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bobbyhugges

sheared objects - not sure if software or hardware

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Hello everyone,

i'm a newbie having assembled my ultimaker 3 days ago,

works really nice, but i have a strange behaviour on some objects :

while the objects from the cura examples or from thingiverse print well, my designs are sheared on the x-axis, for the first layers only.

my workflow is :

blender > stl export > cura > gcode > ulticontroller

here are some picture to describe the problem :

the object designed in blender,

jgpj.png

looks ok in cura,

fvtv.png

is sheared on x- axis when printed :

mm6p.JPG

 

on this last image, all objects where printed with the same settings.

the cubes where some tests i made in blender, one with subdivision, one with triangles instead of quads, as i thought it was a poly problem,

but it didn't make it

did someone encountered this problem before ?

any help would really be appreciated !

cheers,

Julien

 

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Hi Julien, and welcome!

The problem you are seeing is because the head isn't able to return to the right starting point in the x direction on each layer. There are a couple of usual suspects to check. Firstly, check that your short belt for the x motor isn't rubbing on the wooden frame, or otherwise twisting at all. Then secondly, check that all the pulleys for the x-axis (6 of them!) are really tight, and not slipping. Test using a permanent marker to put a mark on the pulley and on the shaft next to it, and then watch to see if they move relative to one another. There must be no slippage.

I believe that UM may include a spare bag of set screws in case the ones that are in the pulleys are not good enough. If so, and you just can't tighten the existing screws enough, try swapping them out for the alternative ones.

 

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Julien we've seen this exact issue many many times by new members so you are not alone. Illuminarti speaks with wisdom. Also check the movement of both axes and if X axis is stickier add a drop of light oil (not grease or wd40).

But I'm pretty sure it's your x axis short belt rubbing the frame which is fixed by adding washers under the plastic spacers.

It's intermittent because it only happens on certain high accelerations or changes in acceleration. Even though you used the same cura settings, the infill for example ends up in a slightly different spot for different shaped parts.

If you do what illuminarti says and it still does this let us know because there are other details we are leaving out.

 

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I would first look into the pulleys, all 12 of them. (don't forget the one on the X and Y motor).

Besides the fact that i think this is the cause, have you checked if your pulleys are aligned with your rods?

Your belts should be parallel with your rods, if they are not more friction will rise when the print head is coming near one of the rods.

After a while, it might also be wise to put some sewing machine oil on those X and rods to keep them going :)

 

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Sander - that's an interesting point about that belt/axis alignment, and one that we often seem to overlook when troubleshooting here... I remember a week or two ago someone was posting about increased friction near the edges of the print area. it makes sense that if the belts aren't properly aligned, then there will be more friction nearer the pulleys where the belt is getting flexed at a sharper angle.

So, thanks for reminding us about that :-)

Also, can you confirm does UM (still?) provide spare set screws for the pulleys, as I've seen mentioned several times, and we now repeat as an article of faith? If so, are they also provided for pre-built printers?

 

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They are included in the kits, and i think from the moment we experienced the silver ones had better grip after a while then the black screws do, we put in the silver ones our selves.

But i don't want to cause a mass-panic reaction if anybody reads this and finds black screws in his/her Ultimaker..

They can loose grip after a while, but don't necessarily do so :)

 

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ok that was a pulley issue, one was not tight enough.

it made it for 2 prints,

then it went bad again.

this time i checked all 12 pulleys, swapped the black screws for the silver ones, and now i have an end stop problem.

when calling auto home from the ulticontroller, the printer makes some noise like in the video from the calibration page

(

), despite the end stop being triggered.

i also checked the wires of the endstop, and checked with a ohmmeter that the signal was ok.

all the belts seem really parallel, no friction, the x axis is running even smoothier than the y axis,

i can't figure it out and would appreciate any advice, thanks !

 

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