Seems like there are many reasons but in my case it was because the metal spindle that comes out of the motor (the part that the belt wraps over) was too tight. In other words, it’s as if the spindle had been hammered hard into the motor body and the grub screws then tightened. So when I removed the motor and tried to spin the spindle by hand it was very stiff.
All I did was loosen the grub screws and tap out the spindle a tiny amount (maybe 1/4 mm). Voila, super smooth and no more sticking.
How did you "tap out the spindle a tiny amount "
Or was it very loose on the drive shaft once the grub screws were loosened>
Thanks, Bill
The spindle is extremely tight on the shaft (even without the grub screws). So I put an adjustable spanner round the spindle and then tapped gently with a hammer on the motor casing. You can see from the photo that the gap is hardly noticeable but it was enough to free it.
There was another thread where the timing pulley was slipping when the motor turned.
It seemed in that case that the timing pulley was too far down the motor - like it is with you - and that the motor’s shaft had this sort of limitation to the flat face:
That is, the grub screw is gripping a circular surface rather than the flat face.
Do you know if your grub screw is against a flat face or the round shaft?
Looks like that pulley might be better off if it was flipped.
I don’t for the simple reason that I cannot get the timing pulley off the shaft. I don’t have a separator tool (sort of reverse pliers) so I tapped the motor away from the pulley with a hammer but don’t want to damage the casing. Both grubs are completely out so it must be an extremely tight fit.
One thing to beware of when fighting with these pulleys is that they are generally not machined from a single billet. Frequently the toothed bit is machined from rod then cut to length and the two ends press fitted onto it. It’s relatively easy to split, bend or completely remove the thin end flange by pushing or pulling on it. I have found it useful to have a spare before attacking a stuck pulley…
A puller would be the ideal way to go about removing them as then you’re applying the pressure cleanly to the end of the motor shaft and not relying on the stepper motor bearings to resist the force if it’s really stuck.
My advice is to contact support and get a proper motor assembly. That one may now be damaged in ways that you won’t find out until you’re out of warranty help.
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