Design FMEA 简介,2019/1/10,2,DFMEA is an acronym for: Design Failure Modes and Effects Analysis,What is DFMEA?,2019/1/10,3,FEMA 的好处,FEMA更关注于预防而不是补救措施：在生产之前的设计阶段，只消耗了15%的成本，但决定了95%的价值。 在设计阶段越早发现问题，采取纠正措施的成本就越低。 FEMA可以记录并跟踪采取的措施以降低风险。,2019/1/10,4,High-Level Process Map,Identify FMEA Project Scope,Understand the Dev Scope,Design FEMA: 12 steps process,Which high risk areas should the team focus the FMEA efforts?,What are the inputs, outputs, controls, noise, and unintended results of the focused scope?,Which design failure modes are the riskiest? What actions will the team take to prevent them from occurring?,2019/1/10,5,Boundary or extent of the analysis Defines what is included and what is not Understand system functional requirements Understand voice of customer Will avoid: Analyze into areas that are not important Establishing the wrong team,Identifying the Project Scope,2019/1/10,6,Understand the Dev Scope P-Diagram,Functionality/System /sub-system/Component,Signal,Causes the system to deliver the user intent,Noise Factors,(Unexpected Variation due to external environment, internal, piece-to-piece, customer usage, wear out),Control Factors,(Design parameters whose nominal values can be adjusted by the user or programming modes in the software),Ideal Function,(System output that determines the perceived result),Unintended Results,(Failure Modes),2019/1/10,7,List Function: Use the function from the Functional Diagram and the P-Diagram. List Potential Failure Modes: Look at the unintended result on the P-Diagram. The failure mode is usually the opposite of the intended function. AskIf the function has too much, too little, none, wrong, too late or too early, changes over time? Brainstorm other failure modes.,12 Steps to the DFMEA,2019/1/10,8,Consider, at a minimum five common functional failure modes: Failure to Execute Incomplete Execution Interrupt Timing Failures -blocked interrupt, priority conflicts, etc Delivers incorrect result Executes at incorrect time Consider, at a minimum four common failure modes applied to each interface Failure to update a value Incomplete update of a value Incorrect input values to the interface Update executes at incorrect rate,12 Steps to the DFMEA (cont.),2019/1/10,9,List Potential Effects: If (potential failure mode), Then (what?). The effect is what the customer will see if the failure mode occurs. Assign Severity Rating to Potential Effects: Each business will have specific definitions for all scales. Make sure your team interprets them the same to produce consistent scoring.,12 Steps to the DFMEA (cont.),2019/1/10,10,Assign Severity Rating to Potential Effects (Cont.): Make sure your team interprets all scales the same to produce consistent scoring in order to make your FMEAs comparable.,12 Steps to the DFMEA (cont.),2019/1/10,11,List Potential Causes: Avoid statements like “operator error” or “product malfunction” Tools used to find causes: 5 Why, Fishbone Note: Try to find all causes for the failure mode before moving to another function. Note: Whats the difference between a failure mode, effect and cause? Think of the Failure Mode as what you observe when a failure occurs. The Effect is how the failure impacts the customer. Cause is the most important of these three, find the cause and take action to control them is the main focus of DFMEA.,12 Steps to the DFMEA (cont.),2019/1/10,12,Assign Occurrence Rating DO NOT guess, use historical data to determine the occurrence rating.,12 Steps to the DFMEA (cont.),2019/1/10,13,List Current Controls: Prevention controls are proactive ways to prevent failure simulation models, design specifications, finite element analysis Detection controls detect the cause occurring and warn us to stop an escaping defect from reaching the customer,12 Steps to the DFMEA (cont.),2019/1/10,14,Assign Detection Rating: If there are prevention and detection controls, use the “worst” control, or highest number.,12 Steps to the DFMEA (cont.),2019/1/10,15,Calculate Risk Priority: Reserve Severity 9 and 10 for the most critical failure modes Voting try to obtain consensus Use the mean (could also use median) Defer to “expert” Take the highest rating,12 Steps to the DFMEA (cont.),2019/1/10,16,Use RPNs to Help Decide on High-Priority Failure Modes All high RPN numbers MUST have action! Always work the top RPNs (100 or top 35%) Give special attention to occurrence of 7 and above Give special attention to severity of 8 and above,12 Steps to the DFMEA (cont.),2019/1/10,17,Take Action to Reduce/Eliminate the Risk: Focus actions on the goal of reducing: Occurrence, then Detection, then Severity. Note: A DFMEA is not completed until the product does not exist does exist, its required to continuously evaluate and improve the product design.,12 Steps to the DFMEA (cont.),2019/1/10,18,Take Action to Reduce/Eliminate the Risk (cont.) Use DFSS tools to understand and reduce variation Validate and develop better controls For eac