Prepared by: Thanks and Regards... Mr. U. ARAVIND, B.E., M.I.S.T.E., LECTURER / MECHANICAL ENGINEERING LAKSHMI AMMAL POLYTECHNIC COLLEGE K.R. NAGAR, KOVILPATTI - 628 503 THOOTHUKUDI DISTRICT, TN Mobile No: 9943244068 Email Id: aravindulaganathanmech@gmail.com aravindmech@lapc.in

1. 1
Lakshmi Ammal Polytechnic College
Department of Mechanical Engineering
Subject Name : Special Machines
Subject Code : 32042
Year & Semester : II / IV
Scheme : M
U. Aravind
Lecturer/Mech
LAPC
K.R. Nagar

3. UNIT – 5
CNC MACHINES & ITS
COMPONENTS

4.  NC - Numerical Control
 CNC - Computer Numerical
Control
 MCU - Machine Control Unit
 HMC - Horizontal Machining
Centre
 VMC - Vertical Machining Centre
 UMC - Universal Machining Centre

5. CMM - Coordinate Measuring
Machine
LMB - Linear Motion Bearing
ATC - Automatic Tool Changer
CBN - Cubic Boron Nitride
PCD - Poly Crystalline Diamond
MDI - Manual Data Input

7. Numerical Control (NC)
• NC is defined as Control of
machine slide movements &
various functions by means of
Letters, Numbers and Symbols
• Letters, Numbers and Symbols
forming some sequence is called
Part Program

9. 1.Starting and stopping of
machine tool spindle.
2.Controlling the spindle speed.
3.Positioning the tool tip
4.Guiding the tool in desired
paths
5.Controlling the feed rate.
6.Changing of tool in the spindle

17.  It is a Numerical Control system,
which uses a Computer to perform
all or some of the basic numerical
control functions
In CNC, the program is entered
once and they stored in the
computer memory

22. A CNC system consist of the
following
1.Machine Control Unit (MCU)
2.Operator Control Panel
3.Servo Control Unit & Drives
4.Feedback Devices

23. In CNC systems the part program is
fed into the computer.
Then the instructions are read by the
controller to convert it into signals
that activate the machine tool.
The signals are sent to the machine
tool for performing different
operations.

25. Input
Device
Display
Unit
Drive
System
Machine
Control
Unit
Feed back
devices
Part Program
Motion Data
Miscellaneous
Function
Position Feedback
Velocity Feedback

26. Software of system has 3 major programs
1. Part Program: It has Part
Dimensions, Spindle Speed, Feed rate
2. Service Program: Used to check ,
edit, correct the part program
3. Control Program: Accept the Part
program as a Input data to produce
signals to drive the axes of motion

32. Machine Control Unit (MCU)
 Consists of PLC, Processor,
Memory Devices
PLC control the Spindle ON/OFF,
Coolant ON/OFF, Tool path,
Speed, Feed, Tool Changes
Convert the Program
Commands into Signal

33. Operator Control Panel
Provide the interaction
between User & CNC
system
Consists of Monitor,
Feather touch keyboard,
machine control panel

35. Servo Control Unit & Drives
 PLC gives command signal
to servo drives , this command
signal values are converted
into actual movement on the
machine by servo drives

36. Feedback Devices
 PLC receives feedback signal about
actual movement of the machine tool
through feedback devices
Feedback Devices are Transducers
& Encoders
This feedback signals are compared
with the Input signals and error
correction is done

38.  Storage of more than one part program
Various forms of Data Input
Program Editing
Graphical Display of Cutter path &
shape of the finished job before actually
running the program is possible
Sub program facility for repetitive
machining sequence also possible

40. • Increased Productivity
• High Accuracy
• Reduced Time
• Reduced man power
• Simulation of program is available
• Increased Safety operations
• Lesser Floor place

