An ellipse is an ovular or “squashed” circle. Knowing how to create an ellipse is an essential skill for AutoCAD users. They are widely used in drafting both as full ellipses and also to then be converted into Arcs as the ELLIPSE command is more mathematically controllable than the ARC command. They are especially useful when working when working with 2D projections of a circular 3D object (e.g. a pipe going through a wall or similar).
The Ellipse tool can be found on the Home tab, in the Draw section, and in the middle of the 3 smaller icons on the right side of the section.
This tutorial will show you how to create and work with ellipses. We will look at the 3 methods of creating ellipses in AutoCAD and use the first 2 to create duplicate ellipses. With the third method we will create an “Elliptical Arc” that matches the curve of our initial ellipses.
There is a certain amount of terminology related to ellipses which we will use during the tutorial. Taking a minute to review the illustration below will help clarify things enormously.
METHOD 1: Center Ellipse
The default option for ellipse construction in AutoCAD is Center Ellipse. With Center Ellipse, you start by specifying the centre point and then specify the ellipse’s height and length.
The Center Ellipse tool is the most effective ellipse tool when filling in a specific space, such as a rectangle, with an ellipse (which architects frequently use to represent a bath tub in AutoCAD – see this article for more details designing houses with AutoCAD). To bring up the command, you can either click the Center Ellipse icon, or type “ELLIPSE” into the command line.
After you initiate the ELLIPSE command, a dialogue box will pop up in the command line. It will read ELLIPSE: Specify center of ellipse. This is asking that you choose a center point from which your ellipse will extend. After making sure your snaps and grid are on, click on the intersecting point of your grid that you want to use as the centre of your ellipse.
A new dialogue will come up on the command line.
This is asking that you choose an endpoint for your semi-major axis.
For our simple example, we are going to create a semi-major axis 5 units long. Keeping your snaps on, move the mouse right at a 0 degree angle (from previous click) until the measurement box reads 5.0 and then click again.
When you click, the outline of a circle will appear. You will now be asked to “Specify distance to other axis”, which is the semi-minor axis. If you move the mouse around, you will see the circle change in size as the length of the semi-minor axis changes.
The next input will determine the length of the semi-minor axis. Type 3.0 and hit enter. Your ellipse should now look something like the image below. You’ve now created your first ellipse.
Center Ellipse is a good command for when you are looking for a quick and easy method for creating an Ellipse.
METHOD 2: Axis, End
The next technique for creating an ellipse is AXIS, END. This method creates an ellipse by designating 2 endpoints, and then selecting a width for the ellipse.
In our example we are going to use this method to replicate the ellipse we previously created.
To begin, go to the Ellipse Icon drop-down and click on the Axis, End button .
Once you’ve clicked the Axis, End icon, go ahead and click on a grid intersection. This click serves to determine the Point A from the diagram at the beginning of the tutorial. Points A and B are also referred to as endpoints.
Drag your mouse down till the measurement box reads “6.0”. Before clicking or hitting ENTER, make sure all your measurements are identical to the ones in Figure 9. This second click will determine the location of the “Point B” from the ellipse diagram.
Once all the details match the ones in Figure 9, you can click your mouse or hit ENTER. Just like with our last ellipse, a circle will appear on the screen. We have one last measurement left. The last input will determine the length of the semi-minor axis for this ellipse. Type 2.5 into the measurement box and hit ENTER. An exact copy of our previous creation will appear, and should look like the one as below.
This is the Axis, End method of creating ellipses.
The Axis, End method is convenient when you know the axis lengths that you are need, and are not concerned with center point.
METHOD 3: Arc Ellipse
The last method for creating Ellipses is known as the Arc Ellipse. This is used to create an elliptical arc, which is only part of an ellipse, rather than the whole thing. Instances where this is particularly use are when drawing electric lines or when creating rounded corners.
The tool is a fusion of the ELLIPSE command and the ARC command. We will be using Arc Ellipse to create an elliptical arc that is only 270 degrees, not a full ellipse which would be 360 degrees.
Begin by clicking on the Ellipse tool drop-down as we have before and then selecting the Elliptical Arc icon.
As before, you begin by clicking on a grid intersection. The first 2 clicks will determine the starting point (Point A) and then end point (Point B) of the elliptical arc, similar to the Axis, End method.
After your initial click, drag the mouse vertically down, and type in 6.0 as we have in Figure below and hit ENTER. This sets the length of the semi-major axis.
As before, a circle will appear. Your next click will determine the semi-minor axis of our elliptical arc.
Type in 2.5 into the measurement box and hit ENTER. An ellipse will now appear on your screen identical to the ones we previously made. However, we are not done.
Click once on the quadrant point circled as below.
Half of the ellipse will disappear and your elliptical arc will be as is shown as below.
Now drag the mouse counter clockwise until the angle measurement box shows 90 degrees and looks identical to the one as below. Once it is matched up, you can click.
Your final result will look like following Figure. Three-quarters of an ellipse.
You can edit any of your ellipses by clicking on one of them and using the blue square handles to perform measurement-alterations.
Now you know the basics of each of the three Ellipse-creation methods. You can use these to create any kind of Ellipse you will need, and each ellipse can be scaled, rotated, hatched copied, and modified in any number of ways.
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