RE: [CAD_CAM_EDM_DRO] Heck of a time tuning servo motors.

A shoptask should have a 3:1 ratio timing pulley set up with a 14XL037
timing belt pulley on the motor.
Next, it sounds like you have either or both your gibbs and your
backlash is set too tight. The hand wheels on the XY axis must turn
freely with no apparent drag.
Dan

-----Original Message-----
From: Erik Reikes [mailto:ereikes@...]
Sent: Wednesday, October 09, 2002 8:38 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Heck of a time tuning servo motors.

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


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