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Insight: The Art and Science of Material Selection

Although automobile manufacturing would seem to be a cut-and-dried process, driven by the logic of science and technology (the arts of designing exteriors and discerning consumer preferences, notwithstanding), facts and data don’t necessarily determine everything.

Although automobile manufacturing would seem to be a cut-and-dried process, driven by the logic of science and technology (the arts of designing exteriors and discerning consumer preferences, notwithstanding), facts and data don’t necessarily determine everything. The dynamics surrounding selection of materials and the promotion of alternatives illustrate the degree to which production is both an art and a science. Given the importance of innovation to supplier success today, a better understanding of some of the drivers behind material and process selection is important. Here are some of the relevant factors:

Vehicle positioning. What is appropriate for an entry-level C-segment car is likely to be different for a full-size luxury car (and vice versa). Car vs. truck, sporty vs. family, economy vs. luxury, conservative vs. edgy—all these categories can mean the difference between winning an application for your new material and failing. While price is always a consideration, a more expensive material can still find a niche. A designer put it simplistically in a discussion on carbon fiber potential when he said, "We would be more inclined to use it on a higher-end car [$90,000 and above] because anything goes on those cars and customers don’t mind paying for it." Vehicle positioning is a factor that a supplier can anticipate and plan around through careful targeting.

Evolving circumstances. Every new material involves trade-offs. How the trade-offs are evaluated depends on what is happening in the interplay between all the other components, features, and systems. Use of a more expensive or unusual material is often a relatively late solution to an evolving problem, as the following references illustrate.

  • "Once we see where the weight is ending up, we’ll consider powdered metal. We’ll have been putting parts together, have a few pilot builds, know that we need to increase the material thickness on this part or that, and then we’ll know if we have a weight problem," noted an exhaust systems integrator
  • A few years ago, the Chrysler minivan had a potential problem with the design of a bumper backup beam. The quickest solution was to go to a glass-mat thermoplastic material. A composite molder provided Chrysler 300,000 to 400,000 beams for several years, but for the new model, Chrysler engineers solved the problem with a steel structure and saved money, so that application went away. Chrysler was willing to pay a little bit of a premium for a period of time, but its long-term preference was for a lower-cost solution.
  • GM is returning to steel from magnesium for the instrument panel support on the Silverado/Sierra pickups in 2006, reportedly saying that some changes in other areas of the trucks made it unnecessary to use magnesium IP beams for weight savings.

The ad-hoc nature of these types of decisions, and the fact that they involve information a supplier may not be privy to, complicate a supplier’s ability to influence the outcome.

Interpretation of data. Suppliers can produce all kinds of data and facts for use in comparing material options on cost, design flexibility, durability, material utilization rates, tolerances, the need for secondary operations, and so on. The existence of data does not make gray areas of material selection into black and white, however. The facts can speak differently if you are using a system-wide view or a part-to-part comparison, lifecycle cost vs. initial purchase, or redesign to take full advantage of a material’s properties. And sometimes, it just comes down to the fact that honorable people can disagree. One OEM materials engineer said that a willingness to take risks and confidence in the reliability of test data for predicting the long term could explain why its competitor was comfortable making a larger move into a new material. It is up to the supplier to make the case for its version of reality.

Prior experience. History can influence the decision process, justifiably or not. Consider the situation for a phenolic brake piston supplier when there was an OEM engineer who recalled: "There was a moisture sensitivity issue years ago, where the pistons sucked in moisture and grew once they were assembled with the caliper, so they stuck and the brakes dragged. Even though the switch from wood flour to fiberglass as filler fixed this problem, that kind of baggage takes a long time to get rid of."

There are other factors that can come into play, ranging from national to corporate to individual: differences in regional requirements (e.g. European regulations vs. U.S.); organizational dynamics within a customer; personal familiarity and knowledge level, to name a few. The net effect for a purveyor of a new solution is that there is no efficient approach to large-scale conversion. Gaining approval is a time-consuming matter of winning over one decision-maker at a time. Since many decisions are made on a platform-by-platform basis depending on the needs of the vehicle, it is difficult to get organization-wide agreement, let alone industry-wide consensus on the benefits of a new material.

The environment is dynamic. Proponents of each material are continuously advocating and improving their offering. Personnel move around within the industry and carry their preferences and biases with them. Experienced employees retire and are replaced by less knowledgeable ones who must be educated. Promoting and selling an alternative material is a continuous process. Only some of the factors are within the supplier’s circle of influence, but it is worth trying to understand the complexity of the whole system. 

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