Navigation
 
AutoCAD Tutorial

AutoCAD 2004 Customization Tutorial: Adding Arcs to Shapes

June 13, 2003

 

There are some simple methods to add arcs to shapes. In this tutorial you learn some of them. If you are not familiar with shapes, please read the following tutorials first:

 

1. Download the following drawing file. The file will help you in calculating shape information [Figure 1]. The objects to the right show the direction codes for drawing straight lines and the objects to the left show the direction codes for drawing arcs.

        ► R16_arc_shapes.dwg

Note: If you are using an earlier release of AutoCAD download:
R15_arc_shapes.dwg.


Figure 1 - Click on image to enlarge

2. Open the file in AutoCAD.

3. Disable all running OSnaps but Intersection.

4. Draw a circle [Figure 2]. The diameter of circle is 1 unit.


Figure 2

5. In command line type Notepad and then press Enter twice. The Notepad window appears.

6. Enter the proper code to define the circle [Figure 3].


Figure 3

Notes:

  • The header line defines a shape called CIRCLE. The shape number is 220 and it needs 14 codes to be defined.

  • The 002 stops drawing mode (i.e. pen up).

  • The 003,2 divides all the subsequent sizes by 2.

  • The 005 saves the current location of pen.

  • The 010 moves the pen 1 unit along direction 0 (i.e. positive X direction).

  • The 001 starts drawing mode (i.e. pen down).

  • The 00A indicates that you want to draw an arc. The subsequent code (1,004) specifies the radius of the arc to be 1 unit. The start octant direction is 0 and the end direction is 4 or rather 180 degrees [Figure 01]. In 004 the first number (0) switches to hexadecimal mode, the second number (0) indicates the start octant direction and the last number (4) refers to the end octant direction. The final result is a half circle.

  • The other half circle is drawn with 00A,(1,040). Here the start octant direction is 4 and the end octant direction is 0.

  • The 006 restores the saved pen location.

7. Save the file as "arcs.shp".

8. Start a new drawing.

9. Compile the shape file to create "arcs.shx".

10. Load "arcs.shx" in the new drawing file and then insert the shape.

11. Close the file without saving.

12. In "R16_arc_shapes.dwg" draw a circle and 4 arcs [Figure 4].


Figure 4

13. In Notepad enter the proper code to define the shape [Figure 5].


Figure 5

Notes:

  • The first line specifies the shape number, number of codes you need to define the shape and the shape name.

  • The 002 stops drawing mode, 005 saves the pen direction, 01A moves the pen 1 unit along A direction, and 001 starts drawing mode (pen down).

  • The 00C starts the arc drawing session. This code uses the displacement in X and Y direction along with a bulge factor. Here for example for the first arc, the displacement in X direction is 2 units, in Y direction 0 units and the bulge factor is 127. The bulge factor is 0 for the straight line and 127 for the half circle. The acceptable values are between -127 to 127. You can calculate the bulge factor with the following equation:

Bulge factor = ((2Height)/Displacement)127

  • The 006 restores the saved pen location.

  • With 004,2 any subsequent size will be multiplied by 2.

  • The 007,220 inserts the 220 (circle) as a sub-shape.

14. Save the file. Compile and load it in a new drawing.

15. Insert the shape and then close the new drawing file.

16. In "R16_arc_shapes.dwg" draw a simple combination of straight lines and an arc [Figure 6].


Figure 6

17. Add the proper code to the shape file [Figure 7].


Figure 7

Notes:

  • Here the bulge factor is equal to 64 as Height = 1 and Displacement = 4, thus:

Bulge factor = ((21)/4)127 = 63.5 z 64

18. Compile and load the shape file in a new drawing.

19. Insert the shape in the new drawing file.


About the Author

Alireza Parsai is the founder of cadpanel.com. He is a mechanical engineer with more than 12 years experience with AutoCAD. Alireza is an Autodesk Authorized Author, the AutoCAD consultant for Al Khawarizmi Institute, a contributing editor for Augiworld magazine, a writer for CAD Digest, an instructor for AUGI Training Program, and an elected speaker for Autodesk University 2002. He has written 7 books in Farsi, 3 booklets in English, and more than 30 articles for different magazines and newsletters. You can reach him at alireza.parsai@cadpanel.com or visit his website www.cadpanel.com

More CAD Corner tutorials >>