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Printing in air - another puzzle

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So my print randomly prints in mid air. Its not:

 

  • Nozzle clogged
  • Bed uneven
  • Bad G-code

 

As per the picture you can see it was printing fine then all of a sudden BOOM! lets start the next layer 2 cm higher than normal. This will happen one print, then try again with the same file and it will work out fine. There are no z-hops or retractions at all. You can see nice fat lines printing in mid air, so the nozzle is not clogged.

5a3318f16729b_IMG_24641.thumb.JPG.711edf22f9db740874dbbc430d850254.JPG

Suggestions?

5a3318f16729b_IMG_24641.thumb.JPG.711edf22f9db740874dbbc430d850254.JPG

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Check that the bowden it's really inserted on the ptfe coupler. Check the feeder to see if the filament slips inside. Check the feeder tension to see if it's too low or high and the filament slips. Clean the knurted bolt of the feeder (if it's full of material it can slip) using a metal/nylon brush. Check that there's no heat near the feeder that can make the filament losse strength and be easily crush by the feeder. Check the ptfe coupler has 1mm separation with the steel coupler. Check that the fancap isn't touching the hotend.

Make photos. Front hotend. Feeder. Atomic pulls.

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I have a similar issue. Maybe it's the same, I believe I have found the reason for it.

My issue:

I'm printing a very small object, each layer takes not even a second (so claims Cura).

For some reason, Cura is adding code that moves the head to the side, extrudes a bit, then moves back extruding some more.

When viewing the GCode with Repetier Host, I can see the extranous head movements. They make no sense model-wise, as they're about 2 CM from the model.

I have looked at the GCode and noticed weird G0 codes - immediately before a new layer.

When I set the minimal layer time to 0, the resulting GCode contains no extra movements.

But when I set it back to 5 seconds, the extra movements/extrusions appear.

Not sure if this is intended, but it almost looks like Cura is expecting there to be a wipe tower?

I can't upload GCode files apparently, so here's snippets of the file, containing one layer each (same STL, same settings, apart from delay):

 

M117 Layer 56 of 58G0 X97.767 Y102.634 Z11.300;TYPE:WALL-OUTERG1 F2400 E44.00057G1 F600 X97.233 Y102.634 E44.01829G1 X97.233 Y101.365 E44.06039G1 X97.767 Y101.365 E44.07810G1 X97.767 Y102.634 E44.12021;Small layer, adding delay of 4.386900G1 F2400 E39.62021G0 F4800 X97.767 Y102.634 Z14.300G0 X117.767 Y102.634G4 P4386;LAYER:56

 

 

 

M117 Layer 56 of 58G0 F4800 X97.767 Y102.634 Z11.300;TYPE:WALL-OUTERG1 F3000 X97.233 Y102.634 E44.01250G1 X97.233 Y101.365 E44.05460G1 X97.767 Y101.365 E44.07232G1 X97.767 Y102.634 E44.11442;LAYER:56

 

 

Edited by Guest

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If your minimum layer time is 5 secs and the print needs just a sec to complete a layer, then Cura introduces the code to move the head to one side, as you would expect/want!!

Personally I would suggest you would be better with a minimum layer time of 10 secs. You need to give the layer just printed enough time to cool before printing the next layer. If you have a model with a large area on the x/y axes this will not be a problem as it may take 20,40,60 + secs to print. But with really small models it presents a problem; there are several solutions.

1. If you are printing fast then slow downs to 30 or 20mm/s

2. Make sure your fans are on 100%

3. Print multiple copies concurrently; you need a minimum of three copies due to Cura bug - Cura menu Tools, select item print all at once.

4. Use towers, one tower will not work due to Cura bug.

Up to and including Cura vs. 15.04.4 ( I have not tried the new Cura) it has had an awful bug which for whatever reason has never fixed (@SandervG). If you have two copies or one tower, A&B Cura print in the sequence AB, BA, AB, BA..., rather than AB,AB,AB... If you have three copies or two Towers, ABC; it prints ABC, CBA,ABC,CBA - so you will get one good copy, B

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If the problem is that in mid-print, the print bed suddenly moves down, but the printer just keeps printing as if nothing happened, then this could be caused by the motor drivers (amplifiers) getting too hot. Then their temperature protection activates for a few moments, so the stepper motor gets no more current, and the built plate falls down a bit.

There has been a recent post on this in the hardware section:

https://ultimaker.com/en/community/20998-ultimaker-2-motor-drivers-overheating

Could that be what you are seeing?

Geert

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