Optical and Acoustical Process Control in Hybrid Micromachining Using a Picosecond Pulsed UV-laser and Micro EDM-milling

The manufacturing processes, micro Electrical Discharge Machining (EDM) and micro Laser Beam Machining (LBM), allow a quasi-force- and contact-free machining of numerous materials, regardless of their hardness like hardened tool steels and cemented carbides. Hybrid machining with both processes allows the combination of the process specific advantages while disadvantages can partially be eliminated. Specific advantages of EDM are the achievable high aspect ratios and high processing speeds compared to LBM. However, EDM is limited in miniaturization due to the smallest available electrode diameter while LBM has a high miniaturization potential due to small laser focal spots down to 3 pm and any material regardless of conductivity can be processed by LBM. Especially for hybrid machining of EDM and LBM the process stability and reliability have to be guaranteed anytime for both processes. At the wbk Institute of Production Science a hybrid EDM/LBM-machine has been developed and built up for the combined ablation on a single machine without reclamping of the work piece which is necessary for accuracy increase of ablated structures. The increase of process reliability in the micro-machining processes EDM-milling and laser ablation is presented by using optical and acoustical on-machine sensors for control systems and new control methods. For each machining technology the process controls are explored and transferred to the combined process. Concluding a micro structure from cemented carbide is machined as a demonstrator for precise combined micro machining of EDM and LBM.