Gears printing wonky - Looking for advice

[sawozny]

Greetings, 3D Printing Gurus!



As I don't know if this is a printer, filament, user or design problem, I'm posting in the general forum. If the mods think this question belongs elsewhere, please advise and I'll move it.



I'm trying to print a series of involute gears (17, 19, 22, 26 and 33 teeth, 2mm modules at 20 degree pressure angle, 10mm thick; modeled in FreeCAD, exported to STLs that Cura can slice for my Series 1 Pro). I'm using Taulman 645 Nylon and my glass bed treatment of choice is Garnier Fructis Ultra Strong and I've had great results with it.



When printing the 17 tooth gear (thought I'd start with the smallest gear and see how it goes) I initially had problems with an edge lifting using the Taulman 645 material profile with 0.2mm layer heights and 8mm equilateral tetrahedron infill. I switched from raft to brim and slowed down from 50 to 30mm/s with no improvement. When I made my initial layer 200% thick with neither raft nor brim and I turned off the fan the bottom stuck well but the top wouldn't print properly. After reducing the infill to 5mm and turning the fan back on at the upper layers, I finally got a good print on my 7^th try. Using those parameters, I printed the 19 and 22 tooth gears perfectly, but on the 26 tooth gear I started getting lift on the side again. I've attached the STLs and I?m listing the settings I used to print below (Cura 1.5 for Type A Machines which was the last version they issued).


I'm considering turning the fan back off (maybe the smaller gears had layers so small they weren't able to cool properly causing the hole ridden top layers but these larger gears will and the fan being off will allow more even cooling across the print) or going back to 8mm tetrahedrons for infill (maybe less internal material will reduce the aggregate lateral stress caused by the shrink as filament cools) or even trying turning the raft or brim back on (although the default raft settings for this material profile BARELY adhere to the bed which is why it was the first thing to go when I started troubleshooting bed adhesion problems).


Before I go back to banging my head against the wall, I thought I?d see if anyone on here had been through a similar material / application / experience combination and might have any suggestions to offer. I'm also wondering if, for a prototype, I should even be THAT worried about it. The purpose of the gears is to take a 3600 RPM motor's spin and use is to spin a wheel at a variety of speeds for testing, up to ~10,000 RPM. As all gear pairings have no common factors in the number of teeth, wear will be evenly distributed on the slightly wonky teeth the bed lift produces and nothing is out by more than a millimeter so am I chasing perfection when "good" is close enough? I just find it difficult to accept that a 55mm wide x 10mm high object should be having bed adhesion problems at all and worry I'm missing something stupid / obvious.



Thanks in advance for anything you may have to share.


Scott


Cura Settings:

• Layer Height - 0.2mm
• Shell Thickness - 0.8mm
• Retraction - Enabled
• Bottom / Top Thickness - 1mm
• Infill Type - 3D (it says it makes cubes, but they look like stacked equilateral tetrahedrons to me)
• Infill Distance - 5mm
• Print Speed - 30mm/s
• Print Head Temp - 260C
• Bed Temp - 100C
• No Platform Adhesion (defaults to a skirt just to get material flowing through the head)
• Extruder Nozzle - 0.4mm
• Retraction Speed - 80mm/s
• Retraction Distance - 5mm
• Initial Layer Thickness - 0.2mm
• Initial Layer Line Width - 200%
• Travel Speed - 200mm/s
• Bottom Layer Speed - 15mm/s
• All other speeds set to 0 (use default print speed above)
• Minimal Layer Time for cooling - 3 seconds (I never get anywhere near this fast a layer in practice)
• Fan - Enabled
• Filament Diameter - 1.75mm
• Filament Flow - 100%