Hello. Today I tried first time PETG and I don’t know what seems to be causing this problem. All seems good until last layer. As you can see on photo top right part and littlebit of top left is ok clean, smooth. They are first being printed. But then it get’s worse and I don’t understand why. What cause that print is suddenly so bad? Why it’s not smooth all the way like it is for example with PLA?
I tried that multiple times with littlebit tweaks but it doesn’t seems to help. It looks always the same. I thought that it might be because of long surface area, but then all down parts should be smooth too. What should I do? Thanks for info.
PETG is rather sticky. So it loves to cling to the nozzle much more than PLA.
Make sure you use non-crossing infill (gyroid, honeycomb,…) and surfaces (monotonic, concentric,…).
You’ll probably also want to use retract with wipe but I have not yet used the newer PETG HF, so I can’t be certain on the finer tweaks for that, only the former PETG Basic.
Without knowing the small changes you have already tried - the print image of the top layer looks very much like over-extrusion to me. It seems that too much material is already being used in the lower layers, which becomes more and more noticeable in the following layers over time.
And with PETG in particular, another consequence is that the nozzle quickly becomes full of material on the outside. This can be seen again and again later on in the form of very thick small lumps that suddenly stick to one of the layers (or to the side of it).
I also don’t know which manufacturer made your PETG.
But just off the top of my head:
- with generic PETG, the flow rate is 0.95 by default → yours is probably higher (as with generic PLA 0.98) or if 0.95, then it is already too high for your PETG (reduce by 0.01 to a maximum of 0.02 and try again)
- but I would always tend to recommend → calibrate your material completely
- repeat point 2 for every new non-Bambu material and every now and then when new rolls from the same manufacturer are purchased (to correct small changes in the batches)
So this is my fillament
and this is my setting for it
And I tried to slow the print. I switched nozzle to hardened. I had that new and thought that old one might be problem.
I’ll try to reduce flow ratio and let you know. Sad that it might be waste of fillament 
So what happened is that model had ironing turned on. When I turned it off. It seems ok. I guess the ironing was there for PLA not for PETG.
Sorry for confusion. I didn’t noticed that. Now it seems nice and clean.
2 Likes