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cnc handout
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HistoryHistory
• 1952 – 1st generation NC The first NC-1952 1st generation NC, The first NC-controlled machine for metal processing (relays and electronic tubes)
• 1960 – 2nd generation NC, relays and electronic tubes was replaced with tranistors
• 1965 – 3rd generation, integrated circuits
• 4th generation NC – CNC (computerized t ge e at o C C C (co pute ednumerical Control
CNC Machines examplesCNC�Machines�� examples
• Machine tools for�cutting (lathe,�millingmachine,�machining centre)g )
• CMM�– Coordinate Measuring Machine
Sh l i hi ( b k• Sheet metal�processing machines (press�brake,�punch press,�laser�/�waterjet cutting machine)
• RP�(rapid�prototyping)�and�rapid�manufacturing machinemanufacturing machine
Basic ComponentBasic Component
P t P Machine Control Part Program Machine Control Unit
Processing equipmentStep by step commands
that direct the actions of Microcomp ter andthe processing equipment Microcomputer and
related control hardware that stores the program of instructions and executes
it by converting each command into
mechanical actions of the processing equipmentprocessing equipment
Configurations examples (1)Configurations – examples (1)
Configurations examples (2)Configurations – examples (2)CNC Machines examplesCNC�Machines�� examples
• Machine tools for�cutting (lathe,�millingmachine,�machining centre)g )
• CMM�– Coordinate Measuring Machine
Sh l i hi ( b k• Sheet metal�processing machines (press�brake,�punch press,�laser�/�waterjet cutting machine)
• RP�(rapid�prototyping)�and�rapid�manufacturing machinemanufacturing machine
TerminologyTerminology
3 i• 3�axis– Movement along 3�axes is�CNC�controlled (also called
2½D hi i )2½D�machining)
• 4�axis�– 6�axis– 3�axes�+�1�to�3�rotation(s)
• 7�axis– Combines milling and�turning�in�one machine
• Active tools– Motor�driven�tools in�a�machine that�normally does
not�have this
Positioning and fixturingPositioning and�fixturing
• 3�2�1�Method
Secondary supportsSecondary supports
• For�flexible�(thin walled)�components
Machine vice (skruvstäd)Machine vice�(skruvstäd)
• Easy�to�operate
• Does not position component very accuratelyDoes�not�position�component very accurately
• Deformation�can be�a�problem
Actuators - Motors 2(2)Actuators Motors 2(2)
• Electric motors (Most Common)Electric motors (Most Common)– DC Motors
AC Motors– AC Motors– Step Motors
Linear Motors– Linear Motors• Hydraulic motors (Not commonly used)
Linear DrivesLinear Drives
• To transfer the rotational movement to aTo transfer the rotational movement to a linear movement – Ball screw
Ball screw : http://www.ostergrens.se B ll htt // iBall screw : http://www.ostergrens.se Ball screw: http://www.eie.se
Ball screw 2(2)Ball screw 2(2)
• Why Ball-screw?Why Ball screw?– High efficiency (>90%)
Low heat generation– Low heat generation– No backlash
Hög precision– Hög precision– High resistance to wear
Inserts - CarbideInserts Carbide
Cutting Tools
Summ
ary of cutting technology:
Workpiece m
aterial, parameters, tool
geometry infuence:
� which shapes can be m
achined o or w
hich tool needs to be used � cutting forces
o required power
o deflections � costs (cutting tim
e vs tool wear)
� chip control � surface roughness � vibrations
This means that the C
NC
programm
er m
ust be a skilled machinist also …
.. two
completely different skills!
