For our next project, we covered 3D printing! I did some 3D printing back in undergrad in my design course, but I was excited to refresh my memory on this tool. We learned about several different types of 3D printing, and I was excited to try the SLA machine in particular, since that one is new to me.

To start the project, I looked on Thingiverse to find some files of impossible objects, i.e. objects that would be impossible or very difficult to manufacture using typical subtractive manufacturing processes. Objects are typically “impossible” if they have joints, small pieces, or an unusual internal geometry. I found two that were interesting – a gyroscope Christmas-present-shaped ornament and an elephant with moveable joints. I decided to go with the elephant for my project.

Before scaling my STL file, I measured the gumball capsules so I could use as much of the space as possible. Using calipers, I found that the capsule was about 1.9 inches wide inside. It was a little more difficult to measure the inside height, but I got a measurement of about 1.4 inches.

Next, I set up my print using the Prusa software. I started by printing two elephants with the FDM method in PLA. I scaled one of them to 30% of the original size and the other to 35% of the original size. Both of them had the same layer size of 0.15 mm, and I added supports everywhere. I also set a 15% infill. The print took about 48 minutes.

They turned out really small, so I tried two others at 55% and 65% of the original size. I kept the same layer size and infill. These turned out a lot better and fit in the gumball capsule pretty well, although the 65% had its trunk slightly squished. Next, I printed two more at 60% and that turned out to be the best size.

I also printed two more on the Bambu machine at 60% for the sake of trying out a new machine. At first I selected the wrong print bed, but the machine showed a warning and I was able to go back to the software, select the right type of bed, and send my file back to the printer.

For my final printing method, I made some elephants on the Formlabs SLA printer. The setup process was pretty similar to Prusa and Bambu, especially considering some of the automatic settings for the supports. The post-processing however, is much more involved. I washed my parts in acetone, and then placed them in the UV curing machine, setting the appropriate time and temperature (15 mins @ 80 degrees C). However, I didn’t realize that the machine hadn’t preheated yet. When I checked back in 15 minutes, expecting my parts to be ready, the machine was still only at 63 degrees C.

It took nearly an hour just for the machine to preheat. I assume my pieces were at least partially curing during this time, but I decided to leave them in for another 15 mins at the proper temperature. Next, I removed the supports, which was much more difficult than it was for the FDM prints. I needed to use the small cutters and the pliers to pry off the support structure. I suspected that the joints on this shape were going to fuse since that had been many other students’ experience and unfortunately I was right. The bottoms of the joints had a bit of separation, but the tops looked totally fused. I tried using the dental pick to chip away at the joints and separate them a bit, but that only served to scratch up the bottom of my elephant.

Disappointing, but I learned some cool new skills for this project.

Cost Type	Cost	Price	Source	Quantity	Total
Materials	PLA (Prusa)	$29.99/kg	Prusa Research	11 g	$3.30
	PLA (Bambu)	$24.99/kg	Hatchbox 3D	11 g	$2.75
	Resin	$199/L	Formlabs	15 mL	$29.85
Labor	Prototyping engineer	$37/hr	Bureau of Labor Statistics	1 hr	$37.00
	Assembler	$18/hr	Bureau of Labor Statistics	1 hr	$18.00
Overhead	Facility cost	Assume $4000 worth of equipment (for one person)	FinModelsLab	Assume 10% of equipment costs	$400.00
				Total	$490.90