Computer Aided Drafting (CAD)
Computer Aided Drafting (CAD)
Chapter 1 –The advantages.
Known as Computer Aided Drafting and also Computer Aided Design, CAD is fast becoming one of the primary means producing drawings across a wide range of industries.
CAD can be divided into two main areas, 2D and 3D.
In 2D CAD it is like drawing on a piece of digital paper inside the computer using digital commands and a mouse, rather than a pencil and a rule.
In 3D CAD you create a 3 dimensional model within the virtual space inside the computer. From this 3D model it is easy to create 2D drawing images.
Before CAD was developed, engineering drawings were drawn in a drawing office one at a time. This is an early image from 1923.
In this environment there were different levels of draftsmen.
- Designer/Draftsmen. These were the people who created the original drawings.
- Editing Draftsmen. These people made amendments to original drawings.
- Copy Draftsmen. These people just copied existing drawings so that they could be released for manufacturing.
- Checkers. These were people who checked what others had drawn to ensure that information was present and mistakes were not.
Drawings would take days or even weeks to complete and were prone to mistakes as engineers would attempt to make and then assembly the parts for the first time.
40 years later in 1963, little had changed, and little would change for another 20 years.
In the 1980’s when CAD was introduced, it was resisted by many of the older draftsmen.
With the development of CAD, more work is produced by less people in a smaller space.
Drawings are clearer, especially after changes have been made to it. Drawings and other data is stored digitally in a central location.
With CAD it is easier to work on multiple applications and from multiple references at the same time.
CAD data can easily be shared with CNC machines, known as CAD/CAM (Computer Aided Design/Computer Aided Manufacture). This decreases the time taken to manufacture parts as they are only drawn once. It also reduces the chances of mistakes being made in copying information from one application to another.
3D images can easily be stress analysed if necessary without the need to build a prototype, this is known as Finite Element Analysis (F.E.A.). This allows parts to be developed and tested, then modified if necessary and retested quickly and cheaply before manufacturing the actual part.
Advantages of using CAD
•Faster drawing. All drawing tools are available by using the mouse.
•More accurate. CAD can work to very small tolerances according to how it is set up.
•Easy to print drawings. Drawings can be quickly and cheaply printed and reprinted.
•Scaling. Drawings can be printed at any scale required, larger or smaller, thus making drawings easier to read.
•Easy to update/change parts. Unlike paper drawings, changes look neat and can be proved quickly.
•Drawings can be e-mailed. This allows a customer or supplier on the other side of the world to see the drawing almost immediately.
•Shared information. CAD parts can be linked to CNC machines reducing errors and saving time.
•Stress Analysis on screen. This allows parts to be developed and tested quickly and at very little cost.
•Reduced storage space. Paper drawings take up a lot of storage space. Many thousands of drawings can be stored on a computer or server hard drive.
•Unlike paper drawings, it is practical to have two or three back-up copies held at different sites, thus eliminating the risk of loosing all data in the event of a fire or flood.
•3D modelling allows you to view the part virtually. This allows the designer to check it from all angles and ensure that it is correct.
•Parts can be assembled and checked for fit before making. This ensures that all parts fit together as they should before they are made.
•3D models can be rendered to produce photo-realistic images. This allows anyone to see what a design will look like before it is made.
•When using a common part, such as a screw, CAD eliminates the need to draw the part over and over again, instead it is inserted from a catalogue of available pre-drawn parts.
CAD – Chapter 1 - Paul Mulder
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