MK2.5: Extruder missing steps and under-extrusion  

Re: MK2.5: Extruder missing steps and under-extrusion

I forgot to mention in the old Hot-End the issue apparently had been the heat-break. Cheers! JM

Re: MK2.5: Extruder missing steps and under-extrusion

I don't know if you checked/tried this, but it worked for me:
*** Examine where the filament is/was on each side of the extruders...you have 2 gears now and you need to examine how they are aligned....I unloaded the filament and noticed that there was some filament where it should not have been...cleaned up the gear(s) and then loosened it and moved it slightly to align with both the other one and the filament itself....you'll take the cover off of the side and notice that when your filament is inserted, it is where is should be....after moving mine slightly (I did not loosen the screw much....just a little and used a small flat head screwdriver to move it just a bit, then tightened it.... now this problem went away (NOTE: I actually printed several parts perfectly prior to this....and what happened was filament was getting ground up on one of the gears since it was riding on the toothed portion a bit....this built up and caused the issue after working for a few prints/hours)
once I had it in the correct alignment, I was able to print things that had given me trouble before with no problems (soft, flexible filaments and copper ,etc with no issues at all....extruding was better than ever.

Hope this helps you.

Re: MK2.5: Extruder missing steps and under-extrusion

Hi Michael,

that sounds like something I should really check thoroughly again. Thank you - I had not thought of this. I'll update the thread in case I find build-up between the gears and of course in case removing it makes the issues go away.

Thanks again and bets regards!
JM

Re: MK2.5: Extruder missing steps and under-extrusion

I want to thank you for this post. I was feeling like I had a failure on my hands since everyone else seemed to have no problems but then your post sounded familiar enough that I checked out things I hadn't before. My problem wasn't exactly the same but had the same effect.

I snapped one side of the Idler piece when putting in the shaft for the gear and bearings which seems to be fairly common, but since it only popped out one side, and I had already burned my bridge to printing another one, I superglued the part back together and reamed it out carefully with a 3MM drill bit (not the 3mm Allen key like I did to break it).
This all looked fine and everything seemed aligned, and I could see the gear through the hole and it seemed to be working fine.
But I too got under extrusion and the laser seemed to be malfunctioning because it would stop the print and ask me to change filament like I had requested a color change. This was how I learned that the laser not only detects filament out, but if the filament is moving too slowly.
Ultimately I opened the idler and everything fell out, the gears, bearings and the part that hold the gear shaft. I thought I was doomed to tear it down reassemble the old way and then print a new part and then re-upgrade. But it seemed like I could possibly get things to hang together just right if I adjusted the tension and hopefully got lucky long enough to get a print. It took several tries and several opening and adjusting, but I got a good print of the new idler, then I rebuilt and all is going great now. I definitely suggest printing that part 2 or 3 times to be sure you have a spare around. 😀

Re: MK2.5: Extruder missing steps and under-extrusion

Thank you, Lance, for reminding me of this open topic/post/thread!

tl.;dr? Jump to "Conclusion", please.

After reading some more and testing some more - while disassembling and re-assembling - I pretty much crossed everything off my check-list one by one. In the end I decided it was time to talk to Prusa3D support - which is excellent by the way - and after going though another long check list and a few tests almost everything pointed towards the hot-end. After a firmware upgrade it became then apparent that actually the stepper motor had been bad the whole time - who would have guessed?

The motor pretty much was the last thing I had suspected. After the firmware upgrade - one change was to reduce power to the stepper motor by firmware - the stepper didn't extrude much at all on the 1st-layer calibration. Instead it sounded like a bad attempt at techno music. My support rep told me this wasn't normal.

A few days ago I swapped the old extruder stepper motor for a new one which had been sent by Prusa3D support for free and since then I had no issues I didn't cause myself.

Conclusion: Extruder stepper motor was bad. Printer prints well since the replacement. Thank you, Prusa3D support!

Cheers! JM

Re: MK2.5: Extruder missing steps and under-extrusion

Thank you, Lance, for reminding me of this open topic/post/thread!

tl.;dr? Jump to "Conclusion", please.

A few days ago I swapped the old extruder stepper motor for a new one which had been sent by Prusa3D support for free and since then I had no issues I didn't cause myself.

Conclusion: Extruder stepper motor was bad. Printer prints well since the replacement. Thank you, Prusa3D support!

Cheers! JM

Having the same exact issues. Is there a check list to ensure it’s the extruder?

Re: MK2.5: Extruder missing steps and under-extrusion

Hi carl.v,

unfortunately none that I know of. Support proposed a firmware upgrade to a firmware that reduced extruder motor power due to a few cases of overheating extruder motors causing issues with clogged nozzles or PTFE tubes inside the hot-end - not 100% certain on the exact issue as I wasn't facing it myself - but the result was a bad stutter of the motor on z-axis calibration. Then support decided to send a new motor and it fixed the issues I had entirely.

I would propose to go threw the steps with the support team and I would almost expect that - since my issues have been resolved for months - Prusa support has a step-by-step check-list for such issues in place by now.

Good luck with resolving the issue. Both my printers are working well for me and have since the last fix a few months ago.

Cheers! JM

Re: MK2.5: Extruder missing steps and under-extrusion

Hi,

I have just finished my upgrade 2 days back, my printer used to work rather well, although it was still not working perfectly, just well. After the upgrade, I just can't get consistent extrusion and I am not sure if it is my adjustment of the bondtech tension or there is something else going on. I have tried a few test prints and I am having different types of extrusion inconsistencies that I can't seem to dial out. Most of the time it is in the form of under extrusion. I am going crazy and I can't seem to get to the bottom of why this is happening. 😥