Faster changeovers via improved SMED empowered by Taguchi / case study on injection molding production

Most of the products require some components or even itself to be produced by injection molding. Independently of whether it's plastic or steel, injection molding is a complex production process in terms of quality since there are a numerous of parameters affect the outcome. Improved changeovers with less time required are inevitable to increase the efficiency of the firm. Till now, the most famous tool for changeover time reduction is Single Minute Exchange of Dies (SMED). Yet this methodology doesn't propose something solid saying how to decrease the longest part of a changeover operation, "trial runs and adjustments". For each item that is produced by injection molding, trial productions are conducted to find out the optimal combination of controllable factors like the temperature of the machine and material, velocity of the screw, pressure of the injection etc to reach desired product quality. These optimal combinations are documented as injection parameters for each item and applied in mass production. In practice, during a changeover session, these standardized production parameters are the initial values of trial runs. Because of the noise effect, it's almost impossible to get the correct product with the first trial after changing the mold. In fact we cannot and also don't need to control everything. Aid of an analytical design of experiment study can lead to find the correct parameter combination with less number of trials. Fewer trials provide shorter setup time. In this study a new methodology is proposed to increase the efficiency level of SMED by adding Taguchi tool to trial runs and adjustment stage in plastic injection molding process. Experimental design, which is used in the design phase before manufacturing in production, is not only a statistical approach but it is also a technique that can be used in research and development activities and support and complete all other quality techniques while minimizing the cost, enhancing the quality, and reinforcing the reliability of the results.