I seldom use a .40mm nozzle much anymore since I mostly do functional prints like these gears. I have found the .60mm nozzle is a good compromise for speed in printing, better strength, and good accuracy.

Interestingly enough, a .40mm will print nearly or as fast as a .60mm nozzle on Bambu printer in general. This because Bambu optimizes their slicer setting for the .40mm nozzle. What it does give up a bit is between layer strength. This is due to to the smaller contact area difference between layers. I can get the same strength with 2 perimeters using a .60mm that would take 3 perimeters with a .40mm nozzle.

There are filaments that do need to be dried before use or even dried as you use them. But they are higher end engineering filaments and they cost real money. You tend to need a real reason to buy them. Despite the fact that many consumer level printers have the ability to print them these days. $50 to $100+ a kilogram or less, is a real barrier to the wide use.

Still, years of experience has taught me that I need dry PETG as it tells me it needs to be dried, and TPU is always dried before use. But PLA is a waste of watts.

I did say it was a lazy design choice. And change gears a mostly made as solid gears. You very seldom see spoke designs. It has to do with casting/machine time costs. So, solid gears are what I think about with change gears. The gears are still cheap to print and they only took a good afternoon to print all 4 gears and the job is done. And the post is about the weird crappy finish I got with GeeeTech PETG. And the simple nozzle swap solving the problem. And at this point, I just want to burn up this spool to just get rid of it. I won't buy this brand again.

Turned out the real design sticker was that I needed a 16mm keyed center hole to fit the banjo shafts. And while 16mm hole just barely fits on a mod 1 20T gear, the 4mm key needed does not. I ended up modeling the 20T and 80T gears as one piece and the single 20T gear needed to be designed with a solid 30mm round attached to it to have some place for the drive key to go.

The upside to doing it how I did things meant that yesterday I used those 3D printed gears as made to do the lathe job I needed to do, burnishing a section of shaft in my lathe. Sometimes you just gotta go for it and hope it works out. I might even reprint them with a better PETG brand like DeepLee or better yet, MatterHackers and make them with 4 or 5 perimeters and 6 top and bottom layers with 80% gyroid infill. I have both on hand. For the few times I might need a .0025" per rev feed, they might well last for years. If I find a #2 and #6 pair of used gear cutters for cheap, I might buy them and machine a set from steel. But even decent gear cutters are stupid expensive. And if I don't have a customer to bill the expense out to, it's probably not worth thinking about.