Welcome to Six Sigma Black Belt, Course 5, Module 5, Additional Analysis Tools. Clearly, Six Sigma relies heavily on a number of analytical tools. However, there are a number of software tools that carry an equal amount of weight and importance in the product and process implementation method. These tools will be showcased in the next several lessons of this module. FMEAs stands for, Failure Mode and Effects Analysis. FMEA provides the organization with a systematic technique to analyze a system for all potential or possible failure modes. Each failure mode is assigned a risk priority number based on the failure mode, effect of the failure and the probability that the failure will occur. Part of an example of an FMEA is shown here, for perspective. Let's talk about the process and components that go into creating an FMEA. Creating an FMEA is very straightforward. There's a significant emphasis on documentation. An FMEA is considered an official document and should have a designated document number. At the top of the FMEA, there will be a number of descriptive elements that must be filled in, including the group that is responsible of the design, person responsible for the preparation of the FMEA, date and the identification of the system under investigation. Each component is then, listed. Each component list each function. Components can have more than one function. Each function cascades into a series of failure modes. For each failure mode, we will capture the effect and cause of the failure. Finally, any existing preventative controls, already in place to abate or at least alert the consumer of the failure. Failures will happen. There is little we can do to economically cease all failures but we at least want things to fail in a safe manner. Risk priority number is the product of P, S and D. Here, P is the probability this failure mode will occur. Values for this index generally range from 1-10. Here, one is virtually no chance and 10 is a near certainty of occurring. S is the severity of the effect of the failure. These values also, range from 1-10. A value of one means, the user will be unlikely to notice, whereas 10 means, that there is an imminent danger to the consumer. D is a measure of the effectiveness of the correct controls to identify the potential failure, prior to release to production. This index also, ranges from 1-10. A value of one means, that it will be detected, whereas a value of 10 means, it most likely will go undetected until it reaches the consumer. Very often, numbers are tied directly to the failure rate and parts per million, number of defects that result based on a normal behavior. Failure modes with the highest RPN need action. Each organization has guidelines on the thresholds required for safety improvement, quality improvement and continuous improvement. When an RPN triggers action, the team will detail actions to be taken to reduce the risk. The failure mode is then reassessed, with the additional action in mind, with a revised RPN, once the corrective action has been completed. Risk assessment is the combination of the severity of failure and the probability of failure. Severity ranges from loss of life or bodily harm to a nuisance issue. Organization should define severity and risk within the context and exposure of their products on the consumer. Organizations should also, set expectations for likelihood of occurrence based on severity. For example, we would never consider a catastrophic failure to occur frequently or even more often than not. If this were the outcome then, our design clearly is not ready for consumer consumption. Another consideration is, of course, the assumption that the consumer is using or making an effort to use the product responsibly and as it is intended to be used. We always have the option to add redundancy mechanisms to abate these risks. It is important to understand the distinction between failure mechanisms and modes. A failure mode is the symptom of the failure. For example, hearing metal grind when you apply the brakes on your car. This is not a failure but a mode or signal that failure is impending. Failure mechanisms are the reasons that cause the failure mode. For instance, for the brakes, the failure mechanism is the loss of pad thickness until the head of the screw is exposed and makes contact with the disk causing the sound we hear. Failure mechanisms cause failure modes. There are many different venues under which an FMEA can be used. Design FMEAs are performed on the product or service at the design level. Design FMEAs are used before products are released, so that all design deficiencies can be detected and corrected. Process FMEAs are performed on the manufacturing processes. They are conducted during the quality planning phase. System FMEAs, comprise part level FMEAs. All part level FMEAs, will combine to form the system. As we move further into the system, the level of detail becomes more extensive and detailed, leading to more failure modes. Our stopping point is mandated by the value to the organization. Functional FMEAs are also, known as Black Box FMEAs. This type of FMEA focuses on the performance of the intended part or device, rather than on the specific characteristics of the individual parts.
