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neo-ninja

Slipping in Y axis - Cant work it out.

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Hi All,

On one of my UM2 machines my prints are slipping in the Y axis. But what is strange is its completely random, sometimes it works fine on the same print and other times it fails. I could do with some advice. The machines are used for prototype work and are almost constantly going and have been going probably around 8k hours.

I have tried:

tightening all the belt nuts.

Reducing the current to the X/Y motor

Making sure the glass is held in place

Making sure the printer head cables are not catching.

Any other ideas? What else could it be?

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Then check the belt tension. Maybe they are too loose. To fix the tension unscrew the pulleys and in theory they will retight with the spring inside the slideblocks. Also, check if there’s no oil on the belt/pulley contact with belts, just in case that’s making them slip.

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Then check the belt tension. Maybe they are too loose. To fix the tension unscrew the pulleys and in theory they will retight with the spring inside the slideblocks. Also, check if there’s no oil on the belt/pulley contact with belts, just in case that’s making them slip.

Done belt tension and they all seem fine. No oil or grease as far as i can see.

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With 8000h use maybe it’s time to check the tooths of the belts. I got one damaged not so long ago.

Maybe someone else has other ideas of stuff to check?

So I have really tried to a few different things today. What i did notice is when the print is moving in the Y axis the belt almost seems to bunch up, it also seems to shift from the left to the right of the top cog.

What i think might be happening is that is the belt is running to the very edge of the top cog and sort of getting caught trying to slip off. I have untighted the tough to get to screw and retighted it but it still seems to be doing that -  if i move the belt all the way to the left it moves to the right still.

I recorded a little video where you can sort of see the belt bunching up

Edited by Guest

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Is that short belt actually tight? It looks to me like it's way too loose. If you pinch the two sides of the belt and push them together, can they touch without excessive force? I'm betting they can. If so, loosen the four screws on the motor, push it down and then re-tighten.

But I kinda doubt it's the belt causing the skipping in Y unless you hear the belt skipping when it happens. I had a machine in the shop a few weeks ago that also randomly skipped around in X or Y (can't remember). I tried everything I could think of including lowering all the settings for jerk/accel etc, wrote some simple gcode to make the head shake back and forth to try and trigger it reliable and so on. I finally replaced the mainboard and everything worked fine again. So one of the drivers was probably a bit toast.

Edited by Guest

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Hi Guys,

So i moved the motor down that has stopped the belt doing the wierd thing, but i have stood there watching while printing and what happens is the belts move to the right and then try to slip off the cogs. But as its not possible it sort of clicks and goes back. I have moved the belts to the left and the keep pulling to the right...

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Any ideas

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So aside from the possible replacement of the belts and the mainboard that have been already suggested, have you checked an obvious thing like making sure the print head moves in the Y-direction freely?

Maybe the shafts with the bronze bushings are dry and/or dirty--it sort of looks like that from one of your pictures. How about the linear ball bearings in the print head--do they move freely?

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So aside from the possible replacement of the belts and the mainboard that have been already suggested, have you checked an obvious thing like making sure the print head moves in the Y-direction freely?

Maybe the shafts with the bronze bushings are dry and/or dirty--it sort of looks like that from one of your pictures.  How about the linear ball bearings in the print head--do they move freely?

So I was more just wanting to confirm what was happening to see if that offered another explanation before i bought a new board etc..

It just seems strange that the belts are moving along and im not sure if thats because they are old or if there is another option.

It moves freely in the Y axis when off and manually pushing. Shafts are oiled with Sowing machine oil. When you say ball bearings in the print head what do you mean?

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It moves freely in the Y axis when off and manually pushing. Shafts are oiled with Sowing machine oil. When you say ball bearings in the print head what do you mean?

By ball bearings I mean the two linear bearings in the print head that the two shafts go through. Unlike the bronze bushings on the X and Y axles, these bearings have recirculating balls in them, hence my use of the term "ball bearings", sorry for the confusion.

I just wanted to make sure that these weren't sticking, and it sounds like you have checked that.

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It moves freely in the Y axis when off and manually pushing. Shafts are oiled with Sowing machine oil. When you say ball bearings in the print head what do you mean?

By ball bearings I mean the two linear bearings in the print head that the two shafts go through.  Unlike the bronze bushings on the X and Y axles, these bearings have recirculating balls in them, hence my use of the term "ball bearings", sorry for the confusion.

I just wanted to make sure that these weren't sticking, and it sounds like you have checked that.

Hi Guys,

SO i got the new belts installed, and the problem persisted. But it also made some crazy clicking sound. Now i am pretty sure it has fried the board. I have swapped the x and y motor on the board and both motors work, but the board doesnt seem to be working on the y axis.

Where is the best place to buy a new board?

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