Please, can you help me understand what you mean by "first piece"?
It seems obvious from the context of the posts so far that we are not talking about "First Article Inspection" which in my experience means checking EVERY dimension and attribute of a part made on the exact production machinery which will be used to continue producing the part. Technically, the First Article is usually
not the very first piece, but, in fact, the first piece once the machinery is tweaked, but before actual production is authorized.
In a Control Plan, in my further experience, producers generally include the following steps:
- First Article Inspection (often redundantly approved by a customer before production can begin if it is a custom part. FAI may be performed under laboratory conditions. The First Article is almost always tagged and reserved for future reference.)
- an inspection plan to take consecutive samples of the production run at predetermined intervals. (in process) These samples are often only inspected for critical characteristics. Almost always, these inspections are performed by the operators at the machine or by inspectors coming to the machine. (Critical characteristics may be crucial fit or function ones or they may be "process critical" ones which flag when a tool may need to be changed because of wear.)
- a plan to use the readings from the inspections in statistical analysis (SPC, Cpk, etc.)
In ten years in a high tech machining environment, I never heard the term "first piece" except as shorthand for First Article Inspection.