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Aluminum for production molding offers lower costs, high quality parts

Aluminum for production molding offers lower costs, high quality parts
Aluminum molds have been used for many years for applications that require lower piece part volumes such as prototype tooling for part R&D, and using materials that don't damage the cores and cavities. However, aluminum is being used more commonly today even in high-volume production molding applications. In fact, according to Darcy King, president of Unique Tool & Mold: "There are not a lot of applications where you can't use aluminum."

Unique was one of the large automotive tooling suppliers that pioneered the use of aluminum for production molds, working in tandem with Honda Motor Co. more than a decade ago to collect data and perform comparison testing on the viability of using aluminum for production tooling. Unique "met or exceeded" Honda's expectations and the automaker chose Unique as one of only two co-management shops capable of building aluminum molds for Honda. "At the end of the day, a mold manufacturer has to ask, 'what do I have that's different than everyone else in order to be successful?'" he said.

King understands that sharing good ideas and new mold technologies with its automotive customers promotes repeat business. "We can develop an entire part for them or design new ways to make a particular part function better," he told PlasticsToday. "We are a leader in aluminum tooling and can save our customers money in that respect. We are one of Tesla's number one suppliers as well, and we've helped them develop their parts, provide program management, 3D material simulation, as well as use the latest and greatest equipment."

King noted that polymer material is the biggest obstacle to using aluminum molds—material such as glass-filled nylon (unless volumes are low) wouldn't be suitable for running in an aluminum mold. ABS or polycarbonate materials that have high-volume requirements would also require steel. "In those cases you'd stay away from aluminum," King said.

Mold manufacturers and OEMs like aluminum because it's much faster to machine, and faster to hand work. However, it requires all the same water lines and plumbing, like molds in steel. One advantage is that aluminum dissipates heat much faster, which molders like for cycle time.

While we typically think of aluminum molds used in large, single-cavity parts for injection molding or thermoforming, King explained that aluminum is "absolutely good" for smaller parts in multiple cavity tools as well. "We've done small parts, medium or large parts," he added. "Is there a sweet spot for the type of parts? The types of plastic used would be key. Materials such as polypropylene, thermoplastic olefins and polyethylene - all depending on the volumes - would be ideal. We can get about 1.2 million parts on a complex aluminum mold."

Another consideration is the rear deck. With aluminum molds a 20% cycle time reduction can be achieved, but the drawback is the manufacturing work cell isn't set up to handle it - "the automation can't keep up," King said.

Unique Tool & Gauge announced that a production aluminum that is now in use in production operations was machined from the largest block of production tooling-grade aluminum ever forged anywhere in the world. Alcan Technologies supplied, through a production licensee, an 11,000 lb. forging of Alumold 500, measuring 70" x 52" x 31". The application for the tool is the front wheel well liners for the Honda Civic sedan, which is produced in the U.S. 

Both OEMs and molders can benefit greatly from using aluminum tooling. In fact, King believes that it's "past time" for OEMs to ask themselves how much money they could be saving by encouraging the use of aluminum tools when and where it makes sense on high-volume programs. "My contention is that aluminum mold are a practical, and proven molding technology, and OEMs and their tier suppliers are leaving money on the table," he stated.

King provided an example to help us understand this point. Take a tool running 150,000 shots per year with a steel tool running a 50-second cycle. That tool would need to run 95 days per year, producing 1584 shots per day. That same part running in an aluminum tool at a 35-second cycle would achieve approximately 30% savings and require approximately 66 days per year of run time. This equates to approximately 638 hours saved. Hours saved means the molder would add press capacity without having to actually add presses!

The level of competitiveness of U.S. molders against China would also increase exponentially. King points to a Plante Moran 2013 North American Plastics Industry Study in which they compare hourly press costs. For a 200-ton machine in Indiana, the average hourly cost is $41.57. In Shanghai, that same tonnage press would cost $37.35, and in the China interior it drops to $29.50.

"If you're a molder, and your Chinese competition is molding in steel, you've just gained the equivalent of 29 shifts of actual molding, not counting set-up time and post-shift operations for your 200 ton press," King said.

Other benefits that Unique's molding partners have discovered when using aluminum tooling include lower tooling and production costs while maintaining part quality and reducing cycle times. Also, because an aluminum mold's weight is half the weight of a P-20 steel tool, there is less wear and tear on molding machines, and less wear and tear on the crane equipment. "With reduced cycle times and clamp pressures, you'll be looking to optimize your molding operations on smaller machines that have a smaller footprint and result in lower operating expenses for your molding operation," said King.

King believes that the use of aluminum tooling constitutes "a true paradigm shift" in automotive plastics because the "selection of the mold material can now serve as the major driver of how the molding process should be designed," King explained. "Now the mold itself has become a major driver of program cost savings."

King offers four key points when considering aluminum tooling:

1)    Production aluminum tooling is a proven, cost-effective technology for high volume automotive applications.

2)    Olefin materials are the sweet spot for aluminum tooling.

3)    Initial success with an aluminum tool requires a true partnership between the OEM, the molder and the toolmaker.

4)    Aluminum tooling saves the OEM money on total program cost, makes any molder more competitive, and can free-up production capacity.

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