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Unit iii tqm


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Unit iii tqm

  1. 1. FAILURE MODE AND EFFECT ANALYSIS (FMEA) Discuss about Failure Mode and Effect Analysis (FMEA) Introduction A failure modes and effects analysis (FMEA), is a procedure in product development and operations management for analysis of potential failure modes within a system for classification by-the severity and likelihood of the failures. A successful , FMEA activity helps a team to identify potential failure modes based on past experience with similar products or processes, enabling the team to design those failures out of the system with the minimum of effort and resource expenditure, thereby reducing development time and costs. . It is widely used in manufacturing industries in various phases of the product life cycle and is now increasingly finding use in the service industry. Failure modes are any errors or defects in a process, design, or item, especially those that affect the customer, and can be potential or actual. Effects-analysis refers to studying the consequences of those failures.Types-of FMEA > Process: analysis of manufacturing and assembly processes > Design: analysis of products prior to production > Concept: analysis of systems or subsystems in the early design concept stages > Equipment: analysis of machinery and equipment design^before purchase > Service: analysis of service industry processes before they are released to impact the customer > System: analysis of the global system functions > Software: analysis of the software functions Process. FMEA is used to identify potential process failure modes by ranking failures and helping to establish priorities according to the relative impact on the internal or external customer. Implementing process FMEA helps to identify potential manufacturing or assembly causes in order to establish controls for occurrence reduction and detection. Furthermore, design and process FMEA document the results of the design and production processes, respectively. Features 1. It is Reliability : Reliability is one of the most important characteristics of any product, no matter what its application. Reliability is also an important aspect when dealing with customer satisfaction, whether the customer is internal or external. 2. Determine the Failure Rate : A vast majority of products follow a very familiar pattern of failure. When no information is known about the reliability (probability of survival) or, conversely, failure of a Product, component, system or process, except the failure rate which is a constant, periods of failure can conveniently be modeled by an exponential distribution. The probability of survival of this type of product using an exponential distribution may be expressed as Where Rj = the reliability or probability of survival t = the time specified for operation without failure 1 = the failure rate . q = the mean time to failure 3. FMEA attempts to detect the potential product-related failure modes:
  2. 2. The technique is used to anticipate causes of failure and prevent them from happening. FMEA uses occurrence and detection probability criteria in conjunction with severity criteria to develop risk prioritization numbers for prioritization of corrective action considerations. This method is an important step in debugging and preventing problems that may occur in the manufacturing process. It should be noted that for FMEA to be successful, it is extremely important to treat the FMEA as a living .document, continually changing as new problems are found and being updated to ensure that the most critical problems are identified and. addressed quickly. Advantages > Improve the quality, reliability and safety of a product process > Improve company image and competitiveness > Increase user satisfaction > Reduce system development tinning and cost > , Collect information to reduce future failures, capture enqineering knowledge . > Reduce the potential for warranty concerns >. Early identification and elimination of potential failure modes .> Emphasize problem prevention > Minimize late changes and associated cost > Catalyst for teamwork and idea exchange between functions > Reduce the possibility of same kind of failure in future The Process FMEA Document The basic philosophy concerning the process FMEA document is almost identical to that of the design FMEA document examined earlier. Process FMEA is, an analytical technique utilized by a Manufacturing responsible Engineering Team as a means to assure that, to the extent possible, potential failure modes and their associated causes mechanisms have been considered and addressed. A process FMEA is required for all new parts/processes, changed parts/processes, and carryover parts recesses in new applications or environments. The process FMEA document should be initiated before or at the feasibility stage, prior to tooling for . production, and take into account all manufacturing operations, from individual components to assemblies. Early review and analysis of new or revised processes is promoted to anticipate, resolve, or monitor potential process concerns during the manufacturing planning stages of a new model or component program. When creating and/or revising the process FMEA document, it may be assumed that the product will meet the design intent as designed. However, knowledge of potential failures due to a design weakness can be included in process FMEA, if desired. Process FMEA does not rely on product design changes to overcome weaknesses in the process, but it does take into consideration a product's design characteristics relative to the planned manufacturing or assembly process to assure that, to the extent possible, the resulting product meets customer needs and expectations. Figure : Design of FMEA Form
