Printing Big Parts with PETG
Hello,
I am relatively new in 3D printing, with experience only with Prusa printers (Mini+ and MK3S+) and use PETG as printing material ( https://en.3dfilament.ch/product-page/purefil-petg-filament-transparent-1kg-1-75mm ). I use PrusaSlicer, print settings "0.20mm SPEED", "Generic PETG". Printing "shorter" parts are perfectly fine. Printing "longer" parts "fails" in 99% of the times, mostly in the 1st or one of the first layers: this is observerd in these both printers where I tried.
What do I mean by "fails": the printed filament starts to accumulate in/glue to the nozzle (remmber, this is normally 1st layer, or one of the first). When the extruder head moves, the filament printed on the print bed glues to this filament in the nozzle and then basically everything sticks to the nozzle from a certain point and the whole print vanishes. How this erratic behaviors starts, I am not sure. However, it is mostly systematic, i.e., if I try to print 5x the same object, this will start to happen mostly at the same instant!
I see this when trying to print "longer" parts. I dont see them in "shorter" parts. E.g., A "longer" part (for the MK3S+) is a frame of 230*60 mm, with 10mm thickness. For the Mini+, it would be a frame of 160*60mm, with 10mm thickness. I have the feeling that if I have holes in that frame (e.g., 20 3mm diameter holes), it makes the printing even more difficult in "longer parts". For comparison, if I print the same frame with 120*60mm (with 10mm thickness), I never have that problem (at least, in the Mini+).
What I tried:
- decreasing max acceleration and speed of the 1st layer - helped somewhat
- clear the nozzle before starting every print - makes the erratic behavior mostly deterministic, as explained above
- applying glue to the printing bed - no change
- change the z offset of the nozzle - apparently, the closer I offset the nozzle to the printing bed, the longer it takes to start the erratic behavior
- increase retraction of the filament - no change
- increase brim - no change
Does anyone know what I am doing wrong, resp. how can I fix it? What information is missing from me so that this becomes clear?
Thank you
Pictures of your first layer would be most helpful
Hard to tell... but sounds like your Z is possibly too low
Please show us your first layer Z calibration.
Cheerio,
RE: Printing Big Parts with PETG
So,
I have been doing a lot of printing with the MK3S+ in the last days. Here is some of the results:
- Following the hints about Z setting/calibration, I went back to the First Layer Calibration. It was originally set to -2.0mm. I went all the way from -1.7mm to -2.2mm in steps of 0.1mm. I realized that -1.7mm is clearly looking like the "too high" picture from the official support of Prusa ( https://help.prusa3d.com/en/article/first-layer-calibration-i3_112364/). -2.0mm is still looking closer to the "too high" than to "good". I went up to -2.2mm, which was looking more similar to the "good" picture. I should have gone further, until I clearly reach the "low" picture, but I haven't, as I had to stop the test. PS: I am using PETG and textured sheet. PS2: yes, my super PINDA might be a bit too height, that is why the +/- -2.0mm instead of the recommended +/- -1.0mm
- I started to clean with Windex before any new print.
With these changes (cleaning print bed with Windex before any new print AND changing First Layer Calibration from -2.0mm to -2.2mm) led to good improvements. I would say that I manage to print a "longer" part (as I have described before) between 30% to 50% of the times that I've tryed (for comparison: before, I could not). Further, the geometrical tolerances and appearance of the printed parts improved clearly (I can compare this with the "shorter" part).
However, I am still not happy with the results. Here are my next steps:- I order Prusament PETG and I will use it. I guess it is waaay more tested and calibrated than the filament that I was using, which should improve realiability/repeteability. - I guess I managed to print "longer" parts only after I have not printed anything before for a long time. So, the point is to investigate how long the printer has to cool down before I can start the printing of a new "longer" part. - Or maybe I have to clean-up the print bed with Windex only when the print bed is cooled down
If anyone has further ideas, what I could be doing wrong, please let me know... E.g., I am not using neither acetone not alcohol to clean up the printing bed. Would that be a good idea?
Thx,
.
That is certainly a plausible explantion. Often new users are too quick to blame the equipment when it's inattention to detail at fault - they haven't yet learned what's important...
But in this case it sounds like you've narrowed down the issue.
You could run through the setup process:
https://help.prusa3d.com/en/guide/9-preflight-check_176167
Or just loose the securing screw and move the (super)PINDA down by ONE thread - then tighten and check it's not lower than the nozzle before recalibrating.
The usual issue with large PETG parts is warping where tricks to shorten long filament runs may help. Don't clean with windex, clean with hot, soapy water. Maintain cleanliness with alcohol. REDUCE ADHESION with Windex or PETG will stick too tight. Refresh the bed surface with acetone perhaps twice a year at most.
Cheerio,
RE: Printing Big Parts with PETG
Answering to all threads that I started this year and did not finalized 😉
I kept the calibration procedure (going at steps of 0.1mm) and finally set it to -2.5mm. After that, I basically did not have anymore problems with first(s) layer(s).