Re: Tormach stepper motors

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@...> wrote:

>
> rocketscientistnate wrote:
> I'm running Gecko 201's with the
> > original steppers, and I thinking that if I trade those out for some
> > new steppers it will probably fix it. I'm looking at some from
> > Tormach, I understand their mills are pretty good so maybe their

motors

> > are too. First I want to make sure the 1200 oz-in is the right size,
> > maybe the 640 oz-in for the z and a axes.
>
> Why do you believe changing the motors will stop it from losing
> steps? Does it do this only on occasion or frequently? Do you
> hear obvious stalls of the motors, or is the positioning just
> creeping over time?
>
> What software are you running? What type of interface do you
> have between the parallel port and the Gecko drives?
>
> There are well-known problems between certain programs, certain
> settings and certain vintages of Gecko drives that misinterpret
> step command right around direction changes. The older Gecko
> 210 drives with the pulse multipliers are the most finicky, but
> you can get almost any Gecko 201 to do the same (lose a step
> often during axis reversal) if the timing between the step
> pulses and the direction signal is not right. I wouldn't lay
> out serious money on new motors until I was sure this problem
> was ruled out.
>
> Jon
>

Jon,
The problem with the old BOSS machines is they big 42 motors are not
suited to the Gecko drives.
They are just too big and require too much power, typically 9 amps to
be reliable.

Most were only 850 to 900 oz/in and with time probably a lot less than
that. The modern 34's can use less power, have faster acceleration and
be far more reliable.

As you say early to mid release Gecko's are the worse. I can get these
to run reliably with the Chinese drives from Keeling but not Gecko's.

I have had a Divisionmaster indexer driving a big Hoffman dividing
head via a 201 Gecko and it has been loosing steps for a while.
Last week I needed some accurate splines so tested the head by setting
to 10 divisions and doing 5 rotations. At the end of the 5 rotations I
was 1/2 a hole [ 5mm ] off the mark.

Just swapping the driver to the Chinese 7.9 amp one and retesting gave
me no visable error at 10 rotations.

I also have a BOSS going thru refit and that is having 1100 oz/in
motors and the Chinese drives fitted.

John S.