Reliability HotWire

Reliability HotWire

Issue 138, August 2012

Hot Topics

Practice Auditing an Actual FMEA

In last month's HotWire article, we discussed the objectives and quality characteristics of effective FMEAs, and the procedure to audit FMEAs using the quality objectives. In this article, an actual FMEA will be evaluated using the FMEA audit procedure.

The following practice audit is an excerpt from the book Effective FMEAs (John Wiley & Sons, © 2012, all rights reserved) and its associated Solutions Manual. Readers are encouraged to study the FMEA in Figure 1 “Excerpt from Hand Brake Subsystem Design FMEA” and attempt to perform the FMEA audit in each of the 10 exercises, before reading the corresponding teaching analysis. The FMEA audit is based on the FMEA Quality Objectives discussed in the July 2012 (#137) issue of HotWire.

Evaluating the Quality of the Bicycle Hand Brake Case Study

Figure 1 is a Design FMEA on a Bicycle Hand Brake Subsystem. It has been selectively modified with errors for evaluation of the 10 FMEA Quality Objectives. The FMEA team is made up of a bicycle design engineer and a bicycle test engineer, in support of a new all-terrain bicycle due to be launched soon. The FMEA was completed 4 weeks after design freeze, after testing had begun. The FMEA team prepared for the FMEA project by studying drawings and sketches for the hand brake subsystem. When the FMEA was completed, the bicycle test engineer thought the result was value added; however, the bicycle design engineer thought the analysis was a waste of time. For each of the 10 exercises, note how well the quality objective was achieved in the FMEA and why.

Figure 1: Excerpt from Hand Brake Subsystem Design FMEA.

Exercise #1

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #1: The FMEA drives product design or process improvements as the primary objective. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, there should be a number of effective design improvement actions in the Recommended Actions column. This FMEA has no design improvement actions and does not meet objective #1.

Exercise #2

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #2: The FMEA addresses all high - risk failure modes with effective and executable action plans. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, every failure effect with high severity (9 or 10) and every failure cause with high RPN (based on FMEA team determination or company mandate) must be addressed with one or more effective actions in the Recommended Actions column. The team or reviewer should ask themselves if the recommendations will reduce the risk identified by high severity or high RPN to an acceptable level. This FMEA does not achieve this objective because the recommended actions only address detection risk and not severity or occurrence risk. For each of the high severity or high RPN line items, there need to be actions (as many as needed) that first attempt to reduce severity (if possible) and reduce occurrence to a very low rating, in addition to reducing detection ratings.

Exercise #3

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #3: The Design Verification Plan (DVP) or the Process Control Plan (PCP) considers the failure modes from the FMEA. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, there needs to be effective actions in the recommended actions column to improve the detection controls for any line item with detection risk identified. Typically this means where the detection rating is not low, and either the severity or RPN is high. This FMEA has good actions in the recommended actions column for each line item where detection risk exists.

Exercise #4

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #4: The FMEA scope includes integration and interface failure modes in both block diagram and analysis. Make note of how well this objective was achieved. Explain.

Teaching Analysis

Since the scope of this FMEA is at the subsystem level, to achieve this quality objective the component interfaces should be included in the Functions column and potential failure modes for these interfaces should be identified and analyzed. The interfaces and integration of the handbrake subsystem with the various other subsystems should be included in the System FMEA. The interaction of the brake lever, brake cable, brake pad, and brake caliper is not well described in the Functions column of this FMEA, and the one failure mode that attempts to deal with interfaces (the last failure mode in the FMEA) is not analyzed.

Exercise #5

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #5: The FMEA considers all major “lessons learned” (such as high warranty and campaigns) as input to failure mode identification. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, all of the field failures for similar bicycle systems should be reviewed to ensure that there is no repeat of such failures within the scope of this FMEA. There is no indication in the problem introduction that this has taken place, and there is no indication in the body of the FMEA that “seen” failure modes have been included. Anyone reviewing this FMEA would have to satisfy themselves that all applicable field failures have been reviewed and will not reoccur.

Exercise #6

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #6: The FMEA provides the correct level of detail in order to get to root causes and effective actions. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, the level of detail must be adequate to clearly identify risk, arrive at root causes, and clearly describe the line item being analyzed. This FMEA does a reasonably good job in level of detail: not too wordy and not missing clarity. Recall from the procedure chapter that each column in the FMEA needs to have the amount of detail necessary to arrive at the next column, as well as providing enough clarity so that someone who was not involved in the FMEA should be able to understand the concept that is being described.

Exercise #7

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #7: The FMEA is completed during the “window of opportunity” from where it can most effectively impact the product or process design. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, the FMEA should begin shortly after the design concept has been identified and finished before design freeze. This FMEA was done late and does not meet this quality objective.

Exercise #8

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #8: The right people are adequately trained in the procedure and participate on the FMEA team throughout the analysis. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, the Design FMEA team needs to be comprised of the right cross - functional team. In this case, there should minimally be representation from bicycle system engineering, hand brake design engineering, test engineering, manufacturing, quality or reliability, and field service. Since the FMEA team was made up of a design and test engineer, this quality objective was not met.

Exercise #9

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #9: The FMEA document is completely filled out “by the book,” including “Action Taken” and final risk assessment. Make note of how well this objective was achieved. Explain.

Teaching Analysis

To achieve this quality objective, each of the columns of the FMEA needs to be procedurally accurate, technically correct, and all columns filled out. In addition to the issues identified above, the columns to the right of Recommended Actions are missing and therefore this quality objective is not met.

Exercise #10

Review Figure 1 to assess how well it achieves the FMEA Quality Objective #10: The time spent by the FMEA team is an effective and efficient use of time with a value - added result. Make note of how this objective can be evaluated.

Teaching Analysis

To achieve this quality objective, all members of the FMEA team should agree that their time was well spent to a value - added result. This FMEA did not have a properly constituted FMEA team. Of the two members who performed the analysis, only one thought the result was value added. Future FMEAs will be poorly represented and attended unless proper teams are established and facilitated.

As an additional note, evaluation of an FMEA for achieving the quality objectives by looking at the FMEA worksheet alone can only partially provide accurate evaluation. The best way to assess how well an FMEA meets quality objectives is to review both the FMEA worksheet and interview the FMEA team.

If you have questions or comments about this article, about the subject of FMEAs, or about the book Effective FMEAs, please send an email to the author at Carl.Carlson@EffectiveFMEAs.com.

About the Author

Carl S. Carlson is a consultant and instructor in the areas of FMEA, reliability program planning and other reliability engineering disciplines. He has 30 years of experience in reliability testing, engineering, and management positions, and is currently supporting clients of ReliaSoft Corporation with reliability and FMEA training and consulting. His new book, Effective FMEAs, is available on Amazon.com. Information about the book and links to useful FMEA articles and aids can be found at www.EffectiveFMEAs.com.