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Model accuracy is the key in rapid prototyping

Model accuracy is the key in rapid prototyping

Hull invented sterolithography in 1983 when he was vice president of UVP, Inc. He patented his process in 1986, when he co-founded 3D Systems Corp., and brought the first stereolithography apparatus to market in 1988. To date, his company has 52 patents in the technology and over 500 installations around the world. The Numerical Controls Society honored him with its Jacquard Award for his work in stereolithography, which has evolved into the $100 million rapid prototyping industry. Great Britain's Rank Foundation awarded him the 1995 Rank Prize for his applications of stereolithography to the advancement of opto-electronics.

Rapid prototyping shows engineers what their designs really look like, but only if the model accurately duplicates the CAD model, says Hull.

Design News: What impact has rapid prototyping had on the design engineering process?

Hull: In the global sense, it's still too early to tell. Nevertheless, at specific companies, there are several examples of rapid prototyping speeding time to market, increasing quality, and lowering costs. For example, in the auto industry, Chrysler estimates it saves $5 million per year over the cost of conventional modelmaking. General Motors now operates more SLA machines than anyone in the world. Mercedes has stated that it won't design a new engine without using the technolog. I am aware that on one manifold project, Rover saved 90% in time and cost. And, Ford, in an application of rapid tooling, reduced development time on a rear wiper motor cover for their Explorer from three months down to four weeks.

Q: As computer simulation tools become more sophisticated, will there still be a need for physical prototypes?

A: Yes. In fact, there will remain a need even with the implementation of virtual reality. People relate to physical objects, especially when you try to communicate the details of something that will eventually be a physical object. Nevertheless, I believe in the value of engineering analysis. A great deal of technology is necessary and available for design.

Q: Is there a need for better software translation between CAD files and prototyping systems?

A: There are good ways now, but the quality of translation varies from supplier to supplier. We developed STL in 1987, and it's the standard for rapid prototyping now. There is also the Contour format for special applications. We are researching new methods, and CAD companies are involved.

Q: What are the biggest limitations of your process?

A: For the last several years, our research and development focus has been on improving the accuracy of how our model duplicates the CAD model. We've made great progress there, but more progress is needed as we get into tooling applications. Now, we see ease of use as critical, and we have made great strides there as well. Ease of use begins with the CAD products that provide the solid models for our process. Ease of use is more important to their effort than it is to rapid prototyping.

Q: What are you doing to find new materials for the sterolithography process?

A: We have a joint research and development effort with Ciba Geigy. The present focus is on material properties such as temperature resistance and toughness. Other materials companies are pushing the envelope too. Current epoxy resins are good compared to the resins available in the early days of this technology.

Q: What is the major significance of your new multi-jet process?

A: It's an easy-to-use tool for giving engineers a first quick look at their products. When we started stereolithography ten years ago, we wanted to develop products that would sit in an engineer's office. As the products evolved, however, they became industrial products for prototype shops. This new product takes the technology inside an engineer's office, where we want it to be. CAD operators can just instruct the machine to make a model, and that's it. It will give engineers time to work out their key design problems.

Q: What is the next breakthrough in rapid prototyping?

A: Rapid tooling--for production dies--is the next big breakthrough. It's a coming revolution. Specifically, the breakthrough will involve injection-molding tooling and short-run or bridge tooling, which will enable manufacturing to test production. Eventually, because of this revolution, design engineers will become tool makers as well. Some companies are experimenting with rapid tooling today, but it may be another three years before the concept is mainstream. The next breakthrough in engineering is to make it possible for engineers to integrate all their design tools, from CAD to rapid prototyping to rapid tooling. Much work remains to be done to get all these tools to work together for true automation of the design process.

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