LEARN MORE

Zones



Click Image to Enlarge

The exterior mirror housings on this 1998 Ford Taurus are produced with a conductive plastic material. This means that the mirrors are painted without the need for a conductive primer, which minimizes the emissions involved in the paint process and helps reduce the price of the component. There is no negative effect on quality. It's the proverbial double-win.

Product And Process Improvement Because It's Right

The United Technologies Automotive Mirror Systems operation in Berne, Indiana, launched the first-ever use of conductive plastics in automotive exterior applications. They didn't have to do it. But the development work that they and their colleagues did is beneficial not only to their customers, but to everyone for whom the environment is an abiding concern.

Necessity is frequently the mother of invention. But sometimes things are developed not because there is a need per se, but because it is a notable improvement on what is presently available. The "necessity" scenario is, generally, reactive; what we're talking about in the second case is getting ahead of the curve. This approach doesn't happen all that frequently, but when it does, it can make a big difference.

A case in point is found at the Berne, Indiana, facility of United Technologies Automotive (UTA; Dearborn, MI). The main business at Berne is producing exterior mirrors for customers including Ford (its biggest customer, accounting for 56.4% of the facility's sales—for a reason that will soon become clear), General Motors, and Toyota. Of the two million or so parts that will be shipped from Berne in 1998, 97.4% will be mirror assemblies. The other 2.6% consist of grilles and garnishes. The facility, which is staffed by 328 people, has full process capabilities for manufacturing these products, including 15 injection molding presses, a complete paint line (which combines automatic, robotic and manual operations), and assembly lines. (It should be noted that the mirror glass used in the assemblies is sourced, not made at Berne.) Generally, the molding operation runs three shifts, paint two, and assembly one (although there are usually a few people who work on a second shift). There is also a development lab.

Electrostatic Improvements. In 1994, says Darrin K. Keiser, Paint Business Unit manager at the plant, electrostatic reciprocators were installed in the paint system. This was done primarily for reasons of labor and materials savings. Essentially, it is a more efficient approach as compared with manual. That is, when applied by hand, there is an efficiency of 20 to 25%; when applied electrostatically, the paint process efficiency is on the order of 50 to 75% (with the greater efficiencies being related to the coating of metal parts).

At this time, some researchers from Ball State University (Muncie, IN) were visiting Indiana manufacturing sites and checking out the emissions that were coming out of the stacks. And what they found at UTA Berne was, to say the very least, surprising. The plant had been emitting volatile organic compounds (VOCs) at a rate of from 230 to 240 tons per year. But the researchers discovered that the level had dropped to 180 tons per year. This was a result of the electrostatic processing. At the time, Keiser was the environmental manager at the plant. The people from Ball State came in and talked with him about the environmental improvement that they'd measured. And as they talked, the idea of being able to do an even better job vis-a-vis emissions emerged.

Realize that there was no pressing need, nothing that was being reacted to. Rather, it seemed like a good idea, especially if, as was the case with making the move to the electrostatic processing, there could be savings realized with regard to materials and labor, which would translate into savings per part for the company's customers.

One of the problems with painting plastics with electrostatics is that plastics are, according to Venkat S. Atluri, business development manager, Midwest Region, GE Plastics, "naturally resistive."

Which means that there must be the application of a conductive primer. And it was determined that it was necessary to put additional primer on the parts at the point where the mirror exteriors were attached to the painting racks.

Searching for the Conductive. The concept that came up was to use a conductive plastic. That could, so they all figured, eliminate the need for the conductive primer. The Ball State people got Keiser and his associates in touch with the Indiana Clean Manufacturing Technology and Safe Materials Institute (CMTI), which is based at Purdue University (West Lafayette, IN).

S. Jean Hall, a process engineer at CMTI, recalls, "Although we talked about conductive plastic as a good solution, in the past, things added to the plastic made the materials too expensive, or they caused degradation of the physical properties."

Given that the object to be painted is (1) an automotive part, so price is an object, and (2) a part that is not only exposed to the elements and all kinds of abuse (e.g., think how many times you've whacked into your side-view mirror in your garage) but must have a Class A surface, the physical properties are vital.

So about six months were spent on a search for the conductive plastic that would do the job. (Which is a good reason why to work with a university-based outfit: they have the time and wherewithal to do the necessary searching.)

