Strings/Threads and Globs (PrusaSlicer/MK3S)  

RE: Strings/Threads and Globs (PrusaSlicer/MK3S)

Posted by: @bobg

These (see attachment) were printed with FilamentPM PLA.  When I started to use this filament I used the same filament profile (in PrusaSlicer) for the Prusa PLA.  And had a severe string/threads problem.  So now I use a profile which I set up for the FilamentPM PLA which is the same as the one for Prusa PLA except that it specifies a 1mm retraction.   I have found some advice online but not for PrusaSlicer/MK3S and therefore not very useful - to me at least.  

Since I still have a string/threads problem (not visible in the photo because the photo does not show the insides) I have to make further adjustment to the profile.  I am thinking about lowering the temp a bit but do not want to aggravate the problem with the blobs/globs/zits.

So I'd appreciate any wisdom anyone is willing to share.

(And, BTW, why don't filament manufacturers publish profiles for their filaments and different slicers and printers?)

Thanks, Bob

 

 Globs.jpg

This can also be a mechanical problem. If too much material is extruded, it gathers at the nozzle, burns out, and eventually comes loose and sticks to the part. It is also possible that the nozzle does not seal at the heatbreak.

I would try:

- reduce flow rate
- calibrate extruder
- reduce temperature
- optimize LA settings
- clean nozzle/hotend
- dry filament

RE: Strings/Threads and Globs (PrusaSlicer/MK3S)

Thanks very much for responding karl-herbert.  It difficult to get a clear view of the heaterblock but it looks like there is melted filament all over it.   It's looks like either some melted filament is finding a way to flow against gravity after it is extruded, or some melted filament is oozing out of the top of the heaterblock.   I'll have to take the print head apart to get a better look and better photos.  Unfortunately I bought the printer already assembled, not realizing how useful it would be to learn skills in building the printer which would be required to maintain the printer.  In other words I have only worked on the print head once and did not find it easy.  That may well be when I made some mistake which is causing the current problem.   It won't be easy find a block time when I can give my undivided attention to the printer.  Thanks again for your help.  I am sure I will be back here with more specific questions.  Bob

RE: Strings/Threads and Globs (PrusaSlicer/MK3S)

Posted by: @bobg

 In other words I have only worked on the print head once and did not find it easy.  That may well be when I made some mistake which is causing the current problem.

 Common mistakes when working on the nozzle and heater block are:

First common mistake is screwing the nozzle in tightly against the block, the nozzle needs to be screwed tightly against the heat break inside the block.  So the heat block needs to be screwed onto the heat break far enough so the nozzle can screw in and hit the heat break without running out of threads.

Other common mistake is not heating the block to 285°C before final tightening of the nozzle against the heat break.  Putting it together cold almost always leads to leaks as the metals expand when hot.

https://help.prusa3d.com/en/article/changing-or-replacing-the-nozzle_2069