Massive, bondline-free tooling block

A candidate for the biggest “bun” from high-density urethane foam?


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Tooling board manufacturer Coastal Enterprises Co. (Orange, CA, US) is certainly used to producing foam for use as composite layup tooling (see "Low-rate layup tools made cost-effective with high-density polyurethane foam," under "Editor's Picks," at top right). Typically, the company manufactures blocks of its Precision Board high-density urethane tooling foam and bonds them together to form a rough tool shape as directed by the customer, which then machines the bonded assembly to its specs. However, a recent aerospace customer, Ascent Tooling Group’s Coast Composites (Irvine, CA, US), needed a large foam tool for a project, and because the tool would be autoclaved at elevated temperature, Ascent wanted no bond lines in the foam that might impact uniform heating. 

Coastal’s president Chuck Miller says, “We had to produce a 1.5m by 3m by 300 mm thick monolithic foam block, at a specified density of 1.2 kg/liter, which was a pretty big deal.” Why such a big deal? According to Miller, this block might be the largest ever made, at that size and density. 

Although Coastal won’t reveal its exact recipe for producing its foam “buns,” or blocks, Miller does say that the large PBHT-75 high-temperature-capable foam block, which included a number of proprietary additives, took a great deal of planning and preparation before the final mixture could be injected into the rectangular metal mold. The injection and reaction process was followed by a controlled cure and postcure. Key to the process, says Miller, is knowing how to successfully control the foam’s reactivity profile and the exotherm generated during the pour and cure process. 

Coast Composites recently took delivery of the 1,180-kg tooling block, and is currently machining it to final profile. “We are seeing the composites industry going more towards bigger tooling,” concludes Miller, “and we’re going along with it.”