  3. 3. The Design FMFA Document The top section in the form is used mainly for document tracking and organization. 1. FMEA Number : On the top left comer of the document is the FMEA Number, which is only needed for tracking. 2. Item : The Item space is used only to. clarify which exact component or process is being analyzed. The appropriate level of analysis should be included here, along with the name and number of the system or sub-system being analyzed. 3. Design Responsibility : The team in charge of the design or process should be identified in the space designated Design Responsibility. The name and company (or department) of the person or group responsible for preparing the document should also be included. 4. Prepared By : The name, telephone number, and address should be included in the prepared by space for use when parts of the document need explanation. 5. Model Number/Year : Both the name and identification number of the system, or component should be included in the Model Number/year space to avoid ' confusion between similar components. 6. Key Data : The data the initial FMEA is due 'should be placed in the Key Date space. 7. FMEA Data : The date the original FMEA was compiled and the latest revision date should be placed in the FMEA date space. 8. Core Team : lathe space reserved for core team, the names of the responsible individuals and departments that have authority to perform tasks should be listed. If the different people or departments involved are not working closely or are not familiar with et ch other, team members' names, departments, and phone numbers should be distributed. 9. Item/Function In this section, the name and number of the item being analyzed : is recorded. This information should be as precise as possible to avoid confusion involving similar items. Next, the function of the item is to be entered below the description of the item. No specifics should be left out in giving the function of the item If the. item has more than one function, they should b ^ listed and analyzed separately. The function of the item should be completely give, including the environment in which the system operates (including temperature, pressure, humidity, and so forth); it should also be as concise as possible. 10. Potential Failure Mode : The Potential Failure Mode information may be one of two things. Fist, it may be the method in which the item being analyzed may fail to meet the design criteria. Second, it may be a method that may cause potential failure in a higher-level system or may be the result of failure of a lower-level system. It is important to) consider and list each potential failure mode. 11. Potential Effect (s) of Failure : The potential effects of failure are the effects of the failure as perceived by the customer. Recall that the customer may be internal or may be the end user of the product. The effects of failure must be described in terms of what the customer will notice or experience. 12. Severity(S) : Severity is the assessment of the seriousness of the effect of the potential failure mode to the next component, sub-system, system, or customer if it occurs. It is important to realize that the severity applies only to the effect of the failure, not the potential failure mode. 13. Classification (CLASS) : This column is used to classify any special any special product characteristics for components, subsystems, or systems that may enquire additional process controls. There should be a special method to designate any item the may require special process controls on the form. .
  4. 4. 14. Potential Causes(S) Mechanism (S) of Failure : Every potential failure cause and /or mechanism must be listed completely and concisely. Some failure modes may have more than one cause and/or mechanism of failure. 15. Occurrence(O) : Occurrence is the chance that one of the specific causes/ mechanisms will occur. This must be done for every cause and mechanism listed. Reduction or removal in occurrence ranking must not come from any reasoning except for a direct change in the design. 16. Current Design Controls : In this portion of the form, the activities that assure the design sufficiency for the failure mode or mechanism are listed. These activities may include, but are not limited to, prevention measure, design validation, and design verification. These controls may be supported through tests, which may include physical testing, mathematical studies. 17. Detection(D) : This section of the document is a relative measure of the assessment of the ability of the design control to detect either a potential cause/ mechanism or the subsequent failure mode before the component, sub-system, or system is completed for production. Most typically, in order to achieve a lower detection ranking in subsequent versions of the document, the planned design control must be improved 18. Risk Priority Number (RPN) : By definition, the Risk Priority Number is the : product of the severity (S), occurrence (O), and detection (D) rankings, as shown below; This product may be viewed as a relative measure of the design risk. Values for the RPN can range from 1 to 1000, with 1 being the smallest design risk possible. 1.9. Recommended Actions : After every concern has been examined and given a risk priority number, the team should begin to examine the corrective action(S) ; that may be-employed, beginning with the concern with the greatest RPN and working in descending order according to RPN. Also, concerns with high severity criteria should be examined with the lead group.of concerns. The purpose of the recommended actions is to reduce one or more of the criteria that constitute the risk priority number. 20. Responsibility and Target Completion Dates : Here the individual or group responsible for the recommended actions and the target completion date . should be entered as reference for future document users. 21. Actions Taken : After an action has been implemented, brief description of the actual action and its effective date should be entered. This is done after the , action has been implemented so future document users may track the progress of the plan. 22. Resulting RPN : After the corrective actions have been identified, the resulting severity, occurrence, and detection rankings should be re-estimated. Then the resulting RPN should be recalculated and recorded. If no actions are taken, this section should be left blank. If no actions are taken and the prior rankings and RPN are simply repeated, future document users may reason that there were recommended actions taken, but that they had no effect. After this section is completed, the resulting RPN s should be evaluated, and if further action is deemed necessary, steps from the Recommended Actions section should be repeated.