The challenge, presented by a large supplier of automobile frame assemblies, was to gain a understanding of what combination of 13 separate parameters created the optimum laser pierced hold in steel. These holes were required for mounting holes and passages in hydro-formed frame rails. Because of the nature of the hydro-forming process these holes had to be added after the rails for formed. The laser pierce process, however, had a large number of parameters (such as focal distance, laser power, oxygen purity, etc.) that needed to be adjusted to provide the optimal results. The criteria for judging the best cut was the surface finish of the hole produced. Because of the large number of parameters that needed to be adjusted a huge number of sample cuts would be required to provide the best hole.
The solution was to create a Design of Experiments matrix utilizing an Excel spreadsheet that allowed the optimum settings to be determined with only a few dozen samples. The result was a huge savings of both time and money as the samples were taken more quickly and the project was completed much faster. Obviously, a test stand was also required to create these sample holes. A laser and laser cutting head as well as a robot were leased for three months so the entire test process had to be completed in three months. A test stand was created with two separate fixtures, one for vertical cuts and one for horizontal cuts. An adapter was also created to mount the cutting head to the robot. A robot program was created that allowed different size holes as well as ovals and squares to be cut. Programming was also required for the cutting head and laser in order to integrate the three separate systems.
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