Meaning
Systematic identification of potential errors within a manufacturing sequence allows engineers to rank the likelihood and impact of failures to prioritize corrective actions and safety guards. The discipline of process failure mode effects analysis evaluates every step of a production line to determine what could go wrong and how it would affect the final customer. It governs the design of quality checks and the implementation of error-proofing devices, stopping at the point where a part leaves the factory or is transformed into a different assembly.
Quality managers use this tool to focus their resources on the most dangerous or frequent failure points. This ensures that the manufacturing process is built with multiple layers of protection against common mistakes.
Risk Assessment
Calculation of the risk priority number involves multiplying the severity of a failure by its frequency and the difficulty of detecting it. When process failure mode effects analysis is conducted, the team assigns a score to each potential problem based on historical data and expert judgment. If a failure could lead to a safety hazard, its severity score is set to the maximum level.
Conversely, a minor cosmetic defect that is easily caught by the operator receives a much lower score. The assessment must be updated whenever the process changes or a new failure is discovered in the field. This ranking allows the engineering team to focus on the top ten percent of risks that cause ninety percent of the problems.
Accurate assessment prevents the waste of money on safety features for events that are almost impossible to happen.
Prevention Strategy
Implementation of physical blocks or electronic sensors stops the identified failures from occurring in the first place. In the framework of process failure mode effects analysis, the most effective strategy is to change the design of the part or the tool so that the error is impossible to make. If a part can be installed backwards, a pin is added to the fixture so that it only fits in the correct orientation.
Conversely, if the error cannot be prevented, a sensor is installed to stop the machine immediately when it happens. The strategy must be verified through testing to ensure that the new guard does not introduce a different type of failure. Good prevention reduces the need for manual inspection and lowers the overall cost of scrap.
Protecting the process at the source is the most reliable way to maintain a high yield.
Severity Ranking
Evaluation of the consequence of a failure determines how much effort should be spent on preventing it. Under process failure mode effects analysis, the highest rankings are reserved for failures that cause a total loss of function or a breach of environmental regulations. If a failure results in a minor inconvenience that the customer can fix themselves, the ranking is low.
Conversely, a failure that results in a product recall or a lawsuit requires immediate and extensive engineering changes. The ranking must be consistent across the entire organization to ensure that risks are compared fairly between different products. Management uses these rankings to decide which projects receive funding for quality improvements.
A clear understanding of severity ensures that the company protects its customers from the most harmful defects. Proper ranking of these effects guides the long-term safety culture of the manufacturing site.
