Deliverables SPECTRUM prototype including regeneration/separation/recycling system Further to technological improvements in the main modules described as result number 3, the main outcome of this project should be the SPECTRUM machine prototype; an ECM system able to attain the following characteristics: - The machining of tough materials with specified high surface quality and no mechanical and/or thermal stress. - Best available technology for purifying and recycling of process waste. The recycling unit will combine different filtration and separation technologies for the metal ions, oxides and hydroxides. - The bipolar pulse generator with electrolyte depassivation effects avoiding short circuit and extending electrode life. In addition, the mechanical vibration of the electrode results in high refreshment of the electrolyte. - A control system (hardware software) that integrates machine modelization and the ECM process. The machine might also incorporate an expert system to predict the optimum process parameter settings for new applications depending on materials, 3D shapes, etc. The prototype shall be by nature an experimental system aimed to test the new devices. More applied research and design will be required before SPECTRUM commercial machines are ready. SPECTRUM machine modules The SPECTRUM machine modules are the main physical devices of the standalone electrochemical machine that includes the recycling of the used electrolyte during machining. Several modules should be developed separately during project execution: - Electrolyte recycling unit: With ECM machining of hard metals the amount of heavy chemical waste dissolved is considerable. Ideally, the recycling system should separate the metal component at the same rate as it is dissolved. The recycling unit will combine different filtration and separation technologies for the metal ions, oxides and hydroxides. Temperature and pH of electrolyte will be controlled between limits in the regeneration tank. - Fluid supply system: A pump in the electrolyte circuit will maintain electrolyte flow and pressure. This system combined with the electrolyte recycling unit should keep the adequate rate of electrolyte refreshment. - Electrode vibration module: this unit generates the vibration of the electrode-tool to the sinking movement feed rate. - Bipolar Power Generator: A pulse generator will be designed with specific control that brings: -- A current pulse, independent on the voltage, to be triggered at moment of minimum distance between electrode and workpiece. -- A reverse polarity depassivation current pulse, to be fired after each working pulse. - Mechanical parts: the frame that fixes and integrates all the parts of the machine. - Control System: a platform to control and monitor the process parameters, and program the whole ECM system. This control system will be composed of control hardware and software. Features may include log of activities and experimental data, remote communication protocols, manufacturing systems integration, etc. These modules will be developed by updating and/or adapting latest technologies and technical solutions to serve the stated specifications for the SPECTRUM machine. The modules will be designed so they can be replaced from one machine to another. This modular approach is important for the future commercialisation of SPECTRUM machines that should be customized to the clients needs and also making easy their maintenance. Fundamentals of ECM: process and material data The structure of the interface metal/electrolyte during ECM was investigated at HHUD. A highly viscous film of oversaturated products is formed and changes the electric properties at the surface. So far, the simulation software of VUB used the properties of diluted solutions. The experiments at HHUD showed, however, that the real data differ up to two decades from that of diluted systems. The physical data of these surface films are determined at HHUD with a flow-through microcell developed in this project. These data were simplified and implemented to the simulation software of VUB to yield more reliable data for modelling. These data concern Fe, Cr, Mn, and Ni as important components of steel. Pulse Experiments under flow conditions are carried out at Bosch and Philips DAP to investigate the special condition of unipolar and bipolar processing. This result comprises efficiency data for N004 steel that give information that can be used in models to calculate machining speed and copying accuracy. Furthermore a model for the ECM process is described that offers insight in the physical phenomena that determine the ECM process. This result will be used by Philips to understand and optimise the ECM production process. SPECTRUM control and modelling software Within the SPECRUM project, a control and modelling software has been developed: the expert system is aimed to predict for a given set of input parameters (material, geometry, process parameters (U,t,...), the shape of the workpiece that will be obtained. This way, it is possible to determine optimum parameter settings for obtaining the desired copying accuracy. Furthermore, the machining depth and time needed to copy the desired shape into the workpiece can be determined beforehand. The control system is needed to adjust the feed rate of the electrode and the process parameters during machining. Possibilities of separation and processing of metal ions One of the main innovations of the SPECTRUM Project refers to the development of an ECM electrolyte regeneration and recycling module, which will allow the re-use of the electrolyte by removing all unwanted components, specially metal ions and hydroxides. The system will also include the processing of the separated components to reusable materials or, if not feasible, to reduce their harm. Philips has found that even metal concentrations in the order of magnitude of 100 ppb cause severe electrode contamination. Research is being done in order to identify and develop the best available technology for purifying and recycling of process waste. The recycling module will combine different separation technologies. Cidetec and Lamik have been focusing on the development of a flocculation + precipitation combined procedure. Moreover, a further purification method for the electrolyte based on electrowinning techniques was tried. A complete experimental work was performed with the aim of attaining the optimum working variables for the both the flocculation + precipitation and the electrowinning processes. On the other hand, Bosch has cantered his research on the development of a separation procedure based on ion selective membrane technology, mainly electrodialysis. Bosch is also trying electroflotation and electrolysis methods. By using the best operation conditions, the following results have been obtained, expressed in terms of metal concentrations in the electrolyte after treatment: Ni = 0.025mg/l = 25ppb, Cu = 0.060mg/l = 60ppb, Cr(VI) = 0.003mg/l = 3ppb, Cr(III) = No detected, Fe = No detected. Lamik and Cidetec are also considering possible methods to monitor and control the electrolyte quality. In this sense, it is very difficult to measure the exact concentration of metal ions (lower than 50ppb in the cleaned electrolyte) in the high concentration (26%w/w) of the supporting electrolyte (NaNO3). The developed system should be implemented in the regeneration module. The results will be used by Lamik to design and build up the ECM electrolyte regeneration and recycling module. 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