3. Cone pulley and Back gear
(d) Apron
4. Headstock
7. Lead screw
5. Tailstock
8. Feed rod
6. Carriage assembly consisting of:

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 Driving clutch
Gear box control control lever Cross slide
Four jaw Tool post Hand wheel
chuck Dead center
Head stock Tool post Ram Clamp
Cross slide slide Ram

Rack
Feed box

Tray
Carriage Screw cutting
Bed engaging lever Screw rod
Leg Carriage traversing
wheel Feed engage Feed rod

Apron

Figure 2: Parts of lathe

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1. Bed: The bed is the foundation part of a lathe and supports all its other parts. It is made of a
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single piece casting of semi-steel (Chilled Cast Iron). The top of the bed is formed by precision-
machined guideways. There will be two sets of guideways, one is flat, and another one is ‘V’ shaped.
The headstock and tailstock are mounted on the inner ways which keep them perfectly aligned
with each other. The bed is sufficiently rigid and good damping capacity to absorb vibration.

2. Main drive: An electric motor mounted in the left leg of the lathe in conjunction with the
transmission system like a belt or gear drive from the motor to the spindle that forms the main
drive of the lathe.

3. Cone pulley and Back gear: The cone pulley, which drives the main spindle through belting, is
driven by the motor. Various spindle speeds can be obtained by shifting the belt on the different
steps of the cone pulley. Spindle speeds can be further varied using a back gear arrangement.

4. Headstock: Headstock is situated at the left side of the lathe bed, and it is the house of the
driving mechanism and electrical mechanism of a lathe machine tool. Headstock transmits power
from the spindle to the feed rod, lead screw, and thread cutting mechanism. A separate speed
change gearbox is placed below headstock to reduce the speed to have different feed rates for
threading. The feed rod is used for most turning operation, and the lead screw is used for thread
cutting operation.

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 5. Tailstock: Tailstock is the movable part of the lathe. It is normally situated on the right side
above the lathe bed. The main function of the tailstock is to support the free end of the long
workpieces and minimizes its sagging. It is also used for holding the tool for performing a different
operation such as drilling, reaming, tapping, etc. Further, the tailstock is used for a small amount
of taper for a long job by offsetting the tailstock.

6. Carriage assembly: The carriage assembly serves to support the cutting tool and rides over the
bedways longitudinally between the headstock and tailstock. It provides three movements to the
tool, such as (i) Longitudinal feed through carriage movement, (ii) Crossfeed through cross slide
movement, and (iii) Angular feed through top slide movement. It is composed of five main parts,
and they are given below:

(a) Saddle: It is an H shaped casting, and it has a ‘V’ and flat guide for mounting it on the
lathe bed guideways and serves as the base for the cross slide.

(b) Cross-slide: it is mounted on the saddle and enables the movement of the cutting tool
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laterally across the lathe bed using crossfeed handwheel. It also serves as the support for a
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compound rest.
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(c) Compound rest: It is mounted on the top of the cross slide and supports the tool post.
It can be swiveled to any angle in the horizontal plane to facilitate the taper turning and
threading operations. It is moved manually by the compound rest feed handle independent
of the lathe crossfeed.

(d) Apron: It is mounted at the front of the saddle beneath and houses the carriage and the
cross slide mechanisms. The apron handwheel moves the carriage assembly manually using
the rack and pinion gears.

(e) Tool post: It is mounted on the T slot of the compound rest, and it is also a topmost
portion of the carriage. The tool post is used to hold the various cutting tools or tool holders
to perform machining operations.

7. Lead screw: A lead screw is also known as a power screw or translation screw. It converts
rotational motion to linear motion. The lead screw is used for thread cutting operation.

8. Feed rod: The feed rod is a stationary rod mounted in front of the lathe bed and facilitates the
longitudinal movement of the carriage during operation like turning, facing, and so on.

