Sorry to report but I’ve got a mangled belt again. I’ll get into the details about what happened below (to the best of my knowledge) but the long and short of it is somehow the belts started winding on the take-up reel BACKWARDS. Eventually it appears the belts worked there way above the belt guards (using v8) and, at least with one belt pinched between the idler and the take-up reel.
I am sorry to report I don’t know exactly what caused the issue because I wasn’t watching it when it occurred but thought it would be worth sharing pictures in case it happens to anyone else - or the pictures help think of a new belt guard that might prevent this failure.
What I know is that I’d just successfully completed a carve (after calibrating with 70.2). Everything was looking good so I gave a command to job 500mm to the right (so I could see the complete work). When I next checked, the machine had moved up to the very top of the workspace and tensioned the TL and TR belts so tight it actually flipped on its side. At that moment I didn’t notice anything wrong (after pulling the belt pins to take off the tension). Later I did a Retract All to set it up again and ended up it like this with some of the belts jammed. (My bad for not watching closely during the Retract either).
Here are pictures of the 2 arms that reversed belt direction on the spool (notice the flat side of the belt is facing out). One belt jammed in the idler and is trashed (why do my failures always happen in the middle of the belt and not at the end? ). The other seems to have stopped before working its way into the gears and seems usable.
@bar - this is the second time I’ll need a new belt and spool. If you are ready in the store, I’m happy to order them there and pay for them vs you providing them gratis.
I’ve taken a bunch pictures from different angles as I disassembled both arms to help document what happened. Since I can only upload 5 pics per post, I’ll follow up with additional replies to include all of them.
It may be a bandaid, but I’m wondering if the belt guard could have a piece that blocks off the path for the belt to loop back in a reverse direction and force it to follow the intended path.
Additionally, how critical do you think it is to use superglue to hold the belt to the spool? Might there be an alternative that isn’t permanent so that when belts need to be replaced it doesn’t require replacing the spool?
Personally, I’d like to have extra belts on hand so that if a belt does get damaged I could swap it out and be up and running quickly.
I would suggest a future redesign that allows for the spools to be easily disassembled to allow for belt replacement. Even after we fix the mangling issue, the belts will stretch overtime and will most likely get weaker until they do eventually fail.
Interesting, I also saw similar behaviour where the TR belt was winding backwards during a retract all. The other 3 belts were retracting in the correct direction.
We’re working on getting them in the store (we just got a whole bunch of spares delivered on Friday).
Shoot an email to Anna@maslowcnc.com and we’ll get you some spares in the mail first thing tomorrow.
I’m curious to understand better what happened to make them spin backwards. I could see that happening while moving if the belt extended all the way out which could then lead to it going the other direction. I have truly no idea how it could happen during retract all because that should just drive the motors at a constant speed in.
I suspect when I did the 500mm move it actually was set to inches and tried to move 500in. I’m guessing there are no checks to stop it from trying to move outside of the workspace so that could explain how it would extend to the end of the belt and keep going and wrap it in the other direction. Like I said, I should have been watching it but wasn’t but given how I found the machine after doing the jog it definitely tried to move beyond the workspace.
Or come up with a scheme where you can extend the belts all the way to the end, save that position, and then have that be the hard stop. Maybe set the motors to the same light resistance as when doing the current Extend All but don’t have a stop and let the user pull the belt all the way out, record the position, then do a Retract All to spool them up again? That would help with packing the belts on the spool too.
How can we prevent that? Maybe we have a setting for the max work area size
and don¢t let it go beyond that?
If you think you are extending, but the belt length is getting shorter, STOP
If you are in comply mode, you need to allow a little backwards movement, but
you can say that if you move back more than say 20cm things are very wrong
(probably less)
). The other seems to have stopped before working its way into the gears and seems usable.
