Session: 03-13-03: Manufacturing: General III

Paper Number: 167143

Tankless Electrical Discharge Machining (EDM) With a 6-Axis Robot 

Electrical Discharge Machining (EDM) is an advanced manufacturing process used to shape and modify metal materials through controlled electrical discharges (sparks) and vaporized tiny amounts of material from the workpiece. In traditional EDM machining, the workpiece needs to be submerged in a dielectric fluid (in a tank) for the sparks to generate between the electrode and the workpiece.

This paper presents our research on placing a workpiece outside of the tank of dielectric fluid, and using an industrial robot manipulator to position the electrode at the workpiece while delivering the dielectric fluid at the spark gap. It is effectively using EDM to mill or cut a part. This configuration would allow the tool to cut at different orientation, up-side-down for example, and outside of a tank.

Imagine having an aircraft fuselage or rocket fuel tank standing up-right, it is impossible to use EDM to cut on these surfaces because of the need to submerge them in a tank of dielectric fluid. Not to mention the tool path necessary to make the cut. A 6-axis robot manipulator can be used to position the electrode on the surface of the workpiece to mill or cut by EDM. Since the cutting force is low, it doesn’t require fixturing of the vehicle, and the cut will be precise with little-to-no warpages or distortions (for example due to heating from a plasma torch).  The robot manipulator can also position the electrode in difficult-to-reach spaces inside of a structure to perform the cutting operation. Based on our experiments, the orientation of the electrode relative to the surface of the workpiece does not inhibit the cutting operation. Since EDM is a relatively slow process, by employing multiple robots in a coordinated fashion, a long tool path can be sectioned up by the robots and can be done quickly.

The preliminary shows the viability of using this method to cut a thin wall workpiece. The tool wear compensation is done by estimating the wear rate and adjusting the tool center point (TCP) accordingly. Simple feedback is used to detect shorting of the electrode to workpiece and it will cause the robot to reverse out on the same toolpath and forward again. The area of improvements are: 1) adjusting the EDM power supply to increase material removal rate, 2) using multiple electrodes and/or multiple robots to reduce operation time for larger workpiece, 3) compensation of electrode wear by tool path compensation or automatic tool feed (similar to electrode feeding in welding).

Presenting Author: Hong-Yue Tang California State University Sacramento

Presenting Author Biography: Assistant Professor at the California State University Sacramento specializing in Sustainable Energy, Advanced Manufacturing, and Robotics.

Authors:

Hong-Yue Tang California State University Sacramento
Saar Medvedovsky California State University Sacramento
Matthew Nichols California State University Sacramento