Improving an Electrostatic Powder Coating Process via Signal to Noise Response Surface

Problem statement: In a coating process, the master plate referenced brightness or color shade was critical to the exterior appearance on aluminum alloy wheels. The quality measures of interest are the metallic paint thickness values on four areas. Because of these lower quality levels, the manufacturer has spent more on the cost of restudy or scrap as well as the longer production time. Approach: An expert system revealed seven process variables affecting those quality characteristics. Taguchi signal to noise ratio or SN of paint thickness values on the outboard spoke area was determined as a process response whereas SN on the remaining areas of window outboard, window between spoke and inboard spoke became merely process constraints. A constrained response surface optimization method and a modified complex method were performed to move the current operating condition towards the optimum. Results: The new settings improved the paint thickness values in terms of both the average and the standard deviation on all critical areas except the window between spoke. Conclusion: As expected, the implementation brings the reduction of the metallic paint consumption and the mismatch level of color shade.