Using ‘Good Judgment’ is the first step in deciding when to start an 8-D.
Often, however, an 8-D is a customer requirement in response to a problem: Feedback from the customer that there is a concern with the product. Sometimes the concern shows up as a Symptom that has been detected by the customer.
Ideally, a measurable will indicate when an 8-D should be started. When an undesirable trend in a process develops, corrective action can be taken to reduce the cause of the variation before a symptom occurs in the process and escapes to the customer.
If the undesirable trend triggers questions, a decision must be made whether the symptom can be fixed by an individual or whether the symptom requires further analysis. Further analysis typically indicates it’s time to assemble an 8-D problem solving team.