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 Lathe specifications: (NOT IN SYLLABUS)

The size of the lathe is specified by the following as shown in Fig.3

1. Swing of the Lathe - Maximum diameter of the workpiece that can be revolved over the lathe
bed.

2. Maximum diameter and width of the workpiece that can swing when the lathe has a gap in bed.

3. Maximum length of the workpiece that can be held will be decided by the distance between
the centers

4. Overall length of the bed.

OVERALL LENGTH OF BED

SWING OF WORK
PIECE OVER LATHE BED
DISTANCE BETWEEN
CENTERS `
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SWING OF WORK
B. M. S. C. E. Bengaluru

PIECE OVER GAP

`
Sangamesh. C. Godi

IN THE BED
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GAP IN THE
BED

LATHE BED

Figure 3: Specification of a Lathe

Work holding device (Chuck)

Round surface
Work piece produced by
machining

Tool

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 Lathe operations (The operations which are in bold font are in syllabus)

Generally performed lathe operations

OVERALL LENGTHare:
OF BED
SWING
(1) Turning: Plain and Taper turning, (2) Facing, (3)OF WORK (4) Thread cutting, (5) Boring,
Parting,
PIECE OVER LATHE BED
DISTANCE BETWEEN
(6) Drilling, (7) Reaming, (8) Knurling,(9) Milling, and (10) Grinding
CENTERS `

1. Plain
` Turning

A single point cutting tool is fed perpendicular to the axis of the workpiece to a known predetermined
depth of cut, and is then moved parallel to the axis of the workpiece and removes the material to form
the machined cylindrical surface.
“Machining operation in which the workpiece is reduced to the cylindrical section of required
LATHE BED
diameter is called Plain Turing”

Depth of cut
4 Jaw chuck
device (Chuck)
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Work piece
B. M. S. C. E. Bengaluru

Round surface
rk piece produced by
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machining
Dead
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center

Feed Machined
Tool Cutting cylindrical surface
tool

Figure 4: Plain turning

2. Taper Turning

“Turning operation on lathe to produce conical surface on the workpiece is called Taper Turning.

α
(D-d)/2

2α Taper angle , α =tan

−1
( D−d
2L )
D
d

Figure 5: Taper turning

Work piece
Taper
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Lathe axis
he axis
Live
center
α

Offset
Taper turning methods: α
Dead
(i) By forming tool, (ii) By swiveling the compound rest, (iii) By tailstock
center offset method,
and (iv) By taper turning attachment
Cutting tool
rest
(i) Taper turning by using forming tool (only for external taper, fixed taper
angle and shorter taper length)
Compound tool rest
α straight edge set at the desired angle.
Form tool has The angle between the straight cutting edge and
the axis of the spindle equals one half the included angle of the taper. In this process, the tool is fed
Guide box
perpendicular to the axis of the rotating work piece, machined surface forms the required conical (taper)
Draw-link
surface.
Work piece This method is limited to shorter taper length and mainly used for chamfering.

Dead Work piece

center Taper surface
α
Lathe axis
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α
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Cutting tool
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Cross slide
Form tool

Compound tool rest

Figure 6: Taper turning by forming tool

(ii) Taper turning by swiveling the compound rest (only for external tapers)

The compound rest of the lathe is swiveled to the required taper angle and then locked in the angular
position (carriage is also locked). For taper turning, the compound rest is moved linearly at an angle
so that the cutting tool produces the tapered surface on the workpiece. This method is suitable for the
steep taper angle requirement. It is limited to short tapered lengths ( because of the limited movement
of the compound rest).

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 L

Work piece
Taper
Lathe axis

α
α
Cutting tool

Compound tool rest

Figure 7: Taper turning by swiveling compound rest

(iii) Taper turning by tailstock offset method (only for external taper)

When the tailstock center (Dead center) is set out of alignment, the workpiece gets taper turned, because
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its axis will be inclined at an angle with the lathe axis (see Fig. 8). Then the carriage is to be moved
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along the lathe axis. Since the size of the tailstock limits the amount of offset, this method is suitable
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for long workpieces having less taper.

