What is PFMEA?

 Process Failure Mode Effects Analysis (PFMEA) is used by manufacturers to detect potential failures that are rooted in the physical process of producing a part. 

Each step of the process is carefully analyzed to identify every possible thing that could go wrong. PFMEA follows a similar process as DFMEA, but looks at failures derived strictly from the process as opposed to design. Planning for mishaps that could occur in the manufacturing process allows preparedness for all scenarios.  PFMEA allows manufacturers to build in process safeguards to offset potential failures from occurring.

A PFMEA should be conducted when any of the following occur:

• Modification to an existing process
• Introduction of new technology, equipment, or process steps to production
• Relocation of a process to a new facility

The primary objective of PFMEA is to identify potential failures associated with the manufacturing process such as human error, equipment malfunctions, and production bottlenecks. PFMEA helps identify the sources of failure and its impact on dependent variables through the manufacturing process.

A Process Failure Mode Effects Analysis (PFMEA) is a structured analytical tool used by an organization, business unit or cross-functional team to identify and evaluate the potential failures of a process. PFMEA helps to establish the impact of the failure and identify and prioritize the action items with the goal of alleviating risk. It is a living document that should be initiated prior to process of production and maintained through the lifecycle of the product.

PFMEA evaluates each process step and assigns a score on a scale of 1 to 10 for the following variables:

• Severity — It assesses the impact of the failure mode (the error in the process), with one representing the least safety concern and 10 representing the most dangerous safety concern. In most cases, processes with severity scores exceeding eight may require a fault tree analysis, which estimates the probability of the failure mode by breaking it down into further sub-elements.
• Occurrence — It assesses the chance of a failure happening, with one representing the lowest occurrence and 10 representing the highest occurrence. For example, a score of one may be assigned to a failure that happens once in every five years, while a score of 10 may be assigned to a failure that occurs more frequently, such as once per hour or once per minute.
• Detection — It assesses the chance of a failure being detected, with one representing the highest chance of detection and 10 representing the lowest chance of detection.
• Risk priority number (RPN) = severity X occurrence X detection. By rule of thumb, any RPN value exceeding 80 requires a corrective action. The corrective action ideally leads to a lower RPN number.

IF RPN Is less than 80 but Severity is more (>8) Action to be planned

10 Step PFMEA Process

1. Review the process

Identify the process and the comprised steps through a detailed diagram. Identify what each step is intended to accomplish.

2. Potential failure mode(s)

Identify potential failure(s) for each step of the process. 

3. Potential effects of failures(s)

If the identified failure(s) were to occur list the impact it would have on production capacity, the next sequential step, or the finished product. 

4. Potential causes of failure

Identity the process elements that could trigger potential failures.

5. Assign a severity ranking

Assign a severity ranking 1 (low risk) – 10 (dangerous) to each of the identified potential failures as a consequence of it actually occurring.

6. Assign an occurrence ranking

Assign an occurrence ranking from 1 (least likely) – 10 (extremely likely) to each failure based on the likelihood it will fail.

7. Assign a detection ranking

Assign detection rankings based easiness of detection before failure happens. (1 easy detection – 10 extremely difficult to detect) 

8. Calculate the RPN (risk priority number)

S x O x D=RPN 1 (low) – 1000 (high risk). Make a determination if the calculated number is acceptable for the failure being analyzed.

9. Develop an action plan

Detail process controls and detection methods to decrease the RPN and implement them into the process. 

10. Recalculate the RPN

Once failure control methods are in place, recalculate the RPN to measure any improvements.