Extruder requires too much force to insert filament
Hi all-
I've built my new MMU2S and I've yet to get a successful multi-material print on it (I've yet to try one even, because even with single-filament prints I've had issues getting the filament to load or unload at least half the time). I've worked out a number of friction issues which seems to have helped my unload issues, but I'm still having my load issues.
I believe the fundamental problem is that the extruder has a problem causing the filament to require too much force to enter the gears.
The symptoms I'm seeing are:
- The MMU2S will push the filament to the extruder, and the extruder's gears will start turning (along with the MMU2S's pulley gears) in the direction pushing the filament into the extruder
- The filament does not proceed forward and the MMU2S's pulley gears start grinding the filament down
- The MMU2S will retract and push the filament again a few times. Very occasionally, the filament will insert properly on one of these times.
- If I manually push the filament through with some force, then it gets caught in the extruder gears and the print proceeds.
- If I bypass the MMU2S and print directly through the extruder, it takes way more force than seems reasonable to get the filament loaded into the extruder.
Here's what I've tried
- Calibrating the IR sensor. As far as I can tell, the calibration is correct and filament is detected by the extruder when I would expect it to be.
- Adjusting the tension on both the extruder idler AND the MMU2S idler. I've tried increasing every combination of increasing & decreasing tension on both -- maybe I'm just not finding the right combination, but it sure doesn't seem to be helping.
It's worth noting that I had no problems inserting / removing filament before the MMU2S upgrade -- so if something is screwed up in my extruder I'm guessing it happened during the upgrade.
Anyone have any ideas that I can try? Any assembly errors that seem possible given this symptom?
Thanks so much!
Best Answer by cprussin:
Aha! I seem to have solved my problem! While trying the solution that @joantabb recommended (thanks! it wasn't my issue, but I appreciate the tip!) I discovered that the Festo fitting on the extruder end of the PTFE tube was slightly unseated, and the filament was catching inside the fitting and never making it to the extruder. I removed the tube and re-seated the fittings and now I don't seem to have my loading problem any more!
The extruder gears still seem tight to me -- certainly tighter than I would have anticipated -- but I suppose that wasn't my problem after all.
In case anyone's interested, the way I figured this out was that, as I was working on Joan's recommendation, I was curious to see how much force would be required for me to get the filament loaded if I applied force right at the extruder (in addition to the force from the MMU2S's pulley motor). So I disconnected the PFTE tube from the extruder, intending to guide the filament from the end of the PFTE tube into the extruder by hand and add some force. But when I disconnected the tube, I noticed the filament wasn't ever making it out of the tube at all and was caught on the fitting!
with the filament out of the extruder, slacken the extruder tension screw off completely, then re tighten until the screw, just touches the spring, with no filament in the extruder... then, making sure that your filament has not been pre ground in a previous attempt, and that it has a nice angled cut on the end, reload your filament to the MMU, then try running a new print, and see if the filaments load as expected.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Solution
Aha! I seem to have solved my problem! While trying the solution that @joantabb recommended (thanks! it wasn't my issue, but I appreciate the tip!) I discovered that the Festo fitting on the extruder end of the PTFE tube was slightly unseated, and the filament was catching inside the fitting and never making it to the extruder. I removed the tube and re-seated the fittings and now I don't seem to have my loading problem any more!
The extruder gears still seem tight to me -- certainly tighter than I would have anticipated -- but I suppose that wasn't my problem after all.
In case anyone's interested, the way I figured this out was that, as I was working on Joan's recommendation, I was curious to see how much force would be required for me to get the filament loaded if I applied force right at the extruder (in addition to the force from the MMU2S's pulley motor). So I disconnected the PFTE tube from the extruder, intending to guide the filament from the end of the PFTE tube into the extruder by hand and add some force. But when I disconnected the tube, I noticed the filament wasn't ever making it out of the tube at all and was caught on the fitting!
Happy Printing!
Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK