Top belt keep pulling out from the X carriage (v4)

Mostly Printed 3D Printer - MP3DP Advice
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I “finished” my MP3DP v4 build a few months back. It looks like I posted a pic of my build on printables on Dec 3, so probably late November was my first print.

I recall when I assembled it all, that I had a heck of a time getting the top belt secured into the X carriage. I did manage to get something that I couldn’t easily pull out just with my hands, so I thought I was probably golden.

The other day, completely out of the blue my Y end stop detached, which caused a fair amount of chaos. One of the effects of that was that the belt that comes into the top right of the X carriage pulled out because the stepper was hammering on it, I suspect.

Since then, I’ve take the X carriage apart 2x to put the belt back in place, but now I can’t even get through a calibration cube without that top belt pulling out from one side to the other. So that’s 3 times the belt has pulled out in about 4 days.

The last time I put it back in place, I assumed that maybe I was pulling the belt too tight. So I kept it as loose as I could get it, and slowly tightened until there were no more missed steps. When you pluck it, it barely makes what I would call a musical note. I don’t think the belt is too tight.

The teeth on the end of the belt seem to be fine, and each time I’ve reassembled I’ve cut a new small piece of belt to use for the lock. I make that piece as long as I can so that it still fits.

Also, perhaps noteworthy, is that it looks like in his builds Ryan is using some wider belts. I used what I had on hand, which is the same belt that my Ender 5 uses.

All of this leads me to a few questions.

  • Could the narrower belt be part of the problem that I just can’t seem to keep it in place?
  • If that isn’t it, what else could I look at to get to the bottom of this?
  • Most importantly, does anyone have any tricks for getting the belt into the slots? The bottom belts are a breeze to get in place, but I’m a pretty good sized dude, and my fingers don’t fit into that tiny little space. I’ve tried needle nose pliers, and tweezer, and chop sticks, and anything else I could think of. It literally take me hours to get those things in there when they pull out.

I’m thinking tomorrow that I may start with a new belt, just to see if that helps; but I’d really love some advice about how to get the belts in place.

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Have pictures of you setup, particularly of the belts and locations that they’re pulling out of?

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Sure thing. Please disregard the state of the work surface. Since I’ve had to take it apart so many times, I’ve not put the effort into tidying it all back up.

Here is the birdseye view

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The right hand side:

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And the left hand side:

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Since taking that picture of the left hand side, I’ve pushed those belts back down into place. Over the last few days, the right has pulled out 2x and the left 1x, if I recall correctly.

I suspect that the twist in the belt on the left maybe causing part of my heartburn here. I hadn’t really noticed that until I took this pictures.

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The V1 design to hold the belts depends on the thickness being gripped in the belts. The 6mm belt will be less stable but if the locking piece is good it shouldn’t twist like that or pull out.

If you fold the belt over just past the slot it won’t be able to pull put.

That works for the first side you connect the belt.

For the other side, pushing in something like a sewing pin will make the joint more solidly wide, and will prevent it from coming out.

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This is what I did for the bottom belts. Folded over, and then pulled into place. But for the top belts, I can’t see how to fold it over past the slot without bringing the belt in at a pretty steep angle. It’s solid part at the end of the slot

I hadn’t thought of shoving something small in there to help hold it all in place. Last night, though, after I wrote this, I glued a small piece of belt to the main belt. Let that set, and did my best to stick it down in there. We’ll see if that holds any better.

Or maybe I’ll just ask for 12mm belts and pulleys for Father’s day. :smiley: