Estlcam is the software I chose to prepare for milling my butterfly capacitor.

After using a CAD program to design the stator and rotor plates for my capacitor, it was time to generate the G-code for my CNC machine. The steps were straightforward.

• Export the faces of the plates from the CAD program into graphics files. This essentially creates accurate line drawings of the parts.
• Edit these line drawings to create a composite pattern of two stator and one rotor plates for efficient cutting. For this, I used QCAD Community Edition. QCAD is open source software which is great for importing, editing and exporting the type of drawing files (DXF or DWG format) used by CAD programs. I wanted to use very accurate software for arranging a cutting pattern that is four inches square.
• Import the patterns into Estlcam, my CAM program. As shown above, Estlcam can be used to create the tool paths, simulate their performance, and then prepare the G-Code for the CNC.

With Estlcam, you set up the tool that you want to use. In my case, this is a 1/8” diameter end mill. You also indicate the speed the tool will rotate, how fast you want to feed the tool across the surface to be cut, how deep you want each pass to cut, and so on.

Then you apply the tool using a specific operation to the contours of the drawing. In my case, there were two types of operations. The first was a profile cut along the outside of the plate perimeters. The second operation was a helical hole in the end holes of the stator and center hole of the rotor plates. These tool paths are shown in yellow above.

You will also see some small gaps in the yellow paths. These are holding tabs – places where you prevent the tool from cutting all the way through. This holds the part in place until you separate it later.

Estlcam does great simulation

To make sure that your CAM tool paths work, you then run a simulation of the G-code, as shown in the lower right insert. This simulation shows the path of the cutting tool in the material. Also, the red lines show the path followed by the tool before, between and after cuts. In addition to showing the movements your CNC will make when actually cutting, you can also make sure that the tool head does not bump into your fixtures or holding clamps.

Now, I am ready to make the cut.