Henning Zeidler

Micro Electro Discharge Machining of Electrically Nonconductive Ceramics

EDM is a known process for machining of hard and brittle materials. Due to its noncontact and nearly forceless behaviour, it has been introduced into micro manufacturing and through constant development it is now an important means for producing high‐precision micro geometries. One restriction of EDM is its limitation to electrically conducting materials.Today many applications, especially in the biomedical field, make use of the benefits of ceramic materials, such as high strength, very low wear and biocompatibility. Common ceramic materials such as Zirconium dioxide are, due to their hardness in the sintered state, difficult to machine with conventional cutting techniques. A demand for the introduction of EDM to these materials could so far not be satisfied because of their nonconductive nature.At the Chemnitz University of Technology and the Fraunhofer IWU, investigations in the applicability of micro‐EDM for the machining of nonconductive ceramics are being conducted. Tests are undertaken using micro‐...

Microelectrical Discharge Machining: A Suitable Process for Machining Ceramics

Today ceramics are used in many industrial applications, for example, in the biomedical field, for high-temperature components or for cutting tools. This is attributed to their excellent mechanical and physical properties, as low density, high strength, and hardness or chemical resistance. However, these specific mechanical properties lead to problems regarding the postprocessing of ceramics. In particular, cutting processes require expensive tools which cause high manufacturing costs to machine ceramics. Consequently, there is a demand for alternative machining processes. Microelectrical discharge machining (micro-EDM) is a thermal abrasion process which is based on electrical discharges between a tool and a workpiece. The advantages of micro-EDM are more and more in focus for ceramic machining. These advantages include the process of being a noncontact technology, an independency of material brittleness and hardness, a low impact on the material, and the achievable microstructures. This paper presents the current state of investigations regarding micro-EDM of ceramics. Beside the process principle of EDM, the used procedures for machining ceramics and insulating ceramics are described. Furthermore several machining examples are presented to demonstrate the possibilities of the micro-EDM process with regard to the machining of ceramics.

Micromanufacturing Of Hard To Machine Materials By Physical And Chemical Ablation Processes

Miniaturization leads to high requirements to the applied manufacturing processes especially in respect to the used hard to machine materials and the aims of structure size and geometrical accuracy. Traditional manufacturing processes reach their limits here. One alternative for these provide thermal and chemical ablation processes. These processes are applied for the production of different microstructures in different materials like hardened steel, carbides and ceramics especially for medical engineering and tribological applications.

Micro Machining of Different Steels with Closed Electrolytic Free Jet

Electrochemical Machining (ECM) with closed electrolytic free jet (Jet‐ECM) is an innovative procedure in micro manufacturing technology which is based on anodic dissolution of metallic work pieces. Main advantage of Jet‐ECM in comparison to other ECM processes is the restriction of the electric current to a limited area by the jet. Micro structured surfaces and complex three‐dimensional micro geometries can be machined by help of different nozzle movements. In this study the Jet Electrochemical Machining is used to generate micro cavities in different steels to investigate the influence of the material properties on the removal process. Current efficiency, machined geometry and surface properties of the processed areas were analyzed and compared.

Indirect Approach to Ultrasonic Superposition in Micro-EDM

Micro Electro Discharge Machining is a well known process for machining microstructures with highest precision in hard and brittle or tough materials. The deeper the structures and therefore higher the aspect ratio, the more difficult it is to remove the ablated particles from the discharge zone and keep the process in stable condition. Flushing can be aided by vibration of either tool or workpiece. Thus, applying ultrasonic vibration to micro EDM has proven to enhance the process significantly. The vibration is most efficiently induced via the tool or workpiece directly to the discharge zone. However, to achieve an ultrasonic vibration of the tool or workpiece, a complex vibration system that operates in resonant mode is needed. Any crucial change of the vibrating parts results in a demanding and therefore expensive adjustment of the vibrating system. With this setup, the application of ultrasonic vibration is only profitable for large scale serial production. In this work a different approach of ultrasonic superposition to the EDM is proposed. A highly focused ultrasonic vibration is induced into the dielectric in a way to directly influence the discharge zone. This indirect ultrasonic superposition can be easily applied since it is independent of the tool or workpiece geometry. Experiments are carried out to examine the effects of the indirect ultrasonic superposition on the EDM process. First results show the possibility of enhancing micro-EDM by this approach.Copyright

Deposition and micro electrical discharge machining of CVD-diamond layers incorporated with silicon

In metal forming, lubricants have to be used to prevent corrosion or to reduce friction and tool wear. From an economical and ecological point of view, the aim is to avoid the usage of lubricants. For dry deep drawing of aluminum sheets it is intended to apply locally micro-structured wear-resistant carbon based coatings onto steel tools. One type of these coatings are diamond layers prepared by chemical vapor deposition (CVD). Due to the high strength of diamond, milling processes are unsuitable for micro-structuring of these layers. In contrast to this, micro electrical discharge machining (micro EDM) is a suitable process for micro-structuring CVD-diamond layers. Due to its non-contact nature and its process principle of ablating material by melting and evaporating, it is independent of the hardness, brittleness or toughness of the workpiece material. In this study the deposition and micro electrical discharge machining of silicon incorporated CVD-diamond (Si-CVD-diamond) layers were presented. For thi...

Manufacturing of Aluminum Metal Matrix Cast Composites with Carbon Based Additives for Thermal Management Applications

This work focuses on the production of new high conductive carbon based MMC (Metal Matrix Composites) or co-cast components obtained by casting processes. These novel thermally conductive structures are designed to face modern heat management challenges in critical fields such as power micro-electronics, automotive and aerospace industries, renewable energy generation as well as highest performance combustion engines. The sought parts will be assembled by different heat conductive aluminum-carbon composites and for this reason different heat conductive MMCs have been studied. Their combination into once cast aluminum part may allow the part to meet applicative needs for heat management challenges. The cast production routes as well as thermal behavior of the obtained materials has been studied by means of numerical (Finite Element Methods) approaches in order to determine the effective thermal conductivity in the different directions of heat dissipation. Some kinds of casting methods have been FEM simulated and then performed practically. TPG/aluminum interface microstructure has been studied.

Micro Electrical Discharge Machining of Tungsten Carbide with Ultra-Short Pulse

Micro EDM (Electrical Discharge Machining) is a known nonconventional process for the machining of hard to cut materials. Due to its ablating nature based on melting and evaporation through heat induced by electrical discharges, it can function independently of the hardness, toughness or brittleness of the workpiece. Thus micro EDM is a possible process to fulfill the requirements of higher precision and high quality in carbide metal machining. Thereby the surface and the roughness of machined carbide metals depend on the discharge energy used. For machining carbide metals with high surface quality pulse generators with ultra-short discharges are required. This paper presents the development of a two-staged pulse generator with the ability to provide ultra-short pulses by using a two-staged pulse. The current and voltage signals of the discharges were recorded and their characteristics were analyzed.

Resource-Efficient Machining of Hard Metals

The main requirements of carbide metal working are higher precision and high quality surface which can be fulfilled by electrical discharge machining. This procedure is accompanied with formation of heat affected zones (white layers) during the discharge process negatively. Therefore, the essential post-processing reduces the efficiency of this process and shows the importance of process energy sources (PES) with ultra short discharge in favor of a clearly differentiated cutting volume. By means of simulations of crater geometry and channel expansion the influence of discharge rise time is defined as determining factor for the cut volume and formation of white layers. The technological section presents two different approaches of realizing ultra-short pulses.