PETG Printing inconsistancies
I have completed my I3 Mk2S pre-built to I3 Mk2.5 upgrade. I ended up having to print each piece one at a time at the center of the bed due to oddities in PETG printing and issues with first layer being extremely inconsistent.
After a few dozen solid prints in PLA on the upgraded unit I have decided to take back out the PETG from my sealed container and try another shot at it. After some calibration of bumping the heat bed from 80, to 85, to 90 for the first layer I now have solid first layers for 70% of my build surface. However the left side of the bed continues to frustratingly refuse to behave. Watching the plastic lay down it looks like the issue is not with bed adhesion overall but with the fact that the filament shifts while laying down and takes a moment to be attracted to the bed for it to adhere.
I tried cleaning with windex, mild dish detergent to remove oils, and denatured alcohol. None of these have helped urge the problem area both on the original build surface and now the new surface to stick like the rest of the platform.
It seems to be issue in movement but I am not quite sure why it is always so consistently bad on one side of the build plate compared to others. Aside from tweaks to temperature and an adjust of of -.765 everything is stock Prusa PETG settings [-.800 is what I get best with PLA]. There is no sign of stick to the nozzle [got a sock for my hot end just to be sure it wasn't just from the odd filament movement and sure enough using it to compensate for that took care of it wanting to curl up and stick to the heat block], just this inconsistent laying on the bed anomaly causing this. Nozzle prints a fine line with no sign of compression of the line against the bed.
Here you can see the acceptable left side vs what happens to the poor left side as it goes to fill:
Here are some layer height square tests. Mostly fine with a little curl on laying down at the top right brim and the oddness in the center left lower square:
Re: PETG Printing inconsistancies
Most of my prints in PETG have gone terribly. They end up stringy and weak. The lines have bad adhesion to one another, which leaves gaps between the (solid) infill and between the outer shells. I've checked the nozzle, it's not clogged. I'm using the stock PTFE hotend, although I've read it's good until above 250.
not hot enough, too much cooling and printing too fast = weak falling apart prints. No Fan/260c/40mm/s = Strongest. Anything less , more fan or faster = weaker. how weak is up to you. a print falling apart sounds like being at the extreme here.... print hottest you can with as low fan you can get away with for overhangs and slow down. increase travel speed to max to reduce stringing/oozing, especially on larger parts with long travel.
unless the filament is shit.