42. NC CNC
NC - Numerical Control CNC - Computer
Numerical Control
Machine is not
controlled by Computer
Machine is Controlled
by Computer
Input is given by
punched tape
Input is directly given
through computer
Reliability is less Reliability is more
Program editing is not
possible
Program editing is
possible

43. Simulation of part
program is not possible
Simulation of part
program is possible
Storing the part
program is difficult
Storing the part
program is easy
Less flexible High flexible
Less Capability High Capability
NC programmers are
skilled persons
Programmer not
necessarily a skilled
person

45. • CNC Turning centre is a machine
tool capable of performing
various Turning & related
operation in one setup under CNC
system
• CNC turning centers are designed
mainly for machining shaft-type
work pieces which are supported
by a chuck

46.  CNC turning centre Tool Turret have
Capacity of 8 to 12 tools
Two axis control:
 Z axis - Parallel to Spindle axis
 X axis - Perpendicular to Spindle axis
Types of CNC turning Centre:
• Horizontal Spindle Turning Centre
• Vertical Spindle Turning Centre

47. Horizontal Spindle Turning Centre

48. Main Parts of CNC Turning
Centre:
•Bed
•Head Stock
•Turrets
•Machine Control Unit (MCU)
•Servo Mechanism

51. Sd,,

52. Vertical Spindle Turning Centre

53. •Vertical CNC lathes widely
used for machine heavy
components.
•Some of these machines can
also be used for milling
operations. Such machines are
sometimes known as turn -
mill centers.

58. • A machining centre consists of
machine tools, usually numerically
controlled, capable of
automatically drilling, reaming,
tapping, milling and boring the
multiple faces of a part with tool
magazine, Automatic tool changer,
automatic pallet changer.

59. Five axis control:
 X axis, Y axis, Z axis - Linear Movement
 A axis - Spindle Tilt
 B axis - Table rotation
Types of CNC Machining Centre:
• Horizontal Spindle Machining Centre
(HMC)
• Vertical Spindle Machining Centre
(VMC)

60. Main Parts of CNC Machining Centre:
• Bed
• Column
• Spindle
• Table
• Servo Mechanism
• Tool Magazine
• Automatic Tool Changer (ATC)
• Automatic Pallet Changer (APC)

62. Horizontal Machining Centre
(HMC)

68. • HMC has its Spindle on Horizontal
Axis
• Used for heavier work piece with large
metal removal
• X axis - Table Longitudinal movement
• Y axis - Spindle Up & down movement
• Z axis - Table movements towards
spindle
• HMC have Rotary table with axis
parallel to Y axis & is called B axis

69. • Tool magazine have tools upto 60 – 120
• Generally these are Single spindle
machines with ATC & APC

70. Vertical Machining Centre
(VMC)

72. • VMC has its Spindle on Vertical Axis
• Used for heavier work piece with large
metal removal
• X axis - Table Longitudinal movement
• Y axis - Table cross wise movement
• Z axis - Spindle Up & down movement
• VMC have Rotary table with axis
parallel to X axis & is called A axis

74. •Tool magazine have upto
60 tools
•Generally these are
Single spindle with ATC
Multi spindle with Turret
Head

79. • In CNC machine tool, each of
the axis of motion is controlled
by axis feed drive mechanism
• Primary axis of motion are
referred as X, Y and Z axis
• Rotary axis : A, B, C identifies
the rotary motion about X, Y
and Z axis

80. TURNING
CENTRE

82. • A CNC turning centre has two axis
X & Z
• Z Axis: Tool Movement parallel
to the Spindle axis
 Z + (Positive) : Tool movement
away from spindle
Z - (Negative) : Tool movement
towards the spindle

83. X Axis: Tool Movement
perpendicular to the Spindle axis
X + (Positive) : Tool movement
away from work piece zero point
X - (Negative) : Tool movement
towards work piece zero point

