Vexta Stepper problem

[David Bean]

I'm running a PRT 60x120. It has Vexta A6497-9412KTG motors on the y axis. One of the motors has movement vertically as the pinion moves. It looks almost like the shaft is bent. Has anyone ever experienced this? Could it be an alignment issue? Vexta does not have a replacement for this motor, is there a direct replacement from another manufacturer that will work with the other Vexta y-axis motor.

Thanks in advance for the info. The knowledge posted by the users of this forum blows me away.

[Brady Watson]

David,
The only way to know for sure if the shaft is bent (very rare & unlikely) is to remove the Y motor and move it under power. It is hard to really see what is going on with the motor still attached. A dial indicator on the shaft will quickly tell you if it is bent or not.

You'll need a 9/16" deep socket, 4" extension and ratchet + a 9/16" box wrench to pull the motor. It's 3.5 turns on the buckle when you put it back on.

Make sure there isn't swarf/chips jammed in the rack and inspect the pinion for wear & check for looseness.

You won't find a replacement from Oriental. It is a ShopBot specific number & a replacement if required is available directly from SB.

-B

[bleeth]

PRT's only came with 1 y motor (unless you have 2 separate z's). Normal PRT's have 2 x motors, 1 y, and 1 z. All Shopbot motors are customized to SB specs so there is no such thing as an off the shelf motor that is identical. SB may have some available. You need to call them. There also may be some people around who have upgraded their motors and still own the old ones.
If you have 2 motors on 1 y carriage then the previous owner customized it. It's possible that it is an alignment issue but due to the way they were made it is unlikely. You can always pull the motor, clamp it down, and make it turn while you check the trueness of the shaft.
There are a few PRT owners who are discussing changing their motors out for new ones right now (See the thread on belt drive gear boxes) and it is possible that there will be a "glut" of used motors available soon!

[David Bean]

Thanks for the replies guys. I am going to remove the motor this morning and further inspect it. Are there any issues with using the controller to power the motor for inspection with it not under any load?

[David Bean]

Took the motor off this morning and saw that the angle iron that holds the motor to the chassis was slightly bent which is throwing off the alignment and wearing the pinion gear. Is this a special gear specifically from Shopbot or will i be able to find it locally. Does anyone have the specifics.

Its 25 teeth,.5 shft dia., about 1.4 overall dia., about .76 overall width.

[Brady Watson]

It's easier to get them right from SB...

They are 20 deg pitch, 20 deg DPA.

-B

[David Bean]

Thanks Brady. I'm going to order 4 new from Shopbot. I am trying to find one locally so i can get my machine back to work today. Excellant article on ramping values. Very informative.