Is a higher resolution encoder better?！

Maybe. There are several factors in choosing an encoder: pulse rate and resolution. With the currently available PC-based CNC controllers, you are limited to a clock rate of 25khz to 45khz (Mach2). With a 250cpr encoder, you will need to generate 1,000 pulses (with quadrature) to make one full revolution. Therefore, with a 25khz clock rate, your maximum rotational speed would be 1,500rpm. With a 45khz clock rate, your maximum rotational speed would be 2,700rpm. If you go to a 500cpr encoder, your resolution will be better, but your maximum rpm will be 1/2 what you'd get with a 250cpr encoder.

For example: If you have a motor geared 2:1 with a 0.200" leadscrew, assuming your motor has enough rpm, with a 250cpr encoder and a 25khz clock rate, your resolution would be 0.0001" and your maximum rapid speed would be 150ipm. That same motor, with a 500cpr encoder would get you 0.00005" resolution, but your rapid speed would drop to 75ipm. At 45khz clock rate, you'd have 270ipm and 135ipm respectively.

Ideally you want to spec your parts so they all reach their limits at the same time. For example, if you have a motor with 1,000rpm maximum speed, and a 25khz clock rate, your ideal encoder would have 375 cpr (1,500ppr with quadrature). However, in the real world you'd probably want to use a 250cpr encoder in this example.

Also, keep in mind that just because you have great resolution doesn't mean you can actually use it. By the time you add up all the inconsistencies and variables in your setup, your encoder resolution is probably the least of your problems!

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