Multimolding applications, whether for appearance or functional reasons, or both, are multiplying, especially in North America. Production technology choices are almost equally varied, including some lower-cost options.
Judging by the noise level surrounding it these days, you would think multimolding (MM)—molding two or more polymers, components, or colors into one part—was just invented. But MM was an active technology in the 1960s; back then, the applications were almost all different colors of the same material. Telephone dials with numbers that never wore off were the best-known example. Since then, multimolding has been growing—but slowly compared to what is happening today.
THEN: The combination of a Weber tool in an Arburg machine was making two-color phone dials in 1963. At far right, another Arburg-Weber combination shows how things have changed.
Why so much noise now? At the most basic level, blame it on the cumulative growth in awareness, particularly among product designers. Designers today see the possibilities multimolding offers for product differentiation and are widening the gamut of applications. Complementing this increased design awareness has been a parallel development of multimolding technologies.
Considering how much multimolding technology is now available surrounding materials, molds, machines, robotics, and full production cells, the only problem may be too much choice. This article takes a very basic look at the options. We say “very” for two reasons: On the supply side, new multimolding technology and ingenious system design are appearing at every trade fair; on the demand side, many designers and manufacturers have already climbed the MM learning curve, and many more are coming along.
The applications tide is still rising, especially in North America, both in terms of numbers and variety. The products we have seen the most of until now—combining colors, hard structure with soft-grip surface—are the tip of a big iceberg.
NOW: A cooperative development between moldmaker Weber and machine maker Arburg, this mold for telephone housings offers another cycle-shortening solution for multimolding. In the photo, the finished two-material housings are being robotically removed while the mold is closed and simultaneous shots are being made and held. In this mold there are three banks of four cavities arranged in a triangular layout, and the mold rotates 120° using a rotary machine platen. The first and second stations mold the two materials sequentially. Concurrently, the third station is exposed by a cutout on the nonrotating mold half for part removal. Another time saver: The mold opens only enough to turn one half; no time is added for the robot to enter and exit.
Form, Function, Fit
Marketers increasingly are seeing how color and texture can make them winners. It can even make them stand out in so-called commodity market segments. As an example, take toothbrushes. Multicolor/multimaterial designs have totally overhauled that market. The attraction of color and the functionality provided by the grip material have created the product differentiation that marketers crave. Hard structure with a tactile grip similarly has changed the markets for hand and power tools. Being different can be worth a lot of money. When asked about MM applications today, Helmut Eckhardt, technical director of Battenfeld Injection Molding Technology, said that he sees much of the new MM activity coming from the following:
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