The document provides an overview of CNC (computer numerical control) machining compared to conventional machining. Some key points include: - CNC machines can precisely reproduce a programmed design and produce thousands of identical parts much faster than conventional machining. - CNC machines can operate continuously without rest, and programming can be easily updated by changing software. - Advanced CNC software allows for machining of complex geometries not possible through manual machining. - CNC machines require less skilled operators than conventional machining once programmed.

1. Introduction to CNC

2. CNC Machining Vs Conventional
Machining
 CNCs programmed with a design that can be
reproduced exactly.
(https://www.youtube.com/watch?v=jrziv0piQ3U)
 CNCs can produce thousands of identical parts in a
relatively short amount of time, much faster than
conventional machining.
 CNCs can continuously be operated, 24 hours a day,
seven days a week, and will only require a short down
time for maintenance.

3.  CNCs can easily be updated by changing the
software
 A visual test of every new program allows designers
to ensure that the desired effect is achieved.
 Advanced software allows CNC machines to make
products that cannot be made by hand, even by the
most skilled machinists available.
 Because the machine does the skilled work, the
machine operator does not need to have advanced
training.
 CNCs only require to be supervised by one worker.

4. NC Applications (Machining)
 Batch and High Volume production
 Repeat and/or Repetitive orders
 Complex part geometries
 Many separate operations on one part

5. Cost-Benefits of NC
Costs
 High investment cost
 High maintenance effort (costly parts)
 Need for skilled programmers
 High utilization required

6. Cost-Benefits of NC
Benefits
 Cycle time reduction
 Non-productive time reduction
 Greater accuracy and repeatability
 Lower scrap rates
 Reduced parts inventory and floor space
 Operator skill-level reduced

7. Older NC Systems

8. Paper Tape
 Strip of paper tape
with holes in it.
 Machine read pattern
of holes and performed
the required operation.

9. Paper Tape Control
(https://www.youtube.com/watch?v=S60sl
N7T0Wg)

10. Paper Tape Control
 Disadvantages
Difficult to identify parts of program.
Programs could be quite large.
Stored on large bulky reels.
Fragile, could rip easily
Can you think of another major
disadvantage?

11. CNC
 Further developments in the computer
allowed it to be used to control the machine
instead of the paper tape.

12. CNC Advantages Vs NC
 Programs could be stored in computer memory.
 Easier to edit.
 More complex parts could be manufactured.
 Use of 3d geometry.
 Networking/file sharing with other computers.

13. Computer Numerical Control (CNC)
 Storage of more than one part program
 Various forms of program input
 Program editing at the machine tool
 Fixed cycles and programming subroutines
 Interpolation
 Acceleration and deceleration computations
 Communications interface
 Diagnostics

14. Advantages Of CNC
 Increased productivity after
programming is completed
 Reliability - reduces human error
 Often eliminates need for special jigs
and fixtures
 Reduces location of part features
 Makes possible the machining of
complex shapes requiring simultaneous
3 axis motion

15. Advantages
 Single part and production runs can be
programmed and machined with minimum
effort and cost.
 Programs can readily be altered and re-run
 Reduced inspection costs (more reliable)
 Once programming, setup and verified the
equipment can be operated by a less skilled
operator.

16. Disadvantages
Initial cost of CNC machine tools
Servicing of equipment
Larger machines require more space
Personnel must be trained in the programming
and operation of this equipment.

17. Components of a CNC System
1. Part program - detailed set of commands to be
followed by the processing equipment
2. Machine control unit (MCU) - microcomputer that
stores and executes the program by converting each
command into actions by the processing equipment,
one command at a time
3. Processing equipment - accomplishes the sequence
of processing steps to transform the starting
workpart into completed part

19.  Direct numerical control (DNC) – control of
multiple machine tools by a single
(mainframe) computer through direct
connection and in real time
 1960s technology
 Two way communication
 Distributed numerical control (DNC) –
network consisting of central computer
connected to machine tool MCUs, which are
CNC
 Present technology
 Two way communication

20. Distributed Numerical Control
Machine
Control Unit
Transformation
Process
Machine
Control Unit
Machine
Control Unit
Central
Computer NC Pgms
BTR BTR BTR
Computer Network

21. Machining Centers
 A machining center can be defined as a machine
tool capable of:
 Multiple operation and processes in a single set-up
utilizing multiple axis
 Typically has an automatic mechanism to change
tools
 Machine motion is programmable
 Servo motors drive feed mechanisms for tool axis’s
 Positioning feedback is provided by resolvers to the
control system

22. Machining Centers
 Example - A turning center capable of OD turning, external
treading, cross-hole drilling, engraving, and milling. All in
machining is accomplished in one “set-up.” Machine may
have multiple spindles.

