Re: [CAD_CAM_EDM_DRO] Stepper Motor Axial Travel under compression

Most stepper motors have axial play that in part is for expansion as the motor get hot. The growth is always away from the mounting face. Here is what I do. Buy a torrington needle thrust bearing NTA411 and two TRA 411 thrust washers for each motors. The bearings are cheap at under $2 each. These are availble at any bearing supply store or on line. Lubricate the needle bearing and place it between two thrust washers and place this assembly over the .250" shaft. Then slide your coupling down until it is snug against the bearing which is now snug against the motor flange. You will now have zero end play. The internal bearing will prevent movement in one direction and the needle thrust bearing will stop movement in the other but will allow for expansion.
Dan Mauch
economical 3D scanner software and kits
low cost stepper and servo motors.
cases for Gecko drives
kits and assembled 3-4 axis drives
www.camtronics-cnc.com
www.seanet.com/~dmauch

----- Original Message -----
From: gldrpilot
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Sunday, March 09, 2008 12:13 AM
Subject: [CAD_CAM_EDM_DRO] Stepper Motor Axial Travel under compression


I recently purchase some stepper motors to build a 4 axis foam cutter
CNC. My intent was to directly drive the lead screws via a coupler
interface between the stepper motor and the lead screw. On examination
of the NEM23 type stepper motors, I notice that if you press on the
motor shaft with some moderate pressure, there is some significant
axial travel under compression. Motors were originally outfitted with
a pully drive pinion.

Couple of questions: 1) Is this axial play a normal stepper motor
design feature? 2) How have other folks isolated the lead screw so as
to avoid this axial play under load?

DC





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