[eneias_eringer]

Ballbar Test on a RF45 CNC mil!


Renishaw Ballbar na Nenexus - YouTube

[LongRat]

The QC20 really is an impressive tool.

[eneias_eringer]

Hello !!

I used a Ballbar in my machine , in general the result was good (Graphic in annex), but the major error was in SERVO MISMATCH , but i use Steppers in my machine !!

I think that this problem is because i use a comp file to compensate the backlash (about 0.10mm to 0.15mm in differents places of the ballscrew).

My question :

Have a configuration on EMC to "correct" the servo mismatch error??

Thanks !!

[SCzEngrgGroup]

"Servo mismatch" indicates that one axis responds more quickly to position change commands than the other, resulting in an oval plot, instead of a circle. The name is misleading only if you take the term "servo" very literally. Both steppers and servos are used as part of a control system, and every control system has a defined gain. Yours, for whatever reason, has a higher gain in one axis than the other. With a true servo system, you might be able to at least partially tune this error out. With steppers, you can't. It is no doubt also at least partially a result of mechanical deficiencies in the system - friction, stiction, backlash, etc. The fact that you feel the need to use backlash compensation means you should *expect* this kind of error, due to the backlash alone.

Regards,
Ray L.

[eneias_eringer]

Thanks Ray!!!!

[rwskinner]

I'm curious why you didn't use the fixed jaw of the vise or the actual table? I would think that the floating jaw could "possibly" introduce errors since, well, it floats.
Still, pretty cool tool.

Richard