Overview Of Failure Mode Effect Analysis

Published Date: 02 Nov 2017

Failure Mode Effect Analysis (FMEA) technique was initially developed in the aerospace industry in the early 1960s as a method of risk and reliability analysis (Bowles and Pelaez, 1995). In addition, it is an analytical and systematic quality planning tool for identifying possible failure in the product service, process design, and assembly stages thereby diagnosing the fault or cause (Evans and Milligan, 2013). The working structure of FMEA is shown in figure 2.1 below.

In general, FMEA is a technique applied in the manufacturing (automotive) industry to produce several components and improve system performance by identifying potential failures through preliminary analysis (Scipioni et al., 2002). During the application of this technique, several components are examined and each must be reviewed to detect possible failures (Bahrami et al., 2012). Failure probabilities, severity/impact of failure, and the detection of failure before occurring are the measures considered in FMEA; multiplying these three measures creates Risk Priority Number (RPN) (Bahrami et al., 2012).

America Automobile Engineering Association combined syrchro engineering with FMEA in the early 1990s in order to improve automobile quality; within the same period, Ford and two other automotive companies (General Motor and Chrysler) came together and published a FMEA handbook to address suppliers issues (Deng et al., 2007). Overall, effective use of this technique will reduce; failures in the field, customer complaints, performance related deficiencies and defects during production (Evans and Milligan, 2013).

C:\Users\sollysoo\Desktop\Quality Assignment\Capture.PNG

Figure 2.1 FMEA Working Structure (Deng et al., 2007).

FMEA is applied in three main cases in the automotive industry (Chrysler LLC et al., 2008):

The first case: involves new processes, new designs, or new technology which is considered as the main scope of FMEA.

Second case: if adjustments are required to be made to an existing process or design. This could be modifications in the regulatory requirements.

Third case: if an existing design is being reused in a new location or a different environment, the impacts of applying it in a new environment should be considered.

2.1 Categories of FMEA

There are two categories of FMEA are (Evans and Milligan, 2013; Ford FMEA handbook 2004; Chrysler LLC et al., 2008):

Design FMEA: this is a technique used in the design stage by team/ design engineer to consider potential failures and possible causes. All systems, components and end items are evaluated. The design team/engineer will possess some documents that will be used in preparing the failure mode analysis in this category. The first step of this process is to develop a list of the purpose of the design; the requirements of the customers acquired from Vehicle Requirements Documents, Quality Function Requirements and etc. should be put into consideration. The main purpose of this is to ensure proper functioning of the product when manufactured.

Process FMEA: is concerned with the reasons for potential failure during manufacturing and assembly and in service. In addition, it is carried out after the design FMEA once the drawings are finalised. Identification of the PFM of the assembly, process, and components are carried out here. PFMEA is used to: reduce down-time, aid fault finding, support risk management, improve performance and etc.

2.2 FMEA Approach in the Automotive Industry

According to the Chrysler LLC et al. (2008) manual, there is no unique process in the development of FMEA; however there are certain procedures to be followed. The main approaches according to the manual are (Chrysler LLC et al., 2008):

Team Identification: a cross functional team should be formed with members that understand the current subject matter. This approach is required because it will benefit the development of the FMEA process and ensure collaboration from all the affected areas. In addition, the selected team leader will choose his/her team members that possess the required experience. The examples of additional resources required for the process and design engineers are shown in table 2.1 below:

All contents from Chrysler LLC et al., 2008

Topics to be considered during FMEA development

Expertise or Relevant Resources

Scope

Customers, Individuals responsible for integration, Program Management

Expectations, functions and requirements

Individuals responsible for integration, customers, Program Management, Safety, Packaging, Materials, Logistics, service operations, Manufacturing and Assembly

Potential FM (Failure Mode)

Individuals responsible for integration, customers, Program Management, Safety, Packaging, Materials, Quality, Manufacturing and Assembly

Consequences and effects of the potential failure

Individuals responsible for integration, customers, Program Management, Safety, Packaging, Materials, Quality, Manufacturing and Assembly, Logistics

Rate of recurrence of the failure

Manufacturing and assembly, Engineering Analysis, Materials, Customers, packaging, statistical analysis, Maintenance

Application of current controls for failure prevention

Maintenance, Materials, Logistics, Packaging, Manufacturing and Assembly, Equipment, Quality

