Aluminum injection molds used to be thought ideal only for low-volume applications using commodity materials. That is changing as OEMs look more closely at tooling costs and cycle times to reduce piece-part pricing, and overall manufacturing cost.
Not long ago, aluminum tooling was considered “soft” tooling that couldn’t withstand the rigors of high-temperature, high-volume injection molding. And it was never to be used with glass-filled materials. However, that’s all changing for a variety of reasons, says Dave Wirth, Midwest sales manager/aluminum mold specialist for Clinton Aluminum & Stainless Steel .
“What we’re seeing now is the perfect storm that’s creating a renewed interest in aluminum for high-volume-production injection molding applications, particularly in the automotive industry,” says Wirth.
Darcy King (left), president of Unique Tool & Gauge, and Al Standaert, technical sales manager, show off a large, high-volume aluminum tool for an automotive application, the Honda Accord rear seat deck tray. This tool has nearly 600,000 shots on it since entering production.
Not that there’s been little interest in past years. According to Wirth, some molders have been using aluminum tooling for years, but not telling anyone about it, using it as a competitive edge. It’s not just the initial mold cost that results in savings; aluminum tooling can also provide a substantial reduction in piece-part costs due to shorter cycle times.
“Everyone is looking at piece-part costs right now,” says Wirth. “Additionally, volumes in automotive have dropped along with model changes, so over the past 15 years we’re seeing shorter product life cycles.”
And it’s not just in automotive. Wirth notes that a number of years ago, a major appliance maker would make 10 million shots off tooling an appliance. Today, because of a shorter product life span, they are averaging 1 million to 2 million shots. Ditto for office furniture, he adds. “If you build an aluminum tool, you can save money on the production cost of the mold, but more importantly, you’ll have a 20%-40% decrease in cycle times, and many of these major OEMs are looking at piece-part cost as the biggest factor,” Wirth says.
A major office furniture OEM looked at the cycle time cost savings for a chair base and found that over 2 million cycles, it saved $0.02/sec. “They could pay for four molds with the money they saved switching from steel to aluminum for the tooling,” explains Wirth.
Honda’s the proof
Aluminum tooling was given a great deal of credibility when Honda Motor Corp., which had done a study on aluminum vs. steel tools some years ago, released it to its supplier base. The company compared softer tool steels (P-20) with 4130/SD18 aluminum, which contains more sulfur for improved machining. P-20 costs more vs. 4130/DS18. Using 4130, Honda saw an 8.6% improvement in material cost. Machining costs improved 8.0%. (See study details below.)
Honda has built several tools using mold supplier Unique Tool & Gauge Inc. (UTG; Windsor, ON) and another company. Darcy King, UTG’s president, says, “The major automakers are interested in aluminum tooling for a number of reasons. We started years ago developing