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« on: August 10, 2008, 06:11:45 PM »
I have been asked to try and clarify the cutter compensation debate (CC) that keeps raging on and on and on.........
The basics
Compensation is not a quick fix.
Cutter compensation is used to adjust the size of a cut area, this can be on the outside or the inside of a component or section of a component.
Compensation has to be planned into the job, it is not easy to adapt afterwards.
When programming the job the tool is programmed on the centre line of the cut.
When programming the part any inside radius can not be smaller than the radius of the cutter to be used.
The machine should never rapid with an active G41 or G42, Mach3 may allow this move just as you can drive your car off a cliff, its not advisable.
You should not change local (G52) or global (G54-G59 Etc.) work offsets while a G41 or G42 is active.
Cutter compensation should not be used for pocketing and area clearance.
How it works
To use CC we have to command a G41 or a G42, the one we use depends on which side of the line we are on and what direction we want to travel. The next consideration is how we move onto the cutter path, we can not rapid straight onto the line and start cutting, we have to create a lead in line. We also have to have lead out lines. This is why you have to pre-plan CC.
A lead line can be a straight line or an arc or a combination of both. Straight line moves are the easiest, arcs give the best blend.
The picture below shows 4 examples of how we can use CC, the top 2 show cutting on the outside of the green line. The bottom two are slots so are cutting on the inside of the green line.
The parts are 10mm wide and 50mm long giving 40 mm centres on the rads. The example code was written for the use of a 2mm dia end mill. Before anybody tells me this is not the best cutter for the job, I don't care.
More later........
Graham.
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G54 G00 G90 G43
T1 M6
S1500 M3
(FIG 1 - CCW INSIDE)
G00 X41.5 Y-2.5
G00 Z1.
G01 Z-2. F900.
G41 X42.5 Y2.5 F1800.
G03 X40. Y5. R2.5
G01 X0.
G03 X-5. Y0. R5.
X0. Y-5. R5.
G01 X40.
G03 X45. Y0. R5.
X40. Y5. R5.
X37.5 Y2.5 R2.5
G01 G40 X38.5 Y-2.5
G00 Z25.
(FIG 2 - CW INSIDE)
G00 X61.713 Y-2.5
Z1.
G01 Z-2. F900.
G42 X60.713 Y2.5 F1800.
G02 X63.213 Y5. R2.5
G01 X100.
G02 X105. Y0. R5.
X100. Y-5. R5.
G01 X60.
G02 X55. Y0. R5.
X60. Y5. R5.
G01 X63.213
G02 X65.713 Y2.5 R2.5
G01 G40 X64.713 Y-2.5
G00 Z25.
(FIG 3 - CCW OUTSIDE)
G00 X41.5 Y42.5
Z1.
G01 Z-2. F900.
G42 X42.5 Y37.5 F1800.
G02 X40. Y35. R2.5
G01 X0.
G03 X-5. Y30. R5.
X0. Y25. R5.
G01 X40.
G03 X45. Y30. R5.
X40. Y35. R5.
G02 X37.5 Y37.5 R2.5
G01 G40 X38.5 Y42.5
G00 Z25.
(FIG 4 - CW OUTSIDE)
G00 X61.074 Y42.5
Z1.
G01 Z-2. F900.
G41 X60.074 Y37.5 F1800.
G03 X62.574 Y35. R2.5
G01 X100.
G02 X105. Y30. R5.
X100. Y25. R5.
G01 X60.
G02 X55. Y30. R5.
X60. Y35. R5.
G01 X62.574
G03 X65.074 Y37.5 R2.5
G01 G40 X64.074 Y42.5
G00 Z25.
G91 G28 Y0 Z0
M30
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