Application of current controls for failure detection

Manufacturing and Assembly, Quality, Customer, Packaging, Logistics, Maintenance

The required recommended actions

Maintenance, Reliability, Customers, Engineering Analysis, Packaging, Logistics, Materials, Quality, Individuals responsible for integration, Manufacturing and Assembly

Table 2.1 Additional Resources (Deng et al., 2007)

Defining Scope: defining the scope of FMEA depends on the type that is being developed that is, Component, System and Sub-system FMEA. However, the process, or defect that will be studied/evaluated must be clearly understood before starting the FMEA because what to include could be as important as what to exclude in the main analysis. The process flow diagrams, bill of materials, process flow diagrams, Interrelationship matrices, parameter diagrams, schematic and etc. are useful when considering the scope of FMEA.

Component FMEA: this is the subset of a sub-system failure mode effect analysis e.g. brake pad being a component of break assembly.

System FMEA: this includes several subsystems e.g. Interior system or Chassis system which focuses on addressing all interactions between systems, subsystems, customers and the environment.

Sub-system FMEA: this is the subset of the system failure mode effect analysis; it addresses all interactions between the sub-systems and other sub-systems or systems.

Defining Customers: Four types of customers are considered when analysing FMEA and they are:

End user: the organisation or individual(s) that in charge of develop the product.

Manufacturing Centres or OEM Assembly: this is where the vehicle is manufactured and assembled in the automotive industry; addressing the interfaces between a product and its assembly process essential in FMEA.

Supply Chain Manufacturing: this is the location of the supplier where manufacturing and assembling of the production is carried out.

Regulations: these are people or bodies (government agencies) that: give rules and regulations, monitors safety compliance and environmental specifications that could hinder the process or product.

Identifying Specifications, requirements and functions: the item/product intent is clarified here and thus, the PFM for each attribute of the requirements/function is determined.

Identifying the PFM: the way in which a process could fail to meet the required requirements (process or design) is defined as the failure mode. The PFM should be defined in technical terms.

Identifying Potential Effects: the effects of the identified potential failure are defined to know the extent or severity of the consequences.

Identifying Potential Causes: possible factors that could cause failure to occur are identified here.

Identifying Controls: possible controls to prevent failure are identified by knowing the main cause and knowing how to detect/prevent them.

Assessing and Identifying Risk: this is carried out is 3 ways and always rated on a scale on 1-10;

Severity: assessment is carried out to find the level/degree of the failure on customers.

Occurrence: this assessment is carried out to determine the probability of the failure.

Detection: this is how well the process controls detect the main reason for a failure.

Risk Priority Number (RPN): this is calculated as the product of occurrence, severity and detection. RPN= OxSxD

Recommend actions: possible actions to prevent the reoccurrence of the failure are recommended.

2.3 Useful Quality tools applied during FMEA

Some of the tools applied during fmea analysis are (Ford FMEA handbook, 2004; Evans and Milligan, 2013; Tague, 2004):

Process flow diagram: is a sequential order of different steps/orders of a process in form of a picture. In addition, it is used in analysing the function and purpose, of a process. A typical PFD is shown in figure 2.2 below:

C:\Users\sollysoo\Desktop\Quality Assignment\Capture2.PNG

Figure 2.2 FMEA Flow Diagram/Chart (Deng et al., 2007)

Ishikawa "Fishbone" Diagram: this is deductive analytical technique or tool used to show effects, cause, and failure modes of an undesired event and the contributing causes. In addition, it used during ‘brainstorming’ i.e. when team members come together to define potential failure modes by considering some elements (people, materials, environment etc.). An example is shown in figure 2.3 below.

C:\Users\sollysoo\Desktop\Quality Assignment\Capture5.PNG

Figure 2.3 Ishikawa "Fishbone" Diagram (Ford FMEA handbook, 2004)

Pareto Analysis/Chart: is a histogram/bar chart with a cumulative line used to prioritise/rank the problem to be solved. In addition, the 80/20 % rule of Juan J. which states that "80% of a problem are from 20% of the causes". Used in FMEA to identify all potential root causes of a problem.

C:\Users\sollysoo\Desktop\Quality Assignment\Capture4.PNG

Figure 2.4 Pareto chart

All the above 3 tools are called root cause analysis tools used in FMEA when analysing potential root causes of PFM; the possible causes are listed on the FMEA form (Tague, 2004).

