7. Numerical Control (NC)
• NC is
machine
various
defined
slide
functions by means
as Control of
movements &
of
Letters, Numbers and Symbols
• Letters, Numbers and Symbols
forming some sequence is called
Part Program
8.
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
10.
11.
12.
13.
14.
15.
16.
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
18.
19.
20.
21.
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.
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
27.
28.
29.
30.
31.
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
34.
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
37.
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
39.
40. • Increased Productivity
• High Accuracy
• Reduced Time
• Reduced man power
• Simulation of program is available
• Increased Safety operations
• Lesser Floor place
41.
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 Simulation of part
program is not possible 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
44.
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
53. • Vertical
used for machine
CNC lathes widely
heavy
components.
• Some of these machines can
also be used for milling
operations. Such machines are
sometimes known as turn -
mill centers.
54.
55.
56.
57.
58. • A machining centre consists of
machine tools, usually numerically
controlled,
automatically
capable of
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)
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
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
73.
74. •Tool magazine have upto
60 tools
•Generally these are
Single spindle with ATC
Multi spindle with
Turret Head
75.
76.
77.
78.
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
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
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:
movement
Y +
Table Crosswise
(Positive)
movements away
: Table
from the
machine column
Y - (Negative) : Table
movements towards the machine
column
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
114. Slide ways
Precise positioning and Repeatability of
tool slides are the major
requirements of CNC
machine
functional
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
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
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
135.
136.
137.
138.
139.
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
145. 5. Arm rotates & go to rest position
AT
C
Spindl
e
Tool
Magazine
146.
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
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
150.
151.
152.
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
154.
155.
156.
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
158.
159.
160.
161.
162.
163.
164.
165.
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
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:
Machin
e
Contr
ol
Unit
Drive
Moto
r
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
177.
178. Closed loop control system:
Machin
e
Contr
ol
Unit
Drive
Moto
r
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
Positionfeed
179.
180.
181. • Transducers are electronic devices
used for converting the physical
quantities like Speed,
velocity, Displacement
Feed,
into
Electronic signals that give feed
back
• Two types of transducers
1.Linear transducer
2.Rotary Transducer
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
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
& device used for
is called Inspection
probing
inspection
Probe
