Engineers at RedEye RPM, Eden Prairie, MN (redeye.com) say they answer the question with: What's the biggest part you need? The largest rapid prototyping (RP) machine can build an ABS part close to 24 X 20 X 24 in. But size is not a limit because of the strength and accuracy of its FDM thermoplastic materials. For example, the company recently built a full-sized landing gear out of polycarbonate. The largest part was about 13-ft long. Fully assembled, the landing gear will be about 16-ft tall. Advanced modeling features in the company's STL editing software, Magics RP from Materialise, Ann Arbor, MI, let RedEye create interlocking features on models that have been cut to fit the production work area. This feature allows precisely bonding finished parts. And because the thermoplastic parts are accurate, the finished parts maintain good tolerances on overall dimensions.