84. MACHINING
CENTRE

88. • A CNC Machining centre has
three axis X , Y & Z
• Z Axis: Up & Down movement
of Spindle & tool
 Z + (Positive) : Tool movement
away from Workpiece
Z - (Negative) : Tool movement
towards the Workpiece

89. •X Axis: Table longitudinal
movement
 X + (Positive) : Table
movements towards right
 X- (Negative) : Table
movements towards left

90. • Y Axis: Table Crosswise
movement
 Y + (Positive) : Table
movements away from the
machine column
 Y - (Negative) : Table
movements towards the machine
column

91. (CMM)

92. •CMM is an Electro mechanical
system designed to determine
the location, orientation,
dimensions and geometry of a
object
•CMM is used to measure
various features of work piece
by using Probes

93. Granite Table

95. • CMM has following major elements
 Stationary Granite measuring table
Length measuring system
Air bearings
Control unit
Probe head
Software

96. Bridge Type
Types of CMM
Cantilever
Type
Horizontal
Type
Gantry Type Column
Type

97. Bridge Type

98. Bridge Type

99. Bridge Type

100. Bridge Type

101. Cantilever Type

102. Cantilever Type

103. Gantry Type

104. Gantry Type

105. Gantry Type

106. Horizontal Type

107. Horizontal Type

108. Column Type

109. Column Type

110. Benefits of CMM
•Flexibility
•Increased Productivity
•Unmanned Operations
•Greater accuracy
•Reduced operator error

111. COMPONENETS

112. CNC MACHINE COMPONENETS
Slide ways
 Friction & Anti friction Slide ways
 Linear motion bearings
 Recirculation ball screw
Automatic Tool Changer (ATC)
Tool Magazine
Feedback Devices
 Transducers
 Encoders
Tool inserts
Inprocess Probing

114. Slide ways
Precise positioning and Repeatability of
machine tool slides are the major
functional requirements of CNC
machines.
The inaccuracies that caused are mainly
due to the stick slip motion when plain
slide ways (metal to metal contact) are
used.
 Slide ways are used for movement
between tool members of machine tool
such as carriage & bed in a lathe

115. Requirement of Good Slide ways:
• Low wear
• Negligible stick-slip
• Low price
• Low co-efficient of friction properties
• Good surface finish on slideway
surface
• High Stiffness

116. Friction
Slideways
Types of
Slideways
Antifriction
Slideways
V - Slideways
Flat Slideways
Round Slideways
Dovetail Slideways
Linear Motion
Bearings
Recirculation
Ball Screw

117. Friction Slideways
1. V - Slideways

118. Friction Slideways
2. Flat Slideways

119. Friction Slideways
3. Round Slideways

120. Friction Slideways
4. Dovetail Slideways

123. Antifriction Slideways
It involves intermediate rolling
member(Balls or Rollers)
between the sliding members,
thus reducing the friction
Low friction, No stick slip,
high load capacity

124. Linear Motion Bearings

127. Recirculation Ball Screw
 Balls rotate between the screw & nut and convert the
sliding Friction into Rolling friction

133. (ATC)

134. •The device used to pick up
a tool from Tool magazine
and replace it with the tool
in the spindle with in 3 to
7 seconds is called ATC
•Reducing idle time during
tool changing operations

140. 1. ATC arm Rotates through 90º from the
Rest position
2. One end grips tool in the magazine &
another end grips tool in the spindle
3. Both tools are pulled out
4. ATC arm rotates through 180º
5. It inserts new tool to the spindle & old
tool to the magazine
6. ATC arm Rotates through 90º & goes to
the Rest position

141. Tool Magazine
ATC
1. Arm comes from the rest position
& Grips both Tools

142. 2. Arm pull the tools from the
Mounting

143. 3. Arm rotates through 180º

144. 4. Carrier Inserts tools

145. 5. Arm rotates & go to rest position
ATC
Spindle Tool Magazine

147. • The system of arrangement which
holds large number of tools is
called Tool Magazine
• It is specified by Storage Capacity
& Shape
• Storage capacity ranges from 12 -
200
• Used in CNC turning centre & CNC
machining centre

