Aluminum vs. steel tooling: Which material is right, and how to design and maintain?

With OEMs hammering their mold suppliers for ways to reduce cycle times, aluminum tooling offers one answer. With its ability to transfer heat from the mold much faster, many OEMs are choosing aluminum. Another benefit is faster machining times, which can reduce the mold-build time by 10-15% in some instances, according to Darcy King, president of Unique Tool & Gauge Inc. (Windsor, ON).

However, there are a number of criteria to consider when determining if an aluminum mold is the right tool for the job. According to King, the first thing that Unique looks at is whether or not the molder that will be producing the parts has experience with aluminum molds. "If the molder is experienced in running aluminum molds, that means an aluminum mold won't be challenging," King told PlasticsToday. "If they haven't had any experience with aluminum-only steel molds-they need some education in the process."

Al Standaert Darcy King
Al Standaert, Technical Sales Manager (Left) and Darcy King, President (Right) of Unique Tool & Gauge.

David Myers, VP of Sales for DRS Industries Inc. , a Holland, OH-based mold manufacturer, concurred. "There's a learning curve to producing parts at production facilities that are only used for molding parts from steel molds," Myers explained to PlasticsToday. "Not only in how you process the parts but how you treat an aluminum mold versus a steel mold.  

"It's not a significant difference, but enough that it can cause problems. Your savings on the cycle time can be offset by the risk element inherent in the learning curve. We find ourselves supporting OEMs with aluminum tools and bringing in the production molder to educate them on aluminum tools," Myers added.

Unique primarily builds steel molds for the automotive industry, but has a long history of building aluminum molds as well. King said that the company also builds 'hybrid' molds that may be primarily steel but might incorporate aluminum inserts in a standing or deep-draw piece, or an area where it's difficult to get water resulting in a hot area that will affect cycle or hurt quality.

Aluminum or steel?
King explained there are several criteria in that will determine if an aluminum mold is suitable for an application. Part design/configuration is a major consideration. "A part has to be adequately designed for the molding process," said King. "We've built aluminum tools with lots of actions and/or poor shut-offs with no problem, but we might use steel shut-offs in an aluminum tool."

Unique Tool & Guage Inc. Part volume is also a critical factor when deciding whether to use aluminum.  "If you have an extremely high volume part, we might lean toward steel and/or at least have specific areas inserts made in steel," said King. "Sometimes we take the hybrid approach in a steel mold and, because aluminum is cost effective and conductive, we'll use aluminum in certain areas."

DRS Industries began life 30 years ago as a pattern shop but has evolved over the years to specialize in aluminum prototype and bridge tooling for both automotive and non-automotive applications. "Because we specialize solely an aluminum tooling for low-volume parts, everyone here

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