Northwestern University Feinberg School of Medicine

Northwestern University Prosthetics-Orthotics Center

Rapid Prototyping Lab

NUPOC Rapid Prototyping Lab

The Computer-Aided Design and Manufacturing (CAD/CAM) Laboratory is where the original research and development on Squirt Shape, an additive fabrication technology for the production of prostheses and orthoses, took place. 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) served as the backbone for the alpha-prototype Squirt Shape system. We also developed a beta-prototype of Squirt Shape that uses a water-cooling method to speed-up socket construction.

The CAD/CAM Lab is equipped with a Stratasys Fusion Deposition Modeler (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. Fabrication is fully automatic and uses a dispensing nozzle to deposit thin layers of liquefied plastic that quickly hardens into a solid. This equipment allows researchers to rapidly fabricate prototypes, thus enabling early error correction and prediction of end product performance.

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. When modification is completed, a data file with positional instructions can be sent to systems like Squirt Shape and Stratasys for fabrication.

We utilize these time and labor saving CAD/CAM resources in many of our projects, including socket development and gait studies of amputees that require multiple prostheses per subject. CAD/CAM enables easy, iterative modifications to socket shape and rapid fabrication of prosthetic sockets.

Rapid Prototyping Lab at NUPOC

Prosthetic socket prototypes created in the Rapid Prototyping lab at NUPOC.