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Not printing uniformly

Posted by GuerillaEngineer 
Not printing uniformly
December 01, 2015 12:34AM
Been having this issue from print 1. Layers start to drift then drifts back to place randomly in the prints usually towards the top end of a print. Between the two pics I changed my extruder feed rate from 93 to 100. That seemed to help with the irregular surface but I still get the drift. What can I calibrate? I've adjusted the Polulu pots. I don't mess with the code at all, I have a nonducted cooling fan.
open | download - img1.jpg (251.6 KB)
open | download - img2.jpg (253 KB)
Re: Not printing uniformly
December 01, 2015 02:26AM
Very small structures can do this due to the difference in movement speed and cooling time.
Before you go overboard try to duplicate the object so instead of one you print two at a time.
If the shifting is still present start with the basics like belt tension, loose grub screws on motors and pulleys and such.
Re: Not printing uniformly
December 01, 2015 08:31AM
It has something to do with the the top end of the second tower. When it finished that second tower, it goes sideways. I'm not sure heat would cause this.

Might be a problem with the model itself. Try cutting the top off of the model and printing just it, in larger sizes, so you can focus on if the model is correct. This will also tell you if there is a heat problem, but I can't see how heat would only move the layers to one side and back again, unless maybe the extruder temp was varying.
Re: Not printing uniformly
December 01, 2015 11:14PM
Snugged up pulleys and set screws. Adjusted a few settings, mainly height and width in slicer. Now it's twisting. Next model will be a little taller. Heat is at 190* C.
open | download - IMG_20151201_200722.jpg (332.6 KB)
Re: Not printing uniformly
December 05, 2015 06:28AM
Try rotating it on the bed.
Re: Not printing uniformly
December 05, 2015 03:46PM
Print two or three at the same time.
To me it still looks like a temp and timing problem, especially the "twist" in the middle.
Also try to print the two or three towers at a reduced speed once you get close to the area with the twist and then again for the thin parts of the top.

I recently replaced the springs holding the bed with much stronger ones and it gives a nice improvement on the prints especially at higher speeds.
Before I could feel the plate virbte back and forth with fast support structures, now it is rock solid and the last wave patterns on the sides of my prints are gone too...
(unrelated though)
Re: Not printing uniformly
December 08, 2015 04:20PM
Replaced heating element and sensor in hotend. I also uograded the springs previously. Saw a noticable improvement. No more twist but other prints are still shifting towards the top.Will try rotating it. Thanks for the input.
Re: Not printing uniformly
December 10, 2015 06:45PM
Print a rectangle that tall. You may have a floppy chassis.
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