hi, i'm running a 2160 on a large woodworking machine with 10hp atc spindle.
i'm having a problem when cutting 3D relief files, in that the axis doing the large number of 'raster' passes slowly drifts, so the relief ends up slightly trapezoidal. The machine isn't out of square, it's just that each pass shifts a small amount from the previous one.
The overall length of each pass is correct, it's only the start and end positions that vary. I have tried generating the toolpath so that it rasters in the other direction, so the other axis is doing all the passes, and the problem occurs in the same way. The drift is always towards the 0 end of the axis.
The error seems to be consistent and linear and always in the same direction, so I'm guessing it can't be random noise. The enoders are A/A- B/B- Z/Z-, I've tried running them single ended but it made no difference. I've also tried powering them from the Galil 5V line rather than the servo amps' own supply. The fact that the same happens in both the main axes seems to suggest it's not an encoder/cable /drive problem.
If I look at the live data record in smarterm or galiltools, with the motor energised the encoder position is perfectly static- if I push against the machine as hard as I can it resists the movement, and I can see the (small) position error appear then disappear as the error is corrected, and the encoder returns to exactly the original position.
I've attached a picture- the inner rectangle is a relief cut with 0.5mm stepover, rastering in the Y axis (up/down in the picture). I also did a larger file as an 'air cut' with the spindle off (to eliminate noise from that source), and you can see the larger rectangle where the extractor brush cleared a path in the dust, showing the angle again.
[by the way, the 'choppy' edge you can see is mostly because it's a ballnose doing a relief, so it's at varying heights when it reached the end of each pass, which makes it look uneven.]
Any ideas?... I'm running out!