Capability Index for Multivariate Processes That Are Non-stable over Time

Summary

A key element of the management process is to pay close attention to the strategies that minimize total production cost. One of the ways of doing this is to minimize stocks. However, planning smaller lot sizes can lead to a shorter time for process set-up and pre-adjustment, which often gives rise to processes that are not stable over time. These processes are characterized by their dual variability: variability between batches (largely attributable to differences in tuning) and variability within the batch (attributable to uncontrolled process factors). In order to build the understanding to this “management process” reality, a new process capability index C _(u,v)(p _o , σ _o ) based on the proportion of conformance of the process and applications at an inferential level are developed. For illustrative purposes, a case study of the manufacture of car hoods and the results of the new methodology are introduced.

Since that autumn sun’s morning, we remember Marisa for all the shared experiences and the values she conveyed. Her courage and drive to improve in all respects have inspired and guided our work towards the continuous improvement and optimization.