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[Solved] Underextrusion  

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miguel angel.p
(@miguel-angel-p)
Active Member
RE: Underextrusion

I think I've found the most probably issue causing the printing problems..

The 3 small side bolts fixing the heatshink were not well tight. This was causing the nozzle as moving downside. This mean clogging the extruder while moving the PTFE tube and retracting everytime. Also this can be causing other issues like not well first layer calibration due to the up-down moving extruder.

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Posted : 25/12/2019 10:17 pm
miguel angel.p
(@miguel-angel-p)
Active Member
RE: Underextrusion

Last hours have been cleaning the hole system (extruder feed gear, hotend, debris, nozzle..) reinstall the hotend with well tight bolts and everything back to print for now.. 

I guess the pressure with PTFE+FILAMENT while retracting and moving makes the hotend loose the bolts tight and moves the nozzle.. not so well designed fitting mechanism with these so little 3 bolts..

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Posted : 26/12/2019 10:23 am
Clive
(@clive)
Trusted Member
RE: Underextrusion
Posted by: @miguel-angel-p

@andrew-d44

Exactly same issue here.. no possible to print ANYTHING...

I have request cancell order and send it back.. not ussable for now

same here, waiting for my RMA

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Posted : 26/12/2019 12:06 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion
Posted by: @miguel-angel-p

I think I've found the most probably issue causing the printing problems..

The 3 small side bolts fixing the heatshink were not well tight. This was causing the nozzle as moving downside. This mean clogging the extruder while moving the PTFE tube and retracting everytime. Also this can be causing other issues like not well first layer calibration due to the up-down moving extruder.

I also tightened mine as a bit of good practice, and I think you are absolutely correct. I overlooked this as I saw the shaving of PTFE and thinking about it, it could be created by the hot end moving up and down in the heat sink. Great spot Miguel!

Posted : 26/12/2019 1:30 pm
jameswilddev
(@jameswilddev)
Eminent Member
RE: Underextrusion

@andrew-d44

I just checked mine.  The bottom heat break screw was completely loose.  The other two appear to be stripped!

Posted : 26/12/2019 4:03 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion

@jameswilddev

Great! Well not, but at least progress is being made. I got through to Prusa Support on the chat this morning. Worth reporting and requesting some new resolution. I noticed that my bottom screw would not take the Allen key but the top two did, so I’ll have a closer look later.

Posted : 26/12/2019 4:06 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion

I just checked mine, they all seem tight, top one is okay, the bottom two are stripped

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Posted : 26/12/2019 4:08 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion

@chris-b2

Are you able to pull the hot end down or notice any play?

Posted : 26/12/2019 4:10 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion

@andrew-d44

No, it's quite rigid
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Posted : 26/12/2019 4:12 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion

@chris-b2

I did notice some dust and strands of filament (and a PTFE shaving) caught in my Bowden tubes, I also experimented for some time with my idler tension and I altered my z height to reduce pressure on the nozzle. Other than that I’m at a loss at what might be causing your issues.

Maybe time to get on line with Prusa support?

Posted : 26/12/2019 4:15 pm
Snow
 Snow
(@snow)
Active Member
RE: Underextrusion

I asked support chat and this was their recommendations:  

Clicking extruder motor You can check the following three areas: Printhead & nozzle Remove the bowden from the heatsink and check if filament can be pushed through (you might need to use the supplied wrench to remove the fitting) Preheat the nozzle and use supplied needle to loosen the clog Do a cold pull: https://help.prusa3d.com/article/lnbcnhg76k-cold-pull

 

Idler Too much tension on the idler can cause high resistance along the filament path. Ensure the filament can move through the bowden tube without having to push it with much force. You can loosen the idler here. PTFE Tube Remove bowden fitting from the printhead and carefully remove smaller PTFE tube from the heatsink Ensure there is no filament in the bottom part of the heatbreak (use a flashlight, the inside must be clean and you should only see metal) If there is any filament visible inside, heat it up, push filament in (without PTFE) and quickly pull out, residual filament should stick on filament, repeat if necessary Afterwards re-insert the heatsink PTFE tube: zPush PTFE into the heatbreak all the way down as much as possible • Loosen the 3 grub screws on the side of the heatsink, then try to push the nozzle up (COLD! Do not preheat it!), you must see PTFE moving up • Re-attach the bowden fitting to the heatsink, tighten it as much as you can, then loosen it by 1/4 turn • Gently push the nozzle against the fitting, and tighten all three grub screws • Tighten the bowden fitting (1/4 turn)

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Posted : 26/12/2019 4:18 pm
mwv liked
Clive
(@clive)
Trusted Member
RE: Underextrusion

@andrew-d44

I've tried all of things too, and changing the nozzle, using an air compressor to blow from the top of the hotend and from the bottom with the nozzle removed.

