Industrial Equipment & Machinery
The bottom line:
The Product needed a strong bond between ceramic and metal.
Here is what the lead engineer said about this project: “This was one of the more difficult problems I've worked on. I almost thought it was too complicated to solve. But by using designed experiments...I was able to sort through the data and understand the process.” (Gregory Ferguson, Quality Digest July 1999)
The product had a ceramic component which was coated with a metallic layer, but the two materials were not bonding properly. Engineers first varied the paste that coated the ceramic part, along with the time and temperature of the paste solution. These experimental parts went through the rest of the metal adhesion process. A Kovar metal strip was brazed to the metallic surface; the force that it took to remove the Kovar strip was measured with a pressure transducer. This force was considered the experimental response i.e. a higher force meant a stronger adhesive bond between the ceramic and the metal.
The three initial factors (variables) produced no significant difference in bond strength. Knowing which process factors are not critical to the final product was a benefit of this work.
With a series of designed experiments over several months, engineers covered every possible factor in the bonding process. They determined a strong correlation between the type of grinding wheel used to prepare the ceramic surface and the final strength of the ceramic:metal bond. Using that certain type of grinding wheel to prepare the ceramic surface was the factor that produced the strongest ceramic:metal bond.