Before manufacturing a new product, companies craft models or prototypes to check designs, assess appearance, test fit and function with other parts, or fine-tune molds and dies for the production line. For decades, prototypes have typically been made by hand from drawings, a slow and expensive exercise. But in recent years, various rapid-prototyping techniques that automatically produce three-dimensional parts from computer-aided-design data have reduced the time from weeks to days or hours.
Automotive, consumer-products and medical-device engineers are among the most avid users, along with service providers that make models for clients. Objects are built additively as a series of very thin layers of resin, extruded plastic or powder that are hardened.