One of 5 XL Nextruder heads clicking and failing prints
I'm pulling what's left of my hair out over here and am hoping for some guidance as to how to proceed. I have a two-head assembled XL ordered on launch day and delivered late summer of last year. It has been working without much problems up until about a month ago where I noticed some prints were occasionally failing with what appeared to be extrusion problems. Shortly afterwards I received the next 3 heads and installed them, which I don't think is pertinent but I figure I should mention it. I've started getting a little more careful about tracking this down and here's what I know so far:
- Extruder 2 is clicking, laying down very inconsistent extrusions with occasional globs and thin spots
- Issue only happens on head 2, zero problems on heads 1,3,4,5
- Issue is inconsistent, print will start and work for a few layers but will nearly always start happening within an hour of printing.
- Issue is worse with PLA than PETG
- Issue does not seem to change in relation to the specific roll of filament used. I can unload the filament from head 2 that's having a problem, load it into another print head, and it'll print all day. Likewise, I can take another working filament from another head, load it into head 2, and I'll start having problems.
- I keep all my filament stored in airtight bins w/ desiccant.
- I've tried adjusting temperature without success.
- Lowered the max volumetric speed which reduced but did not eliminate the problem.
- Backed off the extruder tension screws by two turns, it started skipping, tightened back up by one turn (so now loose from factory by a single turn) and it went back to clicking.
- Printer originally had 0.6 nozzles installed, I switched to 0.4 a while back before this started happening.
- Performed a cold pull with cleaning filament and have run a .35 needle through the nozzle. Cold pull came back looking clean.
- Swapped a new 0.4 nozzle in to see if it helped (upgrade came with a set), no change.
I note that the Mk4 has an option to calibrate the gearbox which I don't think is an option on the XL. I'm thinking about taking this thing apart but am worried that there might be implications there which I don't fully understand, and Prusa hasn't released any guidance that I'm aware of on how best to assemble the XL's Nextruder.
Best Answer by mUltic0re:
did you switch the nozzle in the failing toolhead? if yes you might have overtightened the srew and kinked the stainless tube.
This does sound like a toolhead issue but to rule out the dock and the connectors try switching the toolhead with one of the others - does the problem follow the head or stay with the dock?
Cheerio,
RE: One of 5 XL Nextruder heads clicking and failing prints
Could there be a kink in the PTFE tubing somewhere in the run?
RE: One of 5 XL Nextruder heads clicking and failing prints
Thanks to the suggestions above! Here's what I've done in response:
- Unload filament from extruders 1 and 2, power down printer, and remove extruders 1 and 2 from the dock
- Pull wire harness, filament guide, and strain relief from each head and swap around, Extruder 2 is now in dock 1 with the wires, filament guide, and strain relief that was originally in dock 1, and vice versa. This should isolate the extruder from any issues with the dock or the PTFE filament guide.
- Run dock calibration on docks 1 and 2.
- Run tool offset calibration on all extruders
- Started a job on extruder 1, using same PLA tested originally. Job features some high volumetric rate runs, it's a long flat part where the head can move quickly while running full extrusion. Ran well for about an hour then clogged hard. I wasn't near the printer at the time (F1 race is on!) and came back to a half-printed part and the printer saying it completed.
So it looks like the problem is following the extruder. I'll run the same job again on extruder 2 to confirm.
- Ran
RE: One of 5 XL Nextruder heads clicking and failing prints
So it looks like the problem is following the extruder.
I suggest watching the temperature of the extruder as it extrudes at the highest rate. It could be the heater isn't keeping up with the filament flow and that's causing it to back up and jam. If the temperature drops more than two degrees during heavy extrusion, either you're pushing it out too fast, or the heater is weak.
I had a weak heater on E2 that had the weirdest symptoms. With PLA, it never errored out and sometimes jammed. Sometimes delaminated. Sometimes just went wacko. When I tried printing PCTG, it failed with an error message as that material prints a lot hotter.
I went back and forth with support to no solution from them, and finally, I just bought a heater ($12) and that fixed it.
RE: One of 5 XL Nextruder heads clicking and failing prints
I suggest watching the temperature of the extruder as it extrudes at the highest rate. It could be the heater isn't keeping up with the filament flow and that's causing it to back up and jam. If the temperature drops more than two degrees during heavy extrusion, either you're pushing it out too fast, or the heater is weak.
I've now run another print on tool 2 to confirm it's still working well after the swap and the print completed without drama. The temperature charts for each run on problem-tool 1 and good-tool 2 show a ruler flat nozzle temp. In both cases, 220 with the occasional dip to 219.
Are there any official XL Nextruder dis-/re-assembly guides? I'm kinda thinking of poking around inside of this thing but I also expect there may be procedures involved for a working assembly.
RE: One of 5 XL Nextruder heads clicking and failing prints
did you switch the nozzle in the failing toolhead? if yes you might have overtightened the srew and kinked the stainless tube.
Are there any official XL Nextruder dis-/re-assembly guides? I'm kinda thinking of poking around inside of this thing but I also expect there may be procedures involved for a working assembly.
You are probably still within your warranty period. Contact Prusa Support first; if they agree then you can open it under their directions without voiding the warranty.
Cheerio,
RE: One of 5 XL Nextruder heads clicking and failing prints
did you switch the nozzle in the failing toolhead? if yes you might have overtightened the srew and kinked the stainless tube.
I did! Prior to the upgrade I had purchased 0.4mm nozzles for my existing two heads, not knowing the upgrade kit would later come with a set. I had put those in, well... probably right around the time this started. I just pulled it out to inspect and hey look at how dumb I am:
The good news is that I have a couple spares 😀 Installed it, running tool offset calibration, and will run another test print.
RE: One of 5 XL Nextruder heads clicking and failing prints
So far, so good. No failed prints since swapping the kinked nozzle out.
RE: One of 5 XL Nextruder heads clicking and failing prints
Glad you found it.
RE: One of 5 XL Nextruder heads clicking and failing prints
Glad it was an easy fix and you didn't have to dissassemble the toolhead.