U.S. Auto Scene April 12,1999
By Joseph Cabadas

Robust Engineering Eliminates Unnecessary Expenses at Ford

Staff Writer

Robust engineering is a concept that is hardly talked about in universities. It’s concept first proposed by manufacturing quality guru Dr. Genichi Taguchi of Japan, and , while it was immediately embraced around the world, for many years it was something of a misconception here in the U.S.

"It took America a long time to figure out what Taguchi was talking about (regarding robust engineering)," said Neil Ressler, Ford vice president, Research & Vehicle Technology. "For many years, it was thought that he was talking about design experiments-a tool that was in his portfolio-but in recent years we at Ford have figured out that there is a lot more to it than that."

Robust engineering refers to the elegance of a product’s design, Ressler said. Part of the problem, he said, is that is not an intuitive process as American engineers originally thought. The concept basically involves four elements-the designed experiments process, the "voice of the client," controlling the variation in the quality of parts and "Key Life Tests."

Ford used the design experiment process to improve sound quality of the current Taurus’ power train.

There are many variables that go into making engine sound pleasant, such as the stiffness of the crankshaft, the clearance of the rod bearings, the length of the exhaust system on V6 engine or flexible couplings for the exhaust system.

"The question is, which (items) are important and should be put in, and which can be left out because they just cost money and don’t add anything," Ressler said.

Most auto companies will build prototypes of a vehicle; those prototypes can then be used to verify the vehicles’ subsystems. But this is a less-than efficient verification process because a vehicle never has all of its parts proven, said Roscoe Nash Jr. dean of the Ford Design Institute.

Instead of going through an enormous number of experiments and altering only one item at a time, as normal intuition recommends, Taguchi’s designed experiment process is much simpler, he added.

"You can actually define a set of experiments that doesn’t involve many changes by changing the combinations of independent variables and figuring out the separate contributions of each (variable)," Ressler said.

Ford engineers using the designed experiment process discovered that some components of the conventional logic to reduce noise-tolerance design specifications and materials used-were" simply ineffective" and added to the cost of the vehicle, Ressler said.

A second part of robust engineering is to understand "the voice of the client"-how they perceive the result of your design, Nash said.

The third element to take into account involves the quality of parts and materials. For example, a part that barely meets the manufacturers specifications is not the equal of a part that is better than average. The best result comes when parts meet the desired target level of quality because the variability has then been minimized, Nash said.

Another component of robust engineering is testing vehicle systems using a technique called "Key Life Tests" to see how a system performs in long-duration, normal use, Nash said.

In the past, Ford might have tried testing the strength of a door handle by hanging a 150-pound weight off it, for example. These types of strength tests, however, don’t give a true picture of how that door handle will perform over the life of a vehicle, which is 150,000 miles or 10 years.

" If a normal client’s load on a door handle is 25 pounds, that’s what you want to test for," Nash said.

The results of a survey of the actual use of remote keyless entry systems gave Ford engineers a surprise and illustrates why it is important to test a system based on normal use, said Ford spokesman Jon Harmon.

"When talking to people in the real world about key fobs, we found that they would hit the buttons over and over and over to see how far it worked," Harmon said. "We found out that it was used eight or nine times (more times) than what they had been tested for."

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