HNC CAD: 2D CAD Concepts -

The near "infinite" drawing space!

    If you are used to producing scaled drawings using traditional drafting instruments and standard sheets of paper, the concept of having a limitless drawing area, takes a while to get your mind around. Drawing by hand requires that you work out drawing scales and paper positions before you start to build up your drawing. No need to do that with CAD drawings. Layouts can be more visual and the final presentation can be decided upon just before sending a copy of the detail to a printer.

    Drawings built up on computer, rather than on paper, allow actual sizes to be used whether they are in mm, kilometres, miles or light years!

    • The designer is not limited to the size of a physical piece of paper.
    • Drawings are not limited to 2 Dimensional views or plans but can be 3 Dimensional Models (we will only use 2 Dimensions in this unit and leave the other dimension to a later unit).

    The computer screen used to display drawing details>, is simply a window through which you view the world of your drawing or model. The space you have available to you is, as far as you are concerned, of infinite size.
    You can draw anything you want to, as big as you like or as small as you like. You could for example draw the details of a new nano-technology chip ( getting down to molecule levels) or you could draw the details of the solar system, using actual full size measurements.
    Your screen is basically a viewing box that can act as a powerful microscope or a powerful telescope and bring anything you draw into full view so that you can work on it.
    The following chart gives some idea of sizes or distances that you may be happy with and others that we appear to be around us in our natural environment, with some dimensions that seem difficult to take in.

ObjectDistance in mmStandard Form
Width of an atom0.000000001mm1x10-9mm
Thickness of a human hair0.1mm1x10-1mm
Width of a keyboard key10mm1x101mm
Width of a small computer screen400mm4x102mm
Length of an average family car5,000mm5x103mm
Width of Pembrokeshire College grounds300,000mm3x105mm
From Haverfordwest to Cardiff150,000,000mm1.5x108mm
To the Moon400,000,000,000mm4x1011mm
To the Sun150,000,000,000,000mm1.5x1013mm
To the Nearest Star  40,000,000,000,000,000,000mm4x1019mm
To the Andromeda Galaxy20,000,000,000,000,000,000,000mm2x1022mm
To the Most Distant known Galaxy20,000,000,000,000,000,000,000,000mm2x1025mm
    A CAD system is typically able to handle sizes of 10-40 to 1040. An incredible size range.

    You are able to draw any imaginable object using full size dimensions and use your computer screen to change your viewing position to see a smaller portion (zoom in) or the whole thing (zoom out). Your screen is simply a window on your world.

    How much detail you can realisticly place in your model of objects in the world is dependent upon the storage cpacity and processing power of our computer.

Where to start drawing

    There are many ideas as to how to start setting up a CAD screen to draw a particular object.
    There are a number of ways in which it can be achieved
    • You can just select the type of object you want to place on your drawing, click somewhere on the screen and enter the size of the object. As the program has no prior information as to the size of the object, it is likely that the object will be either too small to see correctly, or too large to fit on the screen.
      This is no problem as a command can be given to re-arrange the viewing parameters so that the object can completely fill the screen so that it can all be seen at the maximum maginification.
    • You could set up a basic screen size using set up profile.
    • You could use a preset drawing page which includes border, title block etc.
    • There is no correct method, just you or your companies prefered way.