The team attempted to use I and J coordinates to create an ellipse. This proved to be an incorrect approach. When the program was entered into the machine the picture drawn on the machine did not at all resemble a “G”. The team went back to the drawing board with another idea at hand. It is also possible to draw arcs using RF coordinates, which required finding radii. An ellipse is drawn with four circles with different radii. Therefore, if the radii of each circle could be determined, then the ellipse could be drawn, using the intersections of each circle as the endpoints of each arc. A problem arose, when it was discovered that AutoCAD uses many more than four circles to draw an ellipse. Consistent intersections could not be found in order to determine the radii and arc lengths. We were left with only two options; first the team could draw an ellipse on AutoCAD using four known circles and construction lines, automatically giving the radii and obviously showing the proper arc endpoints. If this didn’t prove effective, the last resort would be to interface the drawing with the CNC machine, using the computer in the lab, let the software write the program, and look at it to determine how it is done. The program was written using the fundamentally drawn ellipse with construction lines, shown in Figure 2. After entering the program into the machine, a few errors were brought to our attention, and it also gave us gouge warnings at certain lines. Upon the approval of Dr. Radha, however, the program was run and a “G” was fabricated. The following is the Program written to create the design shown in Figure 1. The program starts with tool number 10. This is the 1/8” mill. We used an rpm of 1200, a feed rate of 20.0, and a depth of cut at 0.50. The mill starts by cutting the inside ellipse (path noted by the blue lines). When it reaches the underside of the “G” in the inner el...
