i keep getting those nasty stepper buzz sounds once in a while on rapids that lock up steppers so i loose coordinates. I scaled back on rapids in Mach 3 to 65ipm for X/Y and 60ipm for Z and still once in a blue moon Z freezes doing rapids (especially going up). How can I fight with it? I see some machines accelerate their rapids to 100ipm or so and doing just fine while mine backfires on me even with much slower rapids. Can that be because of the axis acceleration values in Mach3? The problem is that it is hard to tell what change leads to what result since "freeze" happens occasionally and is not reproducable on demand.

i keep getting those nasty stepper buzz sounds once in a while on rapids that lock up steppers so i loose coordinates. I scaled back on rapids in Mach 3 to 65ipm for X/Y and 60ipm for Z and still once in a blue moon Z freezes doing rapids (especially going up). How can I fight with it? I see some machines accelerate their rapids to 100ipm or so and doing just fine while mine backfires on me even with much slower rapids. Can that be because of the axis acceleration values in Mach3? The problem is that it is hard to tell what change leads to what result since "freeze" happens occasionally and is not reproducable on demand.

be honest, do you really need 60ipm on a z-move? What are your accelerations set to? If you are trying to accelerate and the torque required surpasses that torque of your steppers, you'll lose steps. On moves that reverse quickly you will see this (like a z-up which means the stepper is lifting the spindle against gravity).

FWIW,
Jay

theres a few possible reasons for stalling.

1: the torque curve drops off rapidly at a certain rpm. - this is unlikely to be your issue here though.
2: the gibs are too tight and have have sticky spots. does the machine stall in the same place each time?
3: mach 3 pulse width is incorrect. on my machine, i would get random stalling because the pulses were not correct.
4: your acceleration is set too fast. what is it at? 20-40 is probably where it should be on this mill.

i just set up an NM200 to go 150 ipm, acceleration at 40. it runs like butter. but at 175ipm it would stall beacause the big nema42 motors drop of that quickly. it was obvious because all 3 axes would quit at the same speed, even the Z on linear rails.

I've been running my NM135 for a while with the following motor tuning, with no problems:

X: 12700 115.02ipm accel=10 stepPulse=2 DirPulse=2
Y: 12700 115.02ipm accel=10 stepPulse=2 DirPulse=2
Z: 12700 64.98ipm accel=7 stepPulse=2 DirPulse=2

I, too, had trouble with Z occasionally buzz-stalling when run faster than the numbers above.

I've been running my NM135 for a while with the following motor tuning, with no problems:

X: 12700 115.02ipm accel=10 stepPulse=2 DirPulse=2
Y: 12700 115.02ipm accel=10 stepPulse=2 DirPulse=2
Z: 12700 64.98ipm accel=7 stepPulse=2 DirPulse=2

I, too, had trouble with Z occasionally buzz-stalling when run faster than the numbers above.

yeah, the Z on the 135 has limits being dovetail. you have to tighten the gibs alot to remove play, so you devote alot of your torque to overcoming that.

the 200 has linear rails on the Z, so i can go as fast as the motor... which isnt very aparently. still not bad though at 150.

the OP sounds like hes got something else wrong though.