Prof.Harin N Prajapati HOD Mechanical Amriaj College of Engineering & Technology . Ahmadabad ,Gujarat ,Indian

1. Ch-2 [Lec-1 ]
NC & CNC MACHINE TOOLS
Prepared by:
Asst.Prof.Harin Prajapati
(Mechanical Department,ACET)
Subject:- CAM
Code:-2171903

3. • Numerical control (NC) systems are hardware controls in
which most of functions are carried out by electronic hardware
based upon digital circuit technology.
• Numerical Control is a technique for controlling machine
tools or processes using coded command instructions. These
coded command instructions are interpreted and converted by
NC controller into two types of signals namely; motion control
signals and miscellaneous control signals.

7. Punched tape
• Punched tape is used for practical storage of part programs. It is reliable
because the data will not change, although the tape can be physically
damaged. In earlier NC days, punched tapes were used extensively.
Prevalence of computer disks has
• drastically reduced its use. But, still used as backup storage media, when
the computer is down.
Magnetic Tape
• Although it is least costly option for NC part program storage yet not often
used due to its low speed. It is also difficult to locate the right program in
the tape, and vulnerable to contamination and electromechanical fields in
shop floor surroundings.
Computer Disks
• In today’s milieu, computer disks are widely used to store NC part
program. These disks are of two forms; floppy diskette and hard disk. It is
inexpensive, can store large volume data and easy to access.

12. • Programme reader is a device used to read the coded instructions from the
programme of instructions. Programme readers are classified on the basis
of programme input medium as:
(a)Card Readers
(b)Punched Tape Readers
– Mechanical (Electro-mechanical)
– Photo electrical
– Pneumatic
(c) Magnetic Tape Reader

13. The principle of a simple mechanical device for reading the punched tape is shown in
Figure 2.3. If there is no hole in the tape the contacts remain open but when a hole is
present in the tape, its presence is detected by a probe and bending of flexible strip causes
the contacts t close. The presence of holes in the tape causes the switches to close. The
switch is in ON position (hole) or OFF position (no hole) accordingly.

14. The operation of an optical photo electric tape reader is based upon the principle that if a
beam of light falls on a photoelectric cell, the latter generates an electric signal. The
schematic diagram of a photoelectric tape reader is shown in Figure 2.4. The punched
tape is fed between a light source and a series of photo-cells. Whenever a hole is present
in the tape, light from the light source passes through the hole and energizes the
corresponding photo-cell which converts the light energy into electrical energy to produce
a pulse i.e. ON position. The pulse is amplified and processed into a form suited to the
control circuit. When there is no hole, the light from the light source does not reach the
photo-cell, hence no signal is produced and the position is recorded as OFF.

15. A pneumatic tape reader is shown in Figure 2.5. The tape is fed between a series of air jets
(8 No.), covering the complete pattern of holes which is possible to be punched in a block
of information on the tape and tape support plate. The first opening called, main outlet, is
near the tape and second opening is connected to a signal detector. This back pressure is
sensed by the signal detector and position is recorded as '0' i.e. OFF. But if a punched hole
in the tape comes in front of the main outlet, the air is allowed to escape freely and no
back pressure is built up in the supply tube. This loss of back pressure is detected by the
signal detector and position is recorded as '1' i.e. ON. The support plate prevents the tape
from being blown away by the compressed air coming from main outlet.

16. A program reader for magnetic tape is shown in Figure 2.6. The magnetic head serves
both for encoding as well as reading the tape. The magnetic head is an electromagnet and
consists of a high permeability core in the form of a ring with a small air gap and is
energized through a coil winding. The magnetic tape is moved across the opening in the
core. When a magnetized portion of the tape appears in the reading position (i.e. in the
opening) an e.m.f. is induced in the winding. This e.m.f. is amplified and is used in
control of servo system of machine tool.

17. Better control of the tool motion under
optimum cutting conditions.
Improved part quality and repeatability.
Reduced tooling costs, tool wear, and job
setup time.
Reduced time to manufacture parts.
Reduced scrap.
Better production planning and placement of
machining operations in the hand of
engineering.

19. Ch-2 [Lec-2]
NC & CNC MACHINE TOOLS
Prepared by:
Asst.Prof.Harin Prajapati
(Mechanical Department,ACET)
Subject:- CAM
Code:-2171903

20. • CNC controls are soft-wired NC systems as control functions
are controlled by software programs.
• Alternatively, Computer Numerical Control is the numerical
control system in which dedicated, stored program
microprocessors are built into the control to perform basic and
advanced NC functions.
• Control signals in CNC systems are in the form of binary
words, where each word contains fixed number of bits, 32 bits
or 64 bits are commonly used, representing different axial
positions.

