FMEA for Manufacturing and Assembly Process

International Conference on Technology and Business ManagementMarch 26-28. 2012 FMEA for Manufacturing and Assembly Process A. A. Nannikar D. N. Raut R. M. Chanmanwar S. B. Kamble [email protected] VJTI, Mumbai D. B. Patil [email protected] Siemens Ltd., Mumbai 1. Introduction FMEA is a systematic method of identifying and preventing system, product and process problems before they occur. It is focused on preventing problems, enhancing safety, and increasing customer satisfaction. Ideally, FMEA’s are conducted in the product design or process development stages, although conducting an FMEA on existing products or processes may also yield benefits. FMEA is a tool that allows us to:  Prevent System, Product and Process problems before they occur.  Reduce costs by identifying system, product and process improvements early in the development cycle.  Create more robust processes.  Prioritize actions that decrease risk of failure.  Evaluate the system, design, and processes from a new vantage point. FMEA is Description A procedure that examines each item in a system, considers how that item can fail and then determines how that failure will affect (or cascade through) the system. Acronyms  FMEA: Failure Modes and Effects Analysis  FMECA: Failure Modes and Effects and Criticality Analysis 2. Review of Literature Failure Mode and Effects Analysis (FMEA) for ensuring that reliability is designed into typical semiconductor manufacturing equipment (Mario Villacourt 1992). The FMEA is taken during the design phase of the equipment life cycle to ensure that reliability requirements have been properly allocated and that a process for continuous improvement exists. The guide provides information and examples regarding the proper use of FMEA as it applies to semiconductor manufacturing equipment. This Executive Summary is designed in a what, why, when, how format to allow the reader a relatively quick overview of the main issues surrounding an FMEA which are contained in the main part of the Guidance Document itself (IMCA 2002). FMEA does not attempt to give comprehensive answers to the frequently answered questions (FAQs), which are addressed in the main document. 3. Purpose of FMEA The purpose of performing an FMEA is to analyze the product's design characteristics relative to the planned manufacturing process and experiment design to ensure that the resultant product meets customer needs and expectations. When potential failure modes are identified, corrective action can be taken to eliminate them or to continually reduce a potential occurrence. The FMEA also documents the rationale for the chosen manufacturing process. It provides for an organized critical analysis of potential failure modes and the associated causes for the system being defined. The technique uses occurrence and detection probabilities in conjunction with severity criteria to develop a risk priority number (RPN) for ranking corrective action considerations. The FMEA can be performed as either a hardware or functional analysis. The hardware approach requires parts identification from engineering drawings (schematics, bill of materials) and reliability performance data, 501 For example.. electrical systems. as a part of quality assurance that a company should use systematically for total quality control.R.Détermine Failure Mode C. They are specialist having discipline in each system required in design process.Review Requirements R. Although FMEA analyses vary from hardware to software..Functional Block Diagram D. The FMEA consist of following steps:  FMEA Prerequisites  Functional Block Diagram  Failure mode analysis and preparation of work sheets  Team Review  Corrective action R.S. a functional analysis to FMEA on a subassembly is appropriate to use as a case study for the purposes of this guideline. however. Typically. In this process. bearings) to system (i. integrated circuits. The early stages of the equipment life cycle represent the region where the greatest impact on equipment reliability can be made. . Process Improvement FMEA is done in any equipment.Reliable Equipment 502 .R. . As the equipment proceeds through the life cycle phases. Design of Experiments and Fault Tree Analysis.Changes Proposed? C. All indicators from the total quality management perspective and from examination of the equipment life cycle tell us that the FMEA works best when conducted early in the planning stages of the design. possible changes in design and improvement can be made.No Change Required R.F.P. .Get System Description F. A concentrated effort can be placed on the higher RPN items based on the Pareto analysis obtained from the analysis. Who carries out an FMEA? An FMEA team should be well knowledge of the each system. . machinery systems.D. any subsystem FMEA can be performed at any time.C. Thus.F.  Total Quality FMEA is recommended along with Process Analysis Technique. . stepper. 2012 for example mean time between failures (MTBF). However. the functional approach is used when hardware items have not been uniquely identified or when system complexity requires analysis from the system level downward (top-down). and from components (i. it can be initiated at any level (component/assembly/subsystem) and progress in either direction (up or down).Corrective Action Required N.D. DP control systems and other control systems.International Conference on Technology and Business Management March 26-28. 