[SCzEngrgGroup]

I'm still pretty new to a lot of this stuff but couldn't you upgrade to a 75vdc power supply pretty easy? Couldn't you speed up your Rapids that way? From what I've read most steppers that size can Handle 75vdc.

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No, that is completely false. For steppers, optimal voltage is a function of the coil inductance. Arbitrarily increasing voltage will likely result in motor heating, and likely damage to the drivers, unless they are spec'd for the higher voltage. With servos, reduced voltage (i.e. - running the motors at 48V when they're spec'd for 75V) will result in proportionally reduced maximum speed. Even if the voltage were correct, it's not at all likely the stepper power supplies would provide the additional current necessary for the increased torque that is required to be able to increase the performance.

Also, torque ratings between steppers and servos are not remotely the same - the specs have completely different meanings. And, steppers and servos have completely different torque/speed characteristics. So, selecting a servo motor based on the corresponding stepper torque rating will surely result in disappointment, unless the differences are well understood, and factored into the decision. The ONLY way to properly size any drive system is by measuring the actual machine requirements, and doing the math, based on the targeted performance. Guessing rarely turns out well, and is exactly why so many home-build machines turn out to be such disappointments.

As for the idea of "upgrading" only X/Y, that would be foolish. First, many Mach3 version simply do no work correctly when the X axis torque/acceleration performance differs significantly from the X/Y performance. I'm sure this is not a problem with PathPilot. However, on any move involving the Z axis, ALL axes will be slowed down to the performance of the Z axis. For 3D profiling, this would mean almost no improvement in performance on most operations.

Regards,
Ray L.