25. The main components of CNC machine tools are as follows :
1. Input / Output Console.
2. Microprocessor Based control unit.
3. Memory.
4. Feedback unit.
5. Machine Tool.
6. Interfaces.

26. Input / Output
Devices
Machine Tool
Memory (ROM)
Control
program for : Z
Slide
X Slide
Memory (RAM)
Part Program
Feed Back Unit

27. • Input / Output Console : It is the unit through which part program is fed
to the CNC machine tool system and required output is taken out. It
basically consists of monitor and Keyboard.
• Microprocessor : This controller takes input from Input / Output device,
Feedback from feedback unit and actuates the drives as well as the tool
of the machine tool.
• Memory : It consists of RAM & ROM. The RAM stores part program,
while ROM stores
the programs for machine control.
• Feedback unit : The feedback unit takes input from machine tool and
transfers it to control unit for necessary corrections.
• Machine tool : Machine tool is operated by the control unit.
• Interfaces : They are the connections between the different components of
the CNC machine tool system.

28. (a) According to type of Feedbacksystems
1. Open loop type CNC machine.
2. Closed loop type CNC machine.
(b) According to type of tool motioncontrol
1. Finite positioning control CNC machines.
2. Continuous path control CNC machines.
(c) According to programmethods
1. Absolute Programming CNC machine systems.
2. Incremental Programming CNC machine systems.
(d) According to type of controller
1. Hybrid controller CNC systems.
2. Straight controller CNC systems.
(e) According to axis & type of
operations
1. CNC horizontal machining centre.
2. CNC vertical machining centre.
3. CNC turning centre.
4. CNC milling centre.

29. CNC machines can be used continuously and only need to be switched off for
occasional maintenance.
These machines require less skilled people to operate unlike manual
lathes/milling machines etc.
CNC machines can be updated by improving the software used to drive the
machines.
Training for the use of CNC machines can be done through the use of “virtual
software”.
The manufacturing process can be simulated virtually and no need to make a
prototype or a model. This saves time and money.
Once programmed, these machines can be left and do not require any human
intervention, except for work loading and unloading.
These machines can manufacture several components to the required accuracy
without any fatigue as in the case of manually operated machines.
Savings in time that could be achieved with the CNC machines are quite
significant.

30. CNC machines are generally more expensive than
manually operated machines.
The CNC machine operator only needs basic training
and skills, enough to supervise several machines.
Increase in electrical maintenance, high initial
investment and high per hour operating costs than the
traditional systems.
Fewer workers are required to operate CNC
machines compared to manually operated machines.
Investment in CNC machines can lead to
unemployment.

31. The machines controlled by CNC can be classified
into the following categories:
1. CNC mills and machining centers,
2. CNC lathes and turning centers
3. CNC electrical discharge machining
(EDM)
4. CNC grinding machines
5. CNC cutting machines (laser, plasma,
electron, or flame)
6. CNC fabrication machines (sheet metal
punch press, bending machine, or press
brake)
7. CNC welding machines

32. CNC Vertical
Machining Center

33. CNC Turning
Machining Center

34. CNC Laser
Cutting Machine

35. CNC EDM Machine

36. CNC Hydraulic Plate Punching And Marking Machine

37. CNC Four-point Welding Machine

38. Ch-2 [Lec-3]
NC & CNC MACHINE TOOLS
Prepared by:
Asst.Prof.Harin Prajapati
(Mechanical Department,ACET)
Subject:- CAM
Code:-2171903

39. • Direct numerical simultaneously control the operations of a
group of NC machine tools using a shared computer.
• Programming, editing part programs and downloading part
programs to NC machines are main responsibilities of the
computers in a NC system.
• Cincinnati Milacron and General Electric first used idea of
direct numerical control in the mid 60s. By 1970, about a half
dozen vendors marketed their DNC systems .
• Due to high cost of mainframe computers and introduction of
CNC in 1970s,the DNC system couldn’t become popular in
industry.

43. 1. The part program is fed to the
machine through the tapes or
other such media.
2.In order to modify the program,
the tapes have to be changed.
3. In NC machine tool system,
tape reader is a part of machine
control unit.
4.System has no memory
storage and each time it is run
using the tape.
5.It can not import CAD files.
6.It can not use feedback system.
7.They are not software driven.
1. In CNC machine tool system,
the program is fed to the machine
through the computer.
2.The programs can be easily
modified with the help of
computer.
3.The microprocessor or
minicomputer forms the machine
control unit. The CNC machine
does not need tape reader.
4.It has memory storage ability, in
which part program can be stored.
5
.
System can import CAD files
and convert it to part program.
6.The system can use feedback
system.
7.The system is software driven.
1. The part program is fed to
the machine through the
Main computer
2. In order to modify the
program, single computer
is used
3. Large memory of DNC
allows it to store a large
amount of part
program.
4. Same part program can be
run on different machines
at the same time.
5. The data can be processed
using the MIS software so
as to effectively carry out
the Production planning
and scheduling.

