Extruder Motor Skipping and Inconsistent Layers
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@phaedrux Just tried the new thermistor M308 parameter, and ran another pid tune, still having the same issue. If I put my fingers on the filament as Its being fed, I can feel almost like a bump or a jolt every time it skips and doesn't lay down filament. Could it be something in my slicer profile? I'm using PrusaSlicer with the MK2S profile. I've attached a few pics to show what's happening.
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Does it extrude cleanly into free air if you just use DWC to heat the hotend and use the extrude buttons?
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@phaedrux Just tested, it does not extrude cleanly into air when extruding from DWC. Also, when extruding into air, as the motor skips, I can make it skip a bit less by pushing on the filament with my fingers, but that doesn't cure the problem entirely.
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Looking at the print sample, it looks like the gap between bed and nozzle is excessive. This can cause exactly the kind of horrible mess you see here. Of course the 'not extruding cleanly into air' also doesn't help.
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@jens55 Nozzle height could definitely do with an adjustment, but I'd like to see good extrusion first.
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@secretasianman7, yeah, the bit about the motor still skipping and skipping less if you push on the filament is a great big red flag.
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@jens55 Agreed. Feeling very perplexed about the root cause as I've changed out nozzles multiple times, and swapped out the entire hotend, thermistor, heater cartridge and stepper motor to no effect. Quite a strange problem...
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@secretasianman7 said in Extruder Motor Skipping and Inconsistent Layers:
Swapped extruder motors to test if bad stepper. Also changed from a 1amp stepper to 1.5amp stepper to test if underpowered stepper.
So you had the problem before you swapped the extruder motor as well?
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@phaedrux Yes. The perplexing nature of this problem is that it has persisted across multiple motors, drivers, nozzles and hotends. Also across multiple filaments, all PLA.
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Extruder tension problem?
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@phaedrux tried extruder tension in between all levels from very tight to minimal tension. Problem persists
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@phaedrux I'm running firmware version 3.4, any chance that either rolling back to a previous version or trying out 3.4.1 would affect things at all?
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Try disabling the print cooling fan in the slicer and see if the problem persists.
I'm using extruder acceleration of 3000 mm/sec, and extruder jerk speed of 50 mm/sec. You don't want either set too low because if the extruder can't keep up with the printing speed, the controller will limit the printing speed to values that the extruder can keep up with.
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It still seems like your temperatures are out of whack. Can you try increasing the temperature by 5 degrees at a time and testing the extrusion into free air? Keep upping the temp if it still isn't smooth. Stop after 50c or so if it still hasn't improved. The theory is that the hotend isn't actually as hot as it is reporting, so you're not actually melting the filament completely.
Also, how fast are you extruding when you test into free air? Is a slow 1mm/s smoother than a fast 5mm/s?
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@phaedrux Ok we're getting somewhere. I did as you asked, taking note of how much skipping occurred per each set temperature, from 205 to 250, as I extruded into the air. At 205 skipping was constant. Frequency of skipping began to reduce as temperature increased. At 250, skipping occurred noticeably less frequently than at any temperature below that. Though the skipping did still occur enough to mess up any print I would have done.
Also regarding feedrate, yes there is significant difference in skipping with feedrate. 1mm/s provides the least skipping, 2mm/s skipping is very much worse where extrusion barely happens at all, and at 5mm/s motor just vibrates in place with no rotation.
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Alright, then we need to determine if your thermistor is actually a genuine item from E3D or actually something else. Where did you get it?
If the thermistor is something else and the temps are wrong, we'd need to determine what values to actually use. Or perhaps there is something wrong with the assembly causing temps to report incorrectly. Photos of the hotend?
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@phaedrux The current thermistor being used came with the E3D V6 hotend kit which I had purchased from Matterhackers and had shipped to me. I would also like to add that this problem still existed with previous hotend before performing the swap, the previous hotend was an E3d V6 which had came with the original prusa machine which I had ordered in 2018 direct from prusa. For pictures, the hotend is pretty well encased in the extruder assembly. I'd gladly disassemble and take photos, can you please detail exactly what you'd like to see?
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Ok, so it sounds like it's a genuine E3D thermistor, and we have you using the correct settings now.
This may sound silly, but are you sure you're using PLA? Do you have different filament to test with?
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@phaedrux I am sure I'm using PLA as the roll I'm using came as a two pack and I'm using the other roll in an anycubic i3 mega S right next to my machine in question. The problem persisted with a roll of white SUNLU PLA
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@phaedrux An important data point to add. This machine and duet board combo hasn't always produced this issue. Upon very first installing the board and getting things up and running for the first time. I was able to print two decent benchys that were free from this issue. From there, I updated firmware to the latest and ran a pid tune of the original hotend that came with the machine, and that is where this issue began surfacing. At this point hardware feels out of the question to me and this seems to be some form of software issue. Any chance I can factory reset the firmware but keep my config file?
