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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
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
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


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