Week 3: Test Run Complete
This week, I tested out some parts needed for the larynx mold on something simpler: a model of a rib graft. As shown below, the silicone casting worked! However, before getting to the final inverse mold, I had to go through several trials before finding a system that worked, which I will show below.
The key aspect that worked throughout all trials was the flaps on the side. These flaps were used to clamp the two halves together and hold them together while the silicon dried. With my first model, as shown below, the issue was that something had to be printed above the hollowed shape of the mold. meaning that PVA (the glue used to stabilize the polymer printed above what would otherwise be empty space) would remain stuck in the crevices and could not be dissolved in hot water. However, the pegs used to align the two halves worked perfectly.
Models 2 And 3:
In the next two molds, shown below, I changed the way the model was split between the two inverse molds, which fixed the issue of PVA getting stuck in crevices. However, the pegs that I had been using no longer worked, likely because the nozzle would not perfectly line up each layer, causing the pegs to “bulge” at the top and not fit into the holes.
As shown in my last inverse mold, the problem with the pegs was fixed by modeling the top part of the peg to be slightly smaller, so this error could be avoided in future prints. Once I saw that the pegs lined up perfectly and that there was no more PVA stuck in the hollowed section, I filled the two halves with silicone and let it set, resulting in the model at the top
I hope to apply some of the discoveries here to make sure the inverse mold for the larynx works perfectly. I am still in the process of modeling the larynx, and I hope to bring some more updates next week.
Thank you for your reading!
Hartnick CJ, Hansen MC, Gallagher TQ (eds): Pediatric Airway Surgery. Adv Otorhinolaryngol. Basel, Karger, 2012, vol 73, pp 116–122. doi: 10.1159/000334463