44. 1. Classification based on
the motion type.
2. Classification based on
the control loops.
3. Classification based on
the number of axes.
4. Classification based on
the power supply.

45. 1.1Point-to-Point Systems.
1.It is used in some CNC machines
such as drilling, boring and tapping
machines…etc.
2.The control equipment for use with
them are known as point-to-point
control equipment.
3.Feed rates need not to be
programmed.
4.In theses machine tools, each axis is
driven separately.

46.  Pointtopointmode:

48. 1.2 Contouring Systems
(Continuous Path Systems)
It is used in CNC machine tools such as
milling machines.
These machines require simultaneous
control of axes.
Contouring machines can also be used
as point-to-point machines, but it will
be uneconomical to use them unless the
work piece also requires having a
contouring operation to be performed
on it.

52. 2.1 Open Loop Systems
Programmed instructions are fed into the
controller through an input device.
These instructions are then converted to
electrical pulses (signals) by the controller
and sent to the servo amplifier to energize
the servo motors.
The primary drawback of the open-loop
system is that there is no feedback system
to check whether the program position and
velocity has been achieved.

53. Open Loop Systems
the open -loop system is
generally used in point-to-
point systems where the
accuracy requirements are
not critical.
Very few continuous-
path systems utilize
open-loop control.

54. 2.2 Closed Loop Systems
The closed-loop system has a
feedback subsystem to monitor
the actual output and correct any
discrepancy from the
programmed input.
These systems use position and
velocity feed back.
The feedback system could be
either analog or digital.

55. 2.2 Closed Loop Systems
The analog systems measure the
variation of physical variables such
as position and velocity in terms of
voltage levels.
Digital systems monitor output
variations by means of electrical
pulses.
Closed-loop systems are very
powerful and accurate because they
are capable of monitoring operating
conditions through feedback
subsystems and automatically
compensating for any variations in
real-time.

57. 2&3 axes CNC Machines
CNC lathes will be coming under 2 axes
machines. There will be two axes along which
motion takes place.
The saddle will be moving longitudinally on
the bed (Z-axis) and the cross slide moves
transversely on the saddle (along X-axis).
In 3-axes machines, there will be one more
axis, perpendicular to the above two axes.
By the simultaneous control of all the 3 axes,
complex surfaces can be machined.

58. • Machine axes are designated according to the "right-hand
rule", When the thumb of right hand points in the direction of
the positive X axis, the index finger points toward the positive
Y axis, and the middle finger toward the positive Z axis.

64. 5 axes CNC vertical axis machining centre configuration

65. Importance of higher axes machining:
Reduced cycle time by machining
complex components using a single
setup.
 In addition to time savings,
improved accuracy can also be achieved
as positioning errors between setups are
eliminated.
Improved surface finish and tool life by
tilting the tool to maintain optimum tool
to part contact all the times.

67.  Mechanical power unit
refers to a device which
transforms some form of
energy to mechanical power
which may be used for
driving slides, saddles or
gantries forming a part of
machine tool.
 The input power may be of
electrical, hydraulic or
pneumatic.
AC Servo Motor for CNC
Machine Tool

69. Ch-2 [Lec-4]
NC & CNC MACHINE TOOLS
Prepared by:
Asst.Prof.Harin Prajapati
(Mechanical Department,ACET)
Subject:- CAM
Code:-2171903

70. • Power Units
• Encoders
• Controller.

71. The machine control unit (MCU) is the backbone
of CNC systems. Following six functions are
being done by MCU:
• Read coded instructions
• Decode coded instructions
• Implement interpolations to generate axis
motion commands
• Feed axis motion commands to amplifier
circuits to drive axis mechanisms
• Receive the feed back signals of position and
speed for each drive axis
• Implement auxiliary control functions such as
coolant ON/OFF, spindle ON/OFF, and tool
change

72. • Accuracy,
• Repeatability,
• Spindle and axis motor
horsepower,
• Number of controlled axes,
• Dimension of workspace, and
• Features of the machine and
controller.

