CM Trends eZine
Part with Revs and Star Trek
By Steve Easterbrook, CMPIC LLC

This is a subject that gets people fired up. Should “rev” letters be on hardware part numbers? In evaluating part numbering schemes that include "revs" we need to determine why that "rev" letter is there.

(1) Is it just a random letter, not tied to a document (i.e. a dash number scheme). What would that indicate? That would just make the part number an alphanumeric identifier.

(2) Is rev letter so people know what drawing rev to use? What would that indicate? Could this cause some problems?

(3) Is it there to assure some degree of traceability to a drawing/spec... because there is no other way to know how you built something? What would that indicate? Is it good or bad?

(4) Was it the rev scheme in place when everyone started working and no one ever questioned why? What would that indicate? Is it okay or not okay?

(5) Is it for engineering use and not for manufacturing use? What would that indicate?

(6) Is the requirement for a rev letter on a part embedded into some CM tools purchased years ago and the programmer who may know why has since disappeared? What would that indicate? Is it good or bad?

(7) Is the rev letter marked on the part itself? If so, then what is marked on the part if for some reason the part was accepted with a variance (RDW) against it?

(8) What is the part "rev" if the drawing is at Rev A plus 3 approved changes? What if the drawing has not been updated, yet?

(9) If a drawing is changed from Rev A to Rev B because a view needs to be improved, does the part then have to go from Rev A to Rev B also? That would mean an "A" and a "B" part were identical. Is this good or bad?

So what would the answers to (1) - (9) above mean to you if you were advising a company?

Many say no revs on parts. The theory being that documents are revised (via rev letters, rev numbers, rev versions, etc.) and parts are reidentified (new numbers or identifiers). But it does depend on how the above questions are answered and the resources and mindset of the organization.

Ok, now tell me if this is bad: look at the Star Trek Enterprise hull part numbers below – each new production unit has the same base number but different rev (Source: Wikipedia). Are revs on these numbers ok?

USS Enterprise (NCC-1701)
The Federation's first Enterprise - original Star Trek series (1966–1969) and The Animated Series (1973–74), Star Trek: The Motion Picture (1979), and Star Trek II: The Wrath of Khan (1982) before being destroyed in Star Trek III: The Search for Spock (1984).

USS Enterprise (NCC-1701-A)
This ship first appears at the end of Star Trek IV: The Voyage Home (1986) and is the main setting of Star Trek V: The Final Frontier (1989) and Star Trek VI: The Undiscovered Country (1991). Decommissioned.

USS Enterprise (NCC-1701-B)
Service: 2293–2320s
Captain: John Harriman.
Launched at the start of Star Trek Generations (1994). James T. Kirk goes missing during the ship's maiden voyage.

USS Enterprise (NCC-1701-C)
Service: 2332 – 2344
Captain: Rachel Garrett.
This ship appears in the Next Generation episode "Yesterday's Enterprise" (1990). It was destroyed attempting to defend the Klingon outpost Narendra III from Romulan attack.

USS Enterprise (NCC-1701-D)
Service: 2363–2371
Captain: Jean-Luc Picard.
The main setting of Star Trek: The Next Generation (1987–1994). During Star Trek Generations, the Enterprise was lost in 2371 after an attack by a renegade Klingon Bird-of-Prey caused extensive damage, leading to a warp core breach ... the ship became unsalvageable.

USS Enterprise (NCC-1701-E)
Service: 2372 – Active (as of 2387)
Captain: Jean-Luc Picard.
The main setting for the films Star Trek: First Contact (1996), Star Trek: Insurrection (1998), and Star Trek Nemesis (2002).

USS Enterprise (NCC-1701-J)
Service: 26th Century
Captain(s): Unknown
The "Azati Prime" episode of Star Trek: Enterprise involves time travel and features a scene in which the Enterprise-J appears. The Enterprise-J operates in the 26th century.

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