3. Advanced Product Quality Planning in the Automotive Industry

Advanced Product Quality Planning (APQP) is one of the core quality tools mainly developed for use in the automotive industry (AIAG, 2013). The method of establishing and defining the steps/procedures to ensure that customer satisfaction is met when a product is produced is called Product Quality Planning (Chrysler et al., 1995). The main aim of PQP is to ease communication between people involved and to meet the production requirements on time; some benefits of PQP are (Chrysler et al., 1995):

Directs resources for the satisfaction of customers.

Early identification of important changes is promoted.

Avoidance of late changes.

Quality products are provided or produced on time at a very low cost.

The important step in APQP is team identification; a cross functional team should be formed with members that understand the current subject matter. The involvement of other departments apart from the quality department is a requirement i.e. representatives from the manufacturing, quality, sales, customers, field service and etc. should form the initial team (Chrysler et al., 1995).

According to Chrysler et al. (1995) APQP manual, there are mainly five phases in PQP and they are:

Planning and defining the program

Product design and development

Process design and development

Product and process validation

Feedback, assessment and corrective action

All phases are defined according to Chrysler et al. (1995) APQP manual

Planning and Defining: in this phase, the voice of the customer i.e. expectations and needs of the customer are considered and converted into requirement specification. Before proceeding to the next stage, these needs must be well understood. The customer needs and product process determines the input and output of this process. Some inputs are: Voice of customer, Product reliability studies, market strategy/business plan, customer inputs and etc. Outputs are: design goals, management support, process flow charts, Quality goals and reliability and etc.

Product Design and Development: once the first phase is completed, the design and products engineers start working on the product based on the requirements from phase 1 by ensuring that the customer requirements are met. Moreover, potential problems that might occur in the manufacturing state will be feasibly analysed. Some inputs for this phase are: Design goals, management support, product assurance plan, quality goals and reliability and etc. Outputs are: Design Failure Mode and Effect Analysis, Design Reviews, Engineering Specifications, Design Verification and etc.

Process Design and Development: in this phase, the manufacturing engineers assigned are to develop the processes and the related control plans in order to produce quality products. In order to achieve/accomplish the tasks of this phase, the first two phases of PQP must be successfully completed. In addition, the process required to support the design developed in the second phase is created at the quoted quantity, cost and quality level in such a way that the customer requirements and expectations are met. Some inputs are: Design Failure Mode and Effect Analysis, Design Reviews, Engineering Specifications, Design Verification and etc. Outputs are: Process Failure Mode and Effect Analysis, Characteristics Matrix, Process Instructions, Process Flow Chart, Packaging Standards, and etc.

Product and Process Validation: in this phase, an evaluation of a production trial run is carried out to validate the manufacturing processes used. The assigned team validates if the process flow chart and control plan are being followed and verifies if the customer requirements are met. However, any requirement/concern identified should be investigated and addressed before regular production begins. Some inputs for this phase are: Process Failure Mode and Effect Analysis, Characteristics Matrix, Process Instructions, Process Flow Chart, Packaging Standards, and etc. Outputs are: Production Trial Run, Production Control Plan, Production Part Approval, Measurement Systems Evaluation, Quality Planning Sign-off and Management Support, Packaging Evaluation, Preliminary Process Capability Study, and Production Validation Testing.

Feedback, assessment and corrective action: in this phase, the output is evaluated with the presence of special and common variation causes. In addition, the (product) quality planning effort is evaluated for effectiveness. However, variation can be reduced overtime; all the customer requirements must be met in this phase. The inputs are: Production Trial Run, Production Control Plan, Production Part Approval, Measurement Systems Evaluation, Quality Planning Sign-off and Management Support, Packaging Evaluation, Preliminary Process Capability Study, and Production Validation Testing. Outputs are: Customer Satisfaction, Reduced Variation, Delivery and Service.

3.1 Control Plan in APQP

Control Plan is a quality tool used in aiding manufacturing of quality products according to the customer’s requirements; systems used to reduce product and process variation are summarised on the control plan in a written form (Chrysler et al., 1995). However, CP defines the required actions at each stage/phase of the process to ensure all process outputs are in a controlled state, it is a part of the overall quality process that is required to be utilized during production (Chrysler et al., 1995). In addition, it provides process monitoring and control used in controlling characteristics during regular manufacture/production.

