Institute of Machine Tools and Manufacturing

Zürich, Switzerland

Institute of Machine Tools and Manufacturing

Zürich, Switzerland

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Krotz H.,Institute of Machine Tools and Manufacturing | Krotz H.,EMAG eldec Induction GmbH | Wegener K.,Institute of Machine Tools and Manufacturing
International Journal of Advanced Manufacturing Technology | Year: 2015

This paper details the fundamental principles of the machining method spark assisted electrochemical machining (SAEM). SAEM is a further development of the electrochemical arc machining (ECAM) which makes use of the electrochemical discharge phenomenon to machine electrically conductive materials. ECAM is not able to drill micro-holes, but now, using SAEM a postponed electrochemical finishing of the SAEM drilled micro-hole can be realized. The mass flow calibration of a throttle plate can be done immediately after SAEM microdrilling by electrochemical machining (ECM) with a still axis-symmetrically located tool electrode with the same machining equipment, working media, and power source. To enable ECAM to drill micro-holes, its material removal mechanism is improved by combination with the contact arc as an additional mechanism. This mechanism is presented and explained herein. The machining efficiency of the newly developed SAEM is optimized by adjusting the gap control in such a way that the contact arc is generated with an adequate frequency. This reduces the machining time by almost 50 %. Some examples of SAEM drilled micro-holes, for which different electrolytes are used, are presented and the surface and heat affected zone of those micro-holes are examined. © 2015, Springer-Verlag London.


Krotz H.,Institute of Machine Tools and Manufacturing | Krotz H.,Eldec Schwenk Induction GmbH | Roth R.,Institute of Machine Tools and Manufacturing | Wegener K.,Institute of Machine Tools and Manufacturing
International Journal of Advanced Manufacturing Technology | Year: 2013

In this work, single discharges of electrochemical arc machining are examined. The heat-affected zone is analyzed, and a model is set up to simulate the heat transfer into the workpiece. As an input parameter of the simulation, the temperature of the electrochemical arc machining process was determined to be 3,500 K by means of emission spectroscopy. The simulation shows that the diameter of the heat-affected zone is less dependent on discharge duration and heat transfer due to heat flux than on the arc spot diameter. As a result of the investigation, it became clear that varying diameters of the heat-affected zone have to evolve from different diameters of the plasma channel's arc spot. Understanding the heat distribution into the workpiece in electrochemical arc machining with micro-machining parameters allows the further development of a micro-drilling process for electrically conductive materials based on electrochemical arc machining. © 2013 Springer-Verlag London.


Kuffa M.,Institute of Machine Tools and Manufacturing | Kuster F.,Institute of Machine Tools and Manufacturing | Wegener K.,Institute of Machine Tools and Manufacturing
CIRP Journal of Manufacturing Science and Technology | Year: 2016

Grinding low carbon steel with diamond is regarded to be not feasible due to its chemical affinity to iron. A workpiece with comparable low hardness 330 HV30 and low-carbon content is selected. Therefore, cBN is a suitable choice of a superabrasive and thus employed. Its advantages compared to conventional abrasives are higher material removal rate and less wear. The thermal behaviour of the cBN grinding wheel in different environmental conditions is examined. The dry grinding process with a cBN grinding wheel is discussed and compared to wet grinding, grinding with minimum quantity lubrication and CO2 cooling. Increase in material removal rate and low wear rates are targeted. An electroplated, monolayer cBN grinding wheel with open structure design guarantees higher cooling ability and enlarged space for chips. The wear behaviour of the grinding wheel and the thermal damage on the workpiece surface are investigated. Cutting forces and temperatures are measured during the process for different high feed rates and depth of cuts. The thermal damages are evaluated by microscopic texture analysis. Grinding wheel dust contamination and loading connected with a significant temperature increase could be observed under dry environment. Cleaning impact of cooling nozzle on grinding wheel surface led to decreased normal forces and better surface roughness. Cooling impact of minimum quantity lubrication and CO2 cooling appeared less significant than emulsion. © 2016 CIRP.

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