Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.  

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

Hi Samuel, 
I am one of the Moderators on the forum, 

the pictures that you added came out as thumbnail size pictures which don't show a lot of detail, 

as you can see, I have added a second copy of your first picture, and I enabled 'Link to: Media File'

this has the effect of making the picture 'clickable' so that it enlarges when clicked

regards Joan

RE: Persistent problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

Hi Joan,

Many thanks! I can't seem to edit the original post so I'm re-posting it here with better images:

Hi everyone!

I (actually a friend) recently bought a MK3S kit that has been giving us persistent issues. A while ago, 1/5 printing jobs failed but now almost every job fails. When I was assigned to troubleshoot this printer, the printing jobs would fail after x number of layers and the extruder and surroundings looked like this:

The filament would also have the typical grinding issue shape. So something would prevent the filament of running through the nozzle and being extruded. At the moment I use E-PLA with 215 degrees but I've tried with other filament types and I have the same issues.

I then cut the retraction speed in half, untightened the idler but the problem did not go away.

So then I decided to disassemble the whole extruder, cleaned every part and assembled it again. Same issues.

A typical problem I have is this:

I'm not sure you can see but it starts printing at the bottom right corner and the layers are nicely extruded. But as the printer keeps going it seems like the distance between every layer increases and at some point, it stops extruding.

After this, I figured maybe the temperature wasn't high enough so the nozzle gets more and more clogged so I increased the temperature to 230 degrees. The filament temperature range is 190-215 degrees.

I made a simple pyramid shape to print and the first time I got this:

It looked perfect.

I then just simply restarted the printing job with the exact same settings and got this:

Nothing would be extruded.

I then unloaded and loaded the filament and started the same pyramid print job and this time it succeeded again.

After a successful second print, I started the print again and the same error happened. Nothing would be extruded, just small, small parts.

The boat benchy ended up like this:

I'm really going nuts, tried different settings for more than a week now. Do you have any clue what the problem is? Whenever i unload and load the filament it will extrude for a while but then something happens and I need to unload/load the filament again.

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

Looking at your picture your ptfe tube below the extruder gears looks almost chewed up, probably by the gears themselves.  If you have a particle of ptfe down in there that's almost a guarantee of a clog at some point.  I've never seen that many plastic shavings/particles on my printer so something is definitely off.

I would re do a full extruder disassembly to the point where you can get the ptfe tube out,  thoroughly clean everything and inspect the tube for damage /replace if it is and make sure the hotend is free of ptfe bits by doing one or more cold pulls until that's clean too.  One thing that many people do is add the recommended collet clip that helps lock the ptfe in place (stops it coming back up).  For some reason its not part of the prusa build instructions but it is on the E3D.  There's loads on thingiverse for example https://www.thingiverse.com/thing:3499966 print a few out before taking things apart.

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

Thank you for the advice neophyl!

I will definitely try that. The tube was the only part pre-assembled by Prusa so I didn't want to change that. But I will! Thanks. One question regarding the tube... If the end of my filament looks bubbly like this, is that also a lead towards that theory? If I try to pull it through a replacement tube, it gets stuck.

I wanted to try changing filament once again before disassembling everything and switched to Prusa's PETG instead of Addnorth E-PLA. After switching, I could print two of my pyramids in a row. With the PLA I had to unload/load after each pyramid as I wrote in the previous post. So now I'm printing a bigger part, 7h or so, and the first layer is almost done now (~1h in) looking very good. I'll keep you updated on that print.

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

That looks like it coiuld be the 2.2mm neck issue.  Have a read of this thread https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/mk3s-ptfe-jamfor-the-second-time/  

That will certainly tug the ptfe tube upwards due to that wider stub and at that point the ptfe is touching the gears which will rub on it causing potential issues and if another sliver of ptfe gets worn off and into the feed then its clog again and rinse repeat.  The collet reduces the chances of the ptfe moving up but if you pull hard enough it will move. 

Thinking about it one thing I do now, almost without realising it is to heat the extruder and wait a few minutes before printing and when going to remove filament I usually feed a few mm through the extruder first before removing the filament.  I think that way the end is softer as its been fed into the hot end heating area and when you pull it out it will deform enough to come back through the ptfe tube.  If you try and remove it while the stub is cold its just going to block things.  

Many people who suffer it end up buying the unmodified e3d heatbreak which reportedly clears the issue up completely.  Luckily I've not had it happen to me as yet but if it does I will do the same.  I know the reasoning behind Prusa using a modified heatbreak as its needed for the MMU but if you dont have an MMU then its just a problem waiting to happen I think.  

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

Any stub that is 2.2 mm is a sure symptom of the heat break.  The only sure cure is to replace the heat break with a non-Prusa version from E3D.

Just buy the E3D-V6-175 heat break; they are available from Amazon and several other 3D print stores.  But the original brand, not some knock off.  Follow the E3D-V6 assembly instructions as you replace it and you'll avoid a lot of common mistakes made when working on the hot end.

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

Hi, thanks again guys. I'm a bit confused now... I first switched to a PETG filament from Prusa and managed to print two consecutive pyramids. So I figured i should try printing a big box and voila! I then switched to a pretty cheap white PLA and printed out some small parts as you can see on the picture.

After that, I've managed to print lots of things with the white PLA. So it seems like the first filament I had was terrible!? What's confusing me however is that my friend had tried different filaments and all of them failed at some point. I'm guessing there have been a combination of problems. I like that it's working perfect now but I dont' like not knowing exactly what caused the other mess... Except for the bad filament of course... If I continue running into problems of the same kind I will check the tube.

RE: Persistant problems with newly assembled printer. Sometimes it's jammed at start, sometimes it stops printing after a while.

I read one report of the Prusa PTFE tube inner diameter being too small. (I thought they said they drilled it to size)

Making sure your questionable filament slides through it can't hurt.

Filament tolerances can be pretty big.