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IT Help Desk => Open Source Forum => Topic started by: BRE SALAM SONY on August 25, 2010, 06:55:32 AM

Title: AutoCAD Basic Command
Post by: BRE SALAM SONY on August 25, 2010, 06:55:32 AM
Opening AutoCAD
Open up AutoCAD, you should be greeted with a screen asking if you want to open an existing drawing or start from scratch. (Dependant on your version of AutoCAD, the screen will be slightly different - The image shown below is for AutoCAD 2002).

Select 'Create Drawings', then 'Start from Scratch'. Ensure that you select metric (i.e you are telling AutoCAD that you will be drawing in metres and millimetres NOT feet and inches).

AutoCAD will now create a new drawing file named drawing1.dwg.
AutoCAD will default to 'model space'. For now it is sufficient to say that model space is the blank space where all the drawing is carried out. Paperspace (now called Layout space since AutoCAD 2000) isn't really required until we are ready to plot (print) the drawing.

There are many toolbars available in AutoCAD. Go to View > Toolbars from the drop down menu to see them all. For now make sure that the following toolbars are checked:

Draw - Contains AutoCADs most common drawing tools
Modify - Contains all of the common editing commands such as erase, copy etc.
Object Properties - Contains 'layer' information as well as object colours and line style options. (Covered Later).
Standard Toolbar - Contains open & save options as well as zoom & pan options.
Object Snap - AutoCAD's intelligent drawing aid - joins lines at specific points. (Covered later).

Arrange the icons to where is comfortable for you (A typical layout is shown below):

The Command Line

The command line appears at the bottom of the AutoCAD screen (as shown above) and displays the commands entered. Commands can be entered into the command line in text format, or by using the icons or drop down menus. 'Old School' Cad users tend to type each command into the command line, as was required with older versions of AutoCAD. It is much quicker to familiarise yourself with the tool bars and drop down menus. There are times however when commands need to be typed into the command line, these will be covered later.

Drawing Technique - AutoCAD's Co-ordinate system
Just before we start drawing, one more important point. AutoCAD works on a co-ordinate system. When drawing, we can be very precise and specify an exact point in space where a line should begin or end. The 2D co-ordinates system is based on the horizontal and vertical axis named x and y. (This is shown in the bottom left of the AutoCAD drawing area, the X Y icon is called the UCS).

Drawing - Line Command
1)Select the line command from the draw menu (alternatively select line from the 'draw' drop down menu).

2)AutoCAD asks you (in the command line area) to specify a start point. Simply pick an area central to the drawing area (left click of the mouse).

3)AutoCAD now asks for an end point. Select somewhere (left click) to the top right of the drawing area.

4) Now one line is drawn. AutoCAD keeps the line command open so that another line can be drawn beginning exactly where the previous finished. We want to end the command so simply right click to end (AutoCAD 2000 users and above - right click will open a small menu - simply choose 'enter' to end the command).

Drawing - Line Command - Specifying Points
Erase the line we just created. Select the erase command from the menu or from the 'modify' drop down menu.
AutoCAD asks you to select an object, left click the line we drew. Right click to enter the command and delete the line.

Let's imagine we are looking down over a plot of land (plan view). We are going to draw the land boundary from some measurements taken. The land measures 25m x 40m.

1) Select the line command as before. This time for a start point we will specify some co-ordinates (simply an exact point in the drawing area.)

2) We will start our drawing at a point 50m horizontal and 50m vertical from the default UCS location of 0,0. AutoCAD is asking for a start point, type in the command line: 50,50 followed by hitting enter.
Note - AutoCAD's normal co-ordinate system is always relative to the UCS icon position of 0,0.

3) For the next point we'll draw the bottom end of the plot of land. We want a line 25m horizontal from the start point. We can specify co-ordinates from a particular point by including the @ symbol in front of the co-ordinates. This informs AutoCAD that the co-ordinates we are specifying are relative to the last point specified and not to the UCS.
To enter a 25m length horizontal line from the start point the command would be @25,0 (i.e go 25m along, go 0m up).

Now we should have drawn a horizontal line 25m long.
Note - Do not right click to end the line command, this layout can be drawn leaving the command open.

4) We now need a 40m vertical line to represent the right side of the plot of land. This command would be @0,40 (i.e go 0m along, go 40m up).

5) Now for the top of the land. We need to go back horizontally by 25m from the current end position of the vertical 40m line. The command would be @-25,0 (i.e go back 25m, go up 0m).

6) To finish off we need to draw the last line. we need to go 40m vertically down so the command is @0,-40 (i.e go 0m along, go 40m down).

7) Right click to end the draw command.

That's it! We've just drawn a scale drawing of the plot of land from the measurements given from a start point of 50,50 relevant to the UCS.

TIP- If your drawing is only taking up a small area of the screen, try zooming in with the various zoom commands. To quickly view your drawing close up choose zoom extents to see the entire drawing.

Drawing - Rectangle Command

Erase the 4 lines we just drew. We will know try a command that would have drawn the above land layout in one simple command.

1) Choose the rectangle command or select it from the draw drop down menu.

2) AutoCAD asks for the start point. As before, we want to begin 50m horizontally and 50m vertically from the UCS, so enter 50,50 then hit return.

3) AutoCAD now asks for the position of the top right corner of the rectangle we are going to draw. To draw the plot of land we need 25m along and 40m up from the start point, so the command is @25,40

Your drawing should be identical to the one we drew before, but was a lot simpler and quicker to draw.

Have a play around with the line and rectangle commands and familiarise yourself with how they operate.