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MK3s - PLA clogging on every print - heat creep?  

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nirurin
(@nirurin)
Active Member
MK3s - PLA clogging on every print - heat creep?

So here is a picture of the clog. Happens the same every time. 

I've had the printer assembled for like 3 weeks, and didnt have a problem until the last couple days, but now on every print it's clogging the same way (the print doesnt stop, it keeps going, but the head isn't laying down any plastic and the gears are just grinding away at the filament). 

The only thing thats changed is the weather. It's a fairly warm 27C in the room now. But that's not that crazy hot, and a £700 machine shouldn't have to take a holiday when it gets a little warm. 

I've tried - 

1) Disassembling the entire extruder assembly (about 12 times so far, if not more, I've lost count). 

2) Doing multiple cold-pulls. 

3) Increasing the extruder idler tension

4) Reducing the extruder idler tension

5) Decreasing the hotbed temp (from 60 to 55) to try and reduce heat creep. 

6) Changing retraction settings, though I'm currently on 0.8mm so I can't see that being the problem anyway. 

Probably tried some other stuff too that I'm forgetting. 

The blob at the end of the pla pull is 2.17mm, which I believe means the issue is caused by the Prusa "specially designed" heat break? 

Another thing to note, is the extruder motor is EXTREMELY hot. Like I wouldn't want to touch it. So I don't know if this is unrelated to the heat-break creep, or if its contributing to it, or what. 

So here we go. How do I fix this? How do I make the printer print? I can usually get through maybe 1 hour of printing at best before it clogs up and just grinds filament. 

If the problem is unsolvable, and is due to the heat break, then I'll have to follow up direct with prusa for a replacement as this is just insane.

This topic was modified 2 years ago by nirurin
Posted : 26/06/2020 8:10 pm
JoanTabb
(@joantabb)
Moderator
RE: MK3s - PLA clogging on every print - heat creep?

I generally use  Generic PLA profile with 0.4mm retraction and 70C bed temp. filament 215/210C, and have just done a 12 hour print and an 8 hour print on two successive days. No idea what the actual ambient temperature is,  it's night time now, the window is open and the printer is showing 25C  so not a million miles from your temperature range

 

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

Posted : 26/06/2020 9:27 pm
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: MK3s - PLA clogging on every print - heat creep?

@joantabb

My last print was done at 0.4mm retractions, its now 26C ambient, and the bed was 55C and the PLA was increased to 215. 

Still failed after about an hour. 

Anyone else got any suggestions? I assume theres a fix for this, as I live in a cold country so anyone in Europe south of me will have faced this problem . 

Posted : 26/06/2020 11:34 pm
HoyDAviDJ
(@hoydavidj)
Active Member
RE: MK3s - PLA clogging on every print - heat creep?

You basically have two options.  Both work, one is free, one is not.

For the free option, you can adjust how you slice things.  It isn't anything major.  All you need to do is adjust your prints to print at a constant volumetric flow rate.  If you look in some of Proto Pastas blog posts you can see where they had very good results (as well as much cleaner prints) while printing at a constant 3mm^2/s.  You run into plugging issues like you are seeing here when you constantly change the rate at which plastic is flowing which allows it to start to back up and add more mass (albeit ever so slight) which cools it down into a clog.

The other option, that I personally use, is to replace the heat break with a standard E3D heat break.  The heat break that Prusa uses has a very slight taper to it, and this can cause a ton of issues.  I thought I heard they were doing away with it and only had it because of the MMU while the MMU2 didn't need it.   I may be misremembering that they got rid of it, however you can get rid of it yourself and just get a standard E3D one.  If you worried about heat creep due to high temp printing, I would recommend getting the titanium version.  It about twice the price but I have not had an issue with mine since I first started using it about a year and half ago.  

Posted : 26/06/2020 11:35 pm
HoyDAviDJ
(@hoydavidj)
Active Member
RE: MK3s - PLA clogging on every print - heat creep?

@nirurin

What slicer do you use?  Before Prusa took over Sl1cer, I was using Simplify3D but after one of their updates, it made my extruder motor get HOT.  Like, if you hold it for a couple seconds you will get burned.  It would get so hot in some cases that the print would just outright fail, it would stop in the middle of a line being printed, no reset, just full lock up and the only way out was to use the reset button on the front panel.

I looked everywhere for an answer, spent far too many hours trying to see why S3D gcode was doing it but I couldn't figure it out.

I started slicing everything with PrusaSlicer and I haven't had the problem of an overheating extruder since.  However, if I go back to S3D, it will do it again just like it did before.  I have no idea what can be causing this but it sounds very much like you mentioned with your extruder motor getting hot.  With PrusaSlicer it can get warm, as expected, but nowhere near where it used to get with S3D.

Posted : 26/06/2020 11:42 pm
nirurin
(@nirurin)
Active Member
Topic starter answered:
RE: MK3s - PLA clogging on every print - heat creep?

@hoydavidj

Interesting. For these prints I've been using Cura, but with all of the settings copied from PrusaSlicer (all accelerations and jerks etc etc). So in theory it should be the same as Prusa. 

However perhaps I should do an attempt using Slicer, just to see if that makes any difference. 

Posted : 26/06/2020 11:50 pm
fheatherz
(@fheatherz)
Eminent Member
RE: MK3s - PLA clogging on every print - heat creep?

I changed my part fan to a Sunon, which is noisier but pushes more air over the heat sink. So far (knock on wood), no more issues. I have to keep the standard heat break, as I do have an MMU 🙂 

Posted : 27/06/2020 9:56 am
HoyDAviDJ
(@hoydavidj)
Active Member
RE: MK3s - PLA clogging on every print - heat creep?

@nirurin

I thought the same thing.  I couldn't see a difference in the G Code or anything.  I was even using the profile created by Prusa for S3D and for some reason S3D was causing issues.  There is obviously something under the hood that I can't see that is causing it but I will never know.

All I know is switching back to PrusaSlicer has not had the problem return but using an S3D g code will create the same issue again.  

Posted : 28/06/2020 2:44 pm
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