CNC Machining Centres

This presentation gives an information about: CNC Machining centers covering syllabus of Unit-7, Sub: Computer Integrated Manufacturing (10ME61) for BE course.

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1 Hareesha N G, Dept of Aero Engg, DSCE, Blore

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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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3. Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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5. Numerical Control is 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 the data
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6. Data is sent to the machine tool by means of
punch cards or tapes. The reader at the
machine performs no calculations or
interpolations.
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Hareesha N G, Dept of Aero Engg, DSCE,
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7. •A numerical control, or “NC”, system controls many machine
functions and movements which were traditionally performed by
skilled machinists.
•Numerical control developed out of the need to meet the
requirements of high production rates, uniformity and consistent
part quality.
•Programmed instructions are converted into output signals which
in turn control machine operations such as spindle speeds, tool
selection, tool movement, and cutting fluid flow.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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8. • By integrating a computer processor, computer
numerical control, or “CNC” as it is now known, allows
part machining programs to be edited and stored in the
computer memory as well as permitting diagnostics and
quality control functions during the actual machining.
• All CNC machining begins with a part program, which
is a sequential instructions or coded commands that
direct the specific machine functions.
• The part program may be manually generated or,
more commonly, generated by computer aided part
programming systems.

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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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9. •CNC : Computer and Numeric Control
•Conventionally, an operator decides and adjusts various
machines parameters like feed , depth of cut etc
depending on type of job , and controls the slide
movements by hand. In a CNC Machine functions and
slide movements are controlled by motors using
computer programs.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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10. MACHINE UNIT
NUMERICAL
CONTROLLER
NUMERICAL
DATA
(NC CODE)
MANUFACTURING
OPERATOR
PROCESSED
PART
Drive Control
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore

11. All computer controlled machines are able to accurately and repeatedly
control motion in various directions. Each of these directions of motion is
called an axis. Depending on the machine type there are commonly two to
five axes.
Additionally, a CNC axis may be either a linear axis in which movement is in
a straight line, or a rotary axis with motion following a circular path.
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12. Absolute Coordinate System Incremental Coordinate System
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13. •Each axis consists of a mechanical component, such as a slide that moves, a
servo drive motor that powers the mechanical movement, and a ball screw to
transfer the power from the servo drive motor to the mechanical component.
• These components, along with the computer controls that govern them, are
referred to as an axis drive system.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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14. •Using a vertical mill
machining center as an
example, there are typically
three linear axes of motion.
Each is given an alphabetic
designation or address. The
machine table motion side
to side is called the “X” axis.
Table movement in and out
is the “Y” axis, while head
movement up and down
the column is the “Z” axis.

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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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15. If a rotary table is added to the machine table, then
the fourth axis is designated the “b” axis.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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16. •The method of accurate work positioning in relation to the cutting tool is called
the “rectangular coordinate system.” On the vertical mill, the horizontal base line
is designated the “X” axis, while the vertical base line is designated the “Y” axis.
The “Z” axis is at a right angle, perpendicular to both the “X” and “Y” axes.

•Increments for all base lines are specified in linear measurements, for most
machines the smallest increment is one ten-thousandth of an inch (.0001). If the
machine is graduated in metric the smallest increment is usually one thousandth
of a millimeter (.001mm).

•The rectangular coordinate system allows the mathematical plotting of points in
space. These points or locations are called “coordinates.” The coordinates in turn
relate to the tool center and dictate the “tool path” through the work.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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18. Advantages:
•High Repeatability and Precision e.g. Aircraft parts
•Volume of production is very high
•Complex contours/surfaces need to be machined. E.g. Turbines
•Flexibility in job change, automatic tool settings, less scrap
•More safe, higher productivity, better quality
•Less paper work, faster prototype production, reduction in lead times

Disadvantages:
•Costly setup, skilled operators
•Computers, programming knowledge required
•Maintenance is difficult
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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19. •Lathes for metal and plastics
–Used to produce 3D product shapes and moulds
for plastic products.
•Milling machine for mould making and surface
milling.
–Used to produce dies for
die cutting printed products.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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20. •Automated version of a manual lathe.
•Programmed to change tools automatically.
•Used for turning and boring wood, metal and
plastic.
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Blore
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21. •Has 3 to 5 axes.
•Used for wood, metal and plastic.
•Used to make 3D prototypes, moulds, cutting
dies, printing plates and signs.
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Blore
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22. •Controlled by G and M codes.
•These are number values and co-ordinates.
•Each number or code is assigned to a
particular operation.
•Typed in manually to CAD by machine
operators.
•G&M codes are automatically generated by
the computer software.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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23. •The tool or material moves.
•Tools can operate in 1-5 axes.
•Larger machines have a machine control unit
(MCU) which manages operations.
•Movement is controlled by a motors (actuators).
•Feedback is provided by sensors (transducers)
•Tool magazines are used to change tools
automatically.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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24. •Most are made from
high speed steel (HSS),
tungsten carbide or ceramics.
•Tools are designed to direct waste away from
the material.
•Some tools need coolant such as oil to protect
the tool and work.
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25. •Tool paths describes the route the cutting tool takes.
•Motion can be described as point to point, straight cutting or
contouring.
•Speeds are the rate at which the tool operates e.g. rpm.
•Feeds are the rate at which the cutting tool and work piece
move in relation to each other.
•Feeds and speeds are determined by cutting depth, material
and quality of finish needed. e.g. harder materials need
slower feeds and speeds.
•Rouging cuts remove larger amounts of material than finishing
cuts.
•Rapid traversing allows the tool or work piece to move rapidly
when no machining is taking place.
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27. Is a method where a single computer
controls many numerical control machine
tools. These machine tools may or may not
be of a similar nature
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28. Computer Numerical Control (CNC)
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29. oReduces time for
delivery of part
Reduces scrap rate of
material
oReduces tooling
costs
oReduces layout time
oIncreases machine
and tool life

