RE: unable to resolve underextrusion
Out of ideas. Only thing I can think of is the heat break temperature is under-reporting due to a faulty thermistor. Example, it's says it's 35 but it's really 50.
RE: unable to resolve underextrusion
Out of ideas. Only thing I can think of is the heat break temperature is under-reporting due to a faulty thermistor. Example, it's says it's 35 but it's really 50.
So 35 to 40°C would be okay for the heatbreak temp, but 50° would be too much? Unfortunately I have no clue what values would be considered normal...
RE: unable to resolve underextrusion
So 35 to 40°C would be okay for the heatbreak temp, but 50° would be too much? Unfortunately I have no clue what values would be considered normal...
Above 50° PLA will start to soften. What I'm suggesting is maybe the heat break temperature is higher than what is being reported. Just a guess really.
@conrad-2 suggested you test the effort required to *pull* filament through the ptfe tube but you only reported pushing ... this is a test for internal damage/wear of the tube (usually due to extended use of abrasive filament but there can be other causes) - please complete this test.
You definitely have a cooling air flow problem - this *might* have permitted heat creep or perhaps it is a consequence of multiple repair attempts and not the original issue - if the fans are OK then check the shroud and the air flow path.
Cheerio,
RE: unable to resolve underextrusion
This is starting to sound like an intermittent somewhere in the extruder wiring. The fact that under-extrusion started, then stopped, is odd. You've got a new motor, so it's not the motor. The temperatures don't seem off, though I don't know exactly what the heatbreak temperature should be. 38 doesn't seem that high, since people run the whole unit that high. It's a pita, but you've had so much apart already, I'd inspect all the wiring from the extruder motor on back. Look for cracked circuit board traces and bad solder joints. Magnifier and bright light! You won't be able to tell if there's an actual circuit problem, as opposed to a connection problem, but that's all I can think of right now.
RE: unable to resolve underextrusion
I have spent some more time on this matter....
I cannot feel any difference pulling filament through the PTFE tube from either side. It goes through the tube fine.
Since it was suggested that there might be some wiring issue, I have remove the extruder once again. I kept motor, extruder gear and heatsink together but disconnected all cables, even the loveboard, and put everything together again. I could not find any obvious issue with the wiring or the wires themselves. I also gave the fans a closer look and could not find any obvious issues. As mentioned earlier, they are turning properly when printing - at least from what I see I would call it "turning properly as expected". I also cannot see anything that might block the airflow. After putting everything back together, I have run some more testprints. However, still again with very mixed results. At one point or another it starts to underextrude. Printing in normal mode instead of stealth mode does not work at all.
I am waiting now for the shipping / packaging box from Prusa to arrive. The printer will go back for checking to Prusa.
Thank you all for your comments. Your time and input was very much appreciated.
RE: unable to resolve underextrusion
At some point it's probably best to let Prusa put in the time to fix it. I'm surprised your head hasn't exploded! I try not to get mad at machines, but they can certainly get me going. Forgive me, but my brain doesn't want to let go of this. If the Nextruder is clicking, either it can't pull or it can't push. You've covered the pull side by removing everything. You've covered the push side in terms of temperature and such. After a good sleep, I'd probably pull both the tubing and the nozzle, feed filament and run the motor (controls menu) to see how much force the mechanism can generate on the filament over a couple turns of the gear. I don't have a number, but if you pinch the filament and restrain it, I'd expect a significant force before the mechanism clicks or slips.
RE: unable to resolve underextrusion
The problem is most likely caused by a blockage of one of the 4 channels in the E3D Prusa Nozzle - High Flow (my own experience), even extruding diagonally from the nozzle shows this. Reduced flow causes insufficient extrusion. Increased hotend temperature will not help. The channel may be clogged with mechanical dirt that got into the nozzle along with the filament. A partially clogged nozzle like this cannot be cleaned in any sensible way (needle, temperature). I solved a very similar problem - insufficient flow and clicking of the gearbox - by installing the Nextruder V6 Nozzle Adapter + a nozzle from another manufacturer, which has only 3 channels and is therefore less prone to clogging. BondTech CHT Nozzle (E3D V6 high-flow nozzle).I mentioned the problem in the gearbox clicking thread.
TomK
RE: unable to resolve underextrusion
Sorry for the late response. Thank you @conrad-2 for the additional thoughts put into my issue. I have not tried your suggestion yet, though. If I have some time before packaging, I will look into it. Right now the printer is more or less ready for packaging once I receive the box from Prusa.
@tomk-2, thanks for your input as well. That sounds really interesting. Do you think this could be the reason on three different nozzles? I have the original nozzle from my kit and then already got two replacements - obviously the same model - during my troubleshooting efforts with Prusa support.
RE: unable to resolve underextrusion
If it happened to 1 nozzle it's very possible.
3 different nozzles with exactly the same problem? very unlikely IMO.
RE: unable to resolve underextrusion
I think this could be the reason even though it is 3 different nozzles of the same model series. In the overall Prusa Nozzle brass CHT assembly, the 4-channel inlet to the final nozzle size, e.g. 0.4 mm, is really prone to clogging with mechanical dirt. After solving my problem with insufficient extrusion: replacing the Prusa nozzle brass CHT assembly with an adapter + Bontech GF nozzle - see previous post - I also added a filter to clean the filament before entering the main long tube. Since then, I have been printing (PETG and SLA) without problems.
RE: unable to resolve underextrusion
jbpr, would you be willing to take the cover off the gearbox and show us the inside?
I ask because as you might have seen in my thread; after I thought I was no longer experiencing my issue if I eliminated the bowden tube from the equation it very soon resurfaced even without the tube. The next thing I tried was thoroughly cleaning the outside of the extruder gear with isopropyl alcohol (with a brush, on the machine, I took the top cover off for easier access). Since doing that I've not had a single print fail and I've printed multiple of the object that previously would fail every time.
My theory is as I have quite a lot of mechanical sympathy I've put too much grease in the gearbox when I was assembling it. It's clearly not a sealed gearbox and I'm wondering if the excess grease I applied at assembly has slowly seeped out and got on the teeth of the gear. You'd never be able to see it because it's almost clear and the view of the gear is so poor when it's in the print head. Conrad also suggested that it would align with some users experience of flawless prints for a few weeks and then a degradation suddenly without explanation as the excess grease works it's way out of the gearbox and on to the teeth.
Could be worth a few mins?