 

I spent 10 hours trying various things a couple of days ago, the last 4 hours with chat support.  Same result, well, actually worse, I can barely print a single layer now before it cloggs and stops extruding.

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Posted : 26/12/2019 4:21 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion

@chris-b2

I’ve had similar amounts of time invested and the movement of my hot end was the primary cause for me. Sorry you’re having so many troubles. 

I am at a loss with ideas to help now. Only thing I can think of is something I saw on a YouTube video that mentioned an issue with the 4.0.1 firmware. I’m running that version and no problems now.

Posted : 26/12/2019 4:25 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion

@andrew-d44

Yeah, I'm at a loss and support was out of ideas too by the end of our session.

I upgraded the firmware half way through Mondays session, it didn't seem to have any positive or negative effects.

 

I've requested to return the unit, just waiting for them to get back to me with the rma authorisation.

 

I might have another attempt tomorrow and see if I can tighten up the hotend any further.

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Posted : 26/12/2019 4:34 pm
Snow
 Snow
(@snow)
Active Member
RE: Underextrusion

Remove bowden fitting from the printhead and carefully remove smaller PTFE tube from the heatsink Ensure there is no filament in the bottom part of the heatbreak (use a flashlight, the inside must be clean and you should only see metal) If there is any filament visible inside, heat it up, push filament in (without PTFE) and quickly pull out, residual filament should stick on filament, repeat if necessary Afterwards re-insert the heatsink PTFE tube: zPush PTFE into the heatbreak all the way down as much as possible • Loosen the 3 grub screws on the side of the heatsink, then try to push the nozzle up (COLD! Do not preheat it!), you must see PTFE moving up • Re-attach the bowden fitting to the heatsink, tighten it as much as you can, then loosen it by 1/4 turn • Gently push the nozzle against the fitting, and tighten all three grub screws • Tighten the bowden fitting (1/4 turn)

This post was modified 2 years ago by Snow
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Posted : 26/12/2019 4:39 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion
Posted by: @sigfredo-n

Ensure there is no filament in the bottom part of the heatbreak (use a flashlight, the inside must be clean and you should only see metal) If there is any filament visible inside, heat it up, push filament in (without PTFE) and quickly pull out, residual filament should stick on filament, repeat if necessary Afterwards re-insert the heatsink PTFE tube: zPush PTFE into the heatbreak all the way down as much as possible • Loosen the 3 grub screws on the side of the heatsink, then try to push the nozzle up (COLD! Do not preheat it!), you must see PTFE moving up • Re-attach the bowden fitting to the heatsink, tighten it as much as you can, then loosen it by 1/4 turn • Gently push the nozzle against the fitting, and tighten all three grub screws • Tighten the bowden fitting (1/4 turn)

Cold pull is worth a shot as Sigfredo suggests if not already attempted.

Posted : 26/12/2019 4:40 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion

@sigfredo-n

Thanks for the suggestion, but two of the grub screws on the heatsink are threaded, so I can't do the last bit properly.  But I will check for any debris that might be stuck in there.

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Posted : 26/12/2019 4:43 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion

@andrew-d44

Did a couple already, they were clean 🙁

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Posted : 26/12/2019 4:45 pm
Andy
 Andy
(@andy-11)
Eminent Member
RE: Underextrusion

@chris-b2

Have you tried some different filament? I’m using Prusament with good results. I noticed that a lot of people are having issues with hatch box or others.

This post was modified 2 years ago by Andy
Posted : 26/12/2019 4:47 pm
Clive
(@clive)
Trusted Member
RE: Underextrusion

@andrew-d44

I've tried 7 or 8 different rolls, including prusament.  The prusament and my fillamentum seems a little better, but not much.

I just finished printing out a temperature tower for 22 rolls of filament on my mk2 and apart from a little stringing on a couple of rolls they all printed nicely.

The mini seems very sensitive to different filaments, where my mk2 prints anything I throw at it.

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Posted : 26/12/2019 4:55 pm
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