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bearing for X motor slides over to pulley
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Description

I've seen a couple times now where the recess for the bearing for the X motor is too loose and the bearing can slide back and forth in the Y direction and it causes drag on the X axis. The ones I've had before I was able to fix by taking it apart and reseating the bearing and it would stay in place, but this one won't stay in place and it gets sucked into the X pulley every time causing too much drag.
Its hard to see in the pic but the bearing is right u against the pulley and there is a bout a 1mm gap between the bearing and the plastic.

Event Timeline

robert created this task.Jul 16 2019, 6:52 AM
robert triaged this task as Normal priority.
robert created this object with edit policy "LulzBot Hardware Products (Project)".
robert raised the priority of this task from Normal to High.Jul 16 2019, 6:56 AM
west added a comment.Jul 16 2019, 7:52 AM

We could add a M5 washer between the pulley and bearing. this would make it so the pulley wouldnt rub on the inner ring and outer ring of the bearing, just the inner.

logan added a comment.Jul 16 2019, 8:32 AM

Well, it'll work for keeping the bearing from rubbing on the pulley but doesn't keep the bearing in the slot. Installed on this unit I have, the bearing just kinda floats around in that spot and once you put belt tension on it, it kinda tilts

Will at finals just had one that was really loose and the bearing would just slide out of the pocket and rub the pulley like it was magnetized to it.

we could likely modify the printed part to hold the bearing better. Just adding some material around the bearing may help. the bearing pocket on quiver is 4.5mm deep and the one on redgum is 3.25mm deep.
we could also potentially make it to where the bearing clicks into the part, but this may be problematic due to the variance of printed parts we often see

west added a comment.Jul 18 2019, 8:17 AM

I think what we are seeing is already variance in printed parts

we could add an insert and setscrew that holds the bearing in place

logan added a comment.Jul 18 2019, 8:40 AM

We could pull a sample of these parts and see how well the bearing sits there, because I think these are generally running on the loose side but would like to confirm before we make a printed part adjustment. There seems to be very little engagement between the motor shaft and the bearing though. Here is a photo I snapped showing the scoring that resulted from the bearing photographed above:

logan added a comment.Jul 18 2019, 8:42 AM

My suggestions would be to make the motor mount flange a bit thinner, and deepen and tighten the bearing pocket.

west added a comment.Jul 18 2019, 9:00 AM

We cant make the flange thinner. Its as thick as it is so the screws can be below the urface- far enough away from the smooth rod. Before when the flange was closer we would fail esd when zapping the rod because the rod would discharge to the screw, then to the motor and finally, to the bard and cause a reset

logan added a comment.Jul 18 2019, 9:01 AM

So what you're saying is we'd have to shorten the fastener in order to maintain that distance?

west added a comment.Jul 18 2019, 12:51 PM

Potentially since the screws might bottom out in the motor.

west added a comment.Jul 18 2019, 12:54 PM

We could make the bearing retaining piece stick out a little more to better encase the bearing

logan added a comment.Jul 18 2019, 1:07 PM

What amount of tolerance do we currently have on the diameter vs Quiver? Could that be tightened a tad also?

adam added a comment.Jul 22 2019, 9:36 AM

@west @logan how many of these do we need to test? Do we need to fully install them for testing or just fit test a bunch of the bearings?

I installed one on the redgum beta at my desk. I don't see much improvement from this change. Still pretty loose in that pocket. Before installing the X-Motor End to the machine, I notice while mounting the motor that there is now more space between the pulley and the bearing if the bearing is fully seated.


I could probably fit 2 washers in there now. If you put a washer on the pulley and then a bearing on top and put that all in the printed part, there is still space behind the bearing between it and the printed part.
Installed on the machine with belt tension applied, I can see the bearing move slightly as I move the X-Axis side to side.


I would not advise moving forward with this version.

adam assigned this task to west.Jul 22 2019, 11:30 AM
west added a comment.Jul 22 2019, 11:33 AM

Interesting that there is more space since I didnt modify anything related to the depth of the original part. I just padded a little onto the face to reach the full 5mm

Yeah I made sure not to move the pulley or anything when I moved it from one part to the other. With a washer installed between I'm getting a measurement of ~0.8mm between the back of the bearing and the part, so maybe move that back face forward like 0.6mm and we add the washer?

west added a comment.Jul 22 2019, 11:40 AM

Will the washer work? If so sounds good to me

I think the washer might be fine but reduces the amount of engagement the motor shaft has with the bearing. Ideally I think we should not use the washer, move the bearing forward so it is 0.5mm from the pulley, and make it a tighter fit in the hole. I'm not sure how far the bearing needs to come forward, I'd have to do a FreeCAD assembly to make sure.

west added a comment.Jul 22 2019, 11:50 AM

@logan pushed one with a slightly smaller dia and the back padded 0.6mm

adam added a comment.Jul 22 2019, 11:52 AM

Can we check with a selection of other bearings just to rule out bearing diameter variation and be sure that it's printed part variation?

@adam I don't think that's necessary, its a rather loose fit as is and should be a tighter press-fit. With this hole being printed in Z we have less opportunity for the hole to be out of round like we see for those printed in X/Y so I think tightening that diameter is a pretty safe move.

west added a comment.Jul 22 2019, 12:00 PM

the tolerance on the bearing is much tighter that the tolerance on the printed part. So its a printed part thing

adam added a comment.EditedJul 22 2019, 12:01 PM

sounds good - I just didn't want to be in a situation where we modify the printed part to (unknowingly) fit the most out-of-tolerance example we have and end up causing ourselves more issues.

logan added a comment.Jul 23 2019, 9:48 AM

The latest version is great. The bearing snaps in nice and stays in place. Spacing is perfect to allow for the top of the pulleys not always being flat so no additional washer is needed. Good to proceed with this version

west moved this task from Report Issues Here to Needs Review on the Redgum board.Jul 23 2019, 9:50 AM
west reassigned this task from west to Steven.Jul 29 2019, 7:44 AM
Steven closed this task as Resolved.Jul 30 2019, 3:18 PM
Steven added a subscriber: david.hall.

This is now merged into master @david.hall @cmerot @adam