Design issues and process understanding dominate meeting.

The widespread use of lost foam (LF), also known as expendable pattern casting, according to Bruce McMellon, Vulcan Engineering Co., has been delayed only by two things: "The stubbornness and ignorance that all new processes face, and lack of information passed back and forth by users."

This statement by McMellon, chairman of the AFS Lost Foam Technology and Applications Conference, held-September 11-13 in Akron, Ohio, reaffirmed that much discussion of the 33-year-old process centers around design issues and the hesitation of purchasers due to LF naivete.

Nearly 175 metalcasting officials (from 14 nations), gathered to hear 20 presentations while exchanging their own experiences with LF.

Design Factors

"The real mission in LF is to shift the valued-added content of a product from machining and assembly to casting," said Vulcan's Parker Stroom, "while positively affecting overall cost and quality."

Generating this value shift through LF may increase the casting cost. Real machining and assembly costs, however, as well as final product costs, are often significantly reduced.

Just as some parts shouldn't be examined for conversion to LF, he said products with high core content or internal complexity should be considered, as well as parts requiring high machining or those with potential for component integration. The final assembled product should be examined for opportunities to "marry" components into the base casting.

Success in LF, Stroom said, requires metalcaster and customer commitment to:

* learn and understand the foam molding ("white") process;

* process discipline and control;

* continuous improvement through controlled change;

* early participation in product design with simultaneous engineering;

* participating and sharing in fundamental process research and development.

Market Factors

Because of the economic lull several years ago, and the respective dip in manufacturers' product development path, McMellon said, LF leveled after a period of growth, but is growing again. "We've seen a surge in the LF steel market, but the biggest growth is in aluminum, like the rest of the casting market. Nonautomotive jobbing foundries are also becoming full because of workloads."

He noted LF has always offered a number of advantages in near net shape, tremendous environmental benefits, etc., but can now produce materials like never before. "Customers, however, may not feel comfortable with producing LF tooling because of the process' relatively small sourcing base. More job shop foundries need to get into LF for it to grow."

Process Needs

A study by General Motors (GM) determined LF as the process of choice for future aluminum engine components. As a newcomer, however, LF is only beginning to get the technical attention required to propel it toward larger scale production, said GM's Paul Mikkola.

While the LF learning process is progressing rapidly, he said several elements exist where the knowledge, equipment and availability of services are rudimentary. Targeted by GM's R&D plans are sand compaction, sand media, pattern adhesion and materials, pouring and filling dynamics, aluminum alloys, lead-time to production, equipment cost, quality and modeling.

Stressing product quality, Mikkola said, "The customer unhappy with LF will be a terrorist to the process--they'll never specify it again." He also noted that poor production lead times are LF's most limiting factor. "It should take 3 weeks, not 3-9 months."

Lost Foam Chronicles

Chronicling their firm's LF history was GM's Mike Williams and Brunswick Corp.'s (Mercury Marine) Jack Reichart. Williams marked the LF evolution at GM, starting as a pilot process at Pontiac Foundry in the '70s, to the short-lived V6 diesel engine at Massena in the '80s to Saturn, which today produces its aluminum blocks and heads, and iron crankshafts and differential cases in LF.

Reichart described Mercury Marine's LF innovations, namely its: hypereutectic Al-Si alloy to provide a narrow solidification range, low-expansion precision sand process for more dimensionally correct castings and high temperature sand to eliminate liquid styrene problems.