@WilkPolarny, I noticed a few things that I don’t think have been completely touched on here:
The generic profile nearly always outperforms the profile for polymaker in my experience-on every material too.
Your part has a really tall tower that needs stability support for sure. Try tree support. You can lookup my posts on tree support settings for tall objects to see how to adjust the settings for the application.
I think you will have better luck with a different PETG. I my experience, polymaker filaments like this are a bit more hygroscopic than some other options. I’ve printed quite successfully with the hatchbox PETG up to 7-8hrs per print job.
In speculation, your filament is absorbing moisture far faster than you would think and in all the test printing it has gotten moist again. Try drying before printing each time.
The generic PETG profile and the Polymaker Polylite PETG are almost identical. Max vol. speed is 12mm³/s for the generic, wheras it’s 11.5mm³/s for the Polylite profile. I cannot spot any other differences.
The tower prints just fine without any supports. It was mostly related to speed and cooling, that was the issue.
I usually dry filaments to <15% RH and keep them in the AMS at <=10% RH (the lowest the hygrometer can measure). Yes, a low humidity only slows down moisture absorbtion. I highly doubt that 10 days are enough to saturate PETG within such environment and to such an extent, that it would cause issues.
Especially since I’m also having issues with a new and properly dried spool.
For some magical reason, the latest print turned out way better after I additionally:
Trammed the bed. It was over 1mm off at two points. I could even fit three .4mm feeler gauges under one of the edges.
I disassembled, cleaned and reassambled the extruder assembly.
I cleaned the carbon rods according to the maintenance plan, although they were not really gunked up (I only ran about 2.5 spools in total through that machine so far).
One of the three things did it, only the 3D printing gods know why.
It’s still has ugly slopes/overhangs, but it’s something.
Interesting. What was your general procedure for cleaning the extruder assembly?
On a side not, I’ve still not had any success on the overhangs. I did some test prints with PLA and they had the same issue, though not as bad. Adding supports under curved overhangs helped, though they still were not as clean as I’d like. All my test prints start with the overhangs printing immediately after the first layer, so I don’t know if that is related.
In general my working assumptions are:
Linear overhangs below a certain angle are fine (45 degree or less?)
The radius of curved overhangs matters a lot. Smaller features won’t print well, and larger features seem to need supports.
Slowing down only marginally improved the above, though it improved the quality of the non-issue overhangs
I also tried printing a model at a 45 degree angle entirely and adding supports under a non-showing face, changing the overhangs to normal features. This resolved the issue with the overhang quality but I ended up with other issue due to not having supports often enough for the part, so I had a slight sag in one section.
Nothing special, really. I just checked the hot end, disassambled the extruder and cleared and particles/residue from the gears.
PETG does not like overhangs that much it seems. The general rule of thumb (for PLA) is 45 degrees. A lot of people have printed overhang towers to test their settings with their filament. For PETG, I’d assume less than 30°, according to my own observations with my own filament settings.
When it comes to curves, where a lot of acceleration and deacceleration happens, I’d mess with pressure advance to make sure I don’t under- or overextrude. Especially with PETG, I’d get a lot of blobs with the wrong PA and overall settings.
My overhang tests (after calibrating) print “cleanly” up to about 70°, though the layer lines are much more pronounced. That I can tolerate and adjust for. It’s really the marring that comes above those angles on sloped surfaces, though looking through my test prints it does appear to generally be near corners. I’ll have to play more with my acceleration/PA and see what I can get out of it. I have also not yet tried heavily tuning my retraction.
I’ve found I’ve needed to reduce “Sparse infill” speed to prevent the curling. I’m down to 75mm/s but that’s with a .6mm nozzle at .3mm layer height. In addition, I changed from Gyroid to Rectilinear infill pattern. Rectilinear doesn’t cross paths (on the same layer) and I’ve found this change also helped with preventing the tiny curls.
Matte isn’t bad, but shiny generally means the layers are bonded together more strongly. With this particular part, you basically have to make a surface finish tradeoff with the skinny tower being more shiny since it has to print slower.
I’m not too sure what’s causing this. One idea is that it’s filament stuck on the nozzle that scuffs up the surface. You’ll see a similar white discoloration if you sand or scratch the part with something metal.
Hopefully the infill changes above will help.
One last thing related to overhang performance. Make sure the wall printing order is set to “Inner/Outer”.
For overhangs, I would suggest against using “Precise Wall” (not sure if you are, just saw it mentioned above). Since the outer wall isn’t smushed up against the inner wall as much, I would think it has a greater chance of sagging. But, maybe this doesn’t happen, I haven’t tested it. Maybe it will solve your ugly wall issue though, worth trying.
I print 50 degree overhangs all day with no issue. The key is wall printing order and cooling.
I messed around with it a bit, but the printing order seems to have the best effect!
Thanks again for your input and insights. I will continue to experiment and optimize as needed. I will also try other PETG in the future (the one from Bambu if there is any in stock in the EU store), and other manufacturers.
