This assignment’s goal was to 3D print an “impossible object”, one that can’t reasonably be made with any other manufacturing method. I went on to thingiverse, and found a couple of files I wanted to test out. The first file I found was a set of concentric spiral spheres that spun inside each other. I uploaded the stl file to 3dprinterOS, sliced it, and printed it. I came back 6 hours later and found that there were so many supports it would take me hours to remove them all, and I would have to do the same thing four more times. I decided to switch the 3d print I was doing, and found an articulated slug on that I thought was cute.

I uploaded and printed this file, and when I came back in two hours it had printed perfectly, with the only supports I needed to remove the raft to adhere to the bed. I printed this three more times, for a total of four SLA slugs printed on the Prusa FDM printers in the OEDK maker bar. The next challenge was using the Formlabs SLA printers. I opened the file in PreForm, clicked auto-setup, and sent it off the the Form 2. This print turned out terribly, with none of the detail coming out and even the supports a mess.

I tried again, with similar results. With the advice of some lab assistants, I decided that maybe it was a problem with the printer, and switched to using the Form 3 while it was fixed. My next print came out beautifully, but I had forgotten to scale the file so it was too small compared to my other slugs. I went back into PreForm, scaled it up to the same size as my SLA prints, and made sure to edit the supports so none of them would get stuck in the joints.

The next day, I washed the print in isopropyl alcohol and cured it, and when I removed the supports it came out perfectly. There were slight defects where I had to cut off the supports, but the surface finish was quite smooth and very precise. The SLA printing was definitely more difficult to sort out, but the results were rewarding.

In the end, I have five 3D printed slugs that just barely fit in the gumball machine containers.

Cost Estimate:

• 3D printer OS estimates the cost of each PLA print at $0.16, so for four of them it comes out to $0.64
• The final SLA slug used ~20 mL of resin. At $200 per liter of Grey Pro resin from formlabs, this comes out to $4. Adding in some extra for the smaller test prints, this probably totaled around $7.
• The amount of time actually spent working on this project was about 4 hours, so at $15 an hour this is $60. However, the time it takes to just print a file that is already set up is much less, so this would be less of a factor in printing a lot of parts.

The total comes out to $67.64, while the total price of materials was ~$7.64