The research turned up a patented product from Hyperion Catalysis International (HCI; Cambridge, MA) called carbon "fibrils." These are like microscopic macaroni: each fibril has a 0.01-micron outer diameter; and a 0.005-micron inner diameter. The length ranges from 1 to 10 microns. The fibrils are mixed in with the plastic resin prior to molding. Because they are so tiny, there's no discernable effect on the surface of the parts produced with the plastic. The fibrils in the mix are at a low load level: less than three percent of the total weight.

The CMTI people hooked up the people from UTA Berne with HCI personnel. Then it was to the development of the material. UTA uses GE Plastics' NORYL GTX nylon/PPO for its mirror housings. So HCI blended batches of the material, and UTA personnel, working with people from GE Plastics and BASF, the paint supplier, started testing to see how the material would hold up and how well paint would hold on. According to Ronald S. Hendricks, technical manager, Interiors, at the UTA Berne Mirror Systems facility, there were some initial material brittleness problems that GE Plastics worked out. As the goal was to paint the exterior mirror housings for the Ford Taurus/Sable, which the facility is responsible for producing, people at Ford were consulted.

They worked, Hendricks says, "To achieve `paint to darkness.'" He explains that one of the functions of the paint is to keep the sun's ultraviolet rays from hitting, and eventually degrading, the plastic below. Assuring coverage was key. Thus, the painting so that there would be complete darkness from the standpoint of the substrate. Parts were painted with the electrostatic setup without first applying the conductive primer. Then assiduous testing commenced. They baked the mirrors. They froze the mirrors. They modified paint film builds. And they tried it all again. Over and over and over again until they were confident that what they were producing met the requirements for a first-class finish.

One interesting point to this is that although this was purely a development effort, the work being done was being primarily performed by people like Hendricks, at the plant level. To be sure, there were researchers from the participating companies brought into play, but the Berne site was the center of the management and development of the program. (It's worth noting that work is continuing; they are actually at the third generation of material development).

Some two years after the work began in earnest, the material was approved by Ford for the Taurus/Sable exterior mirrors. This translates into an annual build of from 500,000 to 600,000 mirrors per year (two per vehicle). The original material that UTA was using for the mirrors, GE Plastics' GTX 902, was replaced by the fibril-including, electrically conductive GTX 990EP.

Realizing Benefits. So what has been the effect? In the original operation, there was the application of a conductive primer on the plastic housings, followed by the base coat and then the clear coat. Through the use of the electrically conductive plastic, the primer has been eliminated.

This means that (1) the cost of the primer—from $10 to $20 per gallon—is eliminated; (2) the labor needed to apply the primer is taken out; and (3) the VOCs—about 0.03 lb./part—from the primers are also eliminated.

Another benefit derived from the use of the conductive plastics as compared with applying the conductive primer is that there is improved transfer efficiency of the color base coat. According to Keiser, the improvement is on the order of 12 to 15%. Which means that each gallon of base coat—the most expensive of the three materials, as it ranges from $60 to $100 per gallon. There is also a decrease in the VOC emissions per part, from 0.05 lb./part to 0.04 lb./part.

Compared to the conventional process, there is a 25% decrease in the VOCs with the conductive process: from 0.12 lb./per part to 0.08 lb./part (i.e., this reduction is a result of the elimination of the prime coat, the 0.01 lb. reduction in the base coat, and the same 0.04 lb./part rate for the clear coat). This translates into 40,000 lb. of VOCs not being emitted as a result of painting the Taurus/Sable exterior mirrors.

Keiser says that there is actually "a slight increase in the first-time yield" with the conductive plastic process. The reason: by eliminating the primer step, there is the elimination of the possibility that things can go wrong (e.g., dirt contamination) in that step.

They are working at UTA Berne to have other exterior mirrors produced with the conductive plastic and anticipate approval for more vehicle models in the near future.

The Taurus/Sable exterior mirrors represent 4% of all of the painted exterior mirrors produced for light vehicles. Keiser points out that if 100% of those mirrors were produced with conductive plastic 1,000,000 pounds of VOCs could be eliminated.

This is certainly possible because any mirror manufacturer can buy the same material from GE Plastics that's being used at UTA Berne. Asked whether they are concerned about that, Keiser answers that they'd actually like for more manufacturers to use fibril-based materials. For one thing, the demand would help decrease the price of the materials (they're recognizing savings from the elimination of the paint—"We've already put money back in our customer's pocket," Keiser says—but the conductive plastic is more expensive per pound than the nonconductive type). And for another, there would be fewer emissions in the air. Everyone can benefit from that.