Process_FMEA.ppt

1、Process Failure Modes and Effects Analysis,What is FMEA?,FMEA is an acronym for:,Prevention or Detection?,Processes may fail Detection will fail Customers could be hurt Prevention instead of detection = QUALITY,Path to Quality,Detection use historical process data to determine the occurrence rating,

2、6,Tip: A high rating is always bad,37,6,The Occurrence Rating is the probability the cause will occur and cause the failure mode.,38,Assign Occurrence Rating (contd),Optimal volume for reflow Paste on location,List Current Controls,For each cause or each failure mode Controls to prevent or detect,7,

3、Example: Failure Mode Controls,Paste volume too low,Gauge set to desire level Maintenance to monitor correct pressure SPI(Solder Paste Insp.),“Print Pressure Too Low”,List Current Controls (contd) Guidance,Purpose: The purpose of Controls is to prevent an escaping defect from reaching the customer I

4、nput: Control the input, and the output is controlled Validation: Validation of the controls is critical Number: Do all rows on the FMEA need controls listed? The team must decide the risk and answer Prevention: Focus on prevention controls Detection: Ensure detection controls at a minimum,7,List Cu

5、rrent Controls (contd) Prevention,Prevention is best. Detectionis risky. Focus on the inputs Prevention controls inputs Y = f(x) To get the Y, control the x,7,List Current Controls (contd) Detection,If prevention controls cant be found, detection controls are necessary Detection controls detect the

6、cause occurring and warn us to stop an escaping defect from reaching the customer,7,List Current Controls (contd),The Current Process Controls are the controls that prevent or detect the failure mode or potential cause.,7,43,Optimal volume for reflow Paste on location,Assign Detection Rating,For eac

7、h control Ability to detect or prevent either the failure mode or the cause,Detection Scale Bad RatingDefinition 10Defect causes by failure is not detectable 9Occasional units are checked for defects 8Units are systematically sampled and inspected 7All units are manually inspected 6Manual inspection

8、 with mistake-proofing modifications 5Process is monitored (SPC) and manually inspected 4SPC is used with an immediate reaction to out of control conditions 3SPC is above 100% inspection surrounding out of control conditions 2All units are automatically inspected 1Defect is obvious and can be kept f

9、rom affecting the customer Good,8,Be consistent. Cant get better than “7” with manual inspection,侦测到原因的话，分数就可以低，如果侦测到已发生的结果，那就相对高点。,8,The Detection Rating is the ability to prevent or detect the failure mode or potential cause. If there are prevention and detection controls, use the “best” control ,

10、 or lowest number.,45,Assign Detection Rating (contd),Optimal volume for reflow Paste on location,Guidance Filling in an FMEA,Hint: Follow the flow shown above. Work horizontally. Exhaust causes and controls for one failure mode and its related effect before moving on to another.,A,B,C,D,E,F,G,H,I,J

11、,K,M,L,Calculate Risk Priority,9,Risk Priority Number = Severity x Occurrence x Detection,The RPN Ranks Each Potential Failure by Severity, Occurrence and Detection,Worst,Best,A high number is always bad! Best is an RPN of 1 Worst is an RPN of 1000,48,9,9,RPN = S x D x O Range is 1 to 1000,49,Calcul

12、ate Risk Priority (contd),Optimal volume for reflow Paste on location,Ratings Are Relative,Make sure the team clearlyunderstands the rating scale For example: What does a 1 mean? What does a 10 mean? And everything in between. Reserve Severity 9 and 10 for the most critical failure modes,9,Tip: Afte

13、r you become experienced at ratings, score the ratings after the failure modes and causes are entered. Apply the ratings consistently!,Reaching a Decision on Ratings,Vote try to obtain consensus. Use the mean, but watch for outliers (could also use median). Defer to “process expert.” Take the highes

14、t rating.,9,Use RPNs to Help Decide on High-Priority Failure ModesBenefits of Prioritizing an FMEA,An FMEA lists the potential failure modes, effects and causes of a process The Risk Priority Number (RPN) prioritizes the controls and actions, indicating where controls are needed the most All high RP

15、N numbers MUST have action!,10,Recommended Actions(s),Use RPNs to Help Decide on High-Priority Failure Modes (contd),Always work the top RPNs. The goal of Zero Defects is to never stop. Tools to investigate Use a Pareto or sort RPNs Cause and Effect Voice of the Customer The biggest number is the dr

16、iver of the problem Give special attention to Occurrence of 8 and above Severity of 9 or 10 Use the Classification column on the FMEA to flag these.,10,53,Basing decisions on the RPN alone may result in inefficiency and/or increased risk,Occurrence/Severity Matrix,Occurrence of 8 and above Severity

17、of 9 or 10,Take Action to Reduce or Eliminate the Risk Associated with High-Priority Failure Modes,All high-risk items REQUIRE Actions. Some businesses require actions for all RPNs above a certain score. For example, all RPNs above 100 for Automotive ISO Standard TS16949 If your business requires a

18、certain minimum RPN, make sure that you have Actions for everything above that RPN number. If there is no requirement, the team should decided where to draw the line. As a guideline, start with the top 35%.,11,Take Action to Reduce or Eliminate the Risk Associated with High-Priority Failure Modes,Fo

19、cus actions on the goal of reducing 1) Occurrence, then2) Detection, then3) Severity. Continuously evaluate and improve the process. An FMEA is not completed until the process does not exist.,11,Reduce Severity,Reducing Severity can ONLY be done by Changing the design Changing the process Reducing S

20、everity is the MOST difficult,11,Severity Scale Bad Rating Criteria: A Failure Could 10Injure a customer or employee 9Be illegal 8Render product or service unfit for use 7Cause extreme customer dissatisfaction 6Result in partial malfunction 5Cause a loss of performance which is likely to result in a

21、 complaint 4Cause minor performance loss 3Cause a minor nuisance but can be overcome with no performance loss 2Be unnoticed and have only minor effect on performance 1Be unnoticed and not affect the performance Good,Reduce Occurrence,Understand and reduce variation by using these tools Cause and Eff

22、ect to discover root cause DOE to optimize process. For example, optimize solder paste printing by discovering which parameters give you the best consistency Multi-Vari Studies to understand sources of variation Such as, lot-to-lot, operator-to-operator, time-to-time, machine-to-machine,11,See your

23、Black Belt for help with DOE or Multi-Vari,Improve Detection,Inspection in subsequent station Inspection in-station Mistake proofing templates/ assembly aids SPC with operator reaction SPC automated/institutionalized Error cant occur,11,Understand and improve Detection by improving controls,Re-compu

24、te RPN to Reflect Impact of Action Taken on Failure Mode,After controls are decided, actions are necessary to install the controls Make sure actions are listed for all rows on the FMEA the team decides are necessary for the allowed risk List the actions Ensure a person is listed as responsible Provide a date t