The Polar Array command in the Autocad 3D interface is a useful method of creating complex compound shapes in three dimensions. The examples shown here are flanges cut from sheets of steel and other metal alloys, then lathed and drilled. In the 3D working space we create a cylinder first, for example radius 20mm and height 60mm. This small cylinder will represent the drilled holes – this will be our cutting shape. In this Autocad 3D course you will start to learn about polar array in autocad 3D.
Next draw a larger cylinder, radius 300mm with a height of 40mm. This will represent the flange plate. Now we go to the Views tab and choose the Top View and the Visual Style of Wireframe. Alternatively type VS into the Command line, then 2D for Wireframe. To establish the position of the holes turn Ortho on (F8, or Command +L on the Mac interface), and draw a line with the Line tool 240mm from the centre. Next move the first cylinder to this point, tilt your view, and change the visual style to Realistic (type VS into the Command line then R).
To perform the 3D Array type 3A into the Command line, then select the object to be selected, that is the small cylinder, and hit Enter. Then type P for Polar, and enter the number of copies, for example 12, and the angle of rotation, which is usually 360º. Autocad now asks you to specify the centre of the array – click the centre of the plate. And specify the second point of the rotational axis. This can be a little tricky to do so hold your cursor over the plate until the centre of the bottom surface highlights, then click on it.
The 12 small cylinders should be arrayed with their tops sticking up for easier subtraction. Now use the Subtract tool on 3D Make panel to cut out the holes, as follows: select the main object first, that is the plate and hit Enter. Then select the 12 cutting object, again hitting Enter to finish the command. This should result in a flange with 12 circular holes cut in the rim. You could now chamfer the edges of the holes by 2mm using the Chamfer function. Note that it’s possible to select all the hole edges together. Lastly, create another cylinder, radius 190, height 60. Use this to cut out the central hole of the flange using the usual Boolean Subtraction method.
A further series of cylinders could be created for the various collars around the central hole of the flange. An alternative method would be to create a cross section of one side of the flange. Then create a line for the axis of rotation and use the 3D Rotate command to create the ring of the flange. Then use the method above to create the cutting objects of the drill holes and the Boolean subtraction.
As can be seen, creating objects in the Autocad 3D interface is a fairly straight-forward process. It does require some planning ahead though, to find the most efficient method, more information can be found here.