4. This normally occurs during the design development stages of the equipment life cycle. the goal is always the same: to design reliability into the equipment.M. Mainly failure mode can be set according to the FMEA’s Risk Priority Number (RPN) system. To prevent this failure.e. the FMEA analysis becomes more detailed and should be continued. and is generally performed in a part-level fashion (bottomup).R.E.B. to identify the possible failure modes and find the effect of this failure to the equipment.Review FRACAS Data G. .D.A. .e. An FMEA should contain a practical test programme and the results from those tests. This identification of potential failure mode leads to a recommendation of effective reliability program. When to perform FMEA  Equipment Life Cycle The recommended method for performing an FMEA is dictated by the equipment life cycle. . . furnace). What does it contain? An FMEA covering the complete system (which may include FMEAs of various subsystem manufacturers) should encompass those FMEAs by a review and an analysis of the interfaces between the subsystems.  Collect all available information that describes the subassembly to be analyzed. analysis and corrective action system (FRACAS). Systems engineering can provide system configuration  Compile information on earlier/similar designs from in-house/customer users such as data flow diagrams and reliability performance data from the company's failure reporting. Review schematics and other engineering drawings of the system being analyzed to show how different subsystems. assemblies or parts interface with one another by their critical 503 . subsystem.e. and field replaceable units). FMEA Processes FMEA Pre-requisites  Review specifications such as the statement of work (SOW) and the system requirement document (SRD). subassemblies. It is easy to understand relations of the parts. 2012 Figure 1 Steps of FMEA 5. The recommended way to analyze the system is to break it down to different levels (i. system.. Functional Block Diagram This diagram shows how different parts are interact to each other to verify the critical path.International Conference on Technology and Business Management March 26-28. The above information should provide enough design detail to organize the equipment configuration to the level required for analysis. Alarms. but an RPM is not comparable to RPN’s in another analysis. It is calculated by multiplying the severity. mechanical and electromechanical components. Rating Scale Example: If Severity = 10. An RPM is comparable to other RPM’s in the same analysis. Determining the Risk Priority Number (RPN) RPN is the indicator for the determining proper corrective action on the failure modes. indicates that the effect is very serious and is “worse” than Severity = 1. Visual methods. As a minimum. The engineering team generates the RPN and focused to the solution of failure modes. etc. After the detection by previous method. Failure Mode Analysis and Preparation of Work Sheets  Determine the Potential Failure Mode Answer of asking simply question determines the failure. Recovery methods are. occurrence and detection ranking levels resulting in a scale from 1 to 1000. A Pareto analysis is based on the RPN. 504      . indicates that the failure is not likely to be detected before it reaches the end user is worse than Detection =1. Only design revision can be bringing about the revision in the severity ranking.Retry. effects and causes are determined. Alternate path or redundancy. actuation signals. In this all the possible failure modes. Built-in test (BIT). downstream or at a higher level. High RPN is gives idea for corrective action on failure mode. indicates that the likelihood of occurrence is very high and is “worse” than Occurrence = 1. a severity ranking is used to determine the criticality of the failure mode on the subassembly to the end effect. Preparation of FMEA Worksheets Action takes tasks recommended for the purpose of reducing any or all of the rankings. Detection methods are . Because similar RPN’s can result in several different ways and represents different types of risk. and prescribed design reviews are paramount to determining compliance with design guidelines. Time-out. RPN = Severity × Occurrence × Detection The small RPN is always better than the high RPN. to understand the normal functional flow requirements. 2012 support systems such as power.Local hardware concurrent with operation. Application software exception handling. After finding solution.International Conference on Technology and Business Management March 26-28. examine its relation to:  Preventive maintenance operation  Failure to operate at a prescribed time  Intermittent Operation  Degraded output or operational capability  Design causes Determine Current Controls/Fault Detection Many organizations have design criteria that help prevent the causes of failure modes through their design guidelines. If Detection = 10. plumbing. determining the recovery method is another part. Degraded. Checking of drawings prior to release. improvements can be made. Based on this information. data flow. Determine the Potential Effects of the Failure Mode The potential effects for each failure mode need to be identified both locally (subassembly) and globally (system). If Occurrence = 10. Re-load and retry. That’s the simple question is “What can go wrong?”  Subassembly examples of failure modes  Assembly examples of failure modes  Manufacturing/Process examples of failure modes  Component examples of failure modes The Reliability Analysis Centre (RAC) has developed a document designed solely to address component failure mechanisms and failure mode distributions for numerous part types including semiconductors. Customer satisfaction is key in determining the effect of failure mode. Safety criticality is also determined at this time based on Environmental Safety and Health (ES & H) levels. Determine the Potential Cause of the Failure Most probable causes associated with potential failure modes. Repair and restart. severity should not change  Occurrence may or may not be lowered based upon the results of actions  Detection may or may not be lowered based upon the results of actions  If severity.International Conference on Technology and Business Management March 26-28.methods of prevention and detection. Besides ownership. 