【正文】 arning.Or may endanger operator (machine or assembly) without warning.　 Hazardouswith warning9 Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves nonpliance with government regulation with warning.Or may endanger operator (machine or assembly) with warning.　 Very High8 Vehicle/item inoperable (loss of primary function). Or 100% of product may have to be scrapped, or vehicle/item repaired in repair department with a repair time greater than one hour.　 High7 Vehicle/item operable but at a reduced level of performance. Customer very dissatisfied. Or product may have to be sorted and a portion (less than 100%) scrapped, or vehicle/item repaired in repair department with a repair time between a halfhour and an one hour.　 Moderate6 Vehicle/item operable but Comfort/Convenience item(s) inoperable. Customer dissatisfied. Or a portion (less than 100%) of the product may have to be scrapped with no sorting, or vehicle/item repaired in repair department with a repair time less than a halfhour.　 Low5 Vehicle/item operable but Comfort/Convenience item(s) operable at reduced level of performance. Or 100% of product may have to be reworked, or vehicle/item repaired offline but does not go to repair department. 　 Very Low4 Fit Finish/Squeak Rattle item does not conform. Defect noticed by most customers (greater than 75%). Or the product may have to be sorted, with no scrap, and a portion (less than 100%) reworked.　 Minor3 Fit Finish/Squeak Rattle item does not conform. Defect noticed by 50% of customers. Or a portion (less than 100%) of the product may have to be reworked, with no scrap, online but outofstation.　 Very Minor2 Fit Finish/Squeak Rattle item does not conform. Defect noticed by discriminating customers (less than 25%). Or a portion (less than 100%) of the product may have to be reworked, with no scrap, online but instation.　 None1 No discernible effect. Or slight incovenience to operation or operator, or no effect.PFMEA 8. Determine potential cause(s) of each failure mode 確定每一失效模式的可能原因w A cause of failure is how the failure can occur in the process，失效原因：過程為何會(huì)失效EShould be written in terms of something in the process that can be corrected and controlled，應(yīng)表述為 可糾正或可控制可糾正或可控制 的因素EConsider human error, wearout of tools, ambient conditions, and interactions of factors，如人的過失，工裝磨損、環(huán)境條件以及因素間的相互作用PFMEAw Causes of failure often show up as a chain of events, from immediate cause to root cause失效通常是由一連串的原因造成的，從直接原因到根本原因w It is remended that these chains be developed for each failure mode and recorded on the FMEA form建議針對每一種失效模式，找出原因鏈，記入 FMEA表Euse a tree or fishbone diagram to develop可利用樹形圖或魚刺圖8. Cause(s) of Failure失效原因PFMEA 9. Assess the likelihood of occurrence of each cause評估每種失效原因產(chǎn)生的可能性w Use historical data (as a baseline) ，利用歷史資料E Take improvements into account，并考慮所作的改進(jìn) w Use statistical models and parison with similar processes利用可靠性模型，與類似的過程進(jìn)行比較PFMEA910 Failure almost inevitable，失效幾乎不可避免78 Similar processes that have often failed in the past，以前類似過程常常失效46 Similar processes that have occasional failures，類似過程偶爾失效13 Similar processes that have experienced isolated failures，類似過程僅有過個(gè)別失效9. Assess the likelihood of occurrence of each cause評估每種失效原因產(chǎn)生的可能性PFMEA Occurence (O)Probability Likely Failure Rates*　 Very High: Persistent Failures= 100 per thousand piecesVery High: Persistent Failures 50 per thousand piecesHigh: Frequent Failures 20 per thousand pieces　 High: Frequent Failures 10 per thousand pieces　 Moderate: Occasional Failures 5 per thousand piecesModerate: Occasional Failures 2 per thousand pieces　 Moderate: Occasional Failures 1 per thousand pieces　 Low: Relatively Few Failures per thousand pieces　 Low: Relatively Few Failures per thousand pieces　 Remote: Failure is Unlikely= per