I have a doubt related to the Process control plan /
PFMEA: --- Normally, the process control plan /
PFMEA covers the entire production process from material come in to different processing steps to packing and transportation. However, shall we include supporting activities like m/c and tooling maintenance, equipment calibration, product audit, ... ?
I think this brings up interesting philosophical questions:
1) How do we define the 'edges' of a process? (i.e., everything circumscribed by those edges is within the process, everything else is outside of it)
2) How do we control risks that are defined to be 'outside' the process, and so do not even show up on the PFMEA or control plan, yet could certainly affect the product output?
With regard to #1, its easy to see that a slippery slope develops if we start to expand the edges of the process to include elements such as support items like calibration or maintenance, and pretty quickly it could end up where the 'production process' now includes everything from supply chain ordering to customer delivery.
So, if we do not include all the rest of that 'stuff' in the production process, we cannot simply dismiss it as being without risk.
If, say, room temperature is critical to a production process, then it can be monitored with calibrated temperature sensors. But how do we know those sensors are in spec? If we calibrate them once per year and a year goes by before finding they are out of spec, that could be a lot of product that might be bad. So, we calibrate them more frequently, maybe monthly. Similarly, HVAC maintenance might be adjusted to be more frequent to keep temps in spec. Etc.
The point is that having a separate calibration process, separate maintenance process, etc. obscures (or breaks) the risk interrelationship between these support processes and the production process with its detailed-but-selective risk controls in its PFMEA and control plan.
Of course, I'm not advocating getting rid of a separate calibration process, separate maintenance process, separate training process, etc. But perhaps we could imagine outside of the edges of the core production process that there is a second set of edges (visually, think Venn diagram with core production process as a subset inside a larger set). That surrounding area within the larger edges could be where the support processes are, and where a second PFMEA and control plan could apply. This keeps the risks of the support processes in the context of the production of this specific product. And this could be iterated to a third outer ring, which might be supply chain risks in the context of the production of this specific product.
Just musing...