Unit 1 : Introduction to
Computer Numerical Control
Prepared by : Mr.B.K Patil,DTC
Diploma in Mechatronics Semester 5 CNC Technology
Syllabus
1.0 Introduction to Computer Numerical Control
1.1 Introduction, Numerical Control
Numerical Control Modes, Numerical Control
1.2
Elements & NC machine tools
Diploma in Mechatronics Semester 5 CNC Technology
1.1 INTRODUCTION
• A large variety of components is manufacturedin industries and every
component has its own geometric parameters and hence different machining
requirements.
• For meeting the machining requirements of different components a single
NC system cannot give optimum results. So the CNC machines are designed
to meet specific requirements to make them cost effective.
Diploma in Mechatronics Semester 5 CNC Technology
1.1 HISTORY OF NC
• 1940 ------------- John T Parason.
• 1952 ------------- 1st NC Machine Released.
• NC machine was born because of an urgent need of John C.
Parson’s Corporation, a manufacturer of helicopter rotor blades
could not make templates fast enough.
•
• So in 1947 he invented a way of coupling computer equipment
with Jig borer. Mr. parson used punched cards to operate this
Digitron system.
Diploma in Mechatronics Semester 5 CNC Technology
Growth of NC
• 1955 to 1960 --- 500 NC Machine Installed in USA.
• During 1960 to 1964 ----- 400 more added.
• Till The middle of 60’s Russia, Japan, UK, West Germany were for behind
USA in production of NC m/c tools.
•1947 was the year in which the NC machines born.
• In 1955 about seven companies had tape controlled machines exhibited at
the machine tool show. In 1960 according to the American machinist, there
were one hundred NC machines at the machine tool show in Chicago.
• Japan Entered the NC commercial scene in 60’s & surpassed the USA.
• 1965 – 1970 Computer Introduced.
• 1990 – CAD /CAM Software introduced.
• Present CAD/CAM Scene.
Diploma in Mechatronics Semester 5 CNC Technology
1.2 Numerical Control (NC)
modes
• The
•. system in which actions are controlled by a direct Instruction of
numerical data at some point.
• The system which integrate the data and give commands to the control
system.
• Numerical control is control by numbers.
• On a conventional type machine the operator uses a variety of levers, heels,
and push buttons to control the machine manually.
• In the case of NC machine an electronic control unit directs many of machine
functions,
• These functions including positioning, indexing turret, rotating spindle,
coolant on / off or tool changing, pallet changing etc.
Diploma in Mechatronics Semester 5 CNC Technology
1.2 Numerical Control (NC)
• Controlling a machine tool by means of prepared program, which
consists of blocks or series of numbers, is known as Numerical
control or NC.
•The first NC machine was demonstrated in 1952 at Massachusetts
Institute of Technology (MIT), USA.
Diploma in Mechatronics Semester 5 CNC Technology
1.2.1 Numerical Control Elements
Three basic components of an NC system:
1. Input medium:- Part program or instructions needed to drive the
machine tool components-
Instructions are prepared manually or by use of computer
- Instructions include machining parameters (feed rate, cutting speed);
sequence of actions (e.g., positioning & machine functions)-
Instructions are stored in the form of tape (paper, magnetic); floppy
diskettes; DNC Download to CNC RAM
2. Machine control unit (MCU):
-Electronics & control hardware-Interpret instruction set-Execute
instructions-Monitor results & correct where appropriate
Diploma in Mechatronics Semester 5 CNC Technology
1.2.1 Numerical Control Elements
• 3. Machine tool:-Mechanical structure that performs the
machining, including the components that drive
• each axis of motion (e.g., AC or DC motor; hydraulic actuator;
stepper motor —choice affects speed of response,accuracy and
power capacity)
Diploma in Mechatronics Semester 5 CNC Technology
1.2.2 NC MACHINE TOOLS
The basic objective behind the development of NC machine tools is
the reduction of cost of produc-tion and improvement in product quality.
The major emphasis is directed towards the avoidance of non-
productive time which is mainly due to the number of set ups, set up
time, work piece handling time, tool change time and lead time. NC
machines have been found quite suitable in industries such as the
following.
•For the parts having complex contours, that cannot be manufactured by
conventional machine tools.
Diploma in Mechatronics Semester 5 CNC Technology
1.2.2 NC MACHINE TOOLS
• For jobs requiring many set ups and/or the set ups are very
expensive.
• The parts that are subjected to frequent design changes and
consequently require more expen-sive manufacturing methods.
• The inspection cost is a significant portion of the total
manufacturing cost.
• One or more of the above considerations would justify the
processing of a part by a NC machine tool.
Diploma in Mechatronics Semester 5 CNC Technology
1.2.2 NC MACHINE TOOLS
• For jobs requiring many set ups and/or the set ups are very
expensive.
• The parts that are subjected to frequent design changes and
consequently require more expen-sive manufacturing methods.
• The inspection cost is a significant portion of the total
manufacturing cost.
• One or more of the above considerations would justify the
processing of a part by a NC machine tool.
Diploma in Mechatronics Semester 5 CNC Technology
COST EFFECTIVE “QUALITY”
PRODUCT IN “LESS TIME”.
Diploma in Mechatronics Semester 5 CNC Technology