505 . Response and Target Complete Date . Current Design Controls .A answer of asking simply question determines the failure. OCC—Following recommended corrective action. Occur . occurrence or detection ratings are not improved. RPN . Actions Taken – Following completion of a recommended action.Risk Priority Number. recommended actions must force characteristics to be forwarded to process FMEA for process mitigation  All recommended actions must have a person assigned responsibility for completion of the action  Responsibility should be a name. Potential Cause(s)/ Mechanism(s) of Failure . SEV – Severity ranking. and directed toward mitigating the cause of failure. 2012   Actions  All critical or significant characteristics must have recommended actions associated with them  Recommended actions should be focused on design. additional recommended actions must to be defined.This area lists the person responsible for evaluation of the recommended actions. Potential Local Effect(s) of Failure – subassembly consideration. the FMEA provides for closure of the potential failure mode. not a title  Person listed as responsible for an action must also be listed as a team member  There must be a completion date accompanying each recommended action  Unless the failure mode has been eliminated. RPN—Following recommended corrective action. Potential Failure Mode .Occurrence ranking based on the probability of failure. reduce the severity (based on a design change) if failure mode occurs.Most probable causes associated with potential failure modes. it provides for accountability by assigning a completion date. SEV—Following recommended corrective action. Class .Detection ranking based on the probability of detection. Recommended Actions – Action recommended to reduce the possibility of occurrence of the failure mode. DET—Following recommended corrective action. or eliminating the failure mode  If recommended actions cannot mitigate or eliminate the potential for failure. Detect . or improve the detection capability should the failure mode occur.A safety critical failure mode. Worksheet Table 1 Work Sheet of FMEA Source Book of “Quality and Reliability Management” by Lalit Wankhede  Description Item/Function – Name or concise statement of function performed by the equipment. Unpredictable failure with hazardous effects almost certain.International Conference on Technology and Business Management March 26-28. Inoperable but safe. Safety and Health Severity Code The Environmental Safety and Health (ES&H) severity code is a qualitative means of representing the worst case incident that could result from an equipment or process failure or for lack of a contingency plan for such an incident. scrap loss. design engineering. Very poor performance. are updated. the worksheets are then distributed to the users. It determines how affect the potential failure mode to the customers. Engineering team determines potential problems. Degraded performance. The worksheets may also provide information to other engineering areas. Corrective Action Design Engineering Design engineering uses the completed FMEA worksheets to identify and correct potential design related problems. acceptance testing. the team could suggest a process be changed to optimize installations. Compliance with regulation is unlikely. User dissatisfied. FMEA can be a way to communicate design deficiencies in the manufacturing of the equipment. Very dissatisfied user. etc. This is done because the sensitivities of the design are known and documented. 8. Reduced performance with gradual performance degradation. When the design is finalized. but safe and usable. the engineering team can suggest a statistically based preventive maintenance schedule based on the frequency and type of failure. Non-compliant with regulations. production continuity. Manufacturing From the FMEA worksheets. Team members for FMEA  Process engineer  Manufacturing supervisor  Operators  Quality  Safety  Product engineer  Customers  Suppliers 7. 506 . Probable failure with hazardous effects. Minor effect on performance. Some users may notice. Slight effect on performance. Team Review The engineering team suggested comments and review the worksheet to consider the failure modes based upon RPN’s. Only applies to the effect and is assigned with regard to any other rating. User dissatisfied. Non vital faults will be noticed by many users. This is where the FMEA becomes the basis for continuous improvement. A spares provisioning list can also be generated from the worksheet. technical support and manufacturing. 2012 6. Effect None Very Slight Slight Minor Moderate Severe High Severity Very High Severity Extreme Severity Maximum Severity Rank 1 2 3 4 5 6 7 8 9 10 Source Book of “Quality and Reliability Management” by Lalit Wankhede. The selection of suppliers can be optimized as well.  Environmental. User is slightly dissatisfied. identify possible changes in design. data fill in the worksheet etc. etc. Technical Support From the FMEA worksheets. The worksheets need to reflect the changes until final design of equipment. Table 2 Severity Ranking Criteria Criteria No effect Negligible effect on Performance. Ranking Criteria for FMEA Severity Ranking Criteria Calculating the severity levels provides for a classification ranking that encompasses safety. 