There is a very interesting effect called the Mandalorian – I mean Mandela effect associated with Star Wars: Darth Vader never said, “Luke, I am your father.” He actually said, “No, I am your father.” Look it up if you don’t believe me.

I digress. This is no time for factoids, as the OEDK has stricken back with its final challenge of ENGI 210: chess. Not a normal game of chess, no, but an ultimatum to manufacture a chess set (or eight identical chess pieces) using a multitude of techniques: 3D printing, CNC, and molding and casting. As such, Brian Bishara and Shifan Liu joined forces to summon victory to the rebels.

To begin with, what source of creativity is better than the World Wide Web? Probably human ingenuity, but the Web is more convenient. As such, we took off to Thingiverse for inspiration. We decided to go for an unorthodox chess piece instead of a standard one because a standard piece can simply be bought, so why not exercise some creative freedom? We gleefully surfed and scanned the different possibilities until we found a humorous moai chess piece by SmileyBee. We were set on that until a quick discovery that not one but two other teams are also making moai chess pieces. We had to change course.

Tying back to our Marvel-inspired midterm project, we sought out another MCU character to put in the spotlight. There was a grand total of one option available on Thingiverse: baby Groot by Houby. It was the one and only baby Groot, though, which was great, or so we had thought. We first 3D printed a prototype to see if the height and base diameter were satisfactory, which they were. We then used MeshMixer to cut the piece in half. However, the number of triangles that made up his body was astronomically large to the point that every action took 15 seconds to 1 minute to load. In order lower the triangle count while preserving the fine details of Groot’s cute face, we manually selected every portion of his body but his face and reduced the triangle count until the total count was 10,000. The face also got its own treatment of triangle count reduction, but it was not as pronounced as the rest of the body.

At this point in the course, we should have learned that there was always something that we were unaware of—something that could pose as another obstacle on our path, cause a minor setback, or utterly devastate our progress. When the file was exported and opened with SolidWorks, we noticed something strange: the portion of the piece that is Groot’s head was completely hollow. We tried to fill it, even asking a TA for help, but to no avail. We proceeded to extrude a base anyways and hope for the best. It should have worked with the CNC machine because it is subtractive manufacturing. 3D printing, on the other hand, is additive, so it had to fill up that hollow space with something; otherwise, the print would fail. However, internal supports were never printed, and after a four or five attempts, we realized the futility of our entire work.

We were back to square one (which intriguingly mirrors the course of our work on the midterm project). We were pulled back to the realm of Thingiverse, constrained by its limited number of unique chess piece designs. Contemplating across the line of Disney franchised, we hopped from Marvel to Star Wars, of which there were so many more options to choose from. We ultimately picked a Stormtrooper by pverduijn because it had the least overhang. We used MeshMixer to slice the body into front and back “halves”. I put halves in quotations because the slicing plane is not exactly in the middle, but it is closer to the Stormtrooper’s back; this is to ensure that it does not slice through the deep cavities that make up the Stormtrooper’s eyes. The files were then exported to SolidWorks and appropriately modified to be 3D printed and CNC’d.

After the positive molds were created, they were sprayed with mold release lubricant, and a box of indeterminate size was made out of each by sticking pieces of cardboard in a windmill pattern. Copious amounts of hot glue were used to ensure that the boxes were completely airtight so that no leaks would occur while the silicone mold cured. A 1 cm mark was highlighted above the top of the positive mold, and the volumes of silicone needed were estimated. For the 3D printed mold, a volume of 2.5 cm x  6 cm x 7 cm was measured, and the volume of the Stormtrooper to be subtracted from that was estimated to be a quarter of that volume (we had no reliable way at that moment to know what the volume of a Stormtrooper was; Archimedes’ principle could have been applied with a 3D printed Stormtrooper, but we did not have one). For the CNC mold, a volume of 2.2 cm x 9 cm x 7 cm was measured, and the volume of the Stormtrooper to be subtracted from that was also estimated to be a quarter of that volume.

With our estimated volumes, we made an equal volume of silicone by mixing equal volumes of silicone A and silicone B. However, that was not enough to even fill one of the molds. The volume of the Stormtrooper was grossly underestimated, and a new silicone solution was made to fill up the remaining portions of the mold. A little leak was observed, which was swiftly resolved with hot glue.

The mold was left overnight to cure. The following day, we returned to the OEDK to start casting. The silicone negative molds were detached from their positive counterparts (which was made possible by the usage of the lubricant), and they were held together with rubber bands. Solutions of liquid plastic were made (50 mL for each piece) and poured into the mold until four pristine white pieces were produced.

To produce the dyed pieces, we decided against a homogeneous color and opted for a more chaotic swirl of iridescent colors weaving into each other. This was achieved by mixing in droplets of red and blue dye into the liquid plastic using a straw or a very thin wooden rod. The solutions were once again poured into the mold one at a time until four spectroscopic dyed pieces were produced. There were a couple hiccups: mixing was done too vigorously such that the outcome was a homogeneous color, or blue dye was too concentrated at the head such that it did not solidify properly and had a melted appearance.

Finally, the artefacts of the slightly asymmetrical mold alignment were scraped off with an Exacto knife, and the bases were sanded to yield flat, smooth surfaces that are satisfying to the touch. The Stormtroopers have a final height and base diameter similar to that of a pawn. Future steps include making a piece out of every other Star Wars character to actually get a full 16-piece chess set. Imagine Darth Vader being a king, or R2D2 being a rook.

MONEY TIMEEEEE 🤑

• 272 g silicone A+B cost $9.99 – 200 g were used, giving $7.35
• 2 gal liquid plastic A+B cost $118.99 – 400 mL were used, giving $6.29
• 6″ x 8″ unfinished wood costs $4.25 – 3.375″ x 5″ were used, giving $1.49
• Hot glue + Gloves + SLA + Mold release lubricant + Cardboard + Dye are estimated to be $5
• Labor costs $10/man hour – a total of 22 man hours were spend, giving $220

Cost of entire set: $240.13

Cost of a single piece: $30.02

Since the molds are done, new pieces can be produced at dramatic rates, and the cost of each would decrease.

 

brianbishara, shifanliu