Work piece

Live
center Offset
α
Dead
center

Cutting tool

Compound tool rest

Figure 8: Taper turning by tailstock offset method

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 Work piece

Live
center
(iv) Taper turning by taper twining attachment (Both external and Internal

Offset
α
tapers) Dead
center
It consists of a guide bar, which may be set at the desired angle of taper. When a taper turning
attachment is used, the cross slide is disconnected from the screw. It is attached to a sliding block by a
Cutting tool
rigid connecting link (see Fig. 9). If the carriage (where the tool post is mounted) is now moved along
the lathe axis, then the sliding block will slide over the guide bar, thus moving the cross slide about the
work. The cross slide now follows the guide bar so that the tool moves parallel to the tapered bar, and
Compound tool rest
the taper is produced. Suitable for long tapers with a small angle.

Guide box
Draw-link
Guide bar Work piece
Live
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center Dead
B. M. S. C. E. Bengaluru

center
α
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Cutting tool

Cross slide

Tool post slide

Figure 9: Taper turning by taper turning attachment

4. Knurling

Knurling is the process of embossing a diamond-shaped pattern or to generate a serrated surface on

the workpiece by using the Knurling tool, where a revolving hardened steel wheel presses against the
workpiece. Impression pattern may be straight lines or diamond pattern. The purpose of the knurling
is to provide the grip to hold the part

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 3/4 Jaw chuck

Work piece Knurled surface

Dead
center

Feed

Movement
for depth

Knurling
tool
Tool
post

Figure 10: Knurling operation

Dept. of Mechanical Engg.
B. M. S. C. E. Bengaluru
Sangamesh. C. Godi
Asst. Professor

IME/MODULE 2 - Fundamentals of Machine tools and operations/Dr.Sangamesh.C.Godi 10

 Drilling head

Drilling Machine
Radial arm

Column
“ Drilling is a metal cutting process carried out by rotating cutting tool (Drill) to make circular holes
Arm elevating Drill
in a solid materials” screw Work table

Drilling Tool or Twist drill or Drill bit:

The tool which makes the hole is called “Drill.” It is also called “Twist drill” because it has a sharp,
Base
twisted edge formed around a cylindrical tool provided with a helical groove along the length to allow
the cut material to escape through it (a liquid coolant is used while drilling to remove the heat generated
due to friction and to obtain a better finish for the hole)

Neck Flute Margin Lip

Tang

Flank
Shank Body

Figure 11: Drilling tool or twist drill

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Drilling Machine
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Asst. Professor

“A power-operated machine tool which holds the drill in its spindle, rotating at high speeds and then
manually actuated to move linearly and simultaneously against the workpiece produces a hole is called
drilling machine”.

Classification of drilling machines (NOT IN SYLLABUS - Only for your

information)

1. Portable drilling machine

2. Bench/ Sensitive drilling machine

3. Pillar drilling machine

4. Gang drilling machine

5. Multiple spindle drilling machine

6. Radial drilling machine

1. Portable drilling machine: These machines are small in sizes and can drill holes up to 12 mm
diameter. These machines are used for producing small holes for short depths.

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 2. Bench drilling machine: These are light-duty drilling machines placed on workbenches. These
are also called sensitive drilling machine because of their accurate and well-balanced spindle,
which enable the operator to sense or feel the cutting action and apply the required pressure while
drilling. In these machines, hole sizes of up to 15 mm diameter can be drilled.

3. Pillar drilling machine: These machines are employed for both medium and heavy-duty jobs
and can drill holes of sizes up to 50 mm diameter. It has a robust pillar carrying an adjustable
table and drill mechanism.

4. Gang drilling machine: These are machines that have many drilling heads placed side by side,
and the workpieces mounted on a long common work table. A gang drilling machine mounted with
a drill, a reamer, a countersinking tool, and a tapping attachment on its successive spindles. The
workpiece where multiple operations in the order such as drilling, reaming, countersinking and
tapping operations successively have to be carried out will be moved with a jig to the respective
spindles. Thus various operations can be performed without changing the tools and the spindle
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speeds.
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5. Multiple spindle drilling machine: These machines have the drill head assembly, which has
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several fixed upper spindles driven by one central gear. Hence one can drill several holes
simultaneously. This type of machine is used for mass production.

