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One of the most serious limitations of RP has always been that the materials used in most processes leave a lot to be desired in terms of their physical, thermal and chemical properties. This has meant that in many cases it was necessary to either limit the real-world testing of parts in an application, or that RP parts had to be used simply as patterns to make tougher items out of more durable materials. Material properties have also been a stumbling block in the progress of RP into direct manufacturing. There has, however, been tremendous improvement in RP materials over the years. Ranges of durable resins are now available for fused deposition modeling (FDM) and selective laser sintering, for example. RP technologies such as these offer relatively easy solutions to materials problems because they’re based on merely changing the physical state of an intrinsic material from one form to another. The physical properties of the resultant parts are more related to the mesoscale geometric idiosyncrasies of the particular RP technology rather than material chemistry. Torque applied to stereolithography-generated test part after tempering shows that it twists, but doesn't fracture as does the untreated test part below.   On the other hand, processes such as stereolithography represent more difficult RP material problems. Stereolithography resins undergo complex chemical changes, as well as a phase change that turns them from a liquid into a solid. Such materials must be compatible with diverse machine parameters, while simultaneously resulting in parts with desirable final properties. While this is a more difficult problem, the numerous stereolithography resins available today with a wide range of properties such as flexibility, optical clarity and toughness, proves that the requirements are not mutually exclusive. Continued progress in materials is needed across the spectrum of RP technologies, but a number of secondary methods designed to enhance the properties of RP-generated parts are also now available. These ancillary technologies offer the possibility of circumventing chemistry problems, allowing RP-generated parts to be directly used for more realistic testing or as final production items. One of the more interesting of these processes is RP Tempering which will be offered for license by Catalyst PDG, Inc. starting in January, 2003. The company will not release detailed data sheets or figures until then, but according to the company’s Earl Dunlap, RP Tempering can improve impact resistance by an average of 13 times, and torque capability by 5 times, while tensile strength remains approximately the same as the original material. Above, untreated stereolithography-generated part ruptures and flies apart during impact testing. Tempered part, below, bends but doesn't break as shown in the right frame. All photos courtesy of Catalyst PDG, Inc.   The company says that RP Tempering evolved from their STATTM tooling process and can be applied to parts made by either stereolithography or selective laser sintering. Parts can also resist higher temperatures and will also return to their original shape after cooling. Metal screws can be driven into threaded holes several times without fracture, and snap-fits can be repeatedly used with results similar to final plastic materials. Large parts can pass the UPS drop-test, and parts can also be made either more rigid or more flexible, as desired. For more info contact: Catalyst PDG, Inc. 5201 Park Emerson Dr. Suite M Indianapolis, IN 46236 317-786-4444 Mr. Earl Dunlap, CEO www.catalystpdg.com