The World of AutoCAD Drawings

About AutoCAD

AutoCAD is the undisputed leader of the computer-aided design (i.e., CAD) platforms: This highly evolved program is a product of Autodesk Inc, a US-based company started in 1982, and is the world's most-used application for creating digitized drawings with minute precision.

AutoCAD drawings are used at all stages of design and construction: Engineers and architects start by drawing simple visualizations of their final creation in AutoCAD just like an author first enters the outline of a book into a word processor.

You only have to enter changes: As the object evolves through changes, the AutoCAD drawing is changed accordingly, exactly like the earlier mentioned book would be changed in a word processor: when a change needs to be put in, only the change information has to be entered and not the drawing in its entirety. Lines in the object can be stretched or shortened in an instant, diameters of arcs and circles effortlessly altered. In the process, any dimensions that AutoCAD has drawn (in the metric system, imperial system or both) automatically change their values.

Basic AutoCAD commands: AutoCAD contains myriad tool buttons for drawing lines, circles, arcs, rectangles, 3D boxes, cones, cylinders, spheres and pyramids. These ‘primitives’ can be modified using commands for cutting, joining, extending, skewing, rotating, scaling and merging (this is not an exhaustive list).

2D and 3D AutoCAD Drawings

What 2D and 3D  drawings are: AutoCAD can be used to generate 2D drawings (such as plans or elevations) or 3D drawings (such as the angular view of a boiler system taken from a height of 6 feet and a distance of 10 feet.)

Conserving AutoCAD File Size

The need to conserve: It is in the user’s interest to minimize the size of an AutoCAD drawing file. Large files take longer to open, longer to save, and can slow down the speed at which AutoCAD draws. AutoCAD offers several strategies to the user for keeping file sizes to a minimum. The following are some of them:

XREFs

What an xref is: An AutoCAD drawing can contain drawing objects that are in another AutoCAD drawing file in the same disk folder (an “external file”). These objects are called external references (“xrefs”). The xref’s data is not created a second time in the file that pulls it in (the “working file”). The working file copies the data temporarily from the external file, and destroys the copied data when the working file is closed. This way the size of the working file does not increase when drawing objects in external files are used.

Blocks

What a block is: Another way in which drawing file size is conserved is by the use of “blocks”. If a drawing object appears repetitively in a drawing, instead of storing complete data for that object for every instance of its appearance, the data is stored only once (in a form known as a “block”).

The drafter gives each block a unique name. At every point that the object needs to appear in the drawing, the drafter just inserts this name instead of the actual object. AutoCAD simply refers to the data stored in the block and draws the object without storing the data one more time.

Automating AutoCAD with LISP

When automation is necessary: Very often the same sequence of drawing steps must be performed on various files. (An example would be to change the font in all the labels that appear in drawings).

For such a situation, the sequence of steps can be stored one time in AutoCAD and recalled every time it is needed. The sequence is written in a special language called LISP, which is unique to AutoCAD.

AutoCAD Drawing File Formats

Types of AutoCAD file formats: AutoCAD produces drawing files in several formats. The earliest one was the DXF format; then came the more compact DWG format. Once the Internet became an important communication medium, Autodesk developed a new format containing summary information, the DWF format, which could be quickly uploaded, downloaded or viewed on the Internet.

Autodesk also created a compact program for desktops to view, markup and print DWF files: AutoCAD Design Review, a wonderful software which Autodesk offers as a free download.