Arguments for Significant Part Numbers
Two reasons for using significant part numbers go back to the
beginning of "management information systems." Thirty
years ago, a big computer installation had memory measured in
"K" rather than "M," and it wasn't uncommon
for there to be one or two display terminals (for that was what
they were—cards were used for input, not keyboards) for several
hundred people to share. Not only was there a minimal amount of
information on the computer system in the first place, but access
to that information was very restricted. Additionally, it was very
important that those slow, ponderous mainframes not experience any
problems in their calculations. Error detection and recovery
couldn't be readily programmed into the machine's algorithms, so
the system was made more robust by artificial constraints that
would allow bad data to be easily rejected at the front end. These
constraints led to two uses for part number significance:
first, to replace a needed description field or to allow
access to the description without requiring access to a display
terminal; and secondly, to avoid working on a "bad" part
The first required a part number that actually
conveyed information. In many cases, the part number prefix
revealed the type of part—whether bushing, spring, resistor,
capacitor, etc. That way, the person confronted with that part
number at least knew what list to consult to discover what the
part number represented. That was faster than waiting in line to
use a CRT. The second use required that the part number have a
certain form to be accepted by the computer at all. For example,
it may have required that the part number have three numbers,
followed by a dash, followed by six numbers. This second use led
to additional significance over time, as more plants came on line
in large corporations. At one facility with which I was familiar
in the early 80s, we were allowed four prefixes for our part
numbers—to make sure that they were kept separate from the part
numbers used by other parts of the corporation.
There is little if any reason to consider these
reasons any more. Most organizations now have a CRT that can
access MRP information for every two or three employees—some
have more than one per employee. It's quicker to look the part
number up on the item master when there's a question—and
besides, a description field is almost always displayed alongside
the part number on most screens. More capable software and
distributed computing has effectively removed the second use for
significance as well.
There are still other arguments for
significance. Many of them are based on "what if scenarios:
• What if the system goes down, and I need
to know the description of a part?
• What if I'm out on the road, and I need
to repair a product, or replace a part, and don't know its
• What if I need to order the part, and the
system goes down, and I don't know what to tell the supplier?
• What if I want to have my automated
assembly equipment check to make sure I have the correct part
before putting it on my product?
• What if production is a harsh or
"clean" environment (therefore has little access to
the system), and I need to make sure that we're using the
• What if I want to organize my stockroom
by part type (all the resistors in one set of shelves, all the
hardware in another)?
All of these are perfectly valid reasons for a significant part
numbering scheme, but they can also be accomplished by other
means. The other means are: a properly organized and printed part
number listing, relational databases, and commodity coding. We'll
discuss those briefly after examining some of the arguments for
using nonsignificant part numbers.
To be Continued
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