One day, Erin and Elliot were walking on an island in Animal Crossing. Suddenly, they came across a strange star in the ground.

“What the flip is that?” Elliot asked.

“I don’t know!” Erin replied. “Let’s dig it up and see.”

Erin handed Elliot a shovel and told him to get to work. After 3 hours, he finally dug up the mysterious object. It was a gyroid! But, it was one they had never seen before. They planted it in the ground, watered it, and waited for it to grow.

The next day, they came back, and Elliot dug for another 3 hours to reveal what type of gyroid it was. It was a gyroid that was so special, it had never been discovered before…

AN ENGINOID!

Erin and Elliot wanted to make 8 chess pieces of the Enginoid. So, they got to work.

First, they found a viable Enginoid stl file off of Thingiverse and imported it into Meshmixer. In Meshmixer, they set out to process the files so that they would be ready to 3D print and CNC. First they oriented the file upright and selected a plane cut. They split the Enginoid into two pieces, front and back.

Next, in Solidworks, they processed the Enginoid file further by combining them with 3.5” x 3.5” mold bases. To do this, they mated the appropriate sides of the Enginoid with the bases and centered them. Importantly, they added an air tunnel to prevent air buildup on the arm that is oriented downwards.

Then, they went to the 3D printer and printed the front half of the Enginoid.

Afterwards, they went through hours of trial and error using the CNC machine. Using Carbide Create, they set up both roughing and finishing gcode paths to mill the Enginoid shape. They primarily used an 1/8” CNC bit for the roughing process, which took ~ 40 minutes, not including the fixes along the way. Then, they used an 1/8” CNC ball nose bit for the detailing, which took ~ 30 minutes, also not including the many errors. In the end, they produced a greatly detailed back half of the Enginoid, ready to use.

They had finally acquired both halves of the gyroid. Now, it was time to make the mold. They tightly surrounded both the 3D printed part and the wooden CNC part with cardboard to make a watertight box to pour the molds in.

Then they mixed the two parts of the silicone mold and poured until it fully submerged the Enginoid.

After a few hours, the mold was complete.

Finally, it was time to cast the Enginoids out of plastic. They wrapped the two halves of the mold with 3 rubber bands to ensure no liquid would leak out. However, at the first attempt, they were met with failure. They took too long trying to figure everything out, and the plastic started hardening before the were able to pour everything into the mold. So, they were met with a half finished Enginoid and a lump of plastic.

The next attempt, they managed to pour everything in before it hardened. Sadly, they did not mix enough plastic to fill the entire mold, so the Enginoid was slightly too short. On the bright side, though, the colors they used worked and it made an earthy brown-green marble.

The next 8 attempts were all successful. They learned to work under the tight time constraint of ~ 1:30 – 2:00 minutes before the plastic hardens. They also made a small 3D printed funnel to feed liquid plastic through the air tunnel.

In the end, there were four white and four colored Enginoids.

Afterwards, post processing was as simple as filing and sanding off the excess plastic on the junction of the two mold halves.

Cost Analysis:

• Materials:
  • 3D printer filament – $0.84
  • Wood – 2 in x 4 in x 1.5 ft pine = $0.65
  • 73-25 Silicone Rubber – $33 / pint * 1.375 pints = $45.40
  • Liquid Plastic – $28.5 / quart * 0.9375 quarts = $26.72
• Time:
  • 12 hours * $7.25/hour * 2 people = $174

Total Cost: $247.61 (~$31 per Enginoid)