I am in the process of building a MPCNC, purchased my steppers from V1 and doing the build have an issue with the stepper motor shaft being too short. I searched the forum and found another post that had the same problem, they resolved with plenty of loctite, but there does not appear to be enough grub screw contact with shaft to make this feasible for me.
Attempting to assemble with pulley grub screws on outside, the shaft appears to be about 3mm-3.5mm short - only about 1/2 of the grub screw would contact shaft. With proper drive pulley alignment, Figure 2 shows grub screw/shaft and issue with insufficient grub screw contact.
(New user is only allowed one image to be uploaded… so Figures 1, 3 & 4 are deleted).
Cannot flip pulley around and get pulley close enough to align - grub screws hits the end of the flat and will not slide far enough to align.
Purchased steppers through V1. Shaft extends ~20.8mm above mounting face and ~19.8mm above raised portion of the face. Flat on shaft is ~14.8mm total length. Looks like the spec on the NEMA17 is 23-24mm shaft length.
Any thoughts or comments are appreciated.
Thanks,
Mike
From the one picture it does look like you have another 2mm you can push the pulley on the shaft. My second grub screw also only screwed down half of the stepper, but was never an issue.
Ahhhhh crap let me double check. I slipped in some higher power steppers, The shafts were the same, let me very the length and see if any of the others have short shafts.
The shaft is a touch short. The good thing is flipping the pulley over and leaving the slightest gap on the stepper should just leave enough room for the belt on the idlers.
That is such a bummer, I have been working for months to get those steppers. I am currently waiting on the custom 5 pack box design approval. Back to square one.
That works as well, but the pulleys and idlers are actually a few mm wider than the belt so the offset is still within spec. I just put one together to check, looks good.
I really want these steppers so I am going to keep going with them. I need to add a picture to the docs for this section. All the rest of the machines they fit fine.
It sounds like the only solution is to either get steppers with a longer shaft or shim.
Shimming doesn’t appear to be a great option - The down side of the sim is that there does not appear be enough clearance to tighten the grub screws without removing the stepper motor from the truck. I backed out the mounting screws so they just barely engage and pushed the stepper to simulate shim position, but can’t access grub screws.
If going the angle grinder route, I’ve seen a suggestion to put some sort of sealer (blu-tack, putty, etc.) around the base of the shaft to keep grinding dust from getting in the motor bearings.
Hi Ryan -
Let’s replace the 4 units, keep the Z-axis using one of the steppers I have. Good suggestion.
Thanks for your support - much appreciated,
-Mike
