Product-FMEA

For the Product-FMEA according to the VDA-standard only different type of measures are distinguished, such as measure during development or during customer operation. Typical Design-FMEAs and specially the term System-FMEAs are not directly addressed. Due to the scope the Product-FMEA could be applied on vehicle, system, component, and in case of e.g. semi-conductors on sub-component (or part) level. How the stmcture and how the scope of an FMEA could be tailored based mainly on the complexity and on the product boundary (Fig. 4.46). 

Ford s FMEA handbook also requires a Design-FMEA on system level, in order to ensure that the components interfaces are designed correctly. Aircraft standards require similar approaches also the Product-FMEA according to the VDA standard could provide a similar interpretation. Managing of failure interfaces can often be challenging, since often multiple suppliers need to be coordinated under the directions of OEM. ISO 26262 requires incorporating the coordination as safety activity in the development interface agreement (DIA). 

Failure Mode and Effects Analysis. The system design activity usually emphasizes the attainment of performance objectives in a timely and cost-efficient fashion. The failure mode and effects analysis (FMEA) procedure considers the system from a failure point of view to determine how the product might fail. The terms design failure mode and effects analysis (DFMEA) and failure mode effects and criticaUty analysis (EMECA) also are used. This EMEA technique is used to identify and eliminate potential failure modes early in the design cycle, and its success is well documented (3,4). 

The role of FMEA in designing capable and reliable products... 

Failure in the context here means that product performance does not meet requirements and is related back in the design FMEA to some component/character-istic being out of specified limits - a fault. The probability of occurrence of failure (O) caused by a fault can be expressed as ... 

Once the variability risks, and q, have been calculated, the link with the particular failure mode(s) from an FMEA for each critical characteristic is made. However, determining this link, if not already evident, can be the most subjective part of the analysis and should ideally be a team-based activity. There may be many component characteristics and failure modes in a product and the matrix must be used to methodically work through this part of the analysis. Past failure data on similar products may be useful in this respect, highlighting those areas of the product that are most affected by variation. Variation in fit, performance or service life is of particular interest since controlling these kinds of variation is most closely allied with quality and reliability (Nelson, 1996). 

For example, the characteristic dimension A on the cover support leg was critical to the success of the automated assembly process, the potential failure mode being a major disruption to the production line. An FMEA Severity Rating (S) = 8 is allocated. See a Process FMEA Severity Ratings table as provided in Chrysler Corporation et al. (1995) for guidance on process orientated failures. The component cost, Pc = 5.93 and the number planned to be produced per annum, N = 50000. 

This case study concerns the initial design and redesign of a security cover assembly for a solenoid. The analysis only focuses on those critical aspects of the assembly of the product that must be addressed to meet the requirement that the electronics inside the unit are sealed from the outside environment. An FMEA Severity Rating (S) for the assembly was determined as S = 5, a warranty return if failure is experienced. 

Reliability targets are typically set based on previous product failures or existing design practice (Ditlevsen, 1997) however, from the above arguments, an approach based on FMEA results would be useful in setting reliability targets early in the design process. 

A summary of each of the key tools and techniques considered to be important in the product development process is given in Appendix III. This covers such techniques as FMEA, QFD, DFA/DFM and DOE. Included for each is a description of the tool or technique, placement issues in product development, key issues with regard to implementation, and the benefits that can accrue from their use, and finally a case study. It would be advantageous next, however, to determine exactly what a tool or technique does. In general, the main engineering activities that should be facilitated by their use are (Huang, 1996) ... 

Before setting about the task of developing such a model, the product development process requires definition along with an indication of its key stages, this is so the appropriate tools and techniques can be applied (Booker et al., 1997). In the approach presented here in Figure 5.11, the product development phases are activities generally defined in the automotive industry (Clark and Fujimoto, 1991). QFD Phase 1 is used to understand and quantify the importance of customer needs and requirements, and to support the definition of product and process requirements. The FMEA process is used to explore any potential failure modes, their likely Occurrence, Severity and Detectability. DFA/DFM techniques are used to minimize part count, facilitate ease of assembly and project component manufacturing and assembly costs, and are primarily aimed at cost reduction. 

The so-called Q7 tools and techniques, Cause and Effect Diagrams, Pareto Analysis, etc. (Bicheno, 1994 Dale and McQuater, 1998 Straker, 1995), are applicable to any stage of the product development process. Indeed they support the working of some of the techniques mentioned, for example using a Pareto chart for prioritizing the potential risks in terms of the RPN index for a design as determined in FMEA (see Appendix III). 

