Belts Binding in specific spot
I am currently at my wits end, and have been working on trying to fix this off and on for almost 2 years now, to no avail. No matter what I do, the bottom belt binds up in the exact same spot, every time. I've doubled checked all pulleys are assembled correct, retensioned the belts a dozen times, replaced the belt 3 times, replaced every single pulley at least once, replaced the gear pulleys on the steppers. Bought the upgrade from 3.0 to 3.1. Nothing seems to work, and on reassembly it binds up in the exact same way, every time. Any advice is appreciated, video attached. Thank you in advanced to anyone taking a look.
58 Replies
You can see that the belts move apart and together while you are moving them, this indicates that one of the idlers or perhaps the idler on the motor is not in the right height.
I woud re-check the positions of the idlers, bearings etc.
I know you say that you've checked them, but the fact that the belts are moving together and apart so much does indicate that they are not correctly guided along their path. Something is allowing them to move so much.
optimistic-goldOP•2y ago
I have checked all the pulleys again, none seem out of place or out of alignment.
The part I don't understand that seems different from the many other posts I have already read about this, is that for half the movement of the belt they're fine, they don't move up or down at all, until I hit that specific spot in the belt travel (which is pushing the gantry towards the rear of the printer).
I had this exact same problem on the old single-part idlers, and the new 3-part idler design.
I'm fairly certain that whatever is going on, it's not the idlers. I just don't have any idea what else could be so far out of alignment or causing this. Getting ready to just toss the thing in the trash and give up, because it doesn't make sense.
Other things I've checked and tried:
- Rebuilt the entire frame, ensuring it was perfectly square using both corner to corner measurements, and a laser square.
- Rebuilt the gantry and ensured it was also perfectly square
- Replaced the EVA carriage to a V3
- Replaced every part that comes in the V-Core 3.1 upgrade kit
Nothing I do seems to make any kind of difference. Something, somewhere not obvious, is fundamentally wrong and I have no idea where it could be.
I've sunk so much time and money in to this printer, and getting stuck on the h*cking belts is incredibly demoralizing. All the information out there is "the pulleys aren't stacked right" which is unhelpful as I've re-stacked them, following the guide exactly, measuring every part with calipers to ensure it's exactly the right width, purchased entirely new batches of all the pulley parts and screws.
Not a single thing has made a difference, and it binds up in the exact same spot, in the exact same way, every single time.
I guess the only other possibility is that this is expected when moving the gantry with the machine powered off, by hand, manually. I have never tried it powered on as I'm afraid of damaging something even worse than it already is by doing that. If I spin the stepper by hand, it doesn't seem to get bound up, but the fact I can't move the gantry by hand seems to imply some kind of issue.
I can understand that this is driving you crazy 😉
if the pulleys are aligned and the idlers are correctly assembled, something else must be allowing the belts to crawl up
have you tried increasing the tension on the belts to see if that better allows them to stay in alignment?
perhaps they are so loose that they can crawl up the lip on the idlers, allowing them to move up
that would still mean something is pulling them up / down, but ok - let's start with tension
interrestingly, the belts also seem to move together on one side of the motor assembly that we have in view, thought it's difficult to judge with the shifting focus in the video.
optimistic-goldOP•2y ago
yeah, the camera was not cooperating, heh
I can try and get a better video
That is the specific corner that always has issues, they don't seem to move or shift anywhere else.
optimistic-goldOP•2y ago
optimistic-goldOP•2y ago
And yes, it does appear to only be on one side.
They do move a small bit on the right (video perspective) side, but it's not nearly as much as on the left.
Belt tension feels pretty high from what I can tell, but I don't really have a way to measure it at all.
And I don't have a good frame of reference for how tight the belts should actually be. I've read the paper linked in the guide, but it's extremely technical and dense and hard to parse out the relevant information.
Which, I completely understand from a hobbyist group that teaching is better than telling, but when the teaching is nebulous and confusing, it serves no-one, heh.
It's almost taboo to just ask for a simple explanation, and I've been ridiculed and insulted in other communities for it, so I just gave up asking.
All that to say: I'm pretty sure they are tensioned properly, to the best of my knowledge.
I appreciate the advice and efforts so far, happy to snap any further pictures or video if it might help.