6. Radial drilling machine: Radial drilling machine is used for workpieces, which are too heavy
and also may be too large to mount them on the worktable of the vertical spindle drilling machine.
It consists of a heavy base and a vertical column with a long horizontal arm extending from it.
It can be rapidly raised, lowered, and swiveled in the horizontal plane about the main column to
any desired location. The drilling head can move to and fro along the arm (the head can also be
swiveled only in the universal radial drilling machines) to drill holes at an angle. The combination
of radial arm movement and drill movement offers a great deal of flexibility in moving drill to any
position. The main advantage here is that the workpiece need not be moved.

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 Motor for moving arm
Elevating drive housing

Drill spindle motor

Drilling head

Radial arm

Column

Arm elevating Drill

screw Work table

Base

Figure 12: Radial drilling machine

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Drilling Operation
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Asst. Professor

(i) Drilling, (ii) Boring, (iii) Reaming, (iv) Counter sinking, (v) Counter boring, (vi) Spot facing,
and (vii) Tapping

Drilling is the operation where a cylindrical

hole is produced in a solid metal by introducing
a rotating twist drill into the workpiece. A Work piece
Boring tool
drill is held firmly in the drill chuck of the
W
spindle, and then the rotating drill is slowly
fed to obtain the required depth of the hole.

Figure 13: drilling

Reamer

Work piece

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 Boring is the operation of Work
enlarging
piece an
Boring tool
existing hole using an adjustable cutting tool
Work piece
with only one cutting edge. When a suitable Work piece
Boring
size drill is not available, initially a hole is
drilled to the nearest size, and then using a
single-point cutting tool, the size of the hole is
enlarged to the required size.
Figure 14: Boring

Reaming is the operation of finishing a

Reamer
drilled hole using a multi teethWork
cutter
piececalled
“Reamer”. In general, the hole will be drilled Reamer

to a slightly smaller size, then the reamer is Work piece

mounted in place of the drill, and the reaming

is performed with less speed. In this operation,
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less or a small amount of material will be

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removed to produce a smooth finish on the

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Figure 15: Reaming

drilled surface.

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 Milling Machine

Milling is a process of removing excess material from the work piece with a rotating cutting tool called
“milling cutter”.
Milling cutter is a multipoint cutting tool with cutting teeth formed on the circumference or on the
end face or on the both. The cutter is made to rotate at various spindle speed speeds. However, with
suitable speed and multiple cutting edges, material can be removed at a faster rate and also fine surface
finish can be obtained.
Milling process is used for producing flat, contoured, or helical surfaces, for cutting gear tooth,
keyways, slots etc.
Important note:

1. Whille machining on “LATHE”, the tool is fed against the rotating workpiece

2. In “DRILLING” the rotating tool is fed against a stationary workpiece”

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3. In “MILLING” the workpiece is fed against revolving tool

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Milling Machine

“A milling machine is a power operated machine tool in which the work piece mounted on moving table
is machined to various shapes when moved under a slow revolving serrated cutter”

Classification of milling machines (NOT IN SYLLABUS - Only for your

information)

1. Column and Knee type milling machine

(a) Horizontal milling machine or plain milling machine

(b) Vertical milling machine

(c) Universal milling machine

2. Fixed bed type milling machine

3. Planer type milling machine

4. Special purpose milling machine

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 Milling Operation

(i) Plain milling or Slab milling or Surface milling or Peripheral milling, (ii) Slot milling
and Key way milling, (iii) Angular milling, (iv) Form milling, (v) Straddle milling (Side milling),
(vi) Gang milling, and (vii) End milling, (viii) Face milling

Plain milling (or or Slab milling or

Surface milling or Peripheral milling) is
the operation performed on horizontal milling
machine, where obtained plain, horizontal
surfaces are parallel to the axis of rotating
cutter. The cutter called “plain or slab
milling cutter” has straight or helical teeth
on the periphery of a cylindrical surface.
Figure 16 shows the schematic of the slab
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milling operation.
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Helical tooth cutter removes greater amount of

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Figure 16: Plain milling

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material and produces a smooth surface finish

when compared to the straight tooth cutters.

