Re: [CAD_CAM_EDM_DRO] Re: Stepper motor connection

According to Mariss of Geckodrives, and based on some anecdotal
experience, for (very) slow movements this may work.
In the early days, many tried it, and this was not seen as a practical
solution.

After some relatively low corner speed is reached, around 300 rpm or so
iirc, one or both will very likely start to lose steps.
This has to do, iirc, with the fysical construction of the steppers.

As their electrical construction and magnetic performance is not
absolutely identical, they will have different amounts of back emf.
Has to do with back emf and reluctance I think.
So they have different "magnetic and electrical inertia" to put it in
one way. After a corner speed they start to fight each other.

So, the accepted lore is that it does not work, where you are looking for
1. reasonable performance as one might get out of a modern stepper
2. and a modern microstepping driver
Using a bipolar parallel square motor and driving at the typical,
normal, 25-100 khz speeds typically used today.

Mariss discusses it here, in an older post.

So, the short A. is no, it wont work well,
and for low speeds, maybe, depending.

I suspect that for a simpler driver (maybe half step or full step) and
for low speeds, in some cases it will work and in some cases it wont.
Your driver, windings, voltage, rpm, acc profile and motors and
electrical setup all affect it.

> Now you got my curiosity aroused. What's the mechanical reason?
> Isn't it simply one step per pulse. Are you saying one or both might
> miss a step?
> My application could be described as 'gross movement' however it still
> needs to maintain step accuracy. It will move from one point to
> another with little load change. I will try to balance the arms so it
> has similar load both directions.
>
> As for connection, I would think series would keep the current through
> both motors the same hence 'same torque'.
>

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