The CP document is maintained and applied throughout the life cycle of the product, furthermore, it is used to communicate and document the initial plan of the process control during the early stages of the product life cycle (Chrysler et al., 1995). All in all, CP is a living document that shows the methods of control and measurement systems that is used. Thus, the document should be updated as control methods and measurement systems are evaluated and improved (Chrysler et al., 1995).

The cross functional team should utilize the available information in order to develop a control plan to get a better understanding of the processes involved such as:

Process Flow Diagram

Design Reviews

Special Characteristics

Process/System/Design Failure Mode and Effect Analysis

Lessons Learned

Optimization Method

3.2 Process Analysis

According to the business dictionary (2013), process analysis is "A step-by-step breakdown of the phases of a process, used to convey the inputs, outputs, and operations that take place during each phase. A process analysis can be used to improve understanding of how the process operates and to determine potential targets for process improvement through removing waste and increasing efficiency".

Different types of process present challenges and opportunities for control and reduction of variation. There are several methods/tools used when analysing a work process or some part of a process, some are (Tague, 2004 and Chrysler et al., 1995):

Flow chart

Cause and effect diagram

FMEA

3.3 Implementation of APQP in the Automotive Industry

The following five steps will assist in formulating a good PQP with reduced adverse impact:

Training requirements should be determined. A good understanding of the methodology, methods and techniques described in the APQP manual is required so as to implement them effectively. The training is planned, developed and carried out by the department for the people/team that require training for product development.

A cross functional team should be formed with members that understand the current subject matter. The team will brainstorm, and develop a process flow chart/diagram for the production of the product.

Identification of the advanced quality planning activities. The trained team will use the information obtained from the process flow chart/diagram in the second step to identity the advanced quality planning activities that are in use in the organisation.

Identification of the required quality planning activities required by the organisation. This can be achieved by using the customer input as well as the APQP manual to determine how values/ improvements can be made to improve services and products.

Developing a plan. This is the last stage where the cross functional team develop a product production based on the voice of the customer i.e. the requirements or expectations.

4. Just-In-Time (JIT) for Automotive Industry

The principles listed in Ford’s book (Today and Tomorrow) form the base for the Just-in-Time (JIT) and it helps in eliminating all the sources of waste which covers not needed inventory and scrap in production also. In addition, Just-in-time plays major role in Inventory controlling, Suppliers and purchasing (Alternburg et al., 1999)

4.1 Logistics Condition before JIT

Before implication of JIT there were major issues with transportation which included Location of plant, Deregulation, Transportation regulation, Role of transportation (Alternburg et al. 1999). Due to relocation of factories of automotive industry, logistics turned out to be a major factor for the success of any automotive company; efficient transportation methods were critically needed for effectual JIT process in automotive company (Lambert and Stock, 1993)

4.2 Supplier Relationships and Purchasing methods before JIT

Purchasing was considered to be merely a transaction which was done for immediate requirements at the automotive company before the implementation of JIT (Alternburg et al., 1999). The Supplier relationships also had very short span as they ended the moment a given purchase contract was fulfilled by the supplier for contractor (Heinritz et al., 1991). Before JIT most of the materials as well as parts which were purchased were done so for inventory. Inventories at huge scale were maintained to achieve economies of scale (Wantuck, 1996).

4.3 Quality Revolution with JIT

The Quality movement started by Japanese brought major changes which were important and necessary for supporting implementation of JIT programs (Alternburg et al., 1999). Thus with the Quality Revolution a new quality dynamics emerged in automotive sector; even the US automobile corporations started adopting the quality perspective the customers were being invited to the manufacturing plants for team meetings and inspection tours (Alternburg et al., 1999).

In relation to employee’s also new approached focused on quality, responsiveness and service which laid major emphasis on realizing the importance of people in making any organization successful were adopted (Evans and Lindsay, 1993). Decentralized form of leadership was developed where quality values were being set from the top management (Alternburg et al., 1999). In Japan and US the automobile manufacturers encouraged their suppliers to locate their plants as near to the factories as possible so that small lots of auto parts can be delivered frequently to the assembly lines (Evans and Lindsay 1993).

4.4 Current Transportation Condition in Automotive Industry after applying JIT

The JIT transport process starts with the supplier location and ends at the customer location; it involves three parties working very closely which are supplier, carrier and customer (Alternburg et al., 1999). With JIT the transport relationships needed to be forged and advanced technology like Global Position Systems (GPS) have been used effectively in JIT (Johnson, 1997).

