Once we are finished with the test socket phase of prosthetic fitting, we are ready to fabricate the prosthesis. During this process, we take a temporary plastic socket, and turn it into a strong and durable socket made with carbon fiber. The first step is to transfer the alignment using a vertical transfer jig. The alignment is important because it saves the relationship of the socket over the knee and foot, which greatly impacts how a person walks. Next, a sheet of plastic is placed on a rack in a prosthetic oven until it starts to droop into a bubble. This plastic sheet is vacuum formed around the mold, which will become the flexible inner liner. After this, the first lamination is done using a layer of carbon fiber. This carbon fiber starts as a woven flexible material that is saturated with a resin, which hardens. The socket is then placed in the jig and the correct componentry is setup underneath it. This step is where we build the previously saved alignment back into the socket. Next, the final lamination is done using several layers of carbon fiber. Once this has set, the socket is removed from the mold, and the flexible inner liner is pulled away from the carbon outer frame. Trimlines are drawn on both items, and the material is ground away to the trimlines using a trautman, which looks like a giant dremel tool. The last step is to reassemble the socket over the knee and foot, and then you have a finished prosthesis.
— Bobby Latham, C.P. Columbia, S.C.