Effective Monitoring of Processes with Parts Per Million Defective. A Hard Problem!

Abstract

Many processes have defective rates measured in parts per million (PPM). When the process yields such a high level of quality, traditional methods of process improvement, such as designed experiments, and control charts on the number of defectives or the time between defectives, are no longer effective. However, it may still be desirable to monitor and/or improve such processes. In this article, we take a critical look at attempts to apply control charts in this situation. As an alternative, we suggest that since defectives are so rare, we should carefully study any that are observed. By comparing the characteristics of the defectives to good units, both in terms of their physical dimensions and properties, and the process records from their production, we may be able to identify the key differences. Using this type of retrospective study, the goal is to identify an explanatory continuous variable or variables that can be monitored instead of the number of defectives or the time between defectives.

Cite this work

No public copy is stored for this record, so only the metadata is cited.

Stored only when both papers are in the corpus — 19 citations exist upstream.

Papers that cite the same references — the relational fallback while embeddings are still backfilling.