4.5 Current Supplier Relationships and Purchasing Methods with JIT Application in Automotive Industry

In present automobile industry JIT purchasing needs that the suppliers and manufacturers develop and form long-term relationships which last very long and with the intention that it becomes permanent (Alternburg et al., 1999). With JIT implementation the number of suppliers is also streamlined so that each supplier is the sole provider or specific item or part and purchase agreements are being issued mentioning the time duration also (Alternburg et al., 1999).

In automotive industry major automobile manufacturers not develop relationship with logistic specialists so as to manage the material flow. In addition, the quality of delivered goods in automotive industry has improved by almost100% with the implementation of JIT (Alternburg et al., 1999). Application of statistical process controls by suppliers reduces the unacceptable parts number in drastic manner and final inspect leads to final elimination of defective parts (Alternburg et al., 1999).

6. Complementary tools that could be used in the Automotive Industry

Complementary tools for FMEA:

6.1 Design of Experiments

Design of Experiments (DOE) in FMEA is a method to define the arrangement in which an experiment is to be conducted (Chrysler et al., 2008). An experiment is a study by which certain independent variables are varied according to a predefined plan and the effects are determined (Chrysler et al., 2008). For reliability tests, DOE uses a statistical approach to design a test that will identify the primary factors causing an undesired event (Chrysler et al., 2008). DOE is used as a technique to design an experiment that will identify the root cause(s) of a failure mode, when several causal factors may be contributing to the failure; it is also used when the causal factors are interrelated and it is necessary to learn how the interactions affect the failure mode (Chrysler et al., 2008).

6.2 Sentencing Technique

One problem encountered with FMEA is getting failure modes, effects and causes mixed up; the level the analysis is being carried out can complicate this (Chrysler et al., 2008). Sentencing technique is to make a sentence using failure mode, cause and effect, and to see if the sentence makes sense. A failure mode is due to a cause in addition, the failure mode could result in effects (Chrysler et al., 2008).

To guarantee proper identification, use the sentencing technique to relate cause back to failure mode, not back to effect (Chrysler et al., 2008):

State the failure mode.

Ask what could that failure mode result in - the answer will be the effect.

Ask what could that failure mode be due to - the answer will be the cause.

Complementary tools for APQP:

6.3 Characteristics Matrix

Characteristic matrix is a display of relationship between process parameters and manufacturing stations; the recommended method of developing the characteristics matrix is to number the dimensions and features on the part print and each manufacturing operation (Chrysler et al., 1995). All manufacturing operations and stations appear across the top, and the process parameters are listed down the left-hand column. The more the manufacturing relationship, the more important the control of a characteristic becomes (Chrysler et al., 1995). Regardless of matrix size, the upstream relationships of characteristics are evident. A matrix is shown in figure 6.1 below:

C:\Users\sollysoo\Desktop\Capturemm.PNG

Figure 6.1 Characteristics Matrix (Chrysler et al., 1995)

6.4 Design of Experiments

A designed experiment in the APQP is a test or sequence where potential influential process variable are systematically changed according to a prescribed design matrix. The response of interest is evaluated under the various conditions to (Chrysler et al., 1995):

To identify the influential variables among the ones tested.

Qualify the effects across the range represented by the levels of the variables.

Compare the effects and interactions.

Gain a better understanding of the nature of the casual system at work in the process.

Early application in the product/process development cycle can result in (Chrysler et al., 1995):

Improved process yields

Reduced overall costs

Reduced development time

Reduced variability around a nominal or target value

7. Current Quality Approach in Automotive Industry

The present quality approach is more justified by TQM which is supported by application of quality resources and quality circles and also involves active involvement of employees too (Alternburg et al., 1999). The TQM approach lays tress on long-term advantages which are being derived from continuous improvements made to the systems, products, people and designs (Lambert and Stock, 1993). Hence, the automobile industry also applies and uses quality circles for involving employees effectively in the quality programs of company (Alternburg et al., 1999). Automotive companies also use another tool which is quality sources which allows the material to be supplied to the assembly line without doing incoming inspections (Alternburg et al., 1999). The quality conformance part is implemented at suppliers end and thus the parts are directly sent to assembly line in smaller lots which are enough to complete the present work thus leaving no inventory to clutter shop floor or assembly mistakes (Alternburg et al., 1999).