Hi Len. Might not be related but I'm chasing down a similar issue. I checked my bearing stack and it was correct. I then measured the Mini Precision Shim's and found they are not so precision. 0.93mm. Moving the 2GT Timing Pulley to account for the shim error seems to have solved my end.
optimistic-goldOP•2y ago
2GT?
I'm reasonably sure I measured all the bearing stacks and shims when I did that, but I perhaps missed one. I can measure them all again tomorrow. Shouldn't take long.
did you replace belts?
It could be that you fixed the issue long ago, but belts which were damage now does this up and down move
It is just a guess, as belts on video seems to be quite damaged.
optimistic-goldOP•2y ago
Belts have been replaced 3 times.
Those on the machine now are brand new, where are you seeing that they are damaged?
just one of the frames from video
But as you said, belts were replace,so probably it is not belts
optimistic-goldOP•2y ago
They came out of the bag like that, all the belts I've had have those little fibers sticking out at parts, I just assumed it was normal.
another guess - maybe you overtigtight m4 screws which holds idlers stack in xy joints?
I did it with mines petg parts, it pushed shims into jointers, which did change their reletive hight to the frame
I mean there
is that surface of 3d printed part still flat, or maybe it has socket of shim size
optimistic-goldOP•2y ago
That looks like the carriage ends, which I've checked are all free/not binding.
I've also tried loosening all the screws for that corner that is binding, which doesn't seem to make a difference. All the pulleys are freely spinning, which are tested when I route the belts (I've gotten pretty decent at routing them with the mounts already in-place since I've done it so many times.)
Pulled everything apart again, measured all the bearings/shims, everything is exactly what it should be (shims are all 0.8mm thick, bearing stacks are 11.8mm when fully stacked together) They're all exactly what they should be, my calipers are just not the greatest. They're consistent with the same tool being used, is the important part.
I wonder if there's some kind of local makerspace I can bring this to and have them take a look.
I'm about ready to just toss this thing in the trash, or put it up for free to a good home on FB marketplace or something. Nobody seems to have any answers, or there's something just fundamentally, blatantly obvious wrong that I'm missing. I just don't get it.
magic-amber•2y ago
where are you located len?
i HIGHLY recommend to upgrade to the FMMM Mod
and get rid of the printed motor cages
this basically means getting a additional pair of the motor plates and use them instead of the prnited parts
Printables->FMMM
damn, that rig is dusty
optimistic-goldOP•2y ago
It's been sitting for almost 2 years, heh.
Midwest, IL, West of Chicago
Where can I find these? Google is failing me a bit.
its just another pair of ratrig motor plates
optimistic-goldOP•2y ago
Ah, searching FMMM was better that "full metal motor mounts" heh.
I don't need any printed parts for this, other than what the kit has? I don't have a functional printer at the moment.
correct, you don't need any printed parts for this
optimistic-goldOP•2y ago
Gotcha, I have the BoM here and it seems to make sense. Now if aliexpress would let me stay logged in, that'd be great.
Well, damn, the BOM for the FMMM has the incorrect size for shoulder bolts listed, heh.
Finally got all the parts for the FMMM, but the shoulder bolts purchased as listed are too long.
Heh, and they just straight up sent me the wrong spacers. Welp, that was a waste of 2 weeks.
@ffb_9195
inland-turquoise•2y ago
Why do you thing the length is too long. Did you used also the modified STL´s
This is what I use and shipped to many other user on request.
optimistic-goldOP•2y ago
I asked and several people said no additional printed parts were needed, and I don't have a functional printer to do so anyway. When installing the bolts, they're too long and stick through the plate.
inland-turquoise•2y ago
Use some washers or whatever you have. I modified the motor support STL´s for that reason and due different cap head diameter.
optimistic-goldOP•2y ago
I don't really have anything, but I have to make another order anyway since they sent me the wrong spacers.
inland-turquoise•2y ago
I guess you are US. Within EU I could send you some parts for the mod.
optimistic-goldOP•2y ago
I am in the US, yes.
inland-turquoise•2y ago
A further tipp. Use flanged Hexnuts
optimistic-goldOP•2y ago
I'll try and grab some of those as well, going to go with mcmaster-carr this time as shipping from aliexpress is painfully long.