23. Machining Centers
(https://www.youtube.com/watch?v=C
qePrbeAQoM)

24. SAMPLE
CNC MACHINES
24

25. CNC Drilling

26. CNC TURNING 26

27. CNC MILLING
27

28. CNC LASER CUTTING 28

29. CNC PLASMA CUTTING
https://www.youtube.com/watch?v=f5TwzRW_D
tY
29

30. CNC PRESS 30

31. CNC RAPID PROTOTYPING 31

32. INDUSTRIES MOST AFFECTED by CNC
 Aerospace
 Machinery
 Electrical
 Fabrication
 Automotive
 Instrumentation
 Mold making
32

33. SAMPLE PRODUCTS
OF
CNC MANUFACTURING
33

34. AUTOMOTIVE INDUSTRY
Engine Block
34

35. AUTOMOTIVE INDUSTRY(Cont’d)
Different Products
35

36. AEROSPACE INDUSTRY
Aircraft Turbine Machined by
5-Axis CNC Milling Machine
36

37. CNC MOLD MAKING 37

38. ELECTRONIC INDUSTRY 38

39. RAPID PROTOTYPING PRODUCTS 39

40. Good! Let’s know more about CNC!

41. CNC Motion Controls
P2P Motion Continuous Motion

42. Control Systems
Open loop control system

43. Closed Loop Control System

45. Automatic Tool Changer
 Houses number of tools for use
 Can switch between up to 200 tools stored in a
magazine, drum, or chain

46. Tool Changer Types
AUTOMATIC (SEQUENTIAL) SPINDLE
TURNS ONE INCREMENT IN ONE DIRECTION FOR EACH TOOL
CHANGE; TOOLS MUST BE PLACED IN THE SPINDLE IN THE ORDER
THEY ARE USED
INDEXABLE (RANDOM ACCESS) SPINDLE
TURNS EITHER DIRECTION TO MAKE A SPECIFIC TOOL ACCESSIBLE;
TOOLS CAN BE PLACED IN ANY ORDER AS LONG AS THE COMPUTER
KNOWS THEIR POSITIONS

47. Tool Changer
Types
4
1
2
3
5
6
1
2
3
4
5
6
7
8
SEQUENTIAL SPINDLE
Random Access Spindle

48. Tool Changer Spindle (tool Magazines)
https://www.youtube.com/watch?v=FfX5sh
me01o

49. Tool Changer Spindle
Tool changer spindle capable of holding 60 tools
Courtesy of Toth Industries

50. Automatic Pallet changers
 Mechanism similar to ATC
 Useful to fast loading and unloading of workpieces
 Saves set-up time
https://www.youtube.com/watch?v=JOShWEGKb7g

51. BASIC REQUIREMENT OF NC
MACHINE CONTROL
a. Preparatory functions: which unit, which interpolator, absolute or
incremental programming, which circular interpolation plane, cutter
compensation, etc.
b. Coordinates: three translational, and three rotational axes.
c. Machining parameters: feed, and speed.
d. Tool control: tool diameter, next tool number, tool change.
e. Cycle functions: drill cycle, ream cycle, bore cycle, mill cycle,
clearance plane.
f. Coolant control: coolant on/off, flood, mist.
g. Miscellaneous control: spindle on/off, tape rewind, spindle rotation
direction, pallet change, clamps control, etc.
h. Interpolators: linear, circular interpolation

52. Manual NC programming
Part program: A computer program to specify
- Which tool should be loaded on the machine spindle;
- What are the cutting conditions (speed, feed, coolant ON/OFF etc)
- The start point and end point of a motion segment
- how to move the tool with respect to the machine.
Standard Part programming language: RS 274-D (Gerber, GN-code)

53. Controlling a CNC machine: RS 274
The RS274-D is a word address format
Each line of program == 1 block
Each block is composed of several instructions, or (words)
Sequence and format of words:
N30 G2 X1.4 Y1.4 Z1.4 I1.4 J1.4 K1.4 F3.2 S4 T4 M2
sequence no
preparatory function
destination coordinates dist to center of circle
feed rate spindle speed
tool miscellaneous function

