Guest
Show Posts
1
General Mach Discussion / calibration question for the experts
« on: March 09, 2009, 08:45:23 PM »
First off I'd like to thank those on this board who have helped me to get my project moving forward. This place is a very good resource to have.
So I have my machine running for the most part, but I still have a problem with the axes not moving the correct distance. I set them up originally the way the Mach instructional says, by figuring the pitch and encoder counts, but that was a bit off. So I used the calibrate axis function and it seems to work, but when I cut a test pocket I'm always off way more than I would expect. Cutting a 120mm by 10mm pocket measures out to 119.86mm by 9.88. I would think that it could cut much more accurate than that. I've tried it with and without the backlash comp. Backlash is very minimal anyway, I measured .005" lash in them. By the way, this is a minimal .5mm depth pocket in corian, so very little load on the machine.
I have 5mm pitch ballscrews driven by direct coupled Omron R88M-U20030 servo motors with Omron R88D UP08HA drives. I got this thing running with all the drives set to the default parameters. With the default settings Mach motor setup works out to about 409 pulses per mm. I would have thought this would be accurate enough but perhaps it isn't? The drives have electronic gearing so I could change that if need be. What would be a good avg amount of pulses per mm?
Thanks for any and all help.
Bob
So I have my machine running for the most part, but I still have a problem with the axes not moving the correct distance. I set them up originally the way the Mach instructional says, by figuring the pitch and encoder counts, but that was a bit off. So I used the calibrate axis function and it seems to work, but when I cut a test pocket I'm always off way more than I would expect. Cutting a 120mm by 10mm pocket measures out to 119.86mm by 9.88. I would think that it could cut much more accurate than that. I've tried it with and without the backlash comp. Backlash is very minimal anyway, I measured .005" lash in them. By the way, this is a minimal .5mm depth pocket in corian, so very little load on the machine.
I have 5mm pitch ballscrews driven by direct coupled Omron R88M-U20030 servo motors with Omron R88D UP08HA drives. I got this thing running with all the drives set to the default parameters. With the default settings Mach motor setup works out to about 409 pulses per mm. I would have thought this would be accurate enough but perhaps it isn't? The drives have electronic gearing so I could change that if need be. What would be a good avg amount of pulses per mm?
Thanks for any and all help.
Bob