First Article Inspection
We are probably 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.)
I don't think it is good practice to use the term "first piece" in written correspondence - typically it is verbal shorthand for "First Article."
Also see this definitive thread: What does 1st piece (1st Article) mean to a lay person like myself?
Also see this discussion thread: First Article - Definition Discussion