Originally Posted by
baja_10
Hello,
I'm nearing the end of a very long rebuild on a large 4'x8' Vytek monument laser system that attempted to destroy itself. It started with the linear bearings going out and the gantry rails warping, proceeded to eat the acme rod and finally lock up.
It now has new linear bearings, a new ball screw and the gantry rails are all aligned to withing about 5 thousands of each other. My last remaining problem is a repeating pattern at full speed raster engraving (20 to 30 inches per second) and a pretty pronounced machine shudder when vector cutting small objects at anything over ~2 inches per second. It really has issues with circles smaller than half an inch.
I've measured everything I can and it looks good. Nice sinusoidal waveform when I back drive the motor, no shorts to ground, similar ohm reading on each of the poles, good diode readings on the drivers, etc. However the motor that drives the laser head back and forth on the gantry, the Y motor, (ya, the whole 40 lbs of it, great design lol) cogs when i have it connected to the servo driver. The X motor that moves the gantry does not cog at all.
It seems to me that there is something wrong internally that I can/don't know how to measure. If I do the raster engraving with an exaggerated acceleration mode it will cooperate and produce with little repeating pattern but this nearly doubles the work time on small projects. A loose or tight backlash nut does not seem to affect the pattern. It strikes me as something off in the torque of the motor that matches up with the cogging I'm feeling, that when ran slow enough it can compensate for. I have tried running the sigmawin program but the output plots don't seem to show anything obvious enough for me.
Does anyone have any have any recommendations? At this point I'm ready to ship the motors off to be rebuilt even though the hours are probably not over 5,000.
Y Motor:
SGMG-08K3A-YA11
Y Driver:
SGDA-08AP, Y195
X Motor:
SGMG-03K3A-YA11
X Driver:
SGDA-04AP, Y195