Hotend under extruding and extruder motor skipping an hour into the print
I've spent all day trying to figure this out. I bought my mk3S several months ago and have nothing go wrong with it until today. I woke up to a crash failure this morning and noticed that the print, which is a fairly thin blade shape had under extruded a layer lower down on it that finally failed at around 100mm, causing the crash. I tried reprinting and after an hour or so heard the extruder motor skipping and obviously under extruding. I have been looking everywhere online to fix it and found several other people with similar problems and tried their solutions, but I got no luck. Here's a list of all of the fixes I tried;
Replaced the nozzle,
Disassembled the hotend and made sure everything was clear inside and the nylon tube was intact; it looked fine,
Made sure the axle on the extruder idler was supported on both sides,
Tightened the grub-screw on the motor shaft,
Adjusted the tension on the idler,
Re-sliced the model,
Tried other older models,
So far nothing I have tried has stopped this from happening. Every time I try to reprint, it starts skipping around an hour or an hour and a half into the print. This also started extremely abruptly; It had just finished a similar model literally minutes before I started the one that failed last night, and it printed perfectly. I have had the same problem with another printer that I've had for years; a cheap Kossel Delta kit, and the only solution I found was to replace the hotend entirely. That's not something I want to do to an E3D hotend. Does anyone have any suggestions? Anyone know why it works fine until an hour into the print?
I'm printing with the PLA that came with the printer (Prusment I assume) and the firmware version is 3.7.2-2363
I'll update the firmware tonight, but I doubt that will fix it. I'm pretty sure this is a physical issue.
RE: Hotend under extruding and extruder motor skipping an hour into the print
Just ran a new print with the updated firmware and as I suspected, the problem was not fixed.
RE: Hotend under extruding and extruder motor skipping an hour into the print
If a problem starts well into a print, heat is a likely culprit. Possible causes include:
- Printing in hot room.
- Printing in enclosure with excessive heat (mainly PLA).
- Excessive feed rate (out-running hotend capacity).
- Excessive retractions.
- Over- or under-tight extruder tension screw.
- Friction in feed path.
- Filament feed misalignment.
- Prusa-fied heatbreak (2.2mm notch).
Please confirm you're not printing in a hot environment. Does the failure occur at a consistent feature (e.g. printing large sections of infill, allowing nozzle to come up to full speed)? Have you checked your extruder tension screws and filament feed path?
The only obvious thing I see missing from your list is trying another filament. Is it only one type that fails?
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RE: Hotend under extruding and extruder motor skipping an hour into the print
@bobstro
I did a few more test runs with the same filament, but hotter; same result, and with some Hatchbox PETG, which stripped out twice after the first layer, which it never did before. The room I'm printing in isn't hot maybe around 22C max. The only thing I can think to do now is completely disassemble the hotend and make sure that there is absolutely nothing that could be restricting the flow.
RE: Hotend under extruding and extruder motor skipping an hour into the print
The issue is usually pretty simple - no need to disassemble everything.
A photo of a failed print is significantly better to diagnose from than a few words. Post a photo (clear, high res, and focused) of one of your problem parts and you'll probably get a more specific answer.
And - a very common issue is when folks have torn things apart, they didn't follow the E3D-V6 assembly instructions to the letter. Very small missteps lead to complex issues. And probably why a new hot end works better than one you've "repaired."
RE: Hotend under extruding and extruder motor skipping an hour into the print
Well their's not much to show. A little underextruding on the supports, but the part seems fine until it just stops extruding entirely and the motor starts skipping.
RE: Hotend under extruding and extruder motor skipping an hour into the print
Are you finding the filament snapped off at the top of the extruder (usually below the bondtech gears but protruding from the PTFE tubing), or jamming up lower in the hotend near the heater block?
You might try simply slowing down to see if that helps. If so, some slicer tweaks may be all you need. Otherwise, if the filament snaps up high, check all the feed and friction issues. If down low, you might try a non-Prusafied E3D heatbreak.
On re-reading the original post, is this problem occurring only with this part, or with any print?
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He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Hotend under extruding and extruder motor skipping an hour into the print
The model looks a bit weird; and the layers do too. Areas are skipping long before the top of that print. Even a few weird angles that look like slice problems.
When the printer starts clicking (stops extruding); unload the filament normally, and snap a photo of the filament stub that comes out.
Also, wouldn't hurt to export and zip a 3MF of the platter and post it. And if not sliced in P.Slicer, post the STL zipped up.
RE: Hotend under extruding and extruder motor skipping an hour into the print
Also - you mention the term "crash" - did the printer detect and warn you a crash had occurred? If that has happened, report what the "belt tension" numbers are showing. They really tell a person nothing about the belt tension, but are handy for knowing the overall health and friction happening in the X and Y axes.
RE: Hotend under extruding and extruder motor skipping an hour into the print
@bobstro
It looks like it's getting stuck at the nozzle or right above. I can unload the filament with no issues from the lcd screen and the filament that comes out looks perfectly fine. This is already a pretty slow part at 25mm/s. I think I will try a normal e3d heatbreak. That's a lot cheaper than replacing the whole hotend.
What still baffles me is that this problem came out of the blue with hundreds of hours of printing with the exact same setup before this started and then getting nothing. Could my extruder motor be going bad and not be able to provide enough force?
RE: Hotend under extruding and extruder motor skipping an hour into the print
It looks like it's getting stuck at the nozzle or right above. I can unload the filament with no issues from the lcd screen and the filament that comes out looks perfectly fine. This is already a pretty slow part at 25mm/s. I think I will try a normal e3d heatbreak. That's a lot cheaper than replacing the whole hotend.
That's probably the path of least resistance. There seem to be several factors that tie into this issue, but a heatbreak replacement is simple enough. Do be aware that your heater cartridge and thermistor may be pretty well bonded onto your heater block, so be prepared to replace a few parts. I did a heatbreak + heater block + heat cartridge + thermistor replacement on mine.
As you wait for parts, you can try adjusting retraction settings. I find a 50mm/s retract with 25mm/s de-retract works well, though I've never experienced this particular problem. Simply slowing down overall would be worth testing.
What still baffles me is that this problem came out of the blue with hundreds of hours of printing with the exact same setup before this started and then getting nothing. Could my extruder motor be going bad and not be able to provide enough force?
I suspect it's a combination of things. Enough crud may have built up in the heatbreak, or you may just be hitting a 'lucky' combination of factors. I haven't had the same problem, so I'm not able to suggest much more than the part replacement as recommended in the 3D Printing Noob video.
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He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Hotend under extruding and extruder motor skipping an hour into the print
How hot is your Extruder? I was having this issue on PLA with later firmware and there is a bug report on it - https://github.com/prusa3d/Prusa-Firmware/issues/1757#issuecomment-536875813 Long prints with lots of retractions can cause heat creep softing PLA causing poor feeding.
I've added some Heat Sinks for my Extruder. The other option was to add a cooling fan.
RE: Hotend under extruding and extruder motor skipping an hour into the print
If anywhere along the line you printed anything even mildly abrasive, it might have damaged the polish in the throat of the heat break.
PLA piling up around the extruder gear is the motor induced heat creep symptom. A jam lower in the heat break is the 2.2 to 2.0 step issue, and usually has nothing to do with the extruder motor.
Unloading filament and measuring the stub diameter can confirm a heat break jam. 2.2 mm and you have proof. 2.0 mm and it's unlikely the heat break is involved.