Re: Heck of a time tuning servo motors.

Hi, are those real servo motors or industrial DC motors with encoders
attached? There are differences in rotor structure that may cause
cogging at low voltages. Maybe your motors just get stuck in a cog
when they get somewhat close to a commanded position. Test them by
running them unloaded from a 1 or 2 volt source and see if you can
detect any cogging. Further belt reduction would decrease this effect.
Dean

--- In CAD_CAM_EDM_DRO@y..., "Erik Reikes" <ereikes@r...> wrote:
> So I've finally got my motors mounted to my machine and I'm having a
> heck of a time getting them to operate properly.
>
> The basic problem is the motors seem to stick as they slow down and
> pull huge amounts of current (greater than the 10amps I can see on my
> meter). Every so often they will stop in this state and just sit
> there pulling a ton of current. This of course eventually causes the
> fuses to blow.
>
> I'm getting the sneaking suspicion that my motors just don't have
> enough torque for this application. So they slow down to where they
> should be stopping and just stick there stalled unable to move the
> final last few clicks to get to their commanded position.
>
> Let me run down the specs of everything I've got so if there are any
> glaring errors someone can point out the component that is completely
> wrong.
>
> I'm retrofitting a shoptask 3-1 machine with regular acme lead
> screws. They are 10TPI leadscrews and I have a 2-1 belt reduction to
> the servo.
>
> I'm running G320 gecko servo drive units. These are powered by a CAM
> tronics 36V 25Amp supply.
>
> I've been using master5 to command the geckos.
>
> The servo drives I'm using are Leeson PMDC motors with 100 line
> USDigital encoders attached. I don't have a torque spec on the
> motors and can't find it anywhere on the Leeson sight, but here is
> what I do know : They are labelled 1/8HP, 24VDC, 5.7A, 3300RPM
> motors. They have 3/8" shafts and are labelled model # cm31d33nz1b
>
> I know that I am running 24VDC motors at 36VDC, but I figured for my
> likely duty cycle it would be ok. My real worry is the mystery
> torque amount of the motor. I had assumed based on the size of it
> and my gut feeling based on the available specs that I would be ok.
> Now I'm a bit worried. I will try to loosen up my gibs a bit and see
> if things improve, but this is not the ideal long term case for me.
>
> I supposed the next solution would be to figure a way to gear them
> down further . This would be quite difficult as they are allready at
> 2-1. 3-1 might just be possible with a really thin pulley wall.
>
> Any suggestions?
>
> -Erik Reikes