92. Ch-2 [Lec-5]
1.TOOL MANAGEMENT SYSTEM 2. SUPPLY SYSTEM
3.MONITORING SYSTEM 4.WORK PIECE HANDLING
Prepared by:
Asst.Prof.Harin Prajapati
(Mechanical Department,ACET)
Subject:- CAM
Code:-2171903

93. • TOOL MANAGEMENT SYSTEM
• SUPPLY SYSTEM
• MONITORING SYSTEM
• WORK PIECE HANDLING

94. • Tooling is one of the most important part of
any manufacturing system.
• Tooling system are broadly classified into 2
categories
1) Tool supply system
2) Tool monitoring system

95. • In automated manufacturing sys, the set of
tools have to be supplied to the system and
taken out from the system at regular interval
depending upon the requirement
• The basic concept used in tool supply system
is to use auxiliary tool storage from where the
required tools can be transfer to the main tool
magazine as and when required without much
loss of production time

96. 1. Single Tool Magazine System
2. Multiple Tool Magazine System
3. Interchangeable Tool Magazine System
4. Interchangeable Tool Cassettes System
5. Main And Auxiliary Tool Magazine System
6. Tool Highway System

97. • The single tool magazine system is a
conventional system and has only 1 tool
magazine. There is no auxiliary tool storage
system available.
• The capacity of single tool magazine is 40 to
100 tools.

98. • In this 2 or more smaller tool magazines are used
• Major advantage is machine is kept in working
condition while tool on the 1 tool magazine is
replaced
• Limitation is each tool have small tool capacity
• capacity: 20 to 50 tools

99. • In interchangeable tool magazine system entire tool is
swapped for replacement so that tool resharpening
and replacement into tool can be done
• As entire tool is replaced, thus change over time is
reduced
• However AGV makes the system expensive
• Capacity : 20 to 60 tools

100. Interchangeable Tool Cassette
• 1 Tool magazine divided into number of smaller
segments called tool cassettes
• Each cassettes have limited no. of tools
• Thus instead of changing entire tool magazine, the
cassette is replaced.
• Reduce tool changing time
• Arrangement is slightly complicated
• Capacity : 10 to 20 tools

101. • Each machine tool has 1 main tool magazine and 1
auxiliary tool storage magazine
• Secondary tool magazine is used for storage purpose
• Robot arm stationed between 2 tool magazine can
transfer tool as and when required
• Ensures uninterrupted manufacturing
• Capacity :20 to 40 tools

102. • Each workstation of FMS has a main tool
magazine and there is single auxiliary tool storage
magazine consisting of all tools
• Tool change robot is used for replacing tool
• Individual tool is transported to main tool
magazine by tool changing robot travelling along
the tool highway
• Most widely used system for FMS, ensures
uninterrupted manufacturing
• Capacity : 20 to 40 tools

103. • In order to ensure the satisfactory working of
cutting tool, it is necessary to monitor the tool
while it is performing the cutting operation
• There are 3 methods
1) Tool wear monitoring
2) Tool breakage monitoring
3) Tool life monitoring

104. • The accuracy and surface finish of the
manufactured component depends upon the
condition of cutting tool
• Therefore it is necessary to monitor tool wear
continuously
• Tool wear are broadly classified into 2
categories

106. • In automated machining system like FMS and
transfer lines, the undetected tool breakage
will lead to spoiled job lot
• Therefore it is necessary to have a system that
can detect the breakage of tool and give alarm
to the operator or automatically replace it from
auxiliary tool storage ,magazine

107. 1. Cutting Force Method
2. Tool Length Method
3. Current Loop Method
4. Air Flow Method
5. Infrared Beam Method

108. • In this a force sensor is mounted on the cutting
tool
• Whenever there is breakage, cutting force
instantaneously reduces to zero
• Force sensor gives signal to the controller
• Controller gives the alarm or automatically
changes broken tool

109. • In tool length method the tool length is checked by using tool
probe at the beginning of the cutting operation
• The tool length Is compared with the value stored in tool
register of computer
• Though the system is simple, it can not detect instantaneous
breakage
• The breakage can only be detected only at beginning of next
cycle

110. • In current loop method, a small current is
made flow through the work piece and cutting
tool

112. • The circuit is completed only when the cutting
tool is in touch with the work piece. This
signal is transmitted to MCU
• Thus during operation is tool breaks it results
in circuit breakage.

113. • In this a compressed air is made to flow over
the cutting tool
• The cutting tool breaks the air flow stream

115. • If cutting tool is broken the air flow stream is
continuous without break
• The pressure of continuous air flown stream is
detected by pneumatic switch
• This switch communicates the signal with
MCU
• Thus MCU imitates necessary action

116. • In infrared beam method, the infrared beam is
directed across the cutting tool
• The cutting tool breaks the infrared beam
• If there is breakage in tool, the beam travels
without break
• The uninterrupted beam detects tool breakage

117. • The tool monitoring system keep the continuous
track of the actual time for which each tool was
working
• When new tool enters the magazine, computer
store its life spam under its information
• For safety measures life spam is kept low only
than actual one
• Life spam is deiced by machine parameter data
and tool data
• The tool life monitoring avoids actual breaking

118. Ignite Your mind…
My duty to just Guide
you..