DETROIT - Composite tooling, once confined to the prototype shop, is moving to the factory floor as processors continue to perfect new nonmetal mold materials and show big savings in cost and lead times. At the Automotive Industries Division of Lear Corp., a major effort is under way to develop composite mold materials to increase the responsiveness and flexibility of its manufacturing operations.
Lear is looking to composite tooling for cost savings of as much as 50-60 percent compared with steel and reducing mold construction lead times by 75 percent.
Composite tooling also may give automotive suppliers such as Lear a way to handle an increasing number of low-volume production jobs, as the number of niche vehicles proliferates, and also meet automakers' demands for manufacturing at multiple sites around the world without having to duplicate expensive steel tooling.
``We've got to find a way to maximize our capital investment,'' said Daniel Jannette, vice president of technology at the Lear AI division. ``So we have to run these low-volume tools much faster.''
Part of the answer, and maybe a very important part, is using epoxies, urethanes, polyesters and some exotic materials, such as ceramics, to produce low-cost, rapidly built production tooling.
These materials, often filled with aluminum grains or organic materials such as ground walnut shells, are cast over a model or master of the part and then cured in an oven. The cast composite cavity and mold, often with very little follow up machining or finishing, then is fitted into standard processing machinery to make parts.
Molds made from composite materials, although extremely hard, may not be able to withstand the extreme temperatures and pressures that some processes require and often are run at slower cycle times.
No one is predicting the demise of aluminum and steel as mold materials.
In some applications, such as high-volume, high-pressure injection molding with abrasive materials, composites are unlikely to make much of an impact in the near future. But as prototype shops have perfected composite tools in the past decade or so, many more applications are opening up on the factory floor for composites.
Lear recently put a composite headliner mold into operation and has ordered four more composite molds for headliner production.
The company has tested several materials for composite tools but is reluctant to discuss publicly the precise nature of the material.
General Motors Corp. has been developing its own epoxy tooling material and has used the material successfully to make short-run production stamping dies for sheet metal parts.
GM also is adapting the material, called Superior Tooling and Molding Plastic, or STAMP, for production of plastic parts. Engineers are modifying STAMP to remain stable at the higher temperatures necessary for plastics molding and also to manage heat buildup so the tool does not warp or crack.
GM said a big advantage of STAMP is that shrinkage of the material is negligible once it has been cast into a shape and requires no follow-up machining. By comparison, making prototype tools out of kirksite, a zinc-metal alloy cast with a foundry process, requires ``barbering'' of the surface because of shrinkage of the metal as it cools.
GM estimated that its STAMP material saves 30 percent in cost and time compared with kirksite, which also is used as a prototype mold material in the plastics industry.
Ciba-Geigy Corp.'s Formulated Materials Group in East Lansing, Mich., works with a number of molders to develop composite injection molding tooling for materials such as ABS, nylon, polycarbonate, polyethylene, polypropylene, polystyrene and thermoplastic olefins.
At the SPI Structural Plastics conference in Atlanta in April, Ciba-Geigy technical representative Joseph Subirana presented a paper on composite tooling in which he outlined several advantages:
Composite molds duplicate contours and dimensions of a master or model with great accuracy.
The materials used today for ``soft'' composite injection molds can withstand the temperature and pressure fluctuations re-quired to mold thermoplastics.
Composite molds can be produced in days vs. the weeks or months required to machine metal tooling.
Prime Design Inc., a Cleveland-based mold-making, prototype and limited production shop, uses cast urethane molds and urethane-lined metal molds to produce up to 5,000 parts for customers.
Sales manager Joseph A. Persico Jr. said the process saves about 70 percent compared to building a steel mold and can produce parts with great accuracy and detail. The company recently designed and produced a plastic point-of-purchase display in only three weeks using urethane molds.
``It's an excellent process to use when you're looking at prototype runs,'' Persico said.
Eastman Kodak Co. has been experimenting with epoxy mold making for some 15 years. Early trials were abandoned after a few catastrophic mold failures, but the company's prototype developers continued to experiment.
A key factor in achieving success was adjusting expectations, that is extending cycle times to lighten the load on the composite tooling, said John Fowler, supervisor of plastic development and the fabrication model shop for Kodak in Rochester, N.Y.
Composite tooling, which he describes as ``one of the tools in our toolbox,'' has become very useful at Kodak, which often needs only a relatively few parts molded for some of its products.
``We see it as very important to prototype parts in the final production material,'' Fowler said. ``And it's holding up well for limited production parts. Up to 3,000 parts.''
Composite tooling has ``very good potential'' in vacuum forming, Fowler said.
And, as the material becomes more economical and durable, Kodak also is making more composite injection molds for products that were formerly vacuum molded.
Fowler said composite tooling was most effective when coupled with a prototyping system that can rapidly produce a master or model.
Lead times, he said, can be reduced to ``a couple weeks'' compared with eight to 10 weeks for machining a steel mold.
