Ok so let me start with I have a bad spindle (I’m not sure why it would cause this but I guess it could and it should be said the nice people at inventables are sending me a new one) when I go to zero out the machine everything is fine until the spindle starts spinning. I flip the switch on the spindle still cool even though the spindle is not spinning. Then I give the spindle a little a twist it starts going and all the steppers start moving .001 - .01 at a time randomly. I have already triple checked my wiring, all good there. It happens no matter what controller I’m using. Any advice?
my advice would be to replace the spindle with the one they are sending you
Any idea what in the spindle would activate the steppers?
I think its some kind of electrical interference. Im having an issue with mine where it loses steps and its looking like the spindle is causing it.
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There is another thread on here describing this issue, spindle is spun manually with out power and the steppers twitch. Something to do with the spindle failing and feeding back through the circuitry as I recall.
Oh. That doesn’t sound good.
I had the same problem when my 2nd spindle started it’s death spiral from super prolonged use 
At any rate, the pwm motor driver is not isolated so you could get noise and various other strange things being injected back into the grbl shield when your spindle is having issues.
Try this:
disconnect the yellow wire
turn the spindle switch to the on position
watch and listen to your step motors and see if they still twitch and move about
I’m not setup for logic control this was all through the on / off
Any inductive load like a motor or a relay sends reverse voltage spikes of up to 4x the coil voltage back through your system when power is applied or removed. Because the motor driver is not isolated this can be a problem - especially as spindles are on the fritz because their power is being applied intermittently as bad spots on the armature (or self destructing brushes in my case) are encountered. Flyback/snubber diodes shouldprevent the reverse flow of electricity - I’d be surprised if they are not employed on the board. These high, reverse voltage pikes also travel along the spindle wire which runs along side your stepper motor wires which can create a ghost current in your stepper motors. This could also cause the jumping.
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Sooooo. . . Don’t run it with a bad spindle then? Lol. Thanks for the info
I installed second 24V power supply for Spindle, used that existing 24V power output to Solid State relay for spindle start every time job starts. No hiccups what so ever. Only problem is Spindle speed, I’m adjusting that from new Power Supply’s pot lowering or raising power. Not a big deal.
i got a new spindle from inventables so far so good
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