Introduction

For this project, I decided to create a herringbone planetary gear bearing that I found on thingiverse. To do this I downloaded the .stl file supplied, and uploaded it to PrusaSlicer.

Preparing to Print

I scaled the file down to have a diameter of 4 cm so that it could fit inside the plastic container supplied to me. Because the part is intended to move, I knew that a PLA print would be best, so I decided to print 4 out of my 5 parts out of PLA.

For my fifth part, I used the Prusa resin printer and modified the slicer settings to accommodate the new printer.

PLA Print Outcomes

Due to the size constraints, the bearings would not rotate fresh off the printer, which I had expected. Using an allen wrench, I was able to stabilize the center while forcefully rotating the outside; the bearing would snap and then rotate freely. This worked for the first three prints, but on the fourth attempt, one of the interior gears somehow jumped a tooth, causing the whole bearing to be jammed. Perhaps if I had been more cautious when twisting the bearing this would not have happened, but I am still unsure how it managed to skip a tooth. Regardless, I felt I had comfortably succeeded in achieving the learning outcomes of printing an impossible object out of PLA, as my other three objects worked perfectly and my classmates really enjoyed fidgeting with them.

SLA Print Outcomes

The resin printer I was using had been having issues, so a lab assistant that was experienced with 3D printing supervised my print settings and helped set me up for success on the machine. Our first attempt failed horribly, and we identified the issue to be 3D print remnants within the resin. After cleaning out the resin, we worked together to reformat the settings, taking out the supports, where it failed on the first attempt. Our second attempt was also unsuccessful but was much closer to the desired result. As I anticipated, interior gears were fused to the outer ring, an error caused by the small geometry and the nature of resin printing. This indicated to me that the print would not have been functional, even if the printer had been working. One of the OEDK technicians came over and placed an “Out of Order” sign on the printer, and the lab assistant gave me his sympathies.

Since I’d been checking on the other resin printers periodically, unsuccessfully waiting for an opening for multiple days; since I was quite confident the print would not be functional using resin; and since I felt like I had achieved the learning outcomes associated with learning the strengths and weaknesses of both types of printing, I decided to wash and cure the print and submit it as it was.

Summary

A lot of things went wrong along the way, but I successfully produced multiple working parts and learned a lot about both types of printing, specifically relating to impossible objects and small, moving parts. I was still incredibly pleased with the outcome because I think the parts were incredibly engaging and fun!

Cost

Labor* ($15/hr for 1.5 hr): $22.5

PLA/Resin: Negligible

Printer Usage: Shared resource

Total: $22.5

*Labor time does not including time spent waiting for an open printer or time spent waiting for prints to finish, only time spent actively preparing and sending the part to the printer or troubleshooting.