oReduces storage
problems
oLess setup time
oReduces actual
machining time
Allows rapid design
changes in part Less
jigs and fixtures are
needed
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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30. Top
View
Front
View
Tool Home
1.) X & Y Rapid To Hole Position
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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31. Top
View
Front
View
2.) Z Axis Rapid Move
Just Above Hole
3.) Turn On Coolant
4.) Turn On Spindle
.100”
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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32. Top
View
Front
View
5.) Z Axis Feed Move to
Drill Hole
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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33. Top
View
Front
View
6.) Rapid Z Axis Move
Out Of Hole
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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34. Top
View
Front
View
9.) X&Y Axis Rapid
Move Home
7.) Turn Off Spindle
8.) Turn Off Coolant
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Hareesha N G, Dept of Aero Engg, DSCE,
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Hareesha N G, Dept of Aero Engg, DSCE,
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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37. Top
View
Front
View
Tool At Home
O0001
N005 G54 G90 S600 M03
N010 G00 X1.0 Y1.0
N015 G43 H01 Z.1 M08
N020 G01 Z-.75 F3.5
N030 G91 G28 X0 Y0 Z0
N035 M30
N025 G00 Z.1 M09
Here’s The CNC Program!
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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38. Top
View
Front
View
Tool At Home
O0001
O0001
Number Assigned to this program
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Hareesha N G, Dept of Aero Engg, DSCE,
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39. Top
View
Front
View
Tool At Home
O0001
N005 G90 S600 M03
N005 Sequence Number
G90 Absolute Programming Mode
S600 Spindle Speed set to 600 RPM
M03 Spindle on in a Clockwise Direction
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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40. Top
View
Front
View
O0001
N005 G90 S600 M03
N010 G00 X1.0 Y1.0
G00 Rapid Motion
X1.0 X Coordinate 1.0 in. from Zero
Y1.0 Y Coordinate 1.0 in. from Zero
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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41. Top
View
Front
View
O0001
N005 G90 S600 M03
N010 G00 X1.0 Y1.0
N015 Z.1 M08
Z.1 Z Coordinate .1 in. from Zero
M08 Flood Coolant On
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Hareesha N G, Dept of Aero Engg, DSCE,
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42. Top
View
Front
View
O0001
N005 G90 S600 M03
N010 G00 X1.0 Y1.0
N015 Z.1 M08
N020 G01 Z-.75 F3.5
G01 Straight Line Cutting Motion
Z-.75 Z Coordinate -.75 in. from Zero
F3.5 Feed Rate set to 3.5 in./min.
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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43. Top
View
Front
View
O0001
N005 G90 S600 M03
N010 G00 X1.0 Y1.0
N015 Z.1 M08
N020 G01 Z-.75 F3.5
G00 Rapid Motion
Z.1 Z Coordinate .1 in. from Zero
M09 Coolant Off
N025 G00 Z.1 M09
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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44. Top
View
Front
View
O0001
N005 G54 G90 S600 M03
N010 G00 X1.0 Y1.0
N015 G43 H01 Z.1 M08
N020 G01 Z-.75 F3.5
N030 G91 G28 X0 Y0 Z0
G91 Incremental Programming Mode
G28 Zero Return Command
X0, Y0, Z0
X,Y,& Z Coordinates at Zero
N025 G00 Z.1 M09
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Hareesha N G, Dept of Aero Engg, DSCE,
Blore
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45. Top
View
Front
View
O0001
N005 G54 G90 S600 M03
N010 G00 X1.0 Y1.0
N015 G43 H01 Z.1 M08
N020 G01 Z-.75 F3.5
N035 M30
N030 G91 G28 X0 Y0 Z0
N025 G00 Z.1 M09
M30 End of Program
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Hareesha N G, Dept of Aero Engg, DSCE,
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46. Example: A Milling Operation
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X
Z
Y
(0,0,0)
NC CODE (Word Address Format)

N50 G00 X15 Y12.5 Z0
N55 M03
N60 G01 Z-2.5 F500 M08
N65 G01 X50
N70 G01 Y45
N75 G01 X15
N80 G01 Y12.5
N85 G00 Z0 M09
N90 M04

SPINDLE
STARTED !
SPINDLE
STOP !
4/4/2014
Hareesha N G, Dept of Aero Engg, DSCE,
Blore