148. Tool
Magazine
Tool Turret Disc or
Drum type
magazine
Chain type
magazine
Rack type
magazine
Egg box
magazine
Ring type
magazine
Longitudinal
Magazine

149. Tool Turret
 It is the Simplest form of tool
magazine
 It consists of tool storage without
tool changer
 Turret is indexed in required
position for desired operation
 Tool can be easily identified
 Tool change time is more

153. Disc or Drum Type Tool Magazine
It is the Rotates to get the desired
tool in position with tool change
arm
It carries 12 - 50 tools
If diameter of the disc is large more
number of tools can be hold
It have pockets where the tools can
be inserted

157. Chain type magazine
It is the Capable of storing more
number of tools
Used in machining centre
Tools are inserted into their pockets
which are attached to the chain
 Chain moving on sprocket &
sprockets are driven by motors

166. Rack Tool Magazine
It is the Cost efficient
alternative to usual tool
magazine system
It carries up to 400 tools
It consists of high tool storage
without tool changer

169. Egg box type Magazine

171. Rotary type Magazine

175. • The electronic devices such as
Transducer & Encoders used for
giving the position & velocity of the
machine elements are called
Feedback devices
• Based on feedback control the
systems are classified as
1. Open loop control system
2. Closed loop control system

176. Open loop control system:
Machine
Control
Unit
Drive
Motor
Machine
tool slide
 The machine tool control system in which there is
No feed back devices to compare the actual
position of the cutting tool or work piece with the
input signals are called open loop control systems

178. Closed loop control system:
Machine
Control
Unit
Drive
Motor
Machine
tool slide
 The machine tool control system in which there are
feed back devices to compare the actual position of
the cutting tool or work piece with the input signals
are called open loop control systems
Velocity feed back
Position feed back

181. • Transducers are electronic devices
used for converting the physical
quantities like Speed, Feed,
velocity, Displacement into
Electronic signals that give feed
back
• Two types of transducers
1.Linear transducer
2.Rotary Transducer

182. Linear Transducer
• It is used to measure the Displacement of
machine slide

184. Rotary Transducer (Angular
Position measuring
Transducer)
• It is used to measure the Angular Rotation
of the Lead Screw

190. • Encoders are devices used to
measure the linear movement of
the Machine table
• Any devices that is used to give
positioning feedback to the control it
applies a code or changes
information into coded form

191. • Two types of encoders
1. Linear encoders
2. Rotary encoders

192. Rotary encoders
A rotary encoder is a type of
sensor that when mounted to
the shaft of the motor can
detect its angular position
Its is made from light source,
optical sensor, disc with small
slits cut into it like spokes

195. Linear encoders
Its is made from light source,
optical sensor, glass scale

198. • It is the process of performing the
inspection procedure during
manufacturing operation.
• In this process manufacturing as
well as inspection are done
simultaneously
• The process of inspection is called
probing & device used for
inspection is called Inspection
Probe

199. Method of Probing:
•Contact Probe system
•Non-Contact Probe system

200. Advantages of Probing
•100% inspection is
achieved
•High quality is ensured
•Inspection time is reduced
•Inspection cost is reduced

202.  High speed steel (HSS)
Cemented Carbide
Coated Carbide
Ceramics
High Carbon tool steel
Cast Alloy
Cubic Boron Nitride (CBN)
Poly Crystalline Diamond
(PCD)

204. •Tool inserts are small
carbide pieces having
cutting edges which comes
in various shapes & size
geometries & clamped in
the Insert holder

205. Commonly used shapes
• Round (R)
• Square (S)
• Triangular (T)
• Rhomboidal 80º (C)
• Rhomboidal 35º (V)
• Rhomboidal 55º (D)
• Parallelogram 55º (K)