[Nefastor]

Hi all,

I have a small technical question I haven’t been able to answer satisfactorily by Googling :

Suppose I want to drive a milling machine axis using two ballscrews, each with its own stepper motor. Do I need two stepper motor controllers, or can I just wire both motors to the same controller ?

The motors would of course by identical. The ones I have in mind draw 2A, and I have a 5A-capable controller on hand, but I’ve never heard of anyone driving two motors from one controller. Do you know of any reason I shouldn’t ?

My basis for believing this could work is that some bipolar motors have four stator windings instead of 2, and you can wire them in parallel. I’d be doing the same thing except the windings wouldn’t all be in the same motor.

My reason for trying to do this isn't so much saving money (though I wouldn't spit on that ) it has more to do with safety : I wouldn't want a computer bug to cause one motor to move without the other, as this could destroy my machine tool. By wiring both motors to the same controller, I suppose the only way this accident could happen would be if one of the motors failed... but if it did, the other one would get all the current and die too, so it'd be "safe"

What do you think ?

Thanks for your time !

Jean

[jalessi]

Jean,

Wire the two stepper motors in parallel.

The driver may need to be fairly robust in order to supply double the current.

Jeff...

[Nefastor]

I'm using a CW230 controller, or whatever it's called in your part of the world (I'm from France). It's one of those ACME, made-in-china controllers. It has dip switches so you can set up the current limit from 2 to 5 amps by 0.5A increments, and I've used some to control NEMA-34 beasts with 6.5 N.m torque (4 amps). Barely made it warm to the touch, with no fan on it.

The steppers I would use in a dual-motor configuration are NEMA-23 units with 400 steps. I love those. I use them in 1/5th microstepping mode and that gives me extremely smooth movement. And 400-step motors have twice the torque due to the smaller steps. Also makes them harder to stall at high speed, though they do need a really quick controller.

I'll try to wire two to the same controller and see how it goes. What I am most worried about is that one motor's winding will have a lower resistance than the other motor's, which would cause it to draw more current, maybe to the point of killing it.

I'm optimistic however, because the CW230 can be setup to halve the current when no pulses are sent to the step input.

I'll keep you posted : I think this setup has some interesting advantages, like I said especially for mechanical safety. I'd much rather lose a couple of 40-bucks steppers than bend my mill !!!

Jean