(Continued from part 1)
A while ago I encountered an episode of “How It’s Made” on the Discovery Channel that showed the process of making anatomical models. If you have seen that episode, that sums up how these models are made in a nutshell. The process begins with a design. A prototype is created from the design. From the prototype, a metal mold is made and this mold is then used and reused many times to produce the anatomical models. The models are then trimmed, painted, and assembled. Even though this is considered “mass production,” the entire process is time consuming and requires a lot of “hand made” procedures. This is why anatomical models can be very expensive.
When a design is completely new, the model needs to be sculpted by hand. However, sometimes the anatomical model company already owns a model that is similar to the new design. If such is the case, the original model can be scanned with a 3D scanner and edited using a computer software. The final file is sent to a rapid prototyping machine, where a prototype is created. Some companies own their own rapid prototyping machines. Those who don’t usually send their designs to rapid prototyping service bureaus. This newly created raw model is rarely perfect. To complete the process, a sculptor must smooth the piece and re-carve the fine details.
The next step is mold creation. Metal is chosen for their heat tolerance and durability. The mold design can be tricky because anatomy often have very complicated shapes. In order to avoid undercuts, the design of both the model and the mold needs to be carefully considered. Like the previous process, the mold can also be created off site by another company.
Once the mold is made, a worker fills the mold with materials and churns it so the material fills the entire mold surface. The raw model is removed while still warm and left to cool. During the cooling process, the material shrinks slightly, contributing to the difficulty of fitting multiple parts together in a precise manner. The edges of each model are trimmed, and the models line up on shelves waiting for the next step. Eventually some models are sprayed with a base paint. Sometimes the base color is the color of the material, so the layer of paint isn’t always necessary. Painters then take the models and hand paint them according to a chart to ensure accuracy in all the models. The paint used in this process forms a chemical bond with the material, preventing the paint from being rubbed off easily. Finally, assemblers drill holes and fit the different parts of a model together.