We recently had a periodic re-assessment during which rework became a discussion topic and eventually an OFI.
Among our many other processes, we apply flexomeric coatings to fabricated-complex-shaped flexible polymeric foam materials so as to create multiple-use, practically cleanable patient positioners for medical imaging applications. The general first step in application of the coating is a spray process. This step often, but not always, results in pinholes, which are identified by visual inspection of each part after the first drying step. A subsequent step involves various microtechniques for pinhole patching using small quantities of the same coating. Visual inspection and patching continues until each part is determined to meet specs, i.e. no detectable pinholes.
We don't have the option of engineering out the creation of pinholes. That's been studied in the past. They're inherent to the materials and micromorphologies in question. We don't know of any other materials that would result in end products that would be as safe and effective.
Our work process is formally procedurized, but in a soft way. There isn't a quantification of how many pinholes is too many, or what percentage of total area can be patched, or any other characteristic other than that a part with unpatched pinholes does not meet specs but is eligible for further work, and a part with no remaining pinholes (and other quality characteristics, able to be consistently discriminated) does meet specs.
We've been doing this for approximately 32 years with hundreds of thousands of multiple-use devices sold, and essentially complete user satisfaction. The products are simple, relatively inexpensive and clinically safe and effective.
The involved auditor has asked us to define when the existing production process ends, and rework begins. His argument is that at some point, this patching or touchup process must be rework. He wants the existing procedure to be quantified to the extent possible.
Because of the subjective nature of the process and the vague meaning of rework in the context of such subjective processes, we haven't decided how to proceed. We take OFIs seriously, but we are leaning toward this one being too difficult to do in the way he would like.