【正文】 he FMEA process. The markedup flowchart will give you a powerful visual to refer to throughout the PFMEA. With the process flowchart in hand, the PFMEA team members should familiarize themselves with the process by physically walking through the process. This is the time to assure everyone on the team understands the basic process flow and the workings of the process ponents. For each ponent, list its intended function or functions. The function of the ponent is the valueadding role that ponent performs or provides. Many ponents have more than one function. Return to topStep 2: Brainstorm Potential Failure Modes In Step 2, consider the potential failure modes for each ponent and its corresponding function. A potential failure mode represents any manner in which the ponent or process step could fail to perform its intended function or functions. Using the list of ponents and related functions generated in Step 1, as a team, brainstorm the potential failure modes for each function. Don’t take shortcuts here。 then assign an occurrence ranking to each of those causes or failure mechanisms. We need to know the potential cause to determine the occurrence ranking because, just like the severity ranking is driven by the effect, the occurrence ranking is a function of the cause. The occurrence ranking is based on the likelihood, or frequency, that the cause (or mechanism of failure) will occur. If we know the cause, we can better identify how frequently a specific mode of failure will occur. How do you find the root cause? There are many problemfinding and problemsolving methodologies. One of the easiest to use is the 5Whys technique. Once the cause is known, capture data on the frequency of causes. Sources of data may be scrap and rework reports, customer plaints, and equipment maintenance records. The occurrence ranking scale, like the severity ranking, is on a relative scale from 1 to 10. An occurrence ranking of “10” means the failure mode occurrence is very high, and happens all of the time. Conversely, a “1” means the probability of occurrence is remote. See FMEA Checklists and Forms for an example PFMEA Occurrence Ranking Scale. Your organization may need an occurrence ranking scale customized for a lowvolume, plex assembly process or a mixture of highvolume, simple processes and lowvolume, plex processes. Consider customized occurrence ranking scales based on timebased, eventbased, or piecebased frequencies. See FMEA Checklists and Forms for examples of Custom PFMEA Ranking Scales. (Examples of custom scales for severity, occurrence, and detection rankings are included in this Appendix.) Ret