Comment on An interesting issue
Bluewing@lemmy.world 2 days agoI need to know if the gear train will fit on the banjo of the lathe first. I might run the plastic just to see how long PETG might last. If I want metal change gears, I will either spring for the 100+ dollars needed to buy the proper gears. Or I will spend $60 for the proper cutter and cut my own gears. But I need to be sure they will fit first.
CmdrShepard49@sh.itjust.works 23 hours ago
If it’s just for fitment then all you need at the critical dimensions. You could have just printed the ID of the gear centers to see if they fit on the shift or added a ton of open space on the big gear like how a spoked wheel looks to save lots of filament and print time.
Bluewing@lemmy.world 11 hours ago
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.