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Strange shapes !

Posted by adambrum 
Strange shapes !
April 16, 2018 03:15PM
Im having some headaches trying to get to the bottom of weird dimensional problems.

My machine is a hypercube evolution and was running ok a while back so i know belt paths etc are all ok, frame is solid.

Running marlin firmware, slicing with cura and slic3r

Dimmensions from picture

x bottom 101.15
x top 100.00
y left 100.47
y right 101.13

diagonals are even at 142.55

I have adjusted belt tension in every way with only very minor effect.

rotated 45 degrees which resulted in acceptable sizes 100+-0.1 but was skewed.

I checked a print i did a few months ago and its all square !

I just cant see where its coming from, Any ideas ?

Edited 1 time(s). Last edit at 04/16/2018 05:56PM by adambrum.
Attachments:
open | download - strange shape.jpg (370.9 KB)
Re: Strange shapes !
April 16, 2018 06:44PM
I would measure the print at least a few mm above the bed. If you measure it right at bed level, you have the effect of an unflat or unlevel bed, elephant footing due to too high temperature, etc., all of which disappears a few mm up.



Belt segments labeled A-H must all be parallel to their respective axes. If they are not, prints will be distorted, especially if they are printed away from the center of the bed.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Strange shapes !
April 18, 2018 11:03AM
Found the problem,

Swapped the steel reinforced belts for normal belts and hay presto back to normal just a little tuning for skew and im off running again.

Not sure what happened to the belts, i suspect that they stretched in just one area.
Re: Strange shapes !
April 18, 2018 06:39PM
Steel core belts have some minimum bending radius, and if you bend them around a smaller radius, the wires can break, and then the belt stretches because it's now only a polyurethane belt with little bits of steel in it. Unfortunately, the Chinese steel core belts don't usually come with any specs except for width and pitch, so you have to guess about the radius. Glass core belts bend around all the pulleys in a coreXY mechanism much more easily, and don't seem to mind the smaller bending radius


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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