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Topics Coinjection, Injection Molding, Machinery
Companies & Associations Milacron LLC
BATAVIA, OHIO — It might be a match made in injection molding heaven.
Bemis Manufacturing Co. has teamed up with Milacron LLC to develop what they're calling the industry's largest Servo hybrid coinjection machine, the 1,500 ton Maxima G Servo.
The machine was one of more than 20 on display at an open house at Milacron headquarters, held April 24-25 in Batavia.
According to Milacron, the machine is energy efficient — it uses less than half the energy of comparable hydraulic press — and is the industry's most versatile multi-component Servo machine. It has seven unique process capabilities that can be run a single platform; the system can be configured for sequential or simultaneous injection, stack molding, multi-component and coinjection molding, among other processes.
The machine is the latest partnership between the two companies, who have been working together on coinjection technology for about a decade.
In essence, coinjection, or encapsulation, is molding one material inside of another, creating a part with an outer skin and an inner core.
The technology was patented in the late 1950s and primarily used in Europe, but Sheybogan Falls, Wis.,-based Bemis started working with it in the early '90s. The company acquired a used 700 ton Battenfield machine and was "up and running. Crawling is more like it," said Gary Vande Berg, vice president of engineering for Bemis.
"You've heard the term invention is ugly? This was ugly," he joked in a presentation at the open house.
So Bemis sat down to essentially reinvent coinjection technology. In 1994, they approached Milacron with their results and asked them to design and build a machine. The result was a 725 ton coinjection machine, which ran at the 1994 NPE Show and is still running 24/7, Vande Berg said.
The company now has 32 coinjection machines, ranging from about 300 to 6,600 tons, he said.
The technology allows Bemis to successfully marry business and sustainability.
"You can do anything you want for the environment, but if your business doesn't survive, it isn't going to do much good," Vande Berg said.
Coinjection molding can be used to incorporate recycled or reground "junk" material in plastic parts without sacrificing aesthetics or physical properties.
Bemis can now make coinjected toilet seats with 75 percent recycled content -- 25 percent in the skin and 30 to 50 percent in the core, Vande Berg said.
The company also molds parts for John Deere tractors, using a more expensive, glossy material on the outside and a cheaper material on the inside.
Coinjected parts also have better physical impact properties. They can be up to 2.5 times stronger than a typical monoinjected part, and "that's with junk material on the inside," he said.
Bemis struggled to make a hood for a lawn and garden tractor that had both the necessary impact strength and a glossy finish -- when they tweaked the material to improve gloss, impact strength decreased, and vice-versa, he said. The solution was a coinjected part with an ABS core and a glossy exterior that was also cheaper to manufacture, he said.
Vande Berg also gave examples of how Bemis uses coinjection molding with controlled breakout techniques and gas-assist molding to make chair arms, steering wheels and refrigerator handles.
"You can have totally different physical properties within the same part coming out [of the machine] at the same time," he said.
The company's big revelation came when they realized "coinjection machines weren't really coinjection machines, they were multi material machines," he said.
With help from Milacron, Bemis started working with two-shot molding, then on to sequential injection, then on to using a three-barrel system. A four barrel machine is in the works, he said.
All of these different processes can be run on the same machine with just a few changes in software, he said.
When you take all the different options into consideration, Bemis can offer customers more than 51 different ways to mold a part.
"That doesn't mean we're still always going to be cheapest. But if you've got 51 ways to look at a part, that sure beats two ways to look at a part," he said.
It also allows the company to offer parts with a desired "weird factor."
"If we cannot apply a minimum of one weird factor, we don't quote the part. End of discussion," Vande Berg said. "We're not a clip and ship company. If we can't apply technology, it's not our business."