Gregg Eshelman wrote: > Would a 0.0002" or 0.00005" resolution linear magnetic scale be good enough > to use instead of a servo encoder? > > Still trying to get the guy with the Acra mill in need of a bunch of TLC to > sell it for what it's worth as-is, not for what it'd be worth if it was in > working order? > > The old Anilam Crusader M system uses tachometers and glass scales so any > reason LinuxCNC couldn't use magnetic scales of higher resolution? > > Velocity servo systems with low-resolution encoders can work well, but have limited stiffness. Systems without tach feedback need higher resolution encoders to get good results. .0002" resolution is pretty marginal, 50 uInch resolution is a lot better, but still a little marginal without the tach feedback. The other concern is that you can't tune the servo response properly if there is much backlash between the motor and the linear scale. So, if the backlash is greater than just a few encoder counts, the system will vibrate badly. Getting the backlash down to 50 uInch or less is going to be REAL difficult.
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