Slot milling is the operation of producing

slots in work pieces. The slots can be of varied
shapes such as plain slots, T-slots, Dovetail
slots etc., The operation can be performed
by means of plain milling cutter, end milling
cutter, T-slot cutter, Dovetail milling cutter or
by a side milling cutter.
The cutter to be used is chosen according to
the shape of the slot to be produced. Figure 17
shows the schematic of the cutting of open slot
milling operation.
Figure 17: Slot milling

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 Modern Manufacturing Tools and Techniques:

CNC – Computer Numerical Control

Introduction

Numerical control (NC) refers to control of a machine or a process using symbolic codes consisting of
characters and numerals. The concept of NC was proposed in the late 1940s by John Parsons who
recommended a method of automatic machine control that would guide a milling cutter to produce a
curvilinear motion in order to generate smooth profiles on the work pieces.
The word CNC came into existence when microprocessors and microcomputers replaced integrated
circuit IC based controls used for NC machines
The term CNC stands for ’computer numerical control’, and the CNC machining is a subtractive
manufacturing process that typically employs computerized controls and machine tools to remove layers
of material from a stock piece known as the blank or workpiece and produces a custom-designed part.
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A CNC machine is a computerized programmable machine that is capable of autonomously

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performing the operations of CNC machining. It consists of microprocessor, RAM, ROM, input and
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output devices.
This process is suitable for a wide range of materials, including metals, plastics, wood, glass, foam,
and composites, and finds application in a variety of industries, such as large CNC machining, machining
of parts and prototypes for telecommunications, and CNC machining aerospace parts, which require
tighter tolerances than other industries.

Components of CNC

A CNC system has six following major components or elements: i) Input Device, (ii) Machine Control
Unit (MCU), (iii) Driving system, (iv) Machine Tool, (v) Feedback Devices, and (vi) Display Unit
Figure 18 shows the sequence of working principle of a CNC system

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 Figure 18: Components of CNC
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ˆ Input Device: It is the medium to transmit the part programs to the Machine Control Unit
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(MCU). Punch tape, floppy disk, and USB flash drives are the input devices were employed
earlier. However, in recent days advanced input devices like Serial communication (RS 232 port
and supported cable is used to connect the computer to CNC), Ethernet communication (LAN)
and conversational programming (built in intelligent software for step by step data entry directly
through keyboard) are used.

ˆ Machine Control Unit (MCU): It is the heart of the CNC system. It consists of following units
namely reader unit, memory, processor, output channels, and control panel. With the help of these
units, MCU processes the information received from the input device and transfers appropriate
instructions to machine tool for mechanical actions. It also acts as a feedback controller for precise
positioning of machine table or spindle.

ˆ Driving system: It consists of ‘amplifier circuits’, ‘drive motors’ and ‘ball lead screw’. Its
amplifier circuits receive control signals from the MCU and moves the machine table with the
help of drive motors and ball lead screws in the programmed directions and sequence. Hence it
responds to the pre-programmed instructions by allowing the work piece to get finish with the
desired shape and size.

ˆ Machine tool:CNC machine tools are computer controlled machine tools and performs the actual

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 machining operation, and can be of any type like lathe, drilling machine, milling machine, etc.
The machine tool mainly consists of work table and tool spindles whose motion can be controlled
accurately by the driving ystem that receives commands from the MCU. A part with desired
features is produced by the machine tool.

ˆ Feedback devices: These are the devices used to monitor the positional values of linear and
angular displacements of cutting tool with respective spindle speeds.The linear transducer, and
rotary encoders are used for these purposes. These are classified under ‘positional feedback deices’
and ‘velocity feedback devices’ respectively. The MCU uses the difference between reference signals
and feedback signals and generates the control signal to correct errors in position and speed.

