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edit-mesh

wall problem caused by cura?

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i am struggling since a few days now and really need help or some more input with this i am sorry.

printing this modell, no matter how i rotate it, or which settings i use, results in two different wall dimensions.the left leg (if you watch it as an "U" with the open side showing upwards ) is (and stays) always thicker than the right leg no matter what i do.

if i take the geometry and cut of the shorter walls, it's printing precisely what is told!

i think its a problem how cura is slicing the geometry, but i have no idea how to change it.

i tried to print with different shell thickness, a nozzlesize of 0.8, and tried slicing with sclic3r (no special settings) with no different results.

choosing "external perimeters first" in slic3r only seems to help a little bit, but actually i am not sure why and what i am really doing/changing.

2015 01 13 13.36.44

2015 01 13 13.45.49

can you give me help on that?

 

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hi ultiarjan

sure

https://www.dropbox.com/sh/bf3ikcy4fk3ici1/AAC-eFGorlHFzmRrXOzDGGCIa?dl=0

there is a looooong topic i wrote in the questions and answers section, but i tried to write my findings in this topic above, so it should be not necessary to read the long thread.

in the layerview of cura everything looks ok (for me).

i tried fooling cura by changing the nozzlesize to 0.8., to be able to print with one shell

http://umforum.ultimaker.com/index.php?/topic/7488-trick-cura-to-change-print-path/

 

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You take the two short walls off and it is OK!!

So going back to your original model, starting at the top left, you go left to right along the short wall, then turn right and go top to bottom along the left wall which is having the problem. I wonder if it is that right turn that is causing the problem? Maybe it is positioning itself on the Y axis incorrectly as the turn is made.

I suggest you do two things.

1. Turn off the printer and then move the print head across the printer on the X axis several times to see if you can feel any resistance.

Then do the same thing along the Y axis.

 

If it feels ok then position the print head at the top left corner of the model. Move the print head left to right above the wall and then turn right down the Y axis wall.

If you have resistance on the X or Y then if you are not sure how to fix that I suggest you make a new posting asking for help.

2. If the axes are smooth then I wonder if it is something to do with acceleration away from the top left corner followed quickly by deceleration into the right hand turn. Take a copy of the long central wall on the X axis and paste it to replace the wall removed from the top left corner. So you model is back to where you started but now the top left wall is longer.

 

Print the model with the same settings.

 

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i tried moving the printhead, to look for any resistance and asked my friend if he could find any irregualities...

we couldn't say the printhead was moving ABSOLUTELY smooth and SUPER easy (though you can move it with the little finger)

but there were very very little differences in the force one has to apply...

 

but i don't know how to remove or minimize it and its really not that bad

 

i printed (first 10 layers) of the "U" with a 2x longer vertical left wall with 15-20 mm/s :

left V Wall = 2.2 mm; right V Wall=2.1mm

printed (first 10 layers) the original "U" with the same settings, rotated 90 degrees,

left V wall = 2.3mm; right V wall=1.9mm

printed (first 10 layers) the original "U" with the same settings as usual, with the open side upwards,

left V wall = 2.4mm; right V wall=1.9mm

...

if it's an accelaration problem, why is it always more significant in the left long wall, no matter which axis

and no matter in which (chronological) printing order???

i already put the machines accelvalue down to 1000 with no effect, and don't know what i could do in addition?

 

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The pulleys supplied with Ultimaker Original kits happened to be deformed sometimes. Actually the bore might be not concentric within the pulley. You may take some calipers and check this. If you combine two pulleys with about the same excentricity on one belt with the excentricity aligned the same way you should be able to minimize the effect.

 

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stefan, thank you very much!!!

i just started reading http://umforum.ultimaker.com/index.php?/topic/1611-fixing-pulley-innacuracy/?hl=pulleys

and i am scared ;-)...

pulley wobbling and endcap friction things... seems there are a lot more things to improve/check, i am not sure if i really

want to do that..

but now i will keep an eye on it :-) - THANKS!

 

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One way to check if the pulley roundness is causing this problem. Load the part as you have in the first picture. then use Cura to scale the Y axis (you need to unlock the Lock X,Y,Z together icon). Now with the part longer in the Y direction, use Cura to rotate the part 45 degrees.

If you see reoccurring changes in width, it's a problem with the pulley roundness.

 

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Ok, i fixed some belt tensioners on the long belts with no effect :-(

Also printed the y scaled, 45degree rotated U shape with a little better result:

left wall= 2.1mm and right wall= 2.0mm,

ok then, i tried printing the original shape 45 degrees rotated with the same settings

and something wired happend to the walls

left wall=2.15 mm and left wall has a change from 1.9mm to 2.05mm

i figured out that 2 belt axis had a play of ~2 mm or so, so i fixed a washer on the inside endcaps which cause

a little friction now, i don't know whats worse, having 2mm play on the axis or a little friction on the endcaps???

regarding friction and pulleys i am not sure if this "tilting" shortbelt is normal (sec.17)?

 

 

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ok i did that xy- assembly from scratch, removed a wrong bearing holder which caused that the x-motor short belt wasn't aligned, aligned the y-motor short belt also, thightened all pulleys... et voilà ...

MUCH better print quality !!!

but same problem :-| !

i printed some adjustable endcaps and in some free time (maybe) i will check/change the pulleys ...

for so far thank you guys for the support i learned a lot !!!

 

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