Y Axis Idle bearing - Belt Slipping down

[markwisniowski]

I'm having an issue where the belt keeps slipping down off of the Y Axis idle bearings on the back of the machine. I've tried rotating the screw to try to fix canting but it doesn't seem to work since it's under tension from the belt.

Is my belt too loose? Any tips on keeping the bearings perfectly horizontal?

[aforww]

Feb 23, 2017 3:57:07 GMT markwisniowski said:

I'm having an issue where the belt keeps slipping down off of the Y Axis idle bearings on the back of the machine. I've tried rotating the screw to try to fix canting but it doesn't seem to work since it's under tension from the belt.

Is my belt too loose? Any tips on keeping the bearings perfectly horizontal?

I would raise the drive pulley on the motor up a little bit first. Belts want to operate in a straight line so if one end is low, the other will want to follow. If that didn't help enough, where the belts attach to the plate, try to push them up to towards the bed a bit if there's any room. Either way, the pulleys and bearings need to be close to co planar as possible.

As for the belt, there should be a decent amount of tension. You should be able to "strum" it and get the same kind of sound you would flicking a rubber band under tension.

[Derek the Admin]

Aforww provided an excellent answer. For what it's worth, a little bit of belt walk is acceptable and won't really manifest itself in the cut, but you don't want a bottom out or slip off. Now that I've told you what you already know, I'll add that if you just can not get it to get the way you need it you could go another direction and shim the bottom of that bracket that mounts it with a piece of shim stock.... or a cut up soda can for that matter. That's probably going to be an overcorrection and I'd try to check all the boxes aforww mentioned first before you throw anything else into the mix. One other thing to check is that the rear frame piece actually flushing up the the side frame pieces. For instance, if the top part of the rear frame piece wasn't flush against the side pieces, but the bottom of the rear frame piece was, you would see the behavior you have in the video. Not to say that's it, but that part can contribute.

[markwisniowski]

Alright got it fixed last night. I tried lifting the drive gear on the motor and it helped for a short time but the belt after some time slid down again.

I noticed from the bottom that the belt wasn't riding parallel so I loosened the angle bracket holding the idle bearing down about 5mm and it aligned everything up!

[aforww]

Feb 24, 2017 13:24:38 GMT markwisniowski said:

Alright got it fixed last night. I tried lifting the drive gear on the motor and it helped for a short time but the belt after some time slid down again.

I noticed from the bottom that the belt wasn't riding parallel so I loosened the angle bracket holding the idle bearing down about 5mm and it aligned everything up!

Glad you got it worked out.

[gkr]

I have the same issue as well. Thanks for the workarounds. I've had to implement both.

(1) I had to raise the X-axis idler bearing bracket by a few mm, while adjusting the X-axis pulley appropriately, since the belt tended to raise up on the idler bearing. I also had to adjust the position of belt at the zip-tied holes ever so slightly.

(2) On the Y-axis it was kinda of the reverse (exactly as documented on this thread). I had to lower the Y-axis idler bearing bracket by a few mm, but there isn't much room to go lower anymore. I wish there was one more mm. I also tweaked the positioning height of the Y-axis pulley.

I ran a few small plotting tests, and it seemed to hold up. The X-axis appears to have been corrected better than the Y-axis.

Question: If flanged bearings would have been used on the idler bearings, wouldn't that have been better to keep the belt in place?

Just a thought. Let me know what you guys think?

Thanks for all of your input and insights.

Regards.

[gkr]

Update regarding this issue...

I was able to mostly resolve the X-axis idler bearing issue as documented above.

However, the Y-axis belt kept slipping down despite my best efforts.

Hence, I am trying a new quick and easy (possible) solution, as documented in this post:

millrightcnc.proboards.com/thread/254/m3-cnc-build-first-plots?page=1&scrollTo=2371#

So far it appears to help in my situation. Please note that this workaround will only help if the belt tends to slip down.

Hoping that it helps others who are having this issue as well.

Regards.