Re: [CAD_CAM_EDM_DRO] Re: Question 3Axis(w/4 step motors) machine

Right. It's trouble. Because the driver can only set the total
current- but that current is divided up between the motors and the
picture becomes somewhat complicated as to what current each motor
gets. When not moving, it's pretty much Ohm's Law. But at higher
speeds there will probably be an interaction that will cause one motor
to get too much current and the other too little at some points in time,
and that would contribute to a motor stall.

You can get two drivers and connect the two step/dir wires in parallel
so they step together. However, then it becomes impossible to adjust
electronically if for some reason racking occurs (one motor stalls, or a
screw was turned when it was off). But whatever, it's probably easier
to power off the drivers and fix it by feel with a handwheel anyways.

Danny

CNC 6-axis Deisgns wrote:

> Not at all !
> This is a well-known common question, and will not work except very
> poorly at very low speeds, under 100 rpm.
>
> There are multiple technical explanations about this, some from Mariss
> at geckodrives, who has designed and sold over .5 million stepper drives.
> You need 1 driver / 1 stepper.
>
> IIRC, the reasons have to do with the very small mechanical/electrical
> differences within 2 motors.
> We are talking here about microseconds, and differences of 0.001 degrees
> of turn of the motor, or less, which are enough to make it work very poorly.
> The 2 motors will fight each other, leading to heating, resonance,
> vibration and very poor performance.
>
>
>> Depending upon the ampage of the motors and the drive current that you
>> have from a single axis, you could connect the motors in parallel. I
>> see no reason not to do it, especially if you have trouble driving the
>> two axis in slave mode.....
>> Do test that the motor directions are correct/compatible before
>> mechanically linking them of course!
>> I have read somewhere that it is quite common to do this, but don't
>> ask me where that was!!!
>> Greetings from
>>
>> Andy Mathison
>>
>>
>>
>>
>
>
>
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