How we managed to do it
Based on the drawings provided by the customer and the needs expressed, ONA’s team assessed the suitability of using die sinking EDM technology in the machining of geometrically complicated parts such as the impellers.
In this initial phase, it was essential to correctly define the axis involved in the process, as well as the position and orientation of the workpiece, since both factors significantly affect electrode design and trajectory, machining size and may even compromise the viability of the project itself.
Electrode design and trajectory
Currently, no commercial CAD/CAM software is available on the market that is capable of determining electrode design and trajectory as in the case of other applications, meaning expert knowledge must be drawn upon to develop ad hoc algorithms and methodologies to define such parameters. This means there is no single solution, but each workpiece requires a customised project according to its particular characteristics and needs.
The challenges of machining and milling the electrodes themselves mainly have to do with their complex geometries and the need for very tight tolerances; this means that an error in the electrode leads to an error in the workpiece.
For stable machining of the workpiece, the different EDM parameters must be correctly defined. These parameters are mainly defined by the required surface roughness (the shorter the machining time, the higher the roughness) and geometry (larger areas allow more energy to be applied).
Wear is an unavoidable consequence of the EDM process; it cannot be prevented but it can be controlled and minimised.
Given the difficulty to access the part itself, the dimensional analysis of the part in question is a challenge in itself; so methods like destructive analysis, defining strategic points or using standard measurement elements are some of the possibilities to be considered here.