Stereolithography (SLA) prototypes are constructed from a liquid photopolymer that is selectively cured using an ultraviolet laser. The process begins with a 3D CAD file which is mathematically sliced into 2D cross sections. With the build platform positioned just below the surface of the photopolymer, a scanning system is used to draw the first cross section on the surface of the photopolymer, which adheres to the platform.

When the layer is complete, the elevator assembly lowers the platform into the vat and the next layer is drawn, with each new layer adhering to the previous one. The process repeats itself until the object is completed. Actual build times can range from under an hour to over a day, depending on the photopolymer, laser power, and the object geometry. Typically, a mechanical blade is used to sweep the surface of the photopolymer to ensure an even layer of resin for the next layer.

CNC parts are produced using a Computerized Numerical Control (CNC) machine tool to cut the part from stock metal or plastic material. Starting with 3D CAD data, a CNC programmer develops a program that performs the actual machining. This program can include tool changes as well as the traditional "feeds and speeds" used in manual machining. Depending on the shape of the object to be machined, one or more fixtures may be required.
The primary advantage of CNC prototypes is that they can be produced in the exact material as is planned for the final product. This means that fully functional prototypes can be created for testing in the planned product environment. The primary disadvantage of CNC prototypes is that the time required and the cost of the prototype is highly dependent on the geometric complexity of the prototype.