Exam
ple: Some N
C program
keys SINU
ME
RIK
805
G00
Traversing G
01 Linear interpolation
G02
Circular interpolation clockw
ise G
03 C
ircular interpolation counter clockwise
G10
Polar coordinates, Traversing G
11 Polar coordinates, Linear interpolation
G12
Polar coordinates, Circular interpolation
clockwise
G13
Polar coordinates, Circular interpolation
counter clockwise
G17
Programm
ing in X-Y
plane G
40 End of radius com
pensation G
41 R
adius compensation left (tool stays left
of programm
ed contour) G
42 R
adius compensation right (tool stays
right of programm
ed contour) G
54 U
ser defined origin G
90 A
bsolute programm
ing G
91 Increm
ental programm
ing
X
X
-coordinate Y
Y-coordinate
Z
Z-coordinate A
Angle
U
R
adius I
Interpolation origin X
-coordinate J
Interpolation origin Y
-coordinate K
Interpolation origin Z-coordinate D
1-99 Tool com
pensation D
0 End of tool com
pensation
F
Feedrate S
Spindle speed
T
Tool number
H
H
elp function L
sub-program
M
02 Program
end M
17 Sub-program
end M
30 Program
end M
03 Spindle rotation clockw
ise M
04 Spindle rotation counter clockw
ise M
05 Spindle stop
Specific for Cortini: Tool change has form
at: Tx L6 D
yw
here: "x" is the tool slot position of the new tool
and "y" is the register for tool size compensation
belonging to that tool (L6 is a sub-program for tool
changes)
Some lathes sw
ap G02 and G
03
Vertical latheVertical lathe• Requires less�floor space
• Upside�down mounting possible– Easier chip�removalp
CMM�– Coordinate MeasuringgMachine
• For�instance,�for�inspection
Examples of probesExamples of�probes
Laser probesLaser�probes
• Higher density (more points)
• Suitable for ”reverse engineering”Suitable for� reverse engineering
Sheet metal processing machinesSheet metal�processing machines
Examples:
• CNC press brakeCNC�press�brake
• Punch press
• Laser�cutting machine
• Laser pressLaser�press
• Waterjet cutting machine
• Laser�welding machine
Air bending set�up
CNC Press brake (usually hydraulic)CNC�Press�brake (usually hydraulic)
• CNC�control of�punch (or�die),�finger�stops,�crowning device (bombering)g ( g)
Detailed view (1)Detailed view (1)
Detailed view (2)Detailed view (2)Robot assisted punch pressRobot�assisted punch press
LASER�(Light�Amplification�by�Stimulated�Emission�of�Radiation)
Most used: CO Nd:YAG ExcimerMost used:�CO�,�Nd:YAG,�Excimer
Laser cuttingLaser�cutting• With�or�without gas�(inert/reactive)
• Related:�welding,�hardening,�engraving,�…
Beam guided by mirrors or fiberBeam guided by�mirrors or�fiber
• Nd:YAG,�Excimer laser�beams can be�guidedthrough an�optical fiber�– but less�powerfulg p pthan CO2
Laser cutting machine (example)Laser�cutting machine (example)
6 axis Laser (3D)6�axis�Laser�(3D)
Construction principlesConstruction�principles
Considerations/problemsConsiderations/problems
• Risk�for�overshoot when moving high�massand/or�at�high�speedg p– Speed�reduction (corner�anticipation).�Has�process�
limitations (power density)limitations�(power�density)
– Smart�path planning
d l f ?• How to�avoid tangling of�components?– Drop down table
– Leaving small�”bridges”�until last
Waterjet cuttingWaterjet cutting
• Similar,�but 3�axis�and�2�axis�more common
RP (rapid prototyping)RP�(rapid�prototyping)
i l l (d k hi i )• Material�removal�(desktop�machining)• Layered manufacturingy g
– Adding material– Transforming material (solidification)Transforming material�(solidification)
• Some process�so�good that�one talks�about”rapid manufacturing”rapid�manufacturing– Often,�one of�a�kind�products
• Based on�CAD�drawing or�scanned surfacedata
Example of layered manufacturingExample of�layered manufacturing
Complex Parts – How to program?Complex Parts How to program?
CAM – Computer Aided M f iManufacturing
External CAD systemIntegrated CAD/CAM system
CADProduct design
CAMGeometry Definition
yProduct Design
Neutral formatDefine Operation
Select Tools
Define ToolPaths
Neutral format
e.g. Step, iges
Simulate Toolpath
Postprocess
Simulate Machine
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