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There’s been a lot of talk lately in the industry about the benefits and promise of aluminum tooling for higher volume applications—especially in the automotive industry. Just over five years ago, our company, and later some others, began working with Honda to create standards for aluminum tooling, and many hours of R&D have since gone into helping them achieve their goal of lowering tooling and production costs while maintaining part quality . . . goals previously achieved only with carbon alloy steel.

The most common misconception about aluminum as a production tool material is that it doesn’t have the strength of P20 steel. The reality is that the compressive strength of aluminum is 77,600 psi, while the maximum injection pressure at the front of the screw is just 33,000 psi—regardless of machine size—or just 42.5 percent of aluminum’s maximum compressive strength.

However, our experience has shown that aluminum tooling probably isn’t for every application. It depends on the material, the part being produced, the volumes involved and the number and kind of secondary operations being performed. Planned secondary operations after the molding process should be thoroughly investigated for potential cycle improvements, so that the secondary tooling design can be optimized when possible to match the thermal conductivity advantages inherent in aluminum.

A Competitive Advantage
Our business also has needed to develop new ways of designing tools specifically for aluminum, which allows for softer material, thermal expansion, as well as to develop new operating guidelines, which are different from steel. We’ve worked closely with molders to test and set operating guidelines for presses that normally use steel.

However, aluminum tooling is being used today on selected high volume applications at Honda, as well as with other OEMs, with production runs in the hundreds of thousands already. There are more to come. Here’s why.

Automakers using aluminum tooling can realize savings of five to 10 percent on the construction of new tools for the majority of their applications. Additional benefits include reduced production tooling leadtimes of 10 percent or more versus steel. Photo courtesy of Unique Tool & Gauge Inc.

First, more than 70 percent of the plastic planned for use in a typical auto being designed today will be TPO, PE or PP. These materials are ideal candidates for aluminum tooling. Further, as automakers move to lower volumes, the cost efficiencies of aluminum tooling will make it an attractive candidate for more applications.

Automakers will have the ability to realize savings of five to 10 percent on the construction of new tools for the majority of their applications, as well as the added benefit of reduced production tooling leadtimes of 10 percent or more versus steel. Finally, part production cycle time reductions of 20 to 40 percent—or even more—are readily achievable with aluminum tools, given aluminum’s superior thermal conductivity.

Case Study
Unique Tool & Gauge built the tool for the Honda Accord Rear Tray, which is currently produced at Nissan Chemise America (NCA), of London, OH, and has seen a production run of more than 400,000 parts since August, 2007.

First, let’s discuss cost and time savings. Our own experience shows that on average, tool savings can be significant—up to 10 percent on tools that require higher build-hours. Tools for flat, relatively low profile parts with few build- hours due to lack of mechanics will have less of a cost savings, and possibly even be higher in price, since material prices for aluminum are higher than steel and this will offset any savings created by higher build hour tools.

Tools that have more mechanisms and have more depth require more machining, spotting, drilling and benching, which will save time in aluminum versus P-20 mold steel. For the Honda Accord Rear Tray, we were able to reduce production leadtime and cost.
In production, Honda is currently realizing molding cycle time savings of approximately 20 percent on the Rear Tray tool, although cycle time savings in this case are not the entire story.

“We’re fans of aluminum tooling,” adds Damion Manns, New Model Manager at NCA, “but when considering aluminum versus steel, molders need to look carefully at the amount of value-added they’re putting in at the molding location. If they’re molding a part and then moving it somewhere else in the plant, or shipping it out then you can take full advantage of all the benefits of cycle time reduction, otherwise a careful cost analysis of speed versus cost is required.”

Best Practices
Unique Tool & Gauge has now worked on several aluminum tooling projects for higher volume applications and we’ve developed a short list of best practices that will be of value to tool builders and producers as they consider aluminum tools for higher volume plastics applications.

From a design point of view, applications using less abrasive materials like PP, TPOs or PE, and low visual or hidden parts are probably the best way to go initially. Start with fairly shallow parts in height in die draw which have less side molding pressure, and tools should be designed with fairly flat parting line run offs, and with seal-offs that are not extreme—that is—no less than 5 degrees.

As regards maintenance, issues like flash and parting lines are considerations for any tool, steel included. Production maintenance personnel will need to develop an additional skill set for welding aluminum. Aluminum is not more difficult to weld than steel, but there are differences in process and technique that must be learned.

Focus on the Future
I don’t want to leave the impression that there are distinct limitations to the application of aluminum tooling versus P20 mold steel. Our business hasn’t seen them and we think the future is bright for aluminum tooling.

There are very few technologies available to automotive manufacturers today that can match aluminum tooling’s powerful potential for significant reductions in piece part cost over a broad array of applications.