RE: [CAD_CAM_EDM_DRO] Servo motor question

I would certainly stick with the servos. They
never slip steps!

As far as direct drive...that is fine as long as you don't
exceed the continuous current rating of the motor. More typically
with a 5 TPI screw servos are timing belt reduced 2 or 3 times.
Direct drive would give you as much as 360 ipm. I doubt you need anything
like that so a 2:1 reduction would double your torque
for heavy cuts and still allow 180 ipm. Effective rotor inertia
would be quadrupled- but probably no problem at all with that.

Looks like you may have 750 in oz peak and about half that
continuous. Might be enough if the gibbs are not really tight.

Look up the other specs on your motor if you can. If they
are not available I can come up with a pretty close estimate
based on a physical description and some simple tests.

At that point you can measure the current with say a 0.1 ohm
shunt and a voltmeter. The G340 may also have a current monitor output
that you can use without a shunt.

That can be compared to the continuous current rating of the motor.

Les

Leslie M.Watts
L M Watts Furniture
Tiger Georgia

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-----Original Message-----
From: harry32002001 [mailto:harry320@...]
Sent: Tuesday, June 15, 2004 2:28 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Servo motor question


Hi Group,

I have a BP Series 1 that had a Boss 5 control driving the big old
finned stepper motors. I switched out the steppers with some extra
servomotors and share the drive system that I use for my plasma.
Here's my question for you motor experts, would it be a better match
to use the steppers as opposed to the servos? The reason I ask is
the feed speeds I'm running I.E. 20IPM with a .200 ballscrew and a
1/1 on motor have the servo running at 100RPM. I'm I hurting the
motors and will they last at this speed? They seem to work fine.
Reading the board started me thinking about this, as I read steppers
have low speed torque and servos like higher RPMs. If would seem
steppers would be more appropriate for this speed range. However the
Centroid conversion uses a 1/1 ratio with servos! Maybe they work
with brute power. The servos I using have a Kt 37.5 Oz –in/A,
drivers are G340. Any suggestion or info would be appreciated.
Thanks Harry