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print is distorted in one direction

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Posted · print is distorted in one direction

Hey guys,

I recognized another problem that is really anoying!

My prints are distorted in one direction.

To confirm that this happens only in one direction I printed the same thing twice

and rotated it 90° as you can see here (look at the hole):

IMG 20140604 210251

Can somebody help me on that issue?

Thank you very much in advance!

 

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Posted · print is distorted in one direction

People are going to say "tighten your belts" and that could be it but I don't think so as your infill is touching the borders very nicely.

When that hole is printed, the printer is squirting out a thin line of plastic that has a tendency to cool fast and shrink just a little and start to act like a rubber band for a second before it freezes. In that moment - after it leaves the nozzle, but before it turns solid it is pulling and thinning and it tends to pull off the layer below a bit towards the center of the circle a tiny bit. Also it is pulling on the layer below trying to get *that* layer to also shrink a bit.

The reason the shape is different has to do with the cura slicing changes which has the circle start in a different location. There's nothing wrong with Cura - it's just that it starts the circle at a different spot.

The fix is generally more fan, longer layer time, lower temperatures, slower printing. In that order of importance. So:

1) make sure fan is 100%. Make sure it is blowing and not sucking. consider adding a second fan (a table fan?).

2) make sure layer time is at least 7 seconds if you want this to come out nice. This makes it so that the layer below has more time to cool before the layer above is applied.

3) If you have a UM2, keep the temp no higher than 60C for PLA. I would try 50C even (lower than 40C and you start to get danger of parts not sticking as well). Also lowering nozzle temp to 200 or 190C might help.

4) Printing at 20-30mm/sec might help also as it's possible this is an overextrusion issue on speed changes and printing slower can help that.

 

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Posted · print is distorted in one direction

hey gr5! thank you very much for your answer and your hints!

did you recognized that even the rectangle is deformed?

i measured it and yes - it definitely is!

so... maybe it is really the belt? but IF - which one would it be?

the one on the axis that prints smaller or the other?

 

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Posted · print is distorted in one direction

I bet your steps per mm need to be calibrated in firmware.

Using a ruler or calipers, accurately measure the result of a square you're trying to print that is 100mmx100mm.

Adjust your steps based on the factor that print is off.

Is this a UM1? UM2? Homebuilt machine?

 

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Posted · print is distorted in one direction

Hey Nick! Thank you too for your help!

Sounds good to me - I will definitely try that!

 

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Posted · print is distorted in one direction

I would think that if it is a UM machine, the steps/mm default correctly in the firmware. If so, I would make sure the microstepping jumpers are correct and haven't become dislodged.

I suggest you look on thingiverse for a calibration cube or something of a known dimension so you can measure. If the microstepping setting is the problem, you would see a size change by a factor of 2. So if you print something that is 20mm by 20mm and one side comes out to be 40mm, I'd suspect the microstepping.

 

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Posted · print is distorted in one direction

hey again! i solved the problem - one of the pulleys on a short belt scratched on the frame - I think that slowed the stepper. the last print I made is one of the best I made so far. thank you a lot anyway!

IMG 20140604 234955

:D

 

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Posted · print is distorted in one direction

Hello everyone,

 

I think my problem fits this thread..

I'm also experiencing deformations which are especially visible in circular holes, or where the infill doesn't touches the border.

 

Shall I also do the things mentioned above or is it something different?

 

Thanks!

 

MG 2753 Sml

MG 2754 Sml

MG 2757 Sml

 

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Posted · print is distorted in one direction

Hey achillx!

Is the deformation always in the same direction? I mean if you rotate a model 90° and print it again, what does it look like?

If you move the printhead by hand,is it easier in one direction?

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Posted · print is distorted in one direction

lol. So the last guy I said it probably wan't the belts but it was. Well now on these above images of gray parts I think it *is* the belts. Usually the short belts meaning if this is a UM1 just slide the motors down a little tighter. Also you have a little bit of underextrusion - what print speed, layer height and temp are you using? You might need to either raise the temp or lower the print speed or print thinner layers. 240C is a relatively safe upper limit for PLA so if you are printing cooler than 240C try raising the temp 10 or 15C. If you are already at 240C try cutting back the speed by 30-50% just for kicks so you can see some quality improvements - or maybe you don't care.

 

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Posted · print is distorted in one direction

Hello and sorry for the late reply but I was on vacation in warm and sunny Barcelona!

Anyway..

@ataraxis

I'll print a cube twice and report back the deformation.

Also I need to apply the same force in both directions, but no idea if this counts as easy or difficult, there is no way to describe something so subjective or compare it to a video. Is there a less subjective way to check it?

@gr5

Yes it is UM1.

Also another subjective thing.. I did apply some downwards force to the motors when I was screwing them to the case.

On the third picture there was underextrusion somewhere between 10-15mm.

I printed them with:

220C

60mm/sec

0.15mm height

0.8mm wall

0.6(+0.15)mm top-bottom

23-24% infill

On the top layer is it normal for the lines to not touch each other?

If not is it linked to the low temp thing or the maybe-belts problem?

Thanks again!

 

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