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Smith, Robert (ed.) / The Wisconsin engineer
Vol. 70, No. 6 (March 1966)

Petersen, James I.
The numerically controlled drafting machine,   pp. 28-33


Page 28


The Numerically Controlled
              Drafting Machine
                    By JAMES I. PETERSEN, CIE3
T    HE tec-s(uare, triangle, and
     scale, tools of the engineer
     and draftsman, have basi-
callv, remained inchllanged through
the centuries. So have the time con-
sumning an(l complex rituals of the
drafting process. I)evelopment of
the numerically controlled drafting
machine has changed this, placing
drafting amnong the accomplish-
ments of the computer age.
  This article is written to inform
interested engineers and draftsmen
ahout the numerically controlled
drafting machine, its characteris-
tics, method of operation, and uses.
A brief look at the numerical draft-
ing system  as a whole is made,
followed by a more detailed look
at the numerically controlled draft-
ing machine itself.
  Source reference numbers such
as "(3)", appearing in the report,
refer to sources itemized in the list
of references. The term "numerical
control" is abbreviated "N/C" for
convenience, since it is used
frequently.
COMPONENTS OF THE NUMERI-
  CALLY CONTROLLED DRAFT-
          ING SYSTEM
  The computer has brought many
changes to industry, taking an im-
portant part in production design,
manufacturing, production control,
and quality control. Recently it has
entered the process of drafting
through numerical control. That is,
a system which regulates the action
of one or more machines by auto-
matic interpretation of instructions
which are expressed in the form of
numerals. Interpretation refers to
the conversion from numerals to
distances, angles, and auxiliary
commands such as "drawing pen
up".
            Computer
  The mind and memory of the
N/C drafting system is the com-
puter. It is linked to the drafting
machine by N/C. Geometric
shapes, equations, and instructions
are fed into the computer as input.
Computer output is in the form of
magnetic tape, punched paper or
mylar tape, or punched cards
which contain all the information
necessary for making a drawing,
including auxiliary commands such
as "pen down".
   Numerical Control Director
   The director is the interpreter
between computer and N/C draft-
ing machine. It contains the neces-
sary electrical system and controls
to convert computer output into a
form which will direct the N/C
drafting machine. It has a readout
which gives the exact location of
the pen by coordinates.
  Using a photoelectric tape
reader, the director is able to ac-
cept and read computer punched
tapes up to the rate of 400
characters per minute. It may also
accept as input, punched cards,
magnetic tape, or information
from its manual keyboard. Its out-
put is in the form of electrical im-
pulses to the N/C drafting ma-
chine.
  Figure 1 pictures a director.
Note the coordinate readout at the
THE WISCONSIN ENGINEER
James Peterson is married and lives in
McFarland. His home town is Kenosha,
Wisconsin. Jim, a Junior in Civil Engineer-
ing (Structures), works part-time in the
engineering department of Oscar Mayer
Company here in Madison. He is a former
cheerleader for our Fightin' Badgers and
served one season as Bucky Badger at
football games.
I
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