PETG large print disaster
Hi all
Yesterday I had a large (for me...) PETG print going, but after about 6 hrs disaster struck. As can be seen in the picture, there was a 'blob' in the bottom left of the model and a diagonal groove. The model stuck perfectly to the texture plate, resulting in the plate being whacked off its magnets and displaced by about 1 cm... Also, the filament broke inside the hotend. I tried to get the stuck bit out, but no luck so far. So all in all 80 m of filament and 6 hrs gone and a hotend that probably needs replacing. I obviously would like to print something without constantly having to keep an eye on it. Has anybody experienced this and have you got any ideas / tips to prevent this from happening ? 
The warp pattern on the top is a giveaway.
Either the first layer has partially detached in which case all the usual advice about adhesion applies or the adhesion was good but the print sheet itself lifted off the magnets under strong tension.
Most of the tension comes from thermal contraction as the longer extrusions cool.
The Core One should have protected the print surface from drafts but if you had the door open try again closed ... and perhaps raise the bed temperature by 5° - 10°.
but the underlying problem is better addressed by breaking the long extrusion runs:
Use a fill that does not have long extrusions, honeycomb, gyroid or similar.
Reduce the number of horizontal layers on the top, perhaps put some 'decorative' grooves in the top.
In extremes even clamp the print-sheet down to prevent lifting.
The breaking filament is unusual for PETG although a known issue for damp PLA.
Remove the lid, open the extruder idler, detach the PTFE filament tube and heat the hotend to the printing temperature of the filament plus 5° then take a length of scrap filament and, bypassing the extruder gear, push it down through the nozzle tube by hand — push slowly at first then as fast as it will go finishing by pulling it out as fast as you can.
You may need to temporarily disable some sensors while you do this.
Cheerio,
RE: PETG large print disaster
Hi Diem
Thanks for your answer. I will go with a different fill and fewer top layers. I had extra top layers for strength, so that's a good candidate for the issue.
I've taken the hotend out and am using a craft hot gun - and an oven mitt. What you propose would 'glue' the stuck bit to the extra filament I guess, I will give that a go. Wish me luck.
Thanks again for your reply.
(btw. just for reference if anybody is interested: what I forgot to mention in my 'state of frustration' was that I am using the Core One - which you already mentioned- with the slicer v2.9.3RC1)