THE MAGAZINE FOR COMPUTER APPLICATIONS
Circuit Cellar Online offers articles illustrating creative solutions
and unique applications through complete projects, practical
tutorials, and useful design techniques.

EXPANDING YOUR HORIZONS

Using CAD Mechanical Software in Design Projects
by George Martin

Start ý Drawing The Line ý Scaling New Heights ý Fitting In ý Sources and PDF

DRAWING THE LINE

If youýve ever taken a mechanical drawing or drafting course, you know what controls to look for and how to use them. Both the Quick and Turbo packages enable you to use bisecting lines, perpendicular lines, circles tangent to two lines, dimensioning, and so on. If none of this sounds familiar, an elementary drafting book will provide enough background information. The rudiments of drafting are straightforward.

Letýs take a look at a simple drawing. Figure 1 is the panel cutout for a DB25 connector. If youýre not familiar with this, you can find information in almost any electronic parts catalog. Check out DigiKey for its version (www.digikey.com).

Figure 1ýHere you can see the drawing I did for the DB25 connector with all the dimensions included.

I drew this diagram by first placing the two perpendicular center lines. I then drew two horizontal and two vertical lines parallel to the center lines and offset by the width and height on the main opening (0.225ý and 0.837ý, respectively). Then, I drew the circles (0.132ý radius) that defined the top left and right corners. Next came the 10ý lines that were tangent to those top corner circles. With these 10ý lines in place, I could locate the lower left and right circles that defined the lower left and right radii. Lastly, I added offset lines (0.926ý) that intersected the center line and located the mounting holes (0.120ý in diameter), which I then added. To clean up the drawing, I trimmed all of the lines, leaving only the lines you see in Figure 1 and added dimensions.

It took me about one day to do this first DB25 drawing. I then did the DE9, DA15, and DC37 in about 2 h. The learning curve is steep, but after youýve figured it out, you can really fly. However, Figure 1 has an error. The height dimensions should be 0.225ý and 0.449ý. Iým not going to change this because Iýll probably purchase a punch to make these cutouts. Also, I sort of like the symmetry of matching dimension.

PREVIOUS • NEXT