Filament feeder pressure calibration - filament grinding on retraction

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bpitangaGM
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Joined: 21 Jul 2017, 11:49

Filament feeder pressure calibration - filament grinding on retraction

Post by bpitangaGM » 21 Jul 2017, 12:47

Gentlemen,

I´m having several issues regarding filament retraction. Since I have started to use my printer I had no issues regarding printing of simple geometry pieces. When I tried more complex shapes, full of holes and ridges, the problems kicks in. After some consideration, I´ve noticed that those problems have to do with the fact that those shapes need a lot of retraction for being printed.

The first problem I had was nozzle clogging. After some research, I was able to solve it with less aggressive retraction settings (I'm using 1.5 mm of retraction distance and 30 mm/s of retraction speed).

The second problem, that still remains, is eventual filament gridind, which stops the feeding of the filament and forces me to stop the print to recover from the issue. That also happens more often when the printer is doing a lot of retraction and I´m able to notice when the issue arises in a particular printing job because the gear starts making a clicking or knocking sound. I do suspect it has to do with the pressure between the U shaped bearing and the filament drive gear, which is adjustable by a side screw. I searched a lot through these forums, and Internet in general, and I was unable to find any guidance on the best way to calibrate that screw (the manual is also silent on that).

So, that is my question: what are the necessary steps to calibrate the pressure between the U shaped bearing and the filament drive gear?

Thanks in advance,

Bruno Maia

MrDoom
Posts: 223
Joined: 01 Apr 2017, 10:01

Re: Filament feeder pressure calibration - filament grinding on retraction

Post by MrDoom » 21 Jul 2017, 13:03

Hello bpitangaGM,

For the best results and in high retraction parts you can use 1mm retraction at 15-10mm/s to decrease the ammount of problems, also you should tweak the minimum travel before retraction to avoid so much retractions.

To adjust the filament tension the best way I found is using a 1.25mm drill and setting the bearing so that there is a space of 1.25mm between it and the extruder gear.

You mention the extruder clicking, you should also lower the extruder stepper driver voltage to 0.8v to decrease the chance of that hapening by decreasing the heat at the extruder engine.
There are some instructions here: viewtopic.php?f=8&t=671
I have been using 0.8v on all 5 stepper drivers with no problems and much less heat and noise :)

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bpitangaGM
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Re: Filament feeder pressure calibration - filament grinding on retraction

Post by bpitangaGM » 25 Jul 2017, 01:00

Mr Doom,

I've followed all of your tips. The changes in motor behavior, with the decreased voltage, were awesome. Now I can even touch the motors while they're working. ;)

Thank you very much.

MrDoom
Posts: 223
Joined: 01 Apr 2017, 10:01

Re: Filament feeder pressure calibration - filament grinding on retraction

Post by MrDoom » 25 Jul 2017, 16:30

Nice to know your printer is working :D happy printing

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bpitangaGM
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Re: Filament feeder pressure calibration - filament grinding on retraction

Post by bpitangaGM » 07 Aug 2017, 15:55

After some use, now I can say that the changes in voltage were not without consequences :? . I was noticing that my extrusion was very irregular, creating a lot of blobs on the side of printing. After a lot of trial and error, with no success, I realized the problem could be the extruder motor torque being reduced in consequence of the lower voltage, thus causing skipping of steps.

Based on that, I raised the voltage again and the print quality had turned to normal, improving a lot.

So, I have to recommend against the changes in voltage, at least on the extruder motor.

Regards.

MrDoom
Posts: 223
Joined: 01 Apr 2017, 10:01

Re: Filament feeder pressure calibration - filament grinding on retraction

Post by MrDoom » 10 Aug 2017, 09:36

The values I suggested work fine for me but depending on the assembly or simply the tension you apply to the filament, through tightening the screw on the sides of the extruder, can be enough to make the extrusion much more complicated, it should be biting the filament enough so that the teeth on the gear bite on it but not much more strength is needed :)

João Ferreira
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Joined: 03 Aug 2017, 21:16

Re: Filament feeder pressure calibration - filament grinding on retraction

Post by João Ferreira » 13 Aug 2017, 20:55

Anyone of you guys have tried a spring mechanism on the bearing side of the feeder, to control the pressure on the filament?
I am waiting for a new board and already done this on the 0 extruder side only, to try it out..do you think it could work?

MrDoom
Posts: 223
Joined: 01 Apr 2017, 10:01

Re: Filament feeder pressure calibration - filament grinding on retraction

Post by MrDoom » 16 Aug 2017, 14:49

Hello João, that seems like a very interesting modification, could you make a post explaining how you did it?

Wim Adriaens
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Joined: 18 Mar 2017, 20:42
Location: Belgium
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Re: Filament feeder pressure calibration - filament grinding on retraction

Post by Wim Adriaens » 09 Sep 2017, 18:33

I have the same problem. Did all the suggested things already but no good. On my printer the filament drive gear is barely covering the u-shaped bearing and therefor barely catching the filament. So I will need to adjust that. I hope that will solve te problem.

MrDoom
Posts: 223
Joined: 01 Apr 2017, 10:01

Re: Filament feeder pressure calibration - filament grinding on retraction

Post by MrDoom » 13 Sep 2017, 13:49

Hello Wim, that seems weird, my gear covers the whole u groove on the bearing, but no more that that, if it is the same in your case you might just need to tune the temperature and retractions a little better for your material and add a filament filter with oil to allow better flow of material.

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