"This material, this process, this application is a game-changer."That's Ken Shaner, vp, Manufacturing Engineering at Lear Corp. (Southfield, MI; www.lear.com) talking about a new injection molding technology. Working with Lear, Husky Injection Molding Systems (Bolton, Canada; www.husky.com) has developed the means by which large interior (e.g., instrument panels, door panels) and large exterior panels can be produced with multiple materials—as in TPE over TPO–in a single machine in a single setup. Shaner acknowledged that two-shot plastics processing has been around for the past few years. But for things like toothbrushes and razors. Three years ago, he and his colleagues met with people at Husky and put forth the question: "Why can't we do this on a larger scale?" This led to the so-called "game-changer," which takes the physical form of the Husky 3,150-ton (metric; 3,470 U.S.) Quadloc Tandem Index (QTI) machine to perform the process for large automotive parts.
One of the drivers behind the development of the process is an initiative at Lear that's called the "One Step Manufacturing Process." The QTI system lends itself to this rather well because rather than having additional processes involved in producing a large part with two different materials, it is done in one. This, of course, can provide an advantage in terms of cost and quality.
From an equipment point of view, Husky engineers took the experience they gained in applications such as producing PET bottles with a machine that has two molds rather than one. This additional function means that not only is there a footprint smaller and investment less than that required for two machines (the footprint is 40% smaller; the cost reduction is part/process specific), but because of reduced part handling, the quality of the part can be better. (Transfer molding, moving the part from one machine to another, was attempted but proved to be incapable of providing the dimensional stability that was being sought.) To accomplish the requirements for the multi-material capability that Husky was seeking, a second injection unit was added to the machine. So it is mold/index/mold, all in a single machine.
While Jeff MacDonald, Husky's vp of Automotive, acknowledges that the technology is not proprietary, that it can be purchased by other supplier companies, he points out that Lear has a competitive advantage inasmuch as the company has been working with the equipment supplier in developing the process. Consequently, they have an advantage of as much as two years as compared with anyone that was to put in a purchase order for equipment right now (i.e., not only the time for the machinery and tooling to be developed, but also the amount of time necessary for process development). Shiner says that they have applied for patents on specific part features, tooling conditions and some of the processing specifics, however. He also says that by working with resin providers, they've developed materials that Lear has the lead on.
Shaner points out that there are various benefits, including such things as the elimination of the need to do outside the press assembly of two separate pieces, superior craftsmanship (e.g., better grain definition, sharper radii (as low as 0.5 mm), softer touch), the ability to "dial-in" the sort of characteristics attained when using TPE (e.g., soft, slick, silky), excellent performance and durability due to the consistency of wall thicknesses, consistency of gloss across the surface of the part, and the elimination of buzz-squeak-rattle (BSR) problems that can occur due to the interface of separate plastic pieces (there are two pieces but they can't be separated). There is good recyclability. What's more, he anticipates tooling cost reductions going forward, as well.
Another leg up that this provides is styling and design flexibility. As Shaner puts it, "You just can't design flat, round pieces any more." He says that the parts are more complex and need more attachments to them. "Maybe we can do them in one step." He believes that they're only at the start of what can be achieved.
Right now, Shaner says, they have three orders in hand for customers he's not at liberty to announce. These are a TPE over talc-filled PP door bolster, which is launching now, a TPE over TPO door panel, and a TPE over TPO instrument panel, both of which will go into production in '06. As for the types of vehicles that he thinks the process is best suited for, mid-level cars and SUVs are right. At the upper end, sprayed PUR will continue to hold position (although he thinks that smaller parts may be handled by the two-shot approach) and that at the lower end of the market, hard molded plastic panels will continue to be deployed.