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.