PETG first layer Z adjustment
Sorry for the stupid newbie question. Everyone seems to be talking about increasing Z-distance for the first layer when printing with PETG. Strange thing is that on my printer the distance between print bed and nozzle seems to be increased automatically when printing with the PETG profile. Unfortunately that increase is way too much so that the traces won't fuse together.
- First layer height was adjusted for PLA
- Everything is perfect when printing PLA
- Nozzle to print bed distance is much higher for PETG than for PLA (without doing manual adjustments, just by selecting PET instead of PLA in Slicer)
- The traces of the first layer don't fuse together when printing PETG. There is a gap between the traces
- Live z-adjust isn't really an option because it would crash the nozzle into the print bed when printing PLA again without setting it back first
- Apart from the crappy first layer PETG printing works just fine, although I ended up printing at a slightly lower 235°C as there is quite a bit of stringing at higher temperatures.
- Layer adhesion at 230°C doesn't seem to be as good as with PLA.
Do you also need to set the Z-height separately for PETG and PLA? And if yes, where do you configure this?
Re: PETG first layer Z adjustment
That's how PETG looks like with the same live-z that works perfectly for PLA
Re: PETG first layer Z adjustment
The issue is related to proximity sensor (PINDA) which does not report the same distance from bed and nozzle due to the temperature variations. When you heat your bed and extruder is too close to the bed, pinda will heat too. More the bed temperature is elavated, more you have chances that sensor will be more distracted.
Solution: Before starting the print, keep the extruder on the 'safe' distance. To do so, from menu choose from printer menu Auto Home and then move extruder to let's say 50 mm height.
Repeat PLA test. Turn off printer. Restart with PETG. Not all materials are equal It could be the slight difference +-30 microns to make it perfect. Usually I do not bother.
If it is fine for you, there is way to put Auto Home and 50 height in startup script.
Re: PETG first layer Z adjustment
Thank you for your explanations, Nenad!
I'm not sure what you exactly mean with the "Auto Home" printer menu. There doesn't seem to be a menu entry with that exact naming.
I first manually moved the Extruder, so it's now further away during the heating up phase. Auto Home / Bed leveling however runs after heat-up on the hot heatbed. The resulting print pretty much looks the same as before.
Re: PETG first layer Z adjustment
'Auto Home' is under 'Calibration' That's not so important now 🙂 . With MK2/S i had the same issue when printing ABS. I had to adjust -0.1 mm every time.
To verify my theory, try heat your bed at the same temperature as PLA. If no difference, that's something else. The way around is to specify z-offset correction in slicer software. If you are using slic3r, just create new printer profile Prusa MK2 PETG and enter -0.1 in the field.
Other thing, it looks to me that your first layer is printed little bit too fast.
Re: PETG first layer Z adjustment
Hi Nenad
Sorry for the very delayed reply - I was in vacation.
The main issue was me, not the printer. I re-run the z and first layer calibration and things aren't too bad for both PETG and PLA. For good PETG first layers I still need to lower the nozzle by about -30um. I'll try to create different printer profiles as you suggested.
Thanks again for your help. I really appreciate it!