Algorithms and an extended STEP-NC-compliant data model for wire electro discharge machining based on 3D representations

Abstract

The current paper describes the implementation of the wire electro discharge machining (EDM) algorithms for the STEP-NC project and some possible extensions. Wire EDM uses many working parameters (parameters for spark generation, speed of penetration, etc.) the setting of which needs expert system methods. These expert systems are a coded form of the company knowledge and are based on their experience. The higher information level provided by STEP-NC allows the development of new algorithms to drive the wire. The current way of programming the wire motion is to consider it as a milling tool for 2.5 axis machining operations: the wire trajectory is computed using 2D planar curve offsetting and collision detection algorithms. The use of explicit ruled surfaces allows real 3D offsetting and collision detection.

The paper starts by describing the data model and architecture of the demonstration system which was developed during the project. This can be thought of as a simplified process planning phase. The second part of the paper describes algorithms that have been implemented in the STEP-NC environment for prototype software running on the wire EDM NC controller. The final part describes some open questions that remain at the end of the project.

Keywords:

• STEP-NC EDM
• Ruled surface machining

Acknowledgements

As with the whole STEP-NC effort, the work on the EDM module was conducted by a team. The authors would like to thank all the other members of this team, especially Mr Glantschnig of AMT, Mr Waelder, Mr Crivelli, Mr Reichenbaecher, and Mr Morph of Charmilles, Mr Wyss of Wyss SA, J.-P. Horvath, R. Demellayer, H. Sthioul of EIG HES, Dimitris Kiritsis and Gabor Erdös of EPFL.