This document discusses computer numerical control (CNC) machines. It begins by defining CNC and its evolution from numerical control (NC) machines. It then describes how CNC machines work by using computer code converted from CAD designs to control tool and workpiece movement. The document outlines various applications of CNC in manufacturing like lathes and mills. It provides a brief history of NC machines and discusses advantages and disadvantages of CNC versus traditional machining. Finally, it details the key elements that make up modern CNC machines.

1. PRESENTED BY
MISS LALRIN MUANI K.
3RD YR BPO
CMC VELLORE

2. INTRODUCTION
• CNC is the acronym for computer
numerical control.
• It is an outgrowth of the older term
"NC", which stands for just "numerical
control".
• Numeric control is a programmable
automation in which process is
controlled by numbers, letters and
symbols.
(Computer + NC=CNC)
• CNC refers to the idea of controlling
machine tools programmatically via
computer. With the older "NC" term, A
computer need not be involved. The

3. INTRODUCTION
• This means a computer converts
the design produced by Computer
Aided Design Software (CAD), into
numbers. The numbers can be
considered to be the coordinates of
a graph and they control the
movement of the cutter. In this way
the computer controls the cutting
and shaping of the material.
• CNC can control the motions of the
work piece or tool, the input
parameters such as feed, Depth of
cut, speed, and the functions such
as turning spindle on/off, turning

4. APPLICATIONS
• The applications of CNC include
both for machine tool as well as
non-machine tool areas. Some are
as follows:
 lathe,
 drill press,
 milling machine,
 Grinding unit,
 laser,
 sheet-metal press working
machine,
 tube bending machine etc.

5.  welding machines (arc and resistance),
 Measuring machine,
 electronic assembly,
 tape laying and
 filament winding machines for Composites etc.
• This Technology is applied to Prosthetics and Orthotics field as well.

6. HISTORY
• The first NC machines were built
in the 1940s and 1950s by Prof.
John T Parson.
• Conceived method of using
punched cards containing
coordinate position data to
control the machine tool.
• In 1948, Parson demonstrated
his concept to U.S Air Force
Fig: punched card which contains
command to control automated machinery

7. HISTORY
• CNC machine came to existence
after evolution of computer
around 1980.
• Modern CNC Machine are
improving further as the
technology is changing with
variety of functions according to
applications.
1959 CNC Machine: Milwaukee-Matic-II
was first machine with a tool changer...

8. COMPUTER NUMERICAL CONTROL
ADVANTAGES
• Easier to program
• Easy storage of existing
programs
• Easy to change program
• Avoid human error
• CNC machines are safe to
operate
• Complex geometry is
produced as cheaply as
simple ones
DISADVANTAGES
• Costly setup than manually
operated machines.
• Skilled operators
• Computers, programming
knowledge required
• Maintenance is difficult.

9. COMPUTER NUMERICAL CONTROL
ADVANTAGES
• Short production time
• Greater manufacturing flexibility
• Contour machining (2 to 5 axis
machining)
DISADVANTAGES

10. DIRECT NUMERICAL CONTROL
ADVANTAGES
• Greater computation and flexibility.
• Eliminates use of punched tapes.
• Convenient storage of NC Part Programme
in computer file.
• Direct conversion of data from CAD to NC
program.
• Increases Productivity
• Save time.
DISADVANTAGES
• The only disadvantage of the DNC is
if the computers breaks down, but
the computer is so reliable that this is
unlikely to occur..
• Some type like Terminal-based DNC
system and Network-based DND
system are expensive.

11. NUMERICAL CONTROL
ADVANTAGES
• Higher productivity- reduction in time of
set up, work piece handling time, tool
changing time.
• Reduced non-productive time.
• Reduced fixturing.
• Greater accuracy and repeatability
• Reduced inventory
• Reduced floor requirements.
• Operator skill level reduced
• NC machine are safer to operate.
DISADVANTAGES
• high investment cost.
• High maintenance effort.
• Need for skilled programmers.
• High utilization required.

12. ELEMENTS OF CNC MACHINE
• A CNC machine consists of following 6 major elements:
i. Input device
ii. Machine control unit
iii. Machine tool
iv. Driving system
v. Feedback devices
vi. Display unit

13. INPUT DEVICES
• FLOPPY DISK DEVICE
• SERIAL COMMUNICATION
• USB flash drive

14. MACHINE CONTROL UNIT (MCU)
• the machine control unit is the heart od CNC system. There are two sub-units in
the machine control unit:
• Data Processing Unit(DPU)
• Control Loop Unit(CLU)

15. MACHINE TOOL
• THIS CAN BE ANY TYPE OF MACHINE TOOL OR EQUIPMENT.

16. DRIVER SYSTEM
• The driving system is an
important component of
CNC machine as the
accuracy and repeatability
depend very much on the
characteristics and
performance of the
driving system.
• The driving system is
classified as Spindle
drives and feed drives.
• The spindle drives are
used to provide angular
motion to the work piece
or cutting tool.
• Feed drives are used to
drive the slide or a table.

17. FEEDBACK DEVICES

18. DISPLAY UNIT