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Morandir

Printing at Angle, Skewed features - Help or ideas Bookmark Unfollow

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Greetings,

(Software forum thinks it's a hardware issue, though I'm skeptical as we print test cylinders and nearly identical parts right afterward with no issue.)

I'm having a strange issue with one part printing features at an angle (skewed).

Here is an example of the part:

20170324_091106.thumb.jpg.76e706001da197823d6c33ab7beaf23f.jpg

20170324_091126.thumb.jpg.95955665b6a0e9481919861517194283.jpg

You can see how the features skew, and then straighten out. It's got a couple of us scratching our heads, an we think it may be a singularity in how the slicer handles the part.

Here's the mating part without any issues printed right before this:

20170324_091135.thumb.jpg.a19a1369ceffdcf8452a28a776b67455.jpg

I've checked the belts, etc. we even printed a cylinder the same height as the part to see if that would skew, and it did not. Time to come to the community for help.

Anyone have any ideas?

(Next I'm thinking we change nozzle size...)

Printing:

Ultimaker 2+ Ext, ABS, 0.6mm Nozzle, Bed temp 90C, Nozzle 260C, both Cura 15.4 and Cura 2.4, 100% infill, 100% support, 40mm/s speed.

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Hi,

first - there is no logic in the forum software to categorize posts. Maybe another admin moved it here because this issue is so much in the "WTF?!?!?" realm that one is not sure where to categorize it :)

So did you slice with Cura 15.x and 2.x and you got the same skewed model? Then you can rule out the slicer.

Did you print other models just to see if the problem occurs at the same height? If yes, then it might be a hardware problem (loose pulleys if you didn't regard them already).

Another idea could be overheating stepper drivers which cause the motors to stutter and miss steps. I am not sure how the UM2 board handles this, but with a another board on another printer I have seen this behaviour.

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Nicolinux,  Thank you for your suggestions.  Thought I'd follow up to close it out for any who may find this.  It was effectively an issue with the stepper motor and belt that controls that direction.  We tried printing cylinders and variously sliced objects that did not reproduce the issue.  It was in a region of the plate where the friction on the pulley belt changed quickly.  As best as we could figure, having changes in direction in that region messed with the motors ability to return to the same position, thus it skew the parts in that area.  A cylinder didn't have the issue because it would never stop/start in that orientation, just go round and round.  It was very subtle.

 

We "loosened" the tension on the belt a little to reduce the effect of the friction change and the issue went away.  Shortly after we replaced the belts and haven't seen it since.

Thanks again (a year later)

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