Extruder randomly retracting
Ever since I upgraded to the latest firmware and Slic3r on my MK2, I get random retractions on my first layer. If you watch the screw, you can see it skip backwards when it's supposed to be printing just a clear, flat line. You can see a gif at https://imgur.com/f06Ey0A . It won't embed for some reason.
If I make it through the first layer, everything will be fine for the rest of the print, but I'm only getting through the first layer maybe 10% of the time without these random retractions.
It's worth noting that I've tried four different filaments, and been through all sorts of tweaks on the longer screws keeping the tension on the extruder, but nothing seems to have made any difference. And, to be honest, watching the motor run backwards for a split second makes me pretty sure it's either in the software or in the extruder itself.
Any help would be greatly appreciated.
Re: Extruder randomly retracting
The motor retracts filament when lifting the nozzle for some moves. Perfectly normal.
A better video would be of the part showing where the nozzle isn't extruding.
Re: Extruder randomly retracting
My point is that it shouldn't be retracting in this video: it's just going back and forth filling a flat base layer on the bed. But because it's retracting, instead of getting a clear line, I get gaps.
Re: Extruder randomly retracting
A photo of the part that isn't being printed correctly can also help.
Without looking at the slice, it is impossible to tell if retraction is planned or abnormal. If it's a simple square pattern sure, there shouldn't be much lifting, but if the part is complex, the slicer can do odd things.
That said, it's unlikely - but a bad Einsy motor controller could be wigging out. I'd do more testing to rule out simpler causes. Try printing this.
Re: Extruder randomly retracting
There's a few things that could cause this; here's a few suggestions:
Check the E motor cabling. Make sure it's not pinched between the extruder body and the X axis mount
Change the nozzle; there may be a partial blockage
Make sure you are not printing in silent mode (lower E-motor power)
Increase temp by 10 to 25 degrees (useful if your filament is damp or even wrongly labelled)
Ensure your filament feed is good and that the filament is not tangled on the spool
Clean your drive gears and check alignment with inlet and PTFE
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Extruder randomly retracting
Try printing this.
https://www.thingiverse.com/thing:2700178
Since this being a bed level test and the "retracts" most probably occuring during the 1st layer it could
well be that the live-z is too low.
With the above mentioned low-power settings and a too low nozzle a extruder-step-skip is most likely
which looks pretty well like a retract.
I wouldn´t exclude a broken cable or short what indeed was my 1st thought, too.
But that could be easily tested printing a small object (20x20x20 cube) and checking whether this still happens after the 1st few layers.
Provided a gcode we could have a look if that maybe comes from the slicer (which I believe not).
Re: Extruder randomly retracting
Check the E motor cabling. Make sure it's not pinched between the extruder body and the X axis mount
Change the nozzle; there may be a partial blockage
Make sure you are not printing in silent mode (lower E-motor power)
Increase temp by 10 to 25 degrees (useful if your filament is damp or even wrongly labelled)
Ensure your filament feed is good and that the filament is not tangled on the spool
Clean your drive gears and check alignment with inlet and PTFE
Thanks for all the suggestions!
From the next post:
Re: Extruder randomly retracting
When was the last time you changed your nozzle. For me, it's every 2 to 3 months.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Extruder randomly retracting
When was the last time you changed your nozzle. For me, it's every 2 to 3 months.
Interesting. I've never changed the nozzle at all.
New followup: I redid all the calibration, and it happens even during the built-in Z-level adjustment print. You can see the places that the extruder skipped here:
This occurs on high power, auto power, and silent mode. It's worth noting that if the extruder is going to retract, it'll happen in roughly those spots on the x-axis. It also *always* happens at the end of the pre-print extraction at the front of the bed, in case that adds more information.
Re: Extruder randomly retracting
This really looks like a defect in the wiring, now!
Re: Extruder randomly retracting
It's worth noting that if the extruder is going to retract, it'll happen in roughly those spots on the x-axis.
That does sound as though one of the E motor wires has an internal break. When this happens the break is usually just behind the extruder, where the cable is bent 90 degrees at a couple of points to get into the cable bundle.
You can test it by wiggling the cable bundle while printing the calibration. Do you have the Mk2 or Mk2S? The "S" improved the cable support at the back.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Extruder randomly retracting
I've got the original MK2. Sadly I'm flying out tomorrow for a week, so it's going to be a bit before I can check the wiring. Here's hoping that's it and I'm able to fix it up.
Re: Extruder randomly retracting
Bad wiring or filled teeth on one side of the Bondtech ...
Re: Extruder randomly retracting
Bad wiring or filled teeth on one side of the Bondtech ...
Tim, the Mk2 does not have Bondtech drive gears (unless it has the MMU upgrade) and OP has already stated that the gears are clean.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Extruder randomly retracting
Bad wiring or filled teeth on one side of the Bondtech ...
Tim, the Mk2 does not have Bondtech drive gears (unless it has the MMU upgrade) and OP has already stated that the gears are clean.
Peter
My apologies: if not the Boindtech gear, then whatever this gear is called (from the assembly manual for a Prusa Mk2):
https://manual.prusa3d.com/Guide/5.+Extruder+Assembly/114
That said, a broken wire on a stepper doesn't fit the symptoms. A stepper requires all four wires to move. Breaking any one of them will cause the motor to stop, and not move: wiggle maybe, but no "retraction" is possible. So it would have to be a bad controller or bad firmware.
Re: Extruder randomly retracting
That said, a broken wire on a stepper doesn't fit the symptoms. A stepper requires all four wires to move. Breaking any one of them will cause the motor to stop, and not move: wiggle maybe, but no "retraction" is possible. So it would have to be a bad controller or bad firmware.
Not quite. As with intermittent PINDA failures, the same can also occur with the other cables as I mentioned earlier.
The PINDA cable issues are well documented on these forums; I can't recall having seen such a problem with the E motor. This may well be the first.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Extruder randomly retracting
That said, a broken wire on a stepper doesn't fit the symptoms. A stepper requires all four wires to move. Breaking any one of them will cause the motor to stop, and not move: wiggle maybe, but no "retraction" is possible. So it would have to be a bad controller or bad firmware.
Not quite. As with intermittent PINDA failures, the same can also occur with the other cables as I mentioned earlier.
The PINDA cable issues are well documented on these forums; I can't recall having seen such a problem with the E motor. This may well be the first.
Peter
A stepper requires opposing bipolar fields to step - any broken wire will prevent this. With any broken wire, the motor will at best wiggle to an adjacent full step, leaving any micro-stepped location behind, and while it's possible the half step will be backwards, I doubt we'd see it in a video (1.8 degrees isn't much movement, and falling off a locked microstep would be less than that). I'll concede a wire that is failing intermittently might look like reverse travel, but that'd be dumb luck. If the printer in question has a strong rewind force of the filament, then loss of a wire conceivable could spin the motor backwards, but that's really reaching. And a lost PINDA won't spin the extruder motor backwards, either.
I'm still leaning towards a nozzle plug of some sort - and the video is a red herring (since we can't see what was being printed). I'll step out; perhaps you can get the guy going again.