01 per thousand 0. unreliable design/poor chance for detection No design technique available/Controls will not detect Detection Extremely Likely Very High Likelihood High Likelihood Moderately High Likelihood Medium Likelihood Moderately Low Likelihood Low Likelihood Very Low Likelihood Very Low Likelihood Extremely Unlikely Rank 1 2 3 4 5 6 7 8 9 10 Source Book of “Quality and Reliability Management” by Lalit Wankhede 9. Case Study Perform FMEA on a Pressure Cooker Figure 2 Pressure Cooker 507 .5 per thousand rate of occurrence 1 per thousand rate of occurrence 2 per thousand rate of occurrence 5 per thousand rate of occurrence 10 per thousand rate of occurrence 20 per thousand rate of occurrence 50 per thousand rate of occurrence 100 per thousand rate of occurrence Source Book of “Quality and Reliability Management” by Lalit Wankhede Detection Ranking Criteria This section provides a ranking based on an assessment of the probability that the failure mode will be detected given the controls that are in place. Table 4 Detection Ranking Criteria Criteria Can be corrected prior to prototype/ Controls will almost certainly detect Can be corrected prior to design release/Very High probability of detection Likely to be corrected/High probability of detection Design controls are moderately effective Design controls have an even chance of working Design controls may miss the problem Design controls are likely to miss the problem Design controls have a poor chance of detection Unproven.1 per thousand rate of occurrence 0. The probability of detection is ranked in reverse order. 2012 Occurrence Ranking Criteria The probability that a failure will occur during the expected life of the system can be described in potential occurrences per unit time. Table 3 Occurrence Ranking Criteria Occurrence Rank Criteria Extremely Unlikely Remote Likelihood Very Low Likelihood Low Likelihood Moderately Low Likelihood Medium Likelihood Moderately High Likelihood Very High Severity Extreme Severity Maximum Severity 1 2 3 4 5 6 7 8 9 10 Less than 0.International Conference on Technology and Business Management March 26-28. more cold water input and gas Component Failure Mode Effects on other Components Detection Method Compensating Provisions Jammed open Pressure relief valve Increased gas flow and thermostat operation I .Critical Reasonably probable Water at faucet too hot.Safe Reasonably probable Observe at pressure relief valve Shut off water supply. unless combined with other failure modes Open hot water faucet to relieve pres. reseal or replace relief valve Jammed closed None None I . pressure relief valve compensates Gas valve Jammed open Burner continues to operate. safety valve.. pressure relief valve open (obs.  Thermostat opens circuit through heating coil when the temperature rises above 250° C. and pressure gage). shut off gas. water turns to steam III .) 508 .  Focus – Safety Block Diagram of Pressure Cooker Figure 3 Block Diagram Pressure Cooker Table 5 FMEA is shown in Table Effects on Consequence Failure whole Category Likelihood System Loss of hot water. pressure relief valve opens Water temp. thermostat.Safe Probable Manual testing No conseq.International Conference on Technology and Business Management March 26-28. 2012 Pressure Cooker Safety Features  Safety valve relieves pressure before it reaches dangerous levels. and pressure increase.The analysis will be restricted to the four major subsystems (electrical system. Scope of FMEA for Pressure Cooker  Resolution . ” Tech Monitoring by SRI International. Analysis and Corrective Action System (FRACAS) results once actual failures are observed during test. Motor Industry: A State-of-Art Study. “Failure Mode and Effects Analysis in the U.K. Michael. “Software Factories: Japan. K. IEC Standard. 1991. pressure relief valve compensates Thermostat Fails to react to temp. pressure relief valve opens Water temp. 8. Texas Instruments Inc. 4. 9. production and operation.Procedure for failure modes and effects analysis (FMEA) CEI/IEC 812:1985.Procedure for failure modes and effects analysis (FMEA). 5. B.” Quality and Reliability Engineering International. “Improving Equipment Design Through TPM. Shaw. Matzumura.Critical Remote Water at faucet too hot Fails to react to temp. Technology Transfer #92020963BENG SEMATECH September 30. 2. “FMEA Process. 3. pp.G.” June 1991 Ciraolo. 10. 11. drop Burner fails to function Water temperature too low I . water turns to steam III .. 1–5.” The Second Annual Total Productive Maintenance Conference: TPM Achieving World Class Equipment Management. 1990. Conclusion The failure modes included in the FMEA are the failures anticipated at the design stage.Safe Remote Observe at faucet (cold water) Open hot water faucet to relieve pressure. 6.Safe Remote Observe at faucet (cold water) 10. CEI/IEC812 – Analysis techniques for system reliability . 2012 Jammed closed Burner ceases to operate System fails to produce hot water I . BSI Standard. Effects and Criticality Analysis (FMEA and FMECA). As such. Part 5: 'Guide to Failure Modes. 7. rise Burner continues to operate. 509 . “Failure Mode and Effects Analysis (FMEA)”. 184. BS 5760-5:1991: 'Reliability of Systems. Vol. they could be compared with Failure Reporting.International Conference on Technology and Business Management March 26-28. IMO MSC Resolution 36(63) Annex 4 – Procedures for Failure Mode and Effects Analysis (HSC Code). Take appropriate steps to avoid either possibility. References 1. Mario Villacourt. 6. Dale and P. 1992. Equipment and Components'. April 1991. Semiconductor Group. rises. Analysis techniques for system reliability . Lalit Wankhede “Quality and reliability management”. IEC 60812: 'Analysis Techniques for System Reliability – Procedure for Failure Mode and Effects Analysis (FMEA)’.