Spark Erosion

Ben Tubbing, in Brussels, describes a home-built Electrical Discharge Machine and making gas-turbine components out of Inconel.

Electrical Discharge Machining (EDM) - or Spark Erosion - has great potential for creating complicated shapes and for machining super-hard materials. However, it is not a common technique amongst model-engineers. The purchase of a commercial EDM machine is hardly ever an attractive proposition. At the same time, home-building one requires both mechanical and electronics development. The combination turns many hobbyists away.

I dedicate this article to my father. He is a radio-amateur and electronics enthusiast, and he exposed me to both mechanical engineering and electronics at a very young age. I was never able to choose between the two hobbies, and so EDM is an ideal playground.

This article describes first the home building of an EDM machine, and secondly how it was used to manufacture some initial components of a miniature gas-turbine out of super-alloy Inconel 718.

Photograph 1 shows the most recent piece I made. These are the exit-vanes of a turbine for a miniature gas-turbine, made from Inconel 718. It looks simple enough. However, because of all the techniques involved, it is by far the most difficult object I ever made.

I will describe the project in a spirit of “showing what can be done at home”. Beyond the EDM itself, I will need to deal with the manufacture of 3-D curved shapes through computer-programming and CNC milling. Obviously, nothing will be covered in depth. But I hope the article may provide an inspiration for some to try something different, and in that case I will be happy to go into more detail.

Everything I describe was done with my own equipment. My lathe is a Myford Super 7B, and my mill is a home-refurbished EMCO F1 CNC. For the electronics, I have an old 10Mhz oscilloscope and a few multimeters, nothing unusual.