Reconsidering Aluminum

One mold maker sheds light on the advantages of this material from a machining and handling standpoint. Another argues that it can indeed be a viable alternative to tool steel beyond just prototyping and short-run applications.


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A hybrid mold—that is, one incorporating both steel and aluminum—manufactured at Wepco Plastics, along with the part it’s used to produce. As it does with much of its other work, the company also performs assembly and packaging for this particular job.

David Parmelee of Wepco Plastics says there are two schools of thought about aluminum tooling: Some shops flat-out say “no way,” while others view it as a potentially viable alternative to tool steel, so long as its limitations are taken into account.

Mr. Parmelee is firmly in the latter camp. The vast majority of tools produced at Wepco are 100-percent aluminum, and he credits the Middlefield, Connecticut-based company's expertise with what can and can’t be done with the material for a good portion of its success. “We have molds that have run hundreds and thousands of parts and they’re still good, because we know how to take care of them,” he says. “We even run a lot of glass-filled nylons through the molds, and they work fine. For the price difference, it can’t be beat.”

Beyond price, aluminum is much lighter and easier to handle than tool steel. That’s critical for Wepco because much of the company’s work is large and unwieldy, he says. He adds that the material is easier to cut and disperses heat better, so machining cycles are faster.

Of course, he emphasizes that the material does have limitations. For example, heat dissipation becomes a disadvantage when it comes to hot runners because the plastic resin at the tip of the runner could freeze. In these and other cases, the company often makes hybrid molds incorporating both steel and aluminum. It should also be noted that Wepco specializes in prototype and short-run work. That’s a traditional application area for aluminum molds, and most skeptics of the material seem to focus on production.

Still, Mr. Parmelee isn’t the only evangelist for aluminum. Penned by Bob Lammon of Phoenix Proto Technologies, this article from MMT’s November issue argues that the material can indeed be a viable substitute for tool steel in production applications.

Meanwhile, stay tuned for more on Wepco. The purpose of my conversation with Mr. Parmelee was to gather information for an upcoming article about the shop’s use of a new Mil-Tec cutting tool from Tool Alliance. Featuring high-positive-geometry inserts, the tool has significantly improved productivity on the shop’s aluminum frame inserts. That piece is tentatively scheduled to run in our February issue.