skipping steps with old and new control board.

[shawncnc]

Hi, i have a little desktop cnc. It has nema 17 motors (2.1 oms on both wire pairs) cheap 3 axis grbl controller no limits with ugs running it and all axis move very nice and smooth. It is skipping steps when running a gcode file like it has 0 power but when I jog it even with speed and acceleration high it has a lot of power even if i push on it when moving, the holding power is really high also. $1 is set to 255 so it is holding. I have set the driver current to 690mv, I got a new control board and tried that... no change, done every youtube setup tutorial, and I shielded my spindle wires. The motors and drivers are not much above room temp.

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[shawncnc]

I have also tryed several different power supplies.

[awerby]

Have you tried lowering the acceleration on the axes that are faulting?

[shawncnc]

yes I have gone slower and faster in case it was resonance. In both acceleration and top speed.

[dazp1976]

If they're only room temp can you up the current settings on drivers?. Or even up the voltage of your power supplies?.

[awerby]

You probably need to cut the acceleration more radically than you've done. Cut it in half, and if that doesn't fix anything, cut it in half again. If that doesn't work, you've got to look at the whole machine and figure out what's hanging it up. I don't know if you're running ball screws, rack and pinion, or hardware store all-thread, or what you're using for linear slides - profile rails, round rails, dovetailed slides or what. You don't say what inductance those motors have or how much voltage you're feeding them. But any loss of mechanical advantage, increase in friction, binding, or burst of speed can cause lost steps, especially during cutting, if your motors are as marginal as they seem. NEMA 17 motors are okay for small 3D printers, but work less well for CNC machines that need enough power to overcome cutting forces. You might think about upgrading to low-inductance NEMA 23s.