Chapter 1 fundamentals of cam

Chapter 1
Fundamentals of CAM.
Prepared by: Prof. Rahul Thaker (ACET)
Prepared by: Prof. Rahul Thaker (ACET)

MEANING OF CAM
 “Computer-aided manufacturing (CAM) is
an application technology that uses
computer software and machinery to
facilitate and automate manufacturing
processes”
 CAM is the successor of computer-aided
engineering (CAE) and is often used in
tandem with computer-aided design (CAD).
Prepared by: Prof. Rahul Thaker
(ACET)

MEANING OF CAM
 “Computer-aided manufacturing (CAM) is
the use of software to control machine tools
and related ones in the manufacturing of
work-pieces.”
 To the use of a computer to assist in all
operations of a manufacturing plant,
including planning, management,
transportation and storage.
(ACET)

OBJECTIVE OF CAM
 The use of computers to guide the working
of the industrial processes is known as
computer aided manufacturing or CAM.
 Any factory can be made highly automated
by deploying real time systems and
robotics.
 The purpose of CAM is to ensure that the
error rate is decreased, uniformity of
products is high and precision in the
processes can be achieved.
(ACET)

OBJECTIVE OF CAM : Continue
 For example, the packaging of meat and
related products is fully done by automated
plants from the slaughter of the animal to
the final product. This has also reduced the
labor cost and other operating overheads.
The processes are now fully automated that
they can replace the tools and switch to the
successive processes on their own.
(ACET)

SCOPE OF CAM
 Integrated CAD/CAM/CAE Software like
Pro/Engineer, I-DEAS & CATIA help
manufacturers optimize product concept early
in Design process, enabling them to
significantly improve product quality, while
reducing product development time and cost.
 Moreover people having 3D CAD/CAM/CAE
knowledge have better chances of growth,
immediate employability after completion of
course, graduation and chances of jobs abroad.
(ACET)

NC & CNC MACHINE TOOLS
(ACET)

NC CONTROLS
 Numerical control (NC) is the technique of
giving instructions to a machine in the form
of a code which consists of numbers, letters
of the alphabet, punctuation marks and
certain other symbols.
 Controlling a machine tool by means of a
prepared program is known as numerical
control.
(ACET)

NC CONTROLS : Continue
 “A system in which actions are controlled
by the direct insertion of numerical data at
some point. The system must automatically
interpret at least some portion of this data”
 Instructions are supplied to the machine as
blocks of information. A block of
information commands sufficient to enable
the machine to carry out one individual
machining operation. Each block is given a
sequence number for identification.
(ACET)

 A set of instructions forms an NC program.
“When the instructions are organized in a logical
manner they direct the machine tool to carry out a
specific task. It is thus termed as part program”
 The numerical data which is required for producing a
part is maintained on a punched tape and is called the
part program.
 The part program is arranged in the form of blocks of
information, where each block contains the numerical
data required to produce one segment of the work
piece. The punched tape is moved forward by one
block each time the cutting of a segment is
completed.
(ACET)

 Part programs are written manually or by
using a computer-aided language, such as
Automated Program Tool (APT).
 Preparing the part program for a NC
machine tool requires a part programmer.
The part programmer must possess
knowledge and experience of tools, cutting
fluids, machinability data and fixture
design techniques.
(ACET)

 In NC machine tools , following operations
may be automatic:
I. Automatic starting and stopping of the
spindle;
II. Controlling the spindle speed;
III. Automatic positioning the cutting tool by
controlling the motion of slides;
IV. Controlling the feed rate; and
V. Changing the cutting tools.
(ACET)

Basic Elements of NC Machine
(ACET)

Various types of input media are:
(a) Punched cards
(b) Magnetic tapes and floppy disks
(c) Paper tape
(ACET)

(1)Part Drawing and Part Programming
• Part programme is set of step by step instruction to the
machine tool for caring out the operation.
• Part program is written by using part Drawing and cutting
process parameter
• The set of instruction includes
Instruction position of machine tool spindle with respect
to the work table
Instruction for cutting operation
Instruction for selection of spindle speed, cutting tool etc.
Method of Part Programing
I. Manual Part programming
II. Computer aided Part programming
(ACET)

(2) Programme Tape
• Part programme is entered on the programme tape
• The tape is a long wound roll of the one inch with.
• The programme is entered on the tape in the form of
punched holes ,holes punched with the help of
punching machine.
• Now a day punch line tape is replaced with magnetic
cassettes , floppy disc , pen drive , hard drive
(ACET)

(3)Machine control unit (MCU)
• MCU is heart of NC/CNC machine which consist of some
electronics hard wear that read the NC programme , interpret
it and conversely translates it for mechanical action of
machine tool
• A typical MCU consist following units
Input or tape reader
memory
processor
output channels
control panel
feedback channels
(ACET)

