Page 239 - The Art of Designing Embedded Systems

226 THE ART OF DESIGNING EMBEDDED SYSTEMS

Storage-Obsoleted Drawings
Every Master drawing that is obsoleted will be removed from the cur-
rent Master file and moved to an Obsolete file. Obsoleted drawings will be
filed numerically by drawing number. Where a drawing has been obsoleted
more than once, each old version will be substored by version letter.
The Master will be stamped with a red OBSOLETE stamp. Enter the
date the drawing is canceled next to the stamp. Thus, every Obsolete draw-
ing will have two red stamps: MASTER (with the original release date)
and OBSOLETE (with the cancellation date).
If old ECOs are associated with the Obsoleted drawing, be sure they
remain attached to it when it is moved to the Obsolete file.
Obsoleted artwork and films will be immediately destroyed.
Sometimes one makes a small modification to a Master drawing to
incorporate an ECO-say, if a hand-drawn PC board assembly drawing
changes slightly. In this case duplicate the Master before making the change,
stamp the duplicate OBSOLETE, and file the duplicate.
The reason for saving old drawings is to preserve historical informa-
tion that might be needed to update/fix an old unit.

Master Drawing Book
Whenever a drawing is released or updated, the Master Drawing Book
will be modified by the releasing engineer to reflect the new information.
The Master Drawing Book is a looseleaf binder stored and kept with
the Master drawing file. The Master Drawing Book lists every drawing we
have by number and its current revision level. In addition, if one or more
ECOs is current against a drawing, it will be listed along with a brief one-
line description of what the ECO is for.
Just as important, the Master Drawing Book lists the name of the
electronic version of a drawing. This name is always the name of the file(s)
on the network drive, with the associated directory path listed.
Note that the “Dash Number” (described later under “Bills of Mate-
rials”) is not included in the list, since one drawing might have many dash
numbers.
Thus, the drawing list looks like:

Dwg # Revision Rev date Title Filename
#lo00 A 8- 1-97 Prod A BOM PRODA-ASSY
ECO: PRODA.A.3 Stabilize clock PROD AECO . A
ECO: PR0DA.A. 1 Secure cables PRODAEC0.A
#loo1 B 8-2-97 Prod A Baseplate PRODA-BASE