PFMEA’s Cost a Lot of Resources
In today's manufacturing environment, and especially in the automotive world of IATF 16949, there are expectations that risk prediction and mitigation tools will be used. One important method to accomplish this assessment is a process failure mode and effects analysis, or PFMEA, one of the most under-utilized and under-rated sources of information. It’s a time-consuming, complex process to understand each step/operation of the process and list what things can go wrong or fail. PFMEAs are a required document during the advanced product quality planning stage of any new product that is usually driven by those designing processes and sometimes by a quality engineer to assess the risk of a process. This occurs in coordination with cross-functional teams of individuals, including engineering, quality, production, materials, etc., to understand the quality risk of a new product.
Invariably, after all this work
assessing all the risks, defects
still get to the customer, a
corrective action is required,
and the PFMEA is required
to be updated with the new
occurrence and detection ratings
generating a high RPN
The way that it works is each failure mode (the thing that can go wrong) is reviewed for its severity (how bad would it be if it happened?), occurrence (how often do we think it will happen?), and detectability (if it happened would we catch it?). Each category receives a rating from 1-10, from best to worst, based on an industry standard. Then, each is multiplied against the other to determine a risk priority number or RPN designed to compare and prioritize all risks. Customers generally state that higher rated risk must have an action, but they and the IATF auditors are sometimes more interested in correct ratings than risk mitigation. This is especially true if the customer approves the part submission warrant or PSW indicating they are willing to accept the documented risk.
The Launch Team Does Not Always Get It Right
Invariably, after all this work assessing all the risks, defects still get to the customer, corrective action is required, and the PFMEA is required to be updated with the new occurrence and detection ratings generating a high RPN. Why is this? Although process design engineers try to understand each variable, adding error-proofing would be extremely expensive to prevent every failure or detection in each process step and operation. Let’s face it: excessive capital is not available to this magnitude unless a project includes product safety characteristics, which most likely will be addressed, and other run-of-the-mill characteristics will be left out of the error-proofing plan.
Customer Satisfaction Increases Over Time
So, in the scenario I described above, the best case is that your process design is such that product safety is covered, but you still have those nagging customer quality issues that cause dissatisfaction, leading to diminished customer quality scores that are less than desirable and at some point, the stakeholders want to know what to do about it. Customers will start making new part awarding decisions that are unfavorable to your company because of a lack of solid technical error-proofing, causing defects to be shipped. The last I checked, we don't live in a world of 'Less' but always one of 'More.
Use your PFMEA to Help Develop a Strategy
For a plant quality manager, this scenario causes a very common dilemma. Sorting out all the RPN numbers from most to least became a daunting task, as well as determining what and how the priority is. Again, capital dollars are not boundless, and the question becomes how I come up with a strategy that my leadership could understand when asking for capital. How do I take the known risk and turn it into a strategy that will decrease rejects and improve the customer metric, realizing that I could only get so much capital to work with? How do we ask for capital that will be used proportionately to gain the most reject reduction in the process and eventually to the customer?
A colleague and I quickly realized that what was missing from the RPN equation was the amount of defect reduction we could gain while being the most efficient with the amount of capital we could obtain. So, we created a scale from 1-5 that was based on the amount of money needed to correct an issue, with the least dollars being the highest value and the most dollars being the lowest value; we then multiplied each score against the RPN and sorted values.
‘This highlighted that failure modes with the highest risk or RPN and a lower cost to correct would be prioritized, giving us the best reduction for the lowest capital investment.’
We submitted our capital plan to the corporate leadership team, explained how we got there and the risk reduction, and even predicted our reduction in terms of rejection to the customer. Their confidence in us soared, and we received every dollar we requested. Not too long after our strategy was implemented, our plant won our largest customer Quality Award, which was the first in a multi-plant corporation.
