PETG printing filament issue
Hello I have been printing with my PRUSA MK4 for almost a year, using PETG, I usually just press print and leave it working the entire night, 2 days ago I found this huge mess of printing filament, how do I remove it? what could be a possible cause and solution ?? Thank you in advance for your help
RE: PETG printing filament issue
that is a Blob of Doom.
what has happened, is that the model being printed had lost adhesion with the print bed, and has become stuck on the nozzle,
the printer has no sensor to alert this condition, so it had carried on printing, as if nothing has happened. as the printer extrudes more filament, there is nowhere for the filament to escape to (It normally gets laid on the previous layer and left to cool, ) but i this case the nozzle is surrounded by previously extruded filament so the newly extruded filament simply joins the blob, making it bigger...
I generally raise the extruder until the blob is totally clear of the printbed, then heat the nozzle to above the melting point of the filament and wait... You will probably have to go into the temperature menu on the LCD, to achieve this. after a while, the blob may fall away from the nozzle. however in your case the blob is massive and may not het through enough to fall off, it may need help.
I have used an old soldering iron, to carve the waste off from the outside of the blob, in order to help remove the waste.
the chances are that in your case the waste PETG has totally engulfed the hot end heatsink and also glued itself to the lower X axis bearing retainer and also filled the gap to the extruder heatsink, please ensure that you fave removed all of the waste material, before you try to re use the printer.
If there is any remaining waste filament between the extruder assembly and the X axis parts, it is likely that the nozzle strain gauge will not operate properlt and the printer will try to drill the nozzle through the build plate
the original problem, of the model losing adhesion, was probably caused by a build up of contaminants on the build plate surface (quite probably finger grease, from handling the build plate.
I remove this by washing the buildplate with hot water and dishsoap (in the kitchen sink, after removing it from the printer), the soap solution should be rubbed in well, with a new clean dish sponge, and rinsed off with copious clean hot water. then dried immediately with plain paper towels. 
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
You are not the first.
Search for 'Blob of Doom' to see how others have dealt with them.
Cheerio,