Re: [CAD_CAM_EDM_DRO] Backlash problem?

Well, You are in absoloute per the G90 command. So it is irrelevant what moves you make when you tell the machine to return to X0Y0 it should return to the same spot every time. The only time you can build program end position errors on repitition is in Incremental G91 programming and miscalculating the move to go back to the starting point. Never use Incremental. However, I'm looking at the code more closely. Are you sure Mach2 produced that code exactly like that? You start out in Absolute but your commands are in Incremental then it goes back to absolute??. In absolute the radii are always called out with "I" and "J" values.

If thats not it and you are using servos I'd be looking at possible encoder/motor lead cross-talking. It could be lost steps due to a certain place in the machining process that inducing a heavy load on the axis drive.

If it were a mechanical backlash issue it would still be out the same .033" every time from zero. Not .033" then .066" then .099".

Ron



kdoney_63021 <kdoney_63021@...> wrote:
I have a converted mini mill (yes, I know). When I run a program
which jogs the y axis back and forth 20 times with my current
backlash setting (in Mach2 v6.06) I get a perfect reading
(within .0005). When I run the following program, I get a +.033 creep
in the Y axis for every complete circle:

G0 G49 G40 G17 G80 G50 G90
M6 T1(TOOL DIA. 0.5625)
G64
G20 (Inch)
M04 S0
G00 G43 H1 Z0.1
X0 Y0
G01 Z-0.0010 F15
G2 Y0 X0.4500 R0.2250 F15
Y0 X-0.4500 R0.4500
Y0 X0.46875 R0.46
Y0 X-0.46875 R0.46875
X0.46875 Y0 R0.46875
Y-0.375 X0.09375 R0.375
G00 Z0.1
X0 Y0
...

The control response to this code correctly (it actually generated
this code with its wizard) by cutting a circular pocket (Z is then
decremented and the code is repeated) but it slowly moves +.033 on
the Y axis on every iteration.

I have changed the feed to 1,5,10 and the motor tuning acceleration
and speed to a low and high settings to no avail.

I assume a small calculation round off error but not .033/circle.

Any help would be appreciated.




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