The Computer-Aided Design and Manufacturing (CAD/CAM) Laboratory is where research and development on Squirt Shape, an additive fabrication technology for the production of prostheses and orthoses, takes place. The space consists of a Partner I computer-numerically controlled (CNC) milling machine with four axes of simultaneously controlled motion. The four axes are the x, y, z, and a rotary axis. The CNC mill serves as the backbone of the alpha-prototype Squirt Shape system. We also have a beta-prototype of Squirt Shape that uses a water-cooling method to speed-up socket construction.
The CAD/CAM Lab is also equipped with a Provel d1 mechanical digitizer and Shapemaker software. The mechanical digitizer measures the dimensions of a cast or mold of the residual limb and transfers the data to the Shapemaker software, which creates a three-dimensional computer model. This computer model of the residual limb is modified digitally to relieve pressure in sensitive areas and apply pressure in tolerant areas. Once modification is finished, a data file with positional instructions is sent to Squirt Shape for fabrication.
The CAD/CAM Lab is equipped with a Stratasys Fusion Deposition Modeling (FDM) 400mcTM. This rapid prototyping machine uses data in the form of stereo lithography (STL) files that computers can use to make 3-dimensional objects such as prosthetic sockets, liners and complex, cosmetic coverings. Fabrication is totally automatic and is accomplished by using a dispensing nozzle to deposit thin layers of liquefied plastic which quickly hardens into a solid. This equipment uses a fused deposition modeling (FDM) technique that allows researchers to fabricate rapid prototypes, thus enabling early error correction and prediction of end product performance.
The CAD/CAM Lab also is equipped with an Inspeck 3D Megacapturor, which can digitize complex shapes such as hands, arms, legs, feet, torsos or heads. This optical system projects a sinusoidal pattern onto the surface of an object that is captured by a single camera as 300,000 to 7,800,000 sampled points. Both geometric and texture data are captured. The stripes appear distorted and an analysis of the distorted patterns is used to calculate the 3-D surface shape. This digitizer provides a photographic record as well as a computer image that helps researchers visualize and measure three dimensional shapes.
Both the Stratasys 400mcTM Rapid Prototyping Machine and the Inspeck 3D Megacapturor will have many applications in our laboratory. A VA study (“Feasibility of a Zero-Impingement Socket for Lower Limb Prostheses”), will develop new approaches for the fabrication of sockets and liners for prostheses. In this project, limb digitizing will be used to capture the shape of residual limbs and create three-dimensional computerized models. FDM will be used to produce the structural elements of sockets and to produce molds that will enable customized liners to be cast from elastomeric materials. In addition to the VA study (“Feasibility of a Zero-Impingement Socket for Lower Limb Prostheses”), a different study funded by NIDRR will utilize similar procedures to develop production techniques for low-cost cosmetic gloves for upper-limb prostheses.
In addition, the CAD/CAM resources are utilized in other projects like gait studies of amputees where multiple prostheses per subject are needed. CAD/CAM enables easy iterative modifications to socket shape and rapid fabrication of prosthetic sockets. Such procedures would be very time and labor consuming if performed manually.