It’s the PETG. Specifically, it is the softening on the following parts:
I would recommend the following Y-axis mod for the MK4. I am still running this even on the MK4S, even though the Y-axis was modified on the MK4S.
Edit: Print those in ASA and replace them, tighten all the belts as usual, and I think your printer will be fixed.
My money is on the PETG starting to loosen and you losing tension on the belts.
You have the MK4 in an enclosure–I did too. At some point I stopped being able to print flexibles, but ASA/PCCF was still fine. Prusa support told me that the idler was getting loose and my hotend was losing grip on the fillament.
I had another print where there was a nearly 2-3cm shift in the layers between layer 5 and layer 80. Some of my belts had absolutely lost the plot. I reprinted everything in ASA or PCCF, and while upgrading to the MK4S rebuilt the printer with all ASA/PCCF parts. No problems since.
It could be a case of too much cooling, while simultaneously being too much heat.
If you’re blowing so much air that the filament instantly solidifies when it leaves the nozzle, it’s not going to bond with anything else. It’s also interesting that the first layers are fine (when the part cooling fan is typically not running), but problems start when the part cooling fan turns on.
Have you tried without part cooling at all? Another thing is that your part cooling might be cooling down the tip of the nozzle, causing tiny partial clogs, which are cleared every so often by friction.
Did you notice a difference in print speed when you slowed down? As this is a small print, it could already be as slow as it will be due to minimum layer times.
It could also be that the nozzle spends too much close to the print. What happens if you print 2 or 3 of them?
This is typically more of an issue with PC where you don’t have a part cooling fan running, but maybe it’s the case here too?
Interesting that the extra 10° makes such a difference for ASA and ABS.
I recently started printing with ASA in my enclosed MK4. I might have to try this.
Could you explain what you mean by “full commercial use”?
I would model the part myself, print it myself and check for fit and function. Once the part design and tolerances confirmed, I would then either use a local or remote shop.
Xometry.eu (no affiliation, never used them) appears to be in Europe and outsources to local shops. They have plastic and metal SLS, CNC, sheet metal, and everything else as possibilities. https://xometry.eu/en/direct-metal-laser-sintering/
Another option is to use the Chinese PCB shops. PCBWay has amazing abilities these days: https://www.pcbway.com/rapid-prototyping/manufacture/?type=3&reffercode=TOP
Had this happen to me as well this week after a few months of not using Fusion 360.
Turns out it’s a software update issue. Just close the app every time it fails, and eventually it will manage to update. I have an insanely fast internet connection, so maybe you need to keep it open for a while to download the updates.
Not sure what you need to get approved. Buying a roll of ASA? It’s part of printer maintenance, and making it more reliable in the long run.
And if you don’t have ABS/ASA on hand… why is the printer in an enclosure?