Re: Stepper Motor Resonance ?

["Tim & Heather Smith" <thdsmith-at-bigpond.com>]

Thanks for the info on the dampers Jon. I will look into that

I actually had the motors set up with a 1:2 reduction using a toothed belt.
As a result of where I mounted it all with the larger pulley on the
leadscrew under the table, I couldn't go any bigger with it, and the motor
pulley is already as small as I can go, so that was my max reduction I could
get with a belt.

I am still using the belt drive after the gearbox. (ie. motor thru gearbox -at-
1:2.4 using gears, then belt reduction -at- 1:2).

I still have the "Y" axis running with an identical motor with only a 1:2
belt reduction, and it falls over at similar frequencies.
Actually the motors fail at the same point even if not connected to the
leadscrews, with or with out the gearboxes on them.

The reason I was doing this was to increase the torque, as the motors are a
bit small (Superior Electric M111-fd12)at 625 oz/in (I looked it up this
time). Looking at the specs for these motors,and the problem I am having
now, if I was to build up a Bipolar driver they would have 850 oz/in and
this may be enough with out the gearboxes..... Dunno....

thanks for the feedback.

Tim Smith

p.s. Does anyone know of a source for large steppers in Australia?

>>
>>
>GEARboxes?  With real gears in them?  You should use toothed belts.
> They don't have
>backlash, and the slight stretching of the rubber can absorb some of the
>vibrational energy.
>
>>
>If your gearboxes have backlash equal to even 1/2 of a step, they will
>severely exacerbate any
>resonance problems.  I suspect your backlash is less than 4 steps, or
>your system would go completely
>crazy even at low speeds.  Anyway, if you want to keep the gearboxes,
>you will need to add
>dampers.