Ok, so the real problem is that the motor is insufficient to properly extrude at what would probably be a better temperature? So to compensate, we crank up the temperature to melt the PETG more than usual, which then causes extreme shrinking as it comes out of the nozzle due to the weight of the extrusion pulling on the overly molten plastic? Not really that the filament is shrinking, but being stretched too much?
The reason I ask is because if you are using a 2.0 or 2.2mm nozzle to get 1.75mm filament, that's a huge amount of shrinking. That's about a 12.5%+ reduction.
I guess that begs the followup question... Do people see this kind of shrinkage when printing with PETG? We're usually printing PETG at anywhere from 230-265C, so that would mean I would never get a true .4mm line from my .4mm nozzle, but rather .35mm or less. According to the MatterHackers website:
PETG has a shrink ratio (or shrink rate) of less than 0.004 in/in so printing large surfaces are not a problem when printing on a well-leveled surface.
I'm not trying to be difficult, I just want to understand fully what the issues are so maybe I can find some possible solutions that don't require a lot of trial and error like drilling a new nozzle then hoping I can find a temperature that will give me 1.75mm filament. Could finding a more powerful motor than the GF45 be an answer? It seems we already might not be using the GF45 at it's full potential limiting it to 1.6A. Maybe a stronger power supply so the GF45 can run with a little higher current? Maybe better cooling as the PETG exits the nozzle?