Devices made by processing a thin lead zirconate titanate ceramic plate are used in the ink droplet firing units of ink-jet printers. The desired device shape is obtained by sand blasting the thin ceramic plate, but the formation of cracks in the thin ceramic plate during the sand blasting process has been a problem. The sand blasting process conditions were determined by using these problematic cracks as a characteristic value. The present study, however, reconsidered the processing conditions by performing a parameter design focused on the relation between the input of processing energy and the processed output volume. Specifically, an L₁₈ orthogonal array experiment was carried out, using the number of scans made by the processing nozzle as input and the processing depth as output. Optimization of the processing conditions by means of this parameter design resulted in a 4 db improvement. When production was carried out under the optimized conditions, dimensional variability was reduced to approximately one third of its former value, and the rate of occurrence of the quality problem of processing cracks was reduced to approximately one eighth.

Any corporation involved in making things has a constant need to improve productivity (reduce costs). One productivity improvement strategy is to improve quality and then trade the improved quality for higher production speed, thereby reducing equipment and personnel costs. In this study, a simulation of the mold temperature control system in a plastic molding process was used to perform a parameter design that improved the S/N ratio and sensitivity, and these effects were confirmed on actual molded products. By applying the results of the study and other improvement strategies to the actual molding process, we succeeded in raising its productivity: the molding cycle time was reduced 46% without compromising the current quality level. When the loss concept was used to calculate the return on investment in molds and equipment necessary to introduce the new technique for the processed part, the return was estimated to be 11 million yen per year, showing that the extra investment could be recovered in a short time.