Stepper rear cover

[Hydraumind]

Is there a way to machine the rear cover of the governer motor, like the one used on komatsu excavator. In fact, there is a radial play between the cover and the outer of the bearing and thus the rotor is touching the stator leading to step out error and RPM oscillating couple of time before stabilizing. Is it better to change the hole unit?

 

[digger doug]

Your saying the bearing fit is o.k. and that the outer rabbet fit that locates the cover on the stator is loose ?

Machining removes material, making the fit "looser", I would try some shim stock, cut with scissors, and carefully
wrapped around the rabbet fit.

I have repaired similar parts (3' across though) by rolling the rabbet fit with a roller tool, then re-cutting.

Your cover looks like pot metal though so no rolling it down, could try a build up of epoxy and then remachine.

what do the other (2) parts involved look like ?
1. the bearing race
2. the stator frame

 

[Hydraumind]

These are two photos of the same rear cover taken in two different angle.
In fact the center hole where the bearing fit shows ovality. And the outer rabbet fit that locates the cover on the stator is Ok on the rear and front cover.
I changed the bearings of the front and rear cover and the rotor still touching the stator.
All I found is 20 to 30 micron ovality on the cover but I think this is big enough to make rotor touching the stator because the clearance between statot and rotor on stepper motor is really small, No?
I will try to post a photo of the whole motor disassembled

 

[digger doug]

30 micron = .0012 or so says the online convertor.

.0012 out of round (how did you measure it ?)

Looks like your really going to need to completely measure the stator fits (both ends please)
and the end bells stator rabbet sizes, as well as concentricity to the bearing bore.

 

[Hydraumind]

I am using inside micrometer that measure this size, with 2 micron increments and precision. It is like the cylinder liner bore gauge but used for small sizes, anyway even without measuring it is really obvious that the rotor is touching stator. I'm gonna use aftermarket complete assembly motor even if it doesn't last longer

 

[lantraxco]

Microns or millimeters?

 

[digger doug]

Measuring the bore and the rabbet fit is a first step, now to see if they are still concentric.

BTW how much is the gap between the rotor and stator ?

 

[Hydraumind]

Microns