Page 194 - Engineering drawing from first principles using AutoCAD

Chapter ~

Blocks and technical

diagrams

Layouts and diagrams are generally individually prepared special purpose drawings
presented in a neat and simple style. If the diagram shows a flow of events then details
are arranged so that the sequence, if possible, takes place from left to right or from top to
bottom. Notes, dimensions and other references are positioned to avoid ambiguity.
Remember that the user may not proficient in that particular branch of technology.
At the end of this chapter you will be able to make a block containing information which
can be used in your current drawing or stored for later use elsewhere. Examples of typical
diagrams are given for:

• Pipework and heating layouts.
• Electrical schematic line diagrams.
• Electrical wiring diagram for construction purposes.
• Floor layout diagram for a social event.
• Model Hi-Fi Midi sequencer connections.
A diagram shows the relationships between component parts in a scheme, and uses
symbols or items of clip art joined together in a logical sequence by lines. Generally,
the draughtsman is responsible for the positioning of the various parts and tries to
produce a clear layout which is symmetrical and balanced, containing relevant notes
and information. As far as possible the linework should be open and not appear as a
maze. The CAD COPY, MOVE, and ROTATE features are superb in the respect that,
having drawn the main parts of a diagram on the screen you can then reposition them
as often as is necessary to improve the spacing.
There are symbols libraries for all branches of technology which are available on disc.
Many public libraries also contain copies of British and International Standards, and
symbols can be copied or scanned. Make a practice of keeping a file of those types you
regularly use. CAD programs use a method of making blocks where complete drawings
can be inserted in other drawings and treated as separated units within that drawing.
Examples of this follow.

Making blocks
There are two different types of applications for blocks available and an example of each
is given here.

1. A block can be written to disc as another drawing file to form part of your library of
standard components. This type of block is called a WBLOCI( or world block and gen-
erally saved in a separate directory. In this case the block can be inserted in any other
drawing.
2. Blocks can be made and used for repetition use in the same drawing and the following
village hall seating plan is a typical example.