As we all know, the price of eggs has become increasingly unreasonable by the year. Tired of buying expensive eggs, I decided to 3D print some of my own for this homework. After doing some perusing on Thingiverse, I found that a user had designed some “minimal surface eggs” after mathematically minimal surfaces. I’m still not quite sure what that means, but I thought they looked cool and decided to move forward with printing them.

First, I had to determine the size of the capsule so that I could scale my print accordingly. I used a digital caliper to measure the capsule’s dimensions, finding that it was approximately spherical with a 2″ diameter. I estimated that I would need to scale my print to 65% of the original size for it to fit inside the capsule, so I sought to do a test print on the Bambu printer to figure out the sizing. While setting up the print, I also had to make some choices about support placement. The designer of the egg had warned against having supports go inside the egg as they would be nearly impossible to remove, so I chose the overhang threshold to be 45 degrees and also elected to only use supports for critical areas. I printed at a layer height of 0.15mm, a wall thickness of 1mm, and an infill density of 15% in accordance to the suggested settings for smaller, detailed prints.

Luckily, printing at a 0.65 scale was perfect, with the egg fitting just right inside the capsule. While the supports were easy to remove, the bottom of the egg was slightly unclean due to the minimal supports. However, I decided that I would keep my supports the way I had them for the test print and just post-process later. With that, I printed 4 more eggs on the Bambu (1 extra in case one failed), and sure enough, one did.

With 4 PLA eggs in hand, I needed to print one resin egg with the SLA printer. I scaled my egg to 65% once more, but since the SLA printer prints upside down, I figured I would probably need all the supports that the program suggested, even if they went inside the egg. I printed the egg with all the suggest supports, washed it for 20 minutes, then cured it for 30 minutes.

After that, I (painstakingly) used a tweezer to remove as many supports as humanly possible.

The final step was to post-process my eggs via wet sanding. Since the eggs have a complicated internal geometry with small openings, it was difficult to reach all the areas I needed to sand down. I attempted using a dremel tool with a narrow sanding bit to smooth out some of the rougher areas, achieving medium success.

To clean up the dremel job, I wet-sanded as many areas as I could reach by hand at 120 grit and 220 grit. That gave me my final product.

While I think the final product looked better than the raw prints, they are definitely far from perfectly post-processed. If I were to redo this, I would print with an even thinner layer height to improve the layer details and buy some dremel bits that are narrower so that I can better post-process the interior of the egg.

Cost Breakdown

Materials:

• PLA Filament: each egg used ~33g of PLA based on Bambu’s estimate, so 5 eggs used 165g total. A roll of 1kg filament costs $19.99, so (.165)(19.99) = $3.3
• Resin: I’d estimate that one egg used ~10mL of resin to print. 5L of resin costs $715, so (0.01)(715) = $7.15
• 1 sheet of 120 grit sandpaper = (1/6)(3.27) = $0.55
• 1 sheet of 220 grit sandpaper = (1/6)(3.27) = $0.55

Equipment:

• Makerspace access for $50/month = $3.22 for 2 days

Labor:

• 4 hours @ $12/hr (common wage of jobs at Rice) = $48

Total: $62.77