Looking over everything again to make sure I'm not missing anything.
Just a follow-up, in my recent order I got 35mm shoulder bolts, and removed the printed part from the motor mount corner, and they seem to be just about perfect. 36mm probably would have been exact, but there's plenty of engagement with the top motor mount plate without needing spacers, and there's not really much vertical stress on that part, it's all lateral.
The belts have been sitting wrapped loosely in a pile for too long and have warped at this point I think, so they need to be replaced, again, which means I have to take the entire hotend apart, again, so I'm goint to have to find the patience to do that.
optimistic-goldOP•2y ago
Just thought I'd report back that 35mm shoulder bolts seem to work pretty good without needing additional spacers. Here's what I got, exactly:
optimistic-goldOP•2y ago
Unless I've made some kind of fundamental, horrible error while building my frame, I'm unsure how 40mm shoulder bolts would ever work without needing spacers.
Unless that is the intent, in which case, carry on '.')b
Ah right, there's a printed part required for the shoulder bolts as listed in the BoM.
35mm length should work for those that can't print that, at least.
Hey, I'm having similar issues with binding at these corners of the metal mounts, do you have the BOM and what parts are wrong on it?
optimistic-goldOP•2y ago
I haven't tested anything with the metal mounts as of yet, I need to purchase and route a new belt still. My binding was with the printed parts for the motor mounts. The BoM isn't exactly wrong, it's just slightly confusing on what you need to get, and you need to dig through a bunch of pictures and comments to get additional information.
If you don't have another functional printer for the included spacer STL for the shoulder bolts method, don't get those and use the other BoM
Alright, thanks for the help!
inland-turquoise•2y ago
Wisited the thread again. The printer part is also on original design so it hold the shoulder bold or screw on original design in place. Th printed part is just modified to take account the 40mm of the shoulder bolt.
So you can build you stack without holding the bolt from below during the whole assembly process.
optimistic-goldOP•2y ago
Yeah, without it the 40mm is a bit too long. It's all good though, I got it sorted for now. I just need to replace the entire belt at this point which is very tedious so I haven't got around to it yet. The FMM is all assembled and looks correct. Since I was buying specific spacer sizes, I could have got a few 16mm instead of a 13mm and a 3mm, but it shouldn't matter much.
Final report back on this, it looks like with the FMM installed, new belt cut and routed, that the previous issues were gone. I can only assume there was something about one of the printed parts that wasn't quite printed correctly or wasn't lining up or was putting pressure somewhere, etc. etc.
I appreciate the patience of everyone who chimed in, I know I was a bit frustrated through this and might have been somewhat short. Apologies for that.
Now I get to put the electrical engineering experience I do have to work and finish up the wiring, which I'm fully confident I can handle, heh.
Congratulations!
xenial-black•17mo ago
I have the same issue. Orderd a FMMM an changed am printed Parts.Now i think its time to change the belt. Hope it will be succesful like you.
two spots
and
that second one looks bent like one side of the belt is stretched more than the other. That first pic that belt looks thicker than other areas
I'd replace those belts!
updates pls
Short version - some kind of deformation in the plastic parts led to the belts "walking". Belts walk when the pulleys are not running true, or there is an outside force acting on one part of the belt.
A belt will "walk" to the effective larger diameter side of the pulley. Ie. if you have a tapered pulley, the belt will walk to the large end of the taper every time. This feature is exploited on linishing machines and other belt grinding / sanding machines. The belt "trueing" mechanism is literally an adjustment on the axle angle of one of the pulleys.
Did you manage to fix the deformation
And where was it btw
I switched to fmmm and reprinted my joiners so thats not my issue most likely
Afaik the OP fixed it, the deformation was in the plastic parts, and as a result of either overtightening or deformed parts.
Oh right my bad idk why I thought u were the op
Would I need to change the belts if I had previously overtightened them
I imagine they would have stretched out and warped lightly
If belts are over tightened, depends how badly you damaged them.
It also depends on how much print inaccuracy you're willing to put up with.
Belts are replaceable items when:
There is visible damage to the belt such as severe cracking, thinning / stretching, or teeth missing / damaged.
A belt that is slightly bent / warped will usually straighten itself out when put in a machine with a good setup on the pulleys.