For this project, we were tasked with 3D printing an impossible object that would fit into a gumball capsule. I was inspired by one of my favorite rings on my hand. It has a simple heart knot, but the interwoven aspect gives it more dimension.

I searched Thingiverse.com for a similar concept and came across a Celtic knot heart. It had the complex geometry I was looking for, and because it’s a bit flat, I thought it’d print quickly and without any issues. After re-sizing it to fit the gumball capsule dimensions, I printed it on the FDM Prusa printer. Unfortunately, I had a tough time removing the supports on the back of the heart and I wasn’t satisfied with how they turned out, so I decided to switch to a different object with more height.

 

 

 

 

After some more searching on Thingiverse.com, I found an object called a Solomon seal knot, which looked like the star version of my ring. I re-sized it, sliced it, and found that it would require a lot of supports to be successfully printed. I printed 3 smaller ones to test whether the supports stuck onto the part like with the previous object and found that they snapped right off this time, so I printed 3 more in the correct size. In retrospect, I definitely would’ve placed the 3 stars next to each other to reduce the print time and made them just a bit bigger.

 

 

 

 

 

 

These stars had a lot of texture, and I lightly sanded off some remnants of the supports. There were some areas, particularly where the supports were, that weren’t as smooth and uniform as I would’ve liked. Moving forward, it was time to print them on the SLA printer. The re-sizing and slicing process was very similar as with the Prusa printer, but this time I placed the stars next to each other. After the prints were ready, I did a form wash to remove excess resin and cured them in the UV chamber.

 

I cured my stars with the supports on to make sure the geometry remained intact. Removing the supports after the stars were washed and cured was relatively easy, but it was harder to access the tiny supports in between the areas of overlap. Additionally, I sanded off the little bumps left from the supports on the back, but this caused discoloration. Overall, I prefer the smooth texture of the stars printed with the SLA printer over that of the ones printed with the Prusa printer.

 

 

 

 

 

In conclusion, I’m glad I got to refresh my skills with these two 3D printing methods, since it had been a while since I’d used either. Although 3D printing isn’t my favorite thing to do because it feels like a lot of waiting around, this was a rewarding experience and I learned that there are areas of growth for me. For example, moving forward, I need to figure out how to deal with/prevent the discoloration left from sanding off leftover support bumps on SLA prints and how I can modify the settings to improve the texture of the FDM prints.

 

 

 

 

 

 

 

 

 

cost analysis for 3D Printing

Cost Type	Cost	Price	Source	Quantity	Total
Materials	PLA	$29.99/kg	prusa3d.com	11.88 g	$0.36
	Grey Pro Resin	$199/L	formlabs.com	13.91 mL	$2.77
Labor	Printer Technician	$20.31/hr	salary.com	4 hrs	$81.24
	Quality	$32.56/hr	salary.com	0.5 hrs	$16.28
Overhead	FDM Printer (3 stars = 2 hr print, 80 W)	16.91¢ /kW	electricityplans.com	0.16 kWh	$0.03
	SLA Printer (2 stars = 2 hr print, 60 W)	16.91¢ /kW	electricityplans.com	0.16 kWh	$0.03
Design	Free online	$0	Thingiverse.com	–	$0
Misc.	Waste/scrap	$29.99/kg $199/L	Unused PLA & resin	988.12 g 986.09 mL	$225.86

The total cost for printing the 5 stars using both FDM and SLA printers is $100.71, not accounting for waste.