54. G00 = Rapid linear move
example: G00 X## Y## Z## (X,Y,Z = position)
G01 = Feed linear move
example: G01 F## X## Y## Z## (F=feedrate to move at)
G02 = Circular move CW
example: G02 X## Y## I## J## (XY=end point, IJ=center point)
G02 = Circular move CW
example: G02 X## Y## R±## (R=size of radius arc to swing.
R+ if radius < 180°, R- if radius is > 180°)
G03 = Circular move CCW
example: G03 X## Y## I## J## (XY=end point, IJ=center point)
G04 = Dwell time
example: G04 P## (P=time to dwell. P20000 is 2 seconds)
G28 = Return to reference point
example: G0 G91 G28 X## Y## Z##
(Go to machine XYZ home, passing thru XYZ incremental zero)
G29 = Return from reference point
example: G0 G90 G29 X## Y## Z##
(Go to this XYZ position, returning from home)
G30 = Return to 2nd, 3rd (ect..) reference point
example: Similar to G28
G40 = Cutter (dia.or rad.) compensation off
example: G40 X## Y##
NC Codes (http://diy.haascnc.com/g-and-m-codes)

55. G41 = Cutter compensation to the left of the programmed path
example: G40 X## Y##
G42 = Cutter compensation to the right of the programmed path
example: G40 X## Y##
G43 = Tool length compensation with spindle approach from + side
example: G43 H## Z##
G44 = Tool length compensation with spindle approach from - side
example: G44 H## Z##
G49 = Tool length compensation cancel
example: G49
G45 = Increase end position by tool offset value
example: G45 X## D## (Go to X position, plus offset value in D##)
G81 = Basic drilling cycle - Feed in , rapid out.
example: G81 X## Y## Z## R## F##
G82 = Counter bore cycle - Feed in, dwell, rapid out.
example: G82 X## Y## Z## R## F## P####
G83 = Peck drilling cycle - Feed in peck amount, rapid out, rapid in within .050 of last peck &
repeat until depth is reached.
example: G83 X## Y## Z## R## F## Q##
G84 = Tapping cycle - Feed in, spindle stop, reverse, feed out.
(note: this cycle will vary depending on the machine mfgr.)
example: G84 X## Y## Z## R## F##

56. G85, G86, G87, G88, G89 = Boring cycles. Function & input will vary
depending on the machine mfgr. Variations include....
Feed in, feed out.
Feed in, dwell, feed out.
Feed in, dwell, spindle stop, rapid out.
Feed in, dwell, spindle stop, move insert from wall, rapid out.
Rapid in, dwell, start spindle, feed up, dwell, rapid down, dwell
(reverse counter boring, back facing, back boring cycle).
G90 = Absolute coordinate positioning. Points based from XYZ zero.
example: G90 G00 X## Y## Z##
G91 = Incremental coordinate positioning. Point to point positioning.
example: G91 G00 X## Y## Z##
G92 = Absolute Zero Pre-Set - An old format used to set XYZ Zero.
The current position is set to the values shown in the line.
example: G92 X10 Y5 Z-3
After running this command the current position is X10 Y5 Z-3.
Very strange way to shift zero's. Avoid this code if you can.

57. Common M-codes
 M02 End of Program
 M03 Spindle On Clockwise, Laser, Flame, Power ON
 M04 Spindle On Counter Clockwise
 M05 Spindle Stop, Laser, Flame, Power OFF
 M06 Tool Change
 M08 Coolant On
 M09 Coolant Off
 M13 Spindle On, Coolant On
 M30 End of Program when macros are used

58. Calculate the locations in absolute and
incremental systems

59. Calculate the locations in absolute and
incremental systems

60. NC Codes
Circular Interpolation:
(5.000,2.000)
(7.000,2.000)
N0100 G02 X7.000 Y2.000 I5.000 J2.000
Cut from (5.000,4.000) to
(7.000,2.000) CW
(5.000,4.000)

61. NC Codes
F Code. feed speed.
inch/min (ipm), or ipr.
F code must be given before either G01, G02, or G03 can be used.
N0100 G02 X7.000 Y2.000 I5.000 J2.000 F6.00
S Code. cutting speed code.
It is programmed in rpm.
S code does not turn on the spindle, spindle is turned on by a M code.
N0010 S1000

62. Manual Part Programming Example
2.000
2.000
(6,6)

63. Any Quetions?