【正文】 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(guò)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(guò)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(duì)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(shù)形圖或魚(yú)刺圖8. Cause(s) of Failure失效原因PFMEA 9. Assess the likelihood of occurrence of each cause評(píng)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(lèi)似的過(guò)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(lèi)似過(guò)程常常失效46 Similar processes that have occasional failures，類(lèi)似過(guò)程偶爾失效13 Similar processes that have experienced isolated failures，類(lèi)似過(guò)程僅有過(guò)個(gè)別失效9. Assess the likelihood of occurrence of each cause評(píng)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 thousand pieces10987654321PFMEA Causes and EffectsHarness ClampCauseandeffect chainradius out of spectool is worntool notreplacedlack of maintenance procedureclamp cracksat bendbundle falls outrattling noiseCAUSE chainEFFECT chainPFMEA Causes and EffectsWiring AssemblyEffects TreeCrossed Wire NofunctionFire in PlantOperatorInjuryDamagedEquip.Must repair vehiclePFMEA Causes and EffectsWiring AssemblyCauses TreeCrossed WireBoardErrorOperatorErrorPoorInstruct.NottrainedOper istiredPFMEA 10. List the Current Process Controls列出現(xiàn)有過(guò)程控制w Process controls catch the defect before the product reaches the customer，過(guò)程控制當(dāng)在產(chǎn)品到達(dá)顧客前發(fā)現(xiàn)缺陷 !w There are three Types of process controls, 過(guò)程控制有三種類(lèi)型 : (1) prevent the cause of failure, or reduce the rate of occurrence，防止原因出現(xiàn)或降低其出現(xiàn)的可能性 (2) detect the cause(s) of failure and lead to corrective actions，查明失效的原因并找出糾正措施 (3) detect the failure mode(s)，檢測(cè)失效模式PFMEAw Assign currently used process controls to failure modes and causes，針對(duì)失效模式或原因列出現(xiàn)行的過(guò)程控制手段EUsed on similar processes in the past，以前類(lèi)似過(guò)程如何控制ECan be of any Type: 1, 2, or 3, or any bination，可以是 3類(lèi)或其組合EType 1 controls affect the likelihood of occurrence, if already part of the design，若設(shè)計(jì)中已有體現(xiàn)，則第 1類(lèi)方法可降低原因出現(xiàn)的頻度EIf none, write “None” ，若沒(méi)有，則填 “無(wú) ”。10. List the Current Process Controls列出現(xiàn)有過(guò)程控制PFMEAw Detection is an assessment of the probability that，探測(cè)度為下列事件發(fā)生的概率Ea type 2 control can detect the cause and lead to corrective action, 第 2類(lèi)控制能夠發(fā)現(xiàn)原因并找到糾正措施 Ea type 3 control can detect a failure，第 3類(lèi)控制能夠在不良品到達(dá)顧客前發(fā)現(xiàn)缺陷... before the product reaches the customer!Edetection can also assess how effectively a type 1 control can prevent failure，第 1類(lèi)控制能夠預(yù)防失效的有效程度11. Detecting failure探測(cè)度PFMEA 11. Detecting failure探測(cè)度Detection Rating (D)，探測(cè)度評(píng)分 (D)910 very remote chance this control will detect the cause or failure查明失效或其原因的可能性極小78 remote chance ，可能性很小56 moderat