Discover the art of creating window symbols using polygons in CAD software. Understand the difference between inscribed and circumscribed polygons to draw precise symbols.
Key Insights
- The article provides a step-by-step explanation of creating a window symbol using polygons in CAD, focusing on hexagons inscribed in a 1 1/4 inch diameter circle.
- It highlights the importance of understanding the distinction between inscribed and circumscribed polygons. An inscribed polygon is located inside a circle, whereas a circumscribed polygon surrounds the circumference of a circle.
- Correctly using the polygon tool in CAD requires some elementary mathematical understanding, such as knowing that a diameter is twice the size of a radius, as these values are necessary when specifying the size of the polygon.
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In this video, we will talk about polygons while we work on the window symbol. So let's go to File, New, choose our template.
Let's go to File, Save. This will be called window-symbol, and I'll save it. Then I will go to Layer Properties, create my new layer, A-SYMS, change my color to 120, press ENTER to lock it in, and double-click to activate my layer. Let's close Layer Properties and press CTRL+S to save.
If we check our handout, we can see that our window symbol is a hexagon, a six-sided polygon, and it is inscribed in a 1/4-inch diameter. To understand what that means, I'll first draw a circle with a 1/4-inch diameter, then use the polygon tool to explore what inscribed or circumscribed mean. So, let’s draw this circle together.
Let's go to Circle. I'm going to choose 0,0 for my center point, press ENTER to lock it in, type D, press ENTER to choose diameter, and enter 1/4, press ENTER. Let’s zoom extents, scroll out just a little, and press CTRL+S to save.
Remember, what we’re seeing is a 1/4-inch diameter circle. Now, to find the polygon tool, we will need to go into the flyout for the rectangle tool. After all, a rectangle is a type of polygon where the top and bottom edges are parallel, and the left and right edges are parallel.
The polygon tool creates a regular polygon where all sides are equal, and all the endpoints of those sides align on a circle. Let’s start using the polygon tool to learn a little more. So, I’ll choose Polygon, then press ENTER. The number of sides is the first question asked on the command prompt, so I’ll type 6, press ENTER, and now it asks to specify the center.
The center of this polygon is 0,0, Enter, and now it asks for inscribed or circumscribed. If we choose inscribed, we can press I, Enter, and now we see our polygon beginning to be drawn. In this case, we can see that it’s important to point the cursor in the right direction.
Checking the handout, I see that my hexagon is oriented in this direction, so I will find my zero-degree polar direction, and by checking the command prompt, I see that it says specify radius. Now, we did this on purpose. It’s not possible to specify a diameter for a polygon.
In this case, we need to do a bit of mental math, which will happen often in CAD. A diameter is twice the size of a radius, and 1/4 inch is twice the size of 1/8 inch, so I’ll type 1/8, Enter. That is my inscribed polygon.
Let’s do it one more time, but with circumscribed. I’m going to leave the geometry on my screen. Let’s go back to the polygon tool.
The number of sides is 6, and notice it’s in the greater-than and lesser-than symbols. That means it’s a suggested option. If I want to use 6 again, all I have to do is press ENTER.
The center of this polygon is 0,0, Enter, and this time, let’s press C for circumscribed, Enter. Now, in this case, if I wanted to draw this polygon at the same angle, I cannot use the 0-degree angle. Instead, I need to find 90 or 270 degrees to define that distance.
Now, I will type 1/8, Enter, and we can see that the circumscribed polygon is considerably larger. This is because the distance in circumscribed polygons is represented by the distance from the center of the circle to the midpoint of the line, while an inscribed polygon measures from the center of the circle to the endpoint of the line.
A circumscribed polygon will surround the circumference of a circle. An inscribed polygon will be inside the circle. That’s why I placed the circle here for the example.
Since the handout asks for an inscribed polygon, we can select the circle and the circumscribed polygon, which will be larger. I can use the Delete key to remove both of those geometries. Let’s zoom extents and press CTRL+S to save.
Once again, we will add our attributes towards the end of the course.