ˆ Display unit: It helps the operator to interact with the machine. It also also helps the operator to
verify the part program before starting the machine hence to rectify and correct the malfunctions
in the system if any at the given instant.
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Advantages of CNCs
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1. High productivity

2. Higher precision, with better quality control of products.

3. Improved part quality and repeatability.

4. Reduced tooling costs, tool wear, and job setup time.

5. Reduced scrap.

6. Better production planning and placement of machining operations in the hands of

engineering.

7. The CNC program can be written, stored, and executed directly at the CNC machine.

8. Any portion of an entered CNC program can be played back and edited at will. Tool motions
can be electronically displayed upon playback.

9. Many different CNC programs can be stored in the Machine control unit (MCU).

10. Several CNC machines can be linked together to a main computer. Programs written via the
main computer can be downloaded to any CNC machine in the network. This is known as
direct numerical control or DNC

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 Disadvantages of CNCs

1. Initial cost and maintenance cost are very high

2. Highly skilled and knowledgeable operators are essential

3. CNC machines are not preferable for small quantity batch production

4. Planned support facility is required.

Applications of CNCs

1. Metal removal industries - automotive industries, aerospace industries, and in making

jewelry.

2. Material fabrication industries - thin metal plates to create end products. Drilling
precision holes, flame or plasma cutting, welding and shearing

3. For non-conventional machining industries - where the machining task is difficult to

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perform manually.
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4. Electronics - Computers and motherboards have brains with millions of tiny parts that
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must be made with precision.

5. Firearms - CNC machines are used to create barrels, ammunition clips, pins, triggers, and
several components of the gun. Electrical Discharge Machining (EDM) Applications.

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 3D printing or Additive Manufacturing

Introduction

It is a process of converting a computer Aided Design (CAD) based three dimensional model into real
product by processing the model layer by layer.
The process makes use of interfaced software and hardware components with actuators and sensors
to print the 3D product.
3D printing machine is setup for prinitng the part. This involves initialization of machine, setting
of fill percentage etc. Once the process starts, part is printed layer by layer. printing takes several
minutes or hours depending on the nature and complexity of the 3D model geometry. Further, after the
completion of printing, part is taken out, cleaned and support structures are removed. Post processing
can be done to remove unwanted material and obtain required surface finish. Painting or any other
surface treatment can be carried out to provide the necessary surface characteristics and textures
Dept. of Mechanical Engg.

Classification of Additive manufaturing process (NOT IN SYLLABUS)

B. M. S. C. E. Bengaluru
Sangamesh. C. Godi

1. Fused Filament Fabrication (FFF)

Asst. Professor

2. Stereolithography / Digital Light Processing

3. Powder bed fusion

4. Sheet Lamination techniques

5. Solid Grand Curing

6. Material Jetting Technology

7. Direct Write

8. Direct Energy Deposition

IME/MODULE 2 - Fundamentals of Machine tools and operations/Dr.Sangamesh.C.Godi 21

 Steps involved Additive Manufacturing

Printable 3D models can be created with a computer Aided Design (CAD) packages, through a 3D
scanner or by the plain digital camera and photography software. These models can be saved in
.STL(STEREOLITHOGRAPHY) file format. This will be processed by software ‘slicer’ that
converts the model into a series of thin layers and produces G-code program to a specific type of 3D
printer.
Dept. of Mechanical Engg.
B. M. S. C. E. Bengaluru
Sangamesh. C. Godi
Asst. Professor

Figure 19: Schematic of step involved in Additive manufacturing

Materials used in 3D printing (NOT IN SYLLABUS)

1. Plomer/plastics

2. Metals and alloys

3. Composites

4. ceramics

5. Elastomers

IME/MODULE 2 - Fundamentals of Machine tools and operations/Dr.Sangamesh.C.Godi 22

 1. Polymers/Plastics: polymers are substances containing large molecules composed of many
repeated subunits joined by the same type of linkage. They often form a chain like structure.

(a) Acrylo-nitrate Butadiene Styrene (ABS): is the most common platic material used for
3D printing. It is a very strong plastic which is prepared and made available in filament
(wire) form in variety of colours.

