Win With Co-Injection

The technology gives molders new ways to add value.

How do custom molders in the plastics industry differentiate themselves from a commodity imported from China? That was only one of the questions answered for customers at Milacron Inc.'s Big Machine Open house last December in Batavia, Ohio. Others involved how an injection molder can deliver greater value with the technology -- such as new part characteristics or even a recycling solution.

The event's name answers the first question -- BIG MACHINES! "That's an important part of our value-added approach," says Robert J. Strickley, marketing director.

Star of the event was the Cincinnati Milacron Maxima, the top of the line in a global family of large, two-platen injection molding machines. The 3900-metric ton machine is a co-injection design featuring two 854-ounce electric injection units. The only larger co-injection machine was a special 6000-metric ton unit specifically made for Bemis Corp., Sheboygan Falls, Wis., says Strickley. (Both a custom and proprietary molder, Bemis partnered with Milacron in the 1990s to develop large co-injected machines.)

Strickley says the flight of commodity molding to China and other low-wage producers is driving molders to large-part work and value-added processing. "Large parts don't ship easily or economically, which helps offset the advantages of low-labor cost countries."

One way to add value is by combining a coating step with the molding process. Strickley cites an example where bumper fascias emerge from the mold already coated. The surface film is automatically fed into the mold prior to injecting the plastic. The benefit: no paint shop investment.

Co-injection, which is now a standard option on Milacron's large machines, also gives molders a competitive differentiator. Once common only on smaller machines, co-injection of different plastic materials provides big part molders a greater option for innovative part design. The payoff: more creative options in part characteristics plus new ways of controlling material cost. One example could be the molding of a steering wheel with a rigid core and a soft-touch surface.

Co-injection can easily solve challenges where two materials used individually don't meet performance requirements, explains Steve Kolste, manager of marketing and business development for the Bemis contracting operations.

At Bemis, co-injection reduces cost per part by permitting the use of regrind (recycled) material.

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