Shifting the industry norm, injection-mold manufacturers opt for aluminum
January 2012 - Injection molds, usually made of steel, provide the means to create everything from plastic parts for vehicles to mechanical gears. An affordable and efficient alternative, QC-10, a strong aluminum alloy from Alcoa Global Rolled Products, Bettendorf, Iowa, is allowing injection-mold manufacturers to consider changing from the norm.
“In my experience, any application that’s using unfilled, general-purpose plastic resins and standard mold temperature controllers are great candidates for aluminum,” says Dave Bank, president of Aluminum Injection Mold Inc., LeRoy, N.Y. “That’s probably been the biggest issue the industry has had to overcome. They think the mold has to be steel because it’s been the industry standard forever.” Using aluminum for its injection-mold applications since the 1980s, Bank says the latest alloy from Alcoa Forgings & Extrusions, QC-10, is on the forefront of innovation, because it is stronger and more versatile than previous formulas.
Before the release of QC-10, Bank used Alcoa QC-7 aluminum, which allowed his company to run injection molds and meet thousands of customers’ needs throughout the last three decades. With QC-10, one of the advantages of aluminum over steel is “you don’t have to stop partway through the machining process, like with steel, to heat treat or stress relieve the block,” he says. “We machine right to final impression the first time out, and we machine around the clock, seven days a week.” Bank says Aluminum Injection Mold “takes advantage of lights-out machining because we’re comfortable with the material.”
OEMs weren’t concerned with what materials Aluminum Injection Mold used for the mold itself. “People were more interested in getting the actual molded parts,” Bank says. “Steel molds have been the industry standard for years. Those molds are very expensive.” Bank adds companies have a few more choices today. Aluminum is one and China is another.
Bank found Alcoa’s QC-7 product was less stable than Alcoa’s QC-10. One major issue Bank experienced with QC-7 was thickness inconsistency. With QC-7, material could be as much as 50 percent softer in the middle of the block compared to the outside of the block. The thicker the block, the more inconsistent the middle could be. However, once Bank switched to QC-10, he no longer had thickness consistency issues.
According to Bank, when the company switched to QC-10, it found “no matter what we did to the material, it did not warp at all.” This development “was a whole different mindset to machining molds. It’s harder, much more stable and you can get it in thick blocks,” he says. “The outcome is consistent, stable material through the full thickness.”
Alcoa developed the QC-10 alloy specifically for the production injection and blow molding industry, according to Dave Duff, application engineer, mold plate at Alcoa. “This high-strength aluminum can allow molders to significantly reduce cycle time and piece-part costs. At the same time, molds can be built more quickly, allowing OEMs to bring products to market faster.”
Investment in innovation
Six years ago, Honda of America Mfg. Inc., Marysville, Ohio, started an investigation to lower the cost of tooling for its lower-volume vehicle program. “We saw there was some benefit to the cost of the tool, but our biggest surprise was the difference in cycle time and part quality,” says John Engle of the North American Purchasing Division, Production Engineering/Tool Center. “So we decided to pursue things a little more ardently after our initial program concluded successfully.” Engle says Honda then applied the QC-10 to its higher-volume vehicles.
Although aluminum molds are nothing new, Engle says the difference is higher-strength grades of aluminum have become more widely available in the last several years.
“Reducing cycle time is very important in our business,” says Ron Lietzke, corporate communications, media relations manager, at Honda. “Aluminum cools more quickly than steel does, and one of the biggest advantages is you can shoot more parts because they cool more quickly.” Parts are manufactured faster and require the operation of fewer machines. “The company might be able to produce parts with one machine over two as well as reduce the amount of manpower needed,” Lietzke adds.
Using a less expensive, more versatile material for injection molding directly benefits Honda’s suppliers, who can reduce costs and decrease cycle times. “Honda’s suppliers are benefiting, which benefits Honda because they can come to us with a lower price point,” Lietzke says.
Convincing suppliers to make the switch from steel to aluminum is the hard part. “What I often tell people is when plastics was in its infancy, steel was the default material because aluminum was softer then,” Engle says. “These alloys [such as QC-10] didn’t exist. Had these alloys been available back in the ‘40s and ‘50s, I think aluminum would have been the default material. People got used to and comfortable working with steel, and the biggest hurdle is to start learning a different way to do things.”
Engle says a major benefit of using QC-10 is the material’s durability. “Our highest shot count on an aluminum mold is greater than 1.8 million,” Engle says. “And other than basic preventative maintenance that all molds receive, there has been no additional work required.”
The risk of failure can deter companies from taking on completely new methods or technologies. “There’s risk involved with new technology,” Lietzke says. “While the benefit is long-term, many times the short-term failures discourage change.” By assuming some of that risk, Honda’s success may serve as a positive indicator to other manufacturers considering more cost-effective and efficient processes.
“Sometimes, when people hear of the success we’ve had, they want to jump in with the biggest and most expensive product they have,” Engle says. “Then they are disappointed if they experience failure because they just don’t know enough yet.” Engle says the key is to start smaller and work up to something bigger. “That’s when they see the benefits,” he adds, noting QC-10 is not a cure-all. Some parts, such as clips and fasteners widely used for parts in automotive, “are molded in steel tools and always will be,” Engle says. But “a lot of parts that don’t have thin core sections and things of that nature can reap a lot of benefits.”
Honda currently has more than 100 molds that are producing parts or are in construction for new model launches. “There will be more parts added to the ones made in aluminum,” Engle says.
“When we first started our investigation, there was some activity with other OEMs, but it was more along the lines of going to their suppliers saying they should look into it more. No one really pushed it from the OEM side,” Engle continues. “We at Honda realized that with the way things are going in the plastics industry, margins are so thin, no one was going to do something on their own initiative and then get smacked down for being too adventurous. We knew we needed to check it out.” MM