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sajawors

"Ghost" printing during a long job?

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So this is probably the 6th time now I've tried to print a 20+ hour job and for various reasons, I can never get it to finish. (Improper spooling, print core jam, etc etc.) The latest problem that I can't figure out is that I watch it all day and it's printing fine. I come in the next morning and the printer is still whirring away, but the printcore is a solid 6 - 8 inches above the bed and no material is coming out. It looks like the printhead "thinks" its still printing by it's movement patterns (also evidenced by the fact that the bed has continued to move down), but it has long since stopped feeding material. In both cases so far there's no break in the material on the spool, no clogs in the printhead. If I immediately restart the job, it starts printing again with NO issue (albeit back at minute 1 of the 20+ hour job). Any ideas? Short of me camping out in front of the printer to monitor it for 20 hours straight? 

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Well it's probably grinding at the feeder.  There are many possibilities but I'll give you 4 to think about:

1) CF (carbon fill.  Also glow fill and glass fill) filament can wear out the points on the pyramids in the feeder wheel that grips the filament.

2) Don't mess with the tension - it should be at half way point on the feeder

3) Tons of retractions will do this.  I printed a big ben tower that consistently failed several hours in because it was doing about 20 retractions on the same spot of filament - after going through the feeder 20 times it was ground down such that it couldn't grip it well and soon after it took a "bite" out of the filament and stopped printing like what you see.  You examine retractions in line view in cura - dark blue is non-retracting moves - light blue is retracting moves.  There are cura settings to limit the qty of retractions on the same spot of filament.  Try setting max retraction count to 10 and extrusion distance window to 4.5mm.

4) printing too cold or too fast.  Try lowering speed to 50% in the tune menu when you leave the office.  It will print 2X slower but this is a good experiment to see if the pressure is just too high in the print head.  

 

Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers) and .4mm nozzle:
20mm/sec at 200C
30mm/sec at 210C
40mm/sec at 225C
50mm/sec at 240C
The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion.  Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp.  But don't go over 240C with PLA.

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Thanks for these tips. I will try the half speed and investigate the retractions. It does seem odd that all the jobs I've tried (both, multiple times) all seem to show this behavior at about the same height of job, regardless of how big the job is. Can you tell me how to adjust the tension? The link I found showed every model up to the 3, but not the 3 or 3 ext. It looks like it's one notch above the middle, but I'm not sure who or what would have changed that. 

 

Also, in Cura I don't see anything to change retraction settings. I can turn it off completely ("Enable retraction" box is checked), but I don't see anything about extraction lines or w/e. 

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4 hours ago, sajawors said:

Also, in Cura I don't see anything to change retraction settings. I can turn it off completely ("Enable retraction" box is checked), but I don't see anything about extraction lines or w/e. 

you will need to unhide settings in preferences to see some of the more cool features.

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That's close enough to tension at half way that I would leave it alone.

 

I never do "unhide".  Instead I type in the name or part of the name in the setting in the search box and it will show the hidden settings related to that word.  I already told you the two settings:

 

Try setting max retraction count to 10 and extrusion distance window to 4.5mm.

 

But you could also look at your part in layer view and visually see if there are a lot of retractions roughly where it fails versus the beginning of the print.

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Thank you. For some reason I read "refraction" and not "retraction" so my searches were coming up empty. My bad. >_<

 

Anyway, found the settings and am doing another run now. Will report back if that was it or if I still need halp. Thanks!

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knock on wood, but I think retraction limit / extrusion distance was the fix. It's 23 hours into the aforementioned 27+ hour job and hasn't borked yet, though I should probably go check again just because I'm posting this. >_<

 

thanks for the help!

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