Can aluminum molds compete?

Long known as a defender of the aluminum mold, David Bank has started a new company, AIM, to finally prove what he’s been saying all along.

David G. Bank has been stumping for aluminum molds for a number of years, with some small measure of success. Now, he’s decided to put his money where his mouth is. In March, Bank opened Aluminum Injection Mold Co. (AIM), dedicated to the production of aluminum molds.

Bank, who formerly owned Papago Plastics (which he sold in June 1998), worked for a couple of years as a consultant for Alcoa, pushing its aluminum QC-7 and QE-7. He gave seminars and worked trade shows for Alcoa, touting the material as an optimum mold material. “That was satisfying,” says Bank, “but with the business downturn, Alcoa chose not to renew my contract.”

That’s when Bank discovered he could get good pricing on machine tool equipment. Plus, Cimatron gave him a fair price on its mold design software. About that same time, the company that purchased Papago wanted to move from the building Bank still owned, so on Dec. 16, 2002, Bank took over his building and installed four new Milltronics high-speed CNC machining centers.

Starting the Rochester, NY company was Bank’s way of proving what he’s preached for a number of years: Aluminum is an optimum mold material that can improve processing and provide mold shops with a competitive edge in price and delivery.

One way that Bank gains this edge is through Internet-capable cameras or load sensor systems installed on each machining center, enabling Bank and his employees to monitor the equipment from their homes. This setup allows AIM to run 24/7. “We’ll be able to machine around the clock. I’ll be making injection molds in hours and days, not weeks or months,” Bank says. He feels confident that his shop will more than compete with those in China.

Overcoming Misconceptions

Part of Bank’s mission is also to instruct OEMs how to do the same thing. “I’ll teach other people in the industry how to make and qualify aluminum molds, and run an aluminum mold in a molding press,” Bank says.

However, he realizes that he has a long, uphill battle ahead to convince mold shops that aluminum is the way to go. “We’re fighting a couple of things,” Bank explains. “The moldmaking industry is in terrible shape. Our toolmaker pool is being depleted at a fantastic rate. Who’s going to make these molds? People are not going to China just for good prices, but to have access to the tremendous pool of moldmaking people there.”

Additionally, there’s the perception that aluminum is only for prototype molds or low-volume production tools running unfilled materials. Bank agrees that aluminum is not the “end-all be-all for tooling, but where it fits it fits well,” he adds. And, he reminds us that not all aluminum is created equal; QC-7 is a high-hardness alloy that has proven itself as a mold material. However, most people feel that a mold must be made out of steel, period.

“Aluminum molds offer real benefits once you get past the culture barrier,” Bank says. “Unless you’re going to be running millions and millions of parts, an aluminum tool will work well and run circles around a steel tool—when comparing cycle time—any day of the week. Add to that the fact that you paid less to have the mold made and received it in less time, and it’s a no-brainer.”

Making the Case

This issue of cycle time is one of the biggest advantages to running parts in an aluminum mold, asserts Bank, since aluminum heats and cools more quickly than steel. Also, aluminum is easier on the flow front. “There’s a huge difference from the longest flow length to the gate location, which typically can result in warp and excessive shrink,” he says. “It doesn’t happen as much with aluminum as it does with steel.”

Steel always has hot spots across the mold, no matter how good your cooling channels are, Bank explains. Since aluminum conducts heat five times better than steel, it creates a more uniform temperature throughout the mold. Aluminum immediately takes on the heat of molten plastic at the time of injection, enabling the plastic to flow into the cavity with much less injection pressure, Bank says. As soon as the flow ends, the cooling begins. “If the mold is hot, it’s hot everywhere and if it’s cold, it’s cold everywhere,” he adds.

There are advantages when fabricating the tool as well. Aluminum molds are easier and quicker to build than steel because aluminum is softer to machine. Heavy cuts with large stepovers are common, Bank notes. “I can machine up to 30,000 rpm with travel up to 300 in/min, which is nearly 5 in/sec.” Inserting for undercuts, creating actions, polishing, texturing, hard coating, and the ease of making changes after the mold is complete are all added benefits.

Actions in the mold such as slides or lifters need more man-hours to do the fitting, but for an open and close mold, Bank says he can have the block in and be machining aluminum in far less time than for hardened steels. “I give the CAD file to one person and he develops the file, puts the block in, and starts machining,” says Bank. “Don’t tell me the reasons we can’t, tell me the reasons we can.”

He cites an example of a QC-7 mold that has two slides (also made of QC-7) and runs talc-filled polypropylene. “This so-called prototype mold has run more than 200,000 shots and is still in great condition. It provided all the parts needed before the production tool took over, and it ran approximately 25 percent faster in cycle time. It also provided 40 percent savings in actual dollars for the aluminum over steel, and a time delta of approximately 30 percent less to get the mold done. When we built an aluminum mold to run fan blades for automotive cooling, our nearest competitor made steel molds in 10 weeks. We built an aluminum mold in eight days.”