Reading: The 7 basic quality tools for process improvement. http://asq.org/learn-about-quality/seven-basic-quality-tools/overview/overview.html and sub-pages related to the 7 tools.Quality tools, the
FMEA (Failure Mode and Effect Analysis) With the FMEA method, risks can be localized, their probabilities and consequences estimated, and precautions taken to prevent problems from happening. Different constitutencies: System-FM EA Design-FM EA Process-FM E A Conce ptual phase De sign phase Re alisation T e st phase System- FMEA –Customer –Customer service –Marketing –Process specialists –Development team Design- FMEA - Customer service -Calculations engineers -Manufacturing specialists -Assembly personnel -Development team Process- FMEA -Customer -Inspector/Q -Development team FMEA: ORGANIZATION OF FUNCTIONS Function 1 Function 1.3 Function 1.2 Function 1.1 Function 3 Function 3.1 Function 3.1.1 Function 3.1.2 Function 6 Function 2 Function 2.1 Function 2.2 Function 4 Function 4.1 Function 5 Ov e rall- Function Step 1: Generating a functional tree EXAMPLE FUNCTION TREE Provide rotation Bra ke Rota te dh Acce l e ra te activ ate he ad Move head engage su c t i o n Stop Funktion 2 Function 2.1 Function 2.2 Function 4 Function 4.1 Function 5 CD Player Seal Seal Step 2: for each Function identify and localize extreme risks and dangers:what happens, when ......?
which failures can happen ?
what are the consequences, when.....? FMEA ANALYSIS Pot. failure Pot. failure reason Effects A B E RPA Action Date responsible A B E RPA* FMEA FUNCTION: A: Probability of occurance B: Seriousness of consequences E: Probability of detection Values : 1......10 Risk Probability Assessment RPA = A *B *E Compare to limit x : RPA > xStep 3: Determining sources, controlling consequences, weighting Actions, so that RPA* < x FMEA •Function / component / process step • Lists of parts to be analyzed and/or process steps. Indicate how functions are fulfilled.
• Within the framework of the error analysis, the following steps are executed for every function of the part and/or every process. The results are entered in the corresponding column of the reply form FMEA Column 1: Potential failure • All conceivable types of failures must be entered for the individual part or process.
Check list (incomplete): • Functional performance general • Deformation •Fatigue • Dissolution • Misalignment •Clamps • Corrosion • Dirt entry •Attrition FMEA Column 2: Cause of failure All conceivable failure causes are assigned to every potential failure. The description of the error causes must guarantee that corresponding correcting-measurescan be determined .
Check list (incomplete): • Component failure • Defective assembly • Defective maintenance • False acceptances, specifications • False dimensioning • Defective construction • Defective Material • Quality problemsin the manufacturing process • False heat treatment • False operation • Defective measurement • False instrument FMEA Column 3: Effect of failure • Starting point is the actual occurrence of the failure.
The implications of the failure on the customer and/or user.
Check list (incomplete): • Function not accomplished • Accident of different severity • complicated assembly or disassembly • weakening of the component (leading to rupture?) • Noise pollution • complicated repair • Pollution • unpleasant appearance Compute Probabilities • A: Probability of occurance • B: Seriousness of consequences • E: Probability of detection • Values :1......10 • Compute Risk Probability Assessment RPA = A*B*E (also called RPN, Risk Probability Number) Action • Start dealing with the highest RPA functions, and change the designs to mitigate that problem • Act on all “critical RPAs” • List person responsible for modification, what action is taken, and date.
• Once done, re-compute new RPAs Illustration FMEA • Useful and systematic approach to failure identification and mitigation.
• Also Root Cause Analysis and other similar tools exist and are used in industry • Many web sites have downloadable software and additional information Worksheet Pot. failure Pot. failure reason Effects A B E RPA Action Date responsible A B E RPA*