Norell, M. 1993 The Use of DFA, FMEA, QFD as Tools for Concurrent Engineering in Product Development Processes. In Proceedings ICED 93, The Hague. 

Measurement and review of product realization stages Use of common tools for FMEA, SPC, MSA... 

The requirements of the automotive industry are more demanding than some other industries. Automotive products have to be safe, reliable, and maintainable, protect the occupants, and have minimal impact on the environment in their manufacture, use, and disposal. The automotive sector is a very competitive market and as a consequence costs have to be optimized. There is little margin for excessive variation, as variation causes waste and waste costs money and time. Therefore several methods have evolved to reduce variation. Among them are SPC, FMEA, MSA, and many other techniques The automotive industry believes that the more their suppliers adopt such variation reduction techniques the more likely it will be that the resultant product will be brought to the market more quickly and its production process be more efficient. 

The auditor should establish that the supplier has made provision to link all the processes and should follow trails through departments and processes to verify correct use of outputs from interfacing processes e.g. use of SPC charts, FMEA, MSA, control plans and changes to these when the products or processes change. 

Is FMEA and mistake-proofing applied to each product and process and are the results used to effect beneficial changes to these products and processes ... 

The solution is to perform an FMEA on the product and the process and identify the critical products, processes, and regulations. 

The standard requires the use of a multidisciplinary approach to prepare for product realization including development and review of special characteristics, FMEA, and control plans. 

The primary input data is product design data consisting of Design FMEA... 

Start by doing a risk assessment and identify those things on which continuity of business depends power, water, labor, materials, components, services, etc. Determine what could cause a termination of supply and estimate the probability of occurrence. For those with a relatively high probability (1 in 100) find ways to reduce the probability. For those with lower probability (1 in 10000) determine the action needed to minimize the effect. The FMEA technique works for this as well as for products and processes. 

A failure modes and effects analysis is a systematic analytical technique for identifying potential failures in a design or a process, assessing the probability of occurrence and likely effect, and determining the measures needed to eliminate, contain, or control the effects. Action taken on the basis of an FMEA will improve safety, performance, reliability, maintainability and reduce costs. The outputs are essential to balanced and effective quality plans for both development and production as it will help focus the controls upon those products, processes, and characteristics that are at risk. It is not the intention here to give a full appreciation of the FMEA technique and readers are advised to consult other texts. 

One of the procedures used to determine which sensors are needed to sense process conditions and protect the process is called a Failure Mode Effect Analysis—FMEA. Every device in the process is checked for its various modes of failure. A search is then made to assure that there is a redundancy that keeps an identified source or condition from developing for each potential failure mode. The degree of required redundancy depends on the severity of the source as previously described. Table 14-2 lists failure modes for various devices commonly used in production facilities. 

In order to perform a complete, formal FMEA of a production facility, each failure mode of each device must be evaluated. A percentage failure rate and cost of failure for each mode for each device must be calculated. If the ri.sk discounted cost of failure is calculated to be acceptable, then there arc the proper numbers of redundancies. If that cost is not acceptable, then other redundancies must be added until an acceptable cost is attained. 

It should be clear that a complete FMEA approach is not practical for the evaluation of production facility safety systems. This is because (1) the cost of failure is not as great as for nuclear power plants or rockets, for which this technology has proven useful (2) production facility design projects cannot support the engineering cost and lead time associated with such analysis (3) regulatory bodies are not staffed to be able to critically analyze the output of an FMEA for errors in subjective judgment and most importantly, (4) there are similarities to the design of all production facilities that have allowed industry to develop a modified FME.A approach that can satisfy all these objections. 

Assume that two levels of protection are adequate. Experience in applying FMEA analysis to production equipment indicates that in many cases only one level of protection w ould be required, given the degree of reliability of shutdown systems and the consequences... 

Understanding production process FMEA, Pareto analysis, flow charts [2]... 

The facility is subjected to a process hazard analysis commensurate to the level of hazard the facility represents (i.e., Checklist, PHA, HAZOP, What-If review, Event Tree, FMEA, etc.). The results of these analyses are fully understood and acknowledged by facility management. Where high risk events are identified, quantifiable risk estimation and effects of mitigation measures should be evaluated and applied if productive. 

---