(b) Poly Lactic Acid (PLA): is a biodegradable material which is sourced from natural
products like sugarcane and corn starch. PLA in resin from is used for Digital Light
Processing (DLP) and Stereo lithography. In different coloured filament forms, it is used in
Filament Deposition Modeling (FDM). PLA is not durable as ABS.

(c) Polyvinyl Alcohol Plastic (PVA): is a plastic material suitable for support materials of
the dissoluble variety, normally used in low end home printers.

(d) Poly-carbonate (PC): is used in printers that has nozzle design and operate at high
temperature. It is employed for making low cost plastic fasteners and molding trays.
Dept. of Mechanical Engg.

There are many specialized plastics with specific properties, they are: Nylon or Polyamide,
B. M. S. C. E. Bengaluru
Sangamesh. C. Godi

High Impact Polystyrene (HIPS), Lay brick and Lay wood, F-glass, cellulose, thermoplastic
Asst. Professor

polyester, polyethylene, polypropylene tc.

2. Metals and Alloys: metals like Aluminum, mild steel can be printed layer by layer. Here metal
powders are heated to a phase transition from solid to liquid and then solidified using lasers or
electron beams.

Metal based 3D printing is used in aerospace and automotive industries in order to increase
production rate, improved strength and quality than conventional manufacturing process. other
metallic material like aluminum alloys, cobalt and chromium alloys, Titanium alloys, Nickel based
alloys etc are also used.

3. Composites: these are the materials made from two or more constituents materials with
significantly different properties that, when combined, produce a material with characteristics
different from the individual constituents.

Fibre materials such as carbon fibers are used in 3D printers as atop-coat over plastic materals to
make the part stronger. It is a fast and convenient alernate to metal.

short glass fibers and nanofibers have been added into ABS filaments to improve the mechanical
properties of parts built using Filament Deposition Modeling (FDM)

IME/MODULE 2 - Fundamentals of Machine tools and operations/Dr.Sangamesh.C.Godi 23

 3D printing of composite materials is not mainstream yet, but the research is in progress and is
expected to replace many of the traditional manufacturing process.

4. Ceramics (Non metallic bonds); is a solid material comprising an inorganic compound of

metal, non metal or mettalloid atoms primarily held in ionic and covalent bonds. or Eg:
Earthernware, porcelain, brick.

Various materials in ceramic are being developed commercially for parts subjected to high
temperature environment. Zirconia, Alumina, Silicon Nitride, Zirconsilica etc., are some of such
materails. They are more durable than metalplasic.

5. Elastomers: are a polymers with a viscoelasiticty an very weak intermolecular forces, and
generally less stiff, (elastic properties, Eg: rubber). Elastomers can replace many human like
artifacts and work as an external skin on certain materials.

Advantages of 3D printing (or Additive manufacturing) over traditional

Dept. of Mechanical Engg.
B. M. S. C. E. Bengaluru

manufacturing
Sangamesh. C. Godi
Asst. Professor

ˆ Reduces material wastage

ˆ Reduces the number of operations and tooling

ˆ Reduces the requirement of multiple skilled operators (As it avoids use of multiple machine
operations)

ˆ Reduces production times

ˆ Reduces cost of production as wastage is reduced.

ˆ Provides more freedom for designers

ˆ Complicated parts can be produced

Disadvantages of 3D printing (or Additive manufacturing)

ˆ Unexpected pre and post processing requirements

ˆ High process cost, as technology is upcoming

ˆ Lack of industry standards

IME/MODULE 2 - Fundamentals of Machine tools and operations/Dr.Sangamesh.C.Godi 24

 ˆ Low speed, nt suitable for mass production

ˆ Inconsistent materials

ˆ Hih equipment cost for high end manufacturing.

Dept. of Mechanical Engg.
B. M. S. C. E. Bengaluru
Sangamesh. C. Godi
Asst. Professor

IME/MODULE 2 - Fundamentals of Machine tools and operations/Dr.Sangamesh.C.Godi 25