I'm buying some servos for an old VMC retrofit.
Automation Direct's servos have 2500 count encoder (10,000ppr quadrature). Seems plenty for my 5mm lead ballscrews.
But then I see Yasakawa Sigma 2 motors with 131,072 ppr encoders, Yaskawa Sigma 5 motors with 20-bit 1 million count encoders, and Fanuc motors with 1M and above.
So why use such high count encoders? They'd have to be electronically geared down anyway to get fast rapids due to the limitations of the encoder pulse frequency from even high end MC cards, and I'm guessing that even at low speed, a couple pulses wouldn't even be enough to get the machine to budge due to static friction.
Thanks for any info!