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Computer Aided Drafting and Design


    CADD stands for Computer Aided Drafting and Design.  By using the
computer for the functions normally utilized by hand, a greater amount of
efficiency can be attained.  By drawing lines with a computer on a screen,
corrections can be made without erasing the entire product.  CADD is a lot
like a word processor, letting people draw whatever they choose, print it,
and if corrections are needed, only a small amount of time is needed to
correct it.  CADD has the speed of a technical sketch in the accuracy of a
normal drawing.

    CADD programs can utilize different methods in the way they draw their
pictures.  Some use co-ordinates, which is the standard method, and some
might use inches or centimetres.  The standard method of co-ordinates gives
a product which is compatible with other systems.  One co-ordinate point
might represent 1/10 of a millimetre in actual space.  Then 1 millimetre is
10 co-ordinate points.

    CADD systems were developed along with the computer.  They were
developed very slowly.  They went from being very large, clumsy, elaborate
machines which needed lots of human intervention to one program on a floppy
disk. When the power of computers increased, so did the possibilities of
CADD.

    Images on CADD systems are drawn with the aid of a keyboard, mouse, or
tracking ball.  One selects the starting point of a line, the ending point,
and the line is drawn.  A scale at the bottom of the screen tells how long
the line will be.  On some CADD systems, the computer itself can measure
how long the line will  be while the operator inputs the length of the line.
 Lines are the basis of all drawings.  Straight lines are fairly simple and
quick to make, but what about curved or wavy lines?  That's what different
CADD commands are made for.

    Different CADD commands make different things on the screen possible.
There are commands for dimensioning, labelling, making circles, boxes, etc.
Some generic commands and their functions are:

XYZ up- This allows the operator to rotate, tip, flip, and move the object
by degrees.  Top, front, and rear views are used.  Drawing below:

MOVE- Move means moving the object.  Move can be used left, right, up, down,
forwards, and backwards.  MOVE must be specified by how many units (co-
ordinates) the object must be moved and in what direction.

SCALE- Makes the object smaller or larger, and by what scale.  Eg: reduce
by 50, increase by 50, etc.

LINES- This is the generic drawing command for lines.  A start point and
end point must be indicated.

COLORS- What color the lines or object must be.  The foreground and
backround (in 3-D CADD) can also be specified.

ERASE- Erase line, object, all, or just a part of the screen, which is
specified similar to move.

PLAN VIEW- This command will usuallt draw the 3 views plus a 3-d view of
the object.

ZOOM- Zooms in on the object.

CIRCLE, ARC- Draws the chosen image.

SPLINE- Draws a "wavy" line as like below.

TEXT- Writes text.

COPY- Copies the object, line, etc.

MIRROR COPY- Copies the object in a mirror image.

Some commands, like the ones listed below, might not be availible on all
CADD progarms.  They do specific tasks.  Some are:

Hidden line and Surface Removal- Removes hidden lines and surfaces,
automatically or by the discretion of the operator.

3 Point Perspective Display- Displays the object in the 3-point perspective,
as in technical sketching.

Object and Group Designations- This is usually independent.  This
identifies individual objects on the screen, like a box within a box.

Move Vertex- Molds and re-shapes objects.

    CADD comes in many forms.  3-D CADD uses lines in a 3 Dimensional form.
This is useful in drawing complex buildings and spheres.

    CADD output comes in many forms also.  Images may be produced by
printer, which is less accurate, and by plotter, which draws all lines and
curves by a small pen.  This is the most accurate form of CADD reproduction
and output.

    CADD is widely used in industry.  It is slowly replacing all hand
methods, since it is fast and simple.  A drawing that might take 10 days to
make could now take 10 minutes on computer.  The future of CADD depends of
the demand of the functions for the different programs.  CADD in schools is
being taught also.

    As you can see, CADD is slowly becoming the most widely used system of
industry in the world.  Its functions make design fast and easy, and
without many errors.  Next time you need to finish that drafting project
and have only a few days left- use CADD- it might surprise you.

    (All commands taken and tested on Generic CADD Level One, Draft Choice
US Version, Daft Choice Canada, NorthCAD, and NorthCAD 8:3-D.)