Design of a Precision Electro Discharge Micro Milling Machine

This paper presents the design of a precision electro discharge micro milling machine being designed and built in the Precision Systems Laboratory at the University of Kentucky. This machine will use micro electrodes to mill complex 3D cavities with electrical discharges between an electrode tool (cathode) and a workpiece (anode) submerged in dielectric fluid. The machine entails three axes of motion consisting of a pre-existing XY stage and a new Z stage with spindle. The objectives in designing this machine are to achieve high precision for large workpieces and to develop an open architecture machine controller for micro EDM. The CAD data documenting this machine design is available free through the Open Design Foundation. These solid models can be downloaded by any party, and they may be used, modified, or redistributed as long as the machine remains an Open Design. This paper presents two concepts for the new z-stage and spindle. One concept uses a flexure for fine motion during micro machining, and the spindle is held on a plate that is guided with air bushings to accommodate a range of workpiece heights. The second concept is a conventional vertical column with a head and spindle. The two concepts are compared using error budgets.