Heavy-duty mold analysis.

If you want to perform 3-D mold-filling analysis on complex parts that may have up to 18,000 surfaces or 29,000 elements in a finite-element mesh, and you want to be able to perform as many as seven or eight "what-if" iterations on some of them to try out different gating arrangements or other variations--then you need a supercomputer! That was the conclusion of engineers at Apple Computer, Inc. in Cupertino, Calif. "We at Apple are very particular about the quality of our plastic computer parts," says Brian Guinn, mold flow engineer. He says it was not at all difficult for the company to justify buying a $4.7-million Cray 2E232 supercomputer from Cray Research, Inc., Minneapolis. That's because product sales worth $2.5 million per day could potentially be put at risk if faulty part or tool design caused either a delay in getting product to market or customer dissatisfaction with products in the field.

The Cray supercomputer is dedicated to mold filling and cooling analyses, which Apple performs on virtually every plastic part it designs. Apple uses a supercomputer version of software from Moldflow Inc., Shelton, Conn., which just recently went into general release (see PT, Oct. '92, p. 71). No matter how complex the part design, Apple takes no shortcuts: "We model every feature on a part, and we do it in 3-D," declares Guinn.

The company hires six outside consultants just to build the finite-element models, derived from CAD designs in Unigraphics software. In-house engineers like Guinn perform the actual analysis, at a rate of six to 10 times a day--or more. Apple contracts outside for all its plastics molding. Says Guinn, "We design the core and cavity, we tell them how to gate it and how cool it, and we give them a setup sheet |derived from the mold analysis~ of processing parameters to use as a starting point--though we recognize that the molder may tinker with those values in actual production."

The power of the supercomputer saves considerable time in analyzing complex parts. Analyzing a part with 2000 finite elements, which could take 1.4-2.6 hr to run on a Silicon Graphics workstation (which Apple also uses for smaller jobs), requires just 5.5 minutes on the Cray. Similarly, a really complicated part with 29,000 elements would take a high-powered workstation 11.1 days to analyze; but the Cray cuts that down to 23 hr.

Guinn credits such time savings, and the manufacturing confidence that is gained with mold analysis, for helping Apple to reduce its new product design cycle from two years down to six to nine months.