I finally melted that flaky Y motor

My Y axis motor has done wierd things intermittantly ever since I got it. It was used, so no suprise there, but it finally gave up the ghost last night. I have a spare one and a few more on the way, so as soon as I can extract the old one I’ll be good to go, but it failed in a wierd manner so I figure I should mention what happened in case anyone else runs into the same issue and does a search.

Basically, the motor has failed in such a way that telling it to move 50mm at 100% speed results in it moving 100mm at 200% speed. I’ve pulled the Y motor and put it on the X controller, and it does the same thing on X, and the X motor works fine on the Y controller, so I know it isn’t the board. No idea what actually did fail in the motor. I’m guessing that it’s somewhere in the encoder itself, there are four wires going to the motor, maybe two of them are shorted together and doubling the voltage going to the motor now? I dunno. At any rate, it is an old motor and I’ve used it fairly hard, so it’s not even remotely close to being under warranty. Still seems like an unusual failure mode though. I’ll take it apart once I get it off the frame and see what it is actually doing.

Well, Now that I have the thing apart, I’m no more informed as to why it failed than I was when I started. If there is an encoder in there, it’s somewhere in the front section glued in. The coils look a bit toasty in one spot, but they still aren’t touching. The rear shaft bearing is definitly dead, it makes a nice grindy motion when i try and spin it, so there was some heat there. What actually failed though electrically, no clue.

New motor is in (Now with removable fittings! yay!) and it seems to be working fine. So, /shrug?

Edit: I inadvertantly discovered what the actual problem was. Apperently on the New motor the red wire wasn’t quite all the way seated in the plastic fitting for the disconnect. It worked its way out, and poof, instant double speed double travel on Y again. Sure enough, there is a break in the red wire on the old motor. So whatever that particular wire actually does is what causes the issue. If you see this in your machine, check the wires.

Thanks for the info!

I don’t think that stepper motors have internal encoders.