(3)Machine control unit (MCU) (Continue...)
• MCU performs Following functions
• read coded instruction
• Decode coded instruction
• implement interpolation (linier ,circular, and Helical )v to
generate axis motion commands
• feed axis motion command to amplified circuits for driving
the axis mechanism
• Received the signals of position and speed for each drive axis
• implement auxiliary control function such as coolant or s
pindle on/off , andtool change
(ACET)

(4) Machine Tool
• The Machine tool is operated by MCU
• following function may automated by Machine tool
starting and stopping of the machine tool spindle
controlling the spindle speed
Positioning of tool tip at desires locations and
guiding it along the desired path by automatic
control of the slide motion
Controlling the feed rate
Changing the tool
(ACET)

NC Machine : Advantage
1. Reduced lead time for production.
2. Increased Productivity.
3. Reduction of human error.
4. High degree of accuracy.
5. Less inspection required.
6. Greater machine tool safety.
7. Greater operator safety.
(ACET)

NC Machine : Limitation
1. High initial cost.
2. High maintenance cost.
3. High operational cost.
4. Limited life of tapes.
5. Time consuming punched tape operation.
(ACET)

(ACET)

CNC
 With the recognized trend toward smaller, less
expensive computers, it soon became practical to
apply a single small computer to one machine tool.
This concept came to be called computer numerical
control (CNC).
 The CNC systems were first commercially
introduced around 1970, and they applied the soft-
wired controller approach to good advantage.
 One standard computer control unit could be adapted
to various types of machine tools by programming
the control functions into the computer memory for
that particular machine.
 Today, because of the advantages of CNC, very few
conventional hard-wired NC systems are sold in the
United States. Prepared by: Prof. Rahul Thaker
(ACET)

TYPES OF CNC
1. Machining Centre
• Horizontal
• Vertical
• Universal
2. CNC Turning Centers
3.CNC Milling/Drilling Machines, Plane
Milling Machines
(ACET)

CNC Machine : Advantage
1. Easy to program input.
2. Multiple program storage.
3. Online part programming and editing possible.
4. Greater flexibility of system.
5.Change in system of units possible.
6.Use of Advanced interpolation.
7. Automatic tool dimension adjustment.
(ACET)

CNC Machine : Limitation
1. Higher investment cost.
2.Higher maintenance cost.
3. Required skilled operators.
4. For continuous production , proper planning is
needed.
(ACET)

Conventional vs. CNC machine
(ACET)

Direct Numerical Control : DNC
 DNC was the first of the computer control
systems to be introduced, around 1968. In the
evolution of computer technology, the
computers of that era were quite large and
expensive, and the only feasible approach
seemed to be to use one large computer to
control a number of machine tools on a time-
shared basis.
 The advantage of DNC was that it established
a direct control link between the computer and
the machine tool, hence eliminating the
necessity for using punched tape input.
(ACET)

Direct Numerical Control : DNC
 A manufacturing system in which no. of
machines are controlled by a computer
through direct connection and in real time.
(ACET)

DNC: 1)Behind the Tape Reader
(BTR)
Computer is linked directly to regular NC
controller unit
The connection is made behind the tape reader
Two temporary storage buffers
Less cost
(ACET)

DNC: 2) Special Machine Control
Unit
Regular NC controller is replaced by special MCU
More accuracy in circular interpolation and fast
material removal rates than BTR systems
Most CNC machines are sold with computer
(ACET)

NC, CNC and DNC
(ACET)

Functions of DNC
1.NC without punched tape
2.NC part program storage
Programs must be made available for downloading to CNC machine tools
Part program can be uploaded after editing from CNC machine
Entry of new programs. Editing of programs , deletion of programs
Tool management
Tool offsets can be downloaded in to MCU
Postprocessor
Data processing and management functions
Primary storage and secondary storage
Syntax checking and graphic proving of programs on CNC computer
CNC can be operated directly from DNC computer
Flexibility in shop floor scheduling
Part program preparation
Machinability database for calculating speed/feed
(ACET)

Functions of DNC
3.Data collection, Processing and reporting
Monitor production in the factory
Data processing and report generation by DNC computer
Getting the data about health of the machine in the form of sensor
signals or diagnostic messages which can be used for
preventive/predictive maintenance
Metrological data in the form of dimensional acceptance
4.Communications
Central computer and machine tools
Central computer and NC part programmer terminals
Central computer and bulk memory, which stores the NC programs
CAD system
Shop floor control system
Corporate data processing
Remote maintenance diagnostics system
(ACET)

Advantages of DNC
1.Elimination of punched tape and tape reader
2.Greater computational capability and flexibility
3.Convenient storage of NC part programs in
computer files
4.Programs stored as CLFILE
5.Reporting of shop performance
6.Establishes the framework for evolution of
future computer automated factory (CIM)
7.2-5 % increase in operational efficiency of
CNC machine tools. Cost of DNC installation
can be recovered quickly.
(ACET)

Chapter 1 fundamentals of cam

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