A Sticky Problem !
At a large Defence Contractors in
the 60s, in keeping with most others, all manufactured equipments
were called assemblies and those assemblies contained more assemblies
and these contained sub-assemblies and so on. The subject of
this story is a printed circuit board. It was probably used in
a complex electronic assembly for unscrambling digital data.
When a printed circuit board is designed, one of the collection
of documents, in which all the individual components are identified,
is an "Items List" which carries a table noting (for
each component) a brief description, the manufacturing reference
number and a quantity. This particular circuit board had to be
"conformally coated" to protect it from damage, say
from being in a ship near to corrosive seawater.
The designer duly looked up the code
for the conformal coating material and entered it on the items
list. Some time after being checked and "computerised"
in an all-knowing system, carrying all the codes and sources
of supply for everything, a quantity of the circuit board was
eventually included in an order from a Government Agency.
The Purchasing Department, as a matter
of routine, entered the details of the contract, and purchase
orders for the complete breakdown of the thousands of components
required to build the equipments were duly generated by the manufacturing
computer system.
Over a period of time lots of postmen,
parcelforce vans, supplier's delivery vans and lorries arrived
at the factory gate. The biggest lorry delivered the conformal
coating. Why? It turned out that the code used by the draughtsman
was for a gallon drum of the stuff when all that was needed was
a dip of a paintbrush and a quick wipe. As there were 1000 printed
circuit boards ordered, the computer had calculated that 1000
gallon drums were needed!
This affair was hushed up and nobody found out about the mistake.
That is until many years later when the drums on the bottom of
the heap rusted through and conformal coating leaked across the
garage floor (the garage was where the drums had been hidden
away and was located under the factory). A message went round
the factory "does anyone want any stuff for painting their
garden shed/fence". "If you do, take a carrier bag
with you and meet in the garage after 6 o'clock".
It turned out that in the past when Items Lists were broken down
manually everyone knew about conformal coating and all we ever
needed was a pint or two. How was the computer supposed to know
this?
