You will learn to use basic functions to draw lines or circles, enter text, etc. A brief exercise walks you through the use of these functions. You will also learn how to measure distances and how to locate exact points. This chapter illustrates how to use coordinate methods, such as absolute coordinates, relative coordinates and polar coordinates to measure distances.

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In addition, this chapter highlights important principles in setting up CADD drafting standards. It demonstrates how to set up a prototype CADD drawing for a quick start.
Finally, this chapter shows you how to save drawings and where to store them. In this section, you will learn about data saving functions and safety measures to prevent data loss.

CADD’s drawing functions are used to create each component of a drawing. Fig. 2.1 illustrates the basic drawing components of CADD. As shown, there are many different kinds of lines, arcs, circles, ellipses, symbols, text, dimensions pointers, polylines, borders and patterns. You can complete most of the drawings by using these components of CADD.

To draw any component of the drawing, you need to access a particular function from the Draw menu. There are separate functions to draw text, dimensions, patterns, symbols, and other elements of a drawing. To draw a symbol, such as an octagon, you don't need to draw each side one by one. The Symbol function allows you to instantly insert a symbol into the drawing. Similarly, when you need to draw hatch patterns, borders, or arrows, separate CADD functions enable you to do that.

Drawing a component is quite straightforward. When you enter a command, the corresponding menu displays a prompt that guides you through steps to take. To complete a task, you will need to enter data using the keyboard, make selections from sub-menus, and enter points with the help of a pointing device to indicate where you want to position a drawing component.

The coordinate system is available when a function requires data input in the form of point locations. You may use it while drawing, editing or any time you need to locate a point. The most common coordinate systems are as follows:
 

Note:

The method of entering coordinates varies from one program to another. For example, in AutoCAD, the coordinates can be entered directly in the command window with the keyboard. In MicroStation and Cadkey, special dialog boxes let you enter the coordinates.
 

The positive X values are measured to the right and the positive Y values are measured above the origin point. The negative X and Y values are measured to the left and below. To enter a coordinate, you need to enter both the X and Y values separated by a comma (X, Y).

Example: To locate a point two units to the right and one unit above the origin point, enter X = 2, Y = 1 or (2,1). Similarly, to locate a point two units to the left and one unit below, you need to enter X = -2, Y = -1 or (-2, -1). You can use fractions as needed to enter the exact coordinate values.
 

The Format to Enter Coordinates

Cartesian or polar coordinate values can be entered in two formats:
 

Absolute format is a way of measuring distances from a fixed reference location (origin point), which is the 0,0 location of the coordinate system. Consider this point to be stationary at all times. In some CADD programs this point remains visible at the left bottom corner of the drawing area, while in others it is invisible. You can use this point as a reference to measure any distance in the drawing. Absolute coordinates are primarily used to adjust the alignment of diagrams in a drawing, to align one drawing with another or to make plotting adjustments.

Relative format is a way of measuring distances from the last point entered. All measurements are taken the same way as the absolute coordinates, with the only difference being that the relative coordinates are measured from the last point entered instead of the origin point. When a point is entered, it becomes the reference for entering the next point and so on. This mode of measurement is frequently used for drawing because it is always convenient to place the drawing components relative to each other rather than a fixed reference point.

Note:

Each CADD program uses its own annotations to enter absolute or relative coordinates. The task table located at the end of the chapter shows some examples from leading CADD programs.

When you install a CADD program, it does not have any of the defaults set as per your requirements. You can create a prototype drawing and specify all the defaults that you would like to use. This prototype drawing acts as a template that can be used for all future projects.

When you start a new drawing, you can specify the name of the prototype drawing and all the defaults are taken from this file. This gives you a drawing of a specified size, with border type and all the other defaults set in the prototype drawing. When you start working with CADD, it is better to follow a prototype drawing. It saves a significant amount of time in starting a drawing, because CADD sets everything for you. You are ready to draw instantly.

Most programs allow you to create more than one prototype drawing and save them under different filenames. This is particularly helpful when you are working on several projects that require different drawing standards. Whenever you need to use a specific standard, you can specify the name of that prototype drawing and those defaults are activated.

Refer to CADD PRIMER for further details.