Rapid moves

Rapid prototyping covers a range of technologies that create physical 3D objects from 3D data sources output by solid modelling CAD systems, 3D laser scanners, and CT/MRI scanners.

The technology is currently dominated by ‘additive’ processes developed by companies such as 3D Systems, Stratasys, EOS, Z-Corp and Object Geometries. These build models by joining a range of materials — including liquid plastics, resins and sheet paper/metal — layer by layer using thin, horizontal cross-sections of the computer model to drive the RP equipment.

However, with the recent emergence of high-speed/high-performance machining, the process now includes the traditional subtractive technologies. These use high quality CAM-generated five-axis toolpaths to create 3D objects efficiently on a machining centre or CNC router and have the advantage of a fine finish.

The chief use of RP objects is as functional models, followed closely by visual aids used to test assemblies for fit prior to production, and as patterns for castings. For example, stereolithography (SLA) can be used to provide accurate master parts for design verification and soft tooling prior to injection moulding. Vacuum casting can be used to manufacture production-quality piece-parts from low-cost silicone rubber tooling generated from the SLA masters.