DFMEA简介-谢亮.ppt

Place your image on top of this gray box. If no graphic is applicable, delete gray box and notch-out behind gray box, from the Title Master Design FMEA 简 介 *1 DFMEA is an acronym for: Design Failure Modes and Effects Analysis What is DFMEA? Date2 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 。 Date3 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? Date4 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 Date5 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) Date6 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 Date7 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.) Date8 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.) Date9 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.) Severity of EffectRank Harm To End User10 Be illegal9 Render product or service unfit for user8 Extreme Customer Dissatisfaction7 Partial malfunction6 A loss of performance which is likely to result in a compliant 5 A minor performance loss4 A minor nuisance but can be overcome with no performance loss 3 Only minor effect on performance2 No discernable effect1 Date10 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.) Date11 Assign Occurrence Rating DO NOT guess, use historical data to determine the occurrence rating. 12 Steps to the DFMEA (cont.) Failure ProbabilityRank 1 in 210 1 in 39 1 in 88 1 in 207 1 in 806 1 in 4005 1 in 10004 1 in 100003 1 in 1000002 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.) Date13 Assign Detection Rating: If there are prevention and detection controls, use the “worst” control, or highest number. 12 Steps to the DFMEA (cont.) Chance of Escape DescriptionRate 100%No detection method in place, escape is almost certain 10 90%Unproven or unreliable detection method9 80%Very slight effectiveness in detection8 70%Slight effectiveness in detection7 60%Low effectiveness in detection6 50%Medium effectiveness in detection5 40%Moderately high effectiveness in detection4 30%High effectiveness in detection3 20%Very high effectiveness in detection2 10%Design control will almost certainly detect the potential cause of the failure mode. 1 Date14 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.) Date15 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.) Date16 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.) Date17 Take Action to Reduce/Eliminate the Risk (cont.) Use DFSS tools to understand and reduce variation Validate and develop better controls For each control action, a person is listed as responsible as well as a due date 12 Steps to the DFMEA (cont.) Date18 Re-compute the RPN to evaluate the impact of action taken. DFMEA are “living documents.” Refresh the DFMEA when new information is acquired. After lesson learned Customer complaints Product improvement activities happened (such as DFSS project, DDW and etc) Scope changes 12 Steps to the DFMEA (cont.) Date19 Re-compute the RPN to evaluate the impact of action taken (cont.). Review at regular team meetings even if nothing has changed. Note: Corrective action must require proof of DFMEA corrections to instill the importance and quality of this “living document.” 12 Steps to the DFMEA (cont.) Date20 Try to identify quick wins if possible. Teams should always be prepared to identify and pursue quick win opportunities the ROI can be very high. What an improvement opportunity can be define a