µECM process investigation and sustainability assessment

Abstract

Micro electro chemical machining (µECM) as an alternative machining process gains more attraction in micro and nano industries and gradually finds its place among other non-conventional manufacturing methods. µECM same as ECM aimed at electrically conductive materials; µECM process is based on anodic dissolution of the materials at atomic level. Current progress in µECM has presented valuable improvement in the process control and monitoring, shaping accuracy, simplifying the tool design and the process stability. This makes the µECM an outstanding alternative technology to produce accurate and complex 3-dimensional micro components. However, there is still a gap in application of µECM at research level and industrial level; development and commercialisation of the µECM require huge industrial investment which still needs justification to be attractive for investors. Despite worldwide attempts to investigate and demonstrate the µECM process in full details and develop the µECM technology for the industrial applications, there is still a need for further investigation and research due to the complex and multidisciplinary nature of this process. Currently, this process is very much dependent on operator experience and trial and error approach. The lack of trained knowledgeable operators in addition to the lack of a comprehensive database (combination of materials, electrolytes and machining parameters) have increased the time and the cost of the commercialised development of this technology. A comprehensive analytical literature review highlighted three areas of knowledge gap which can be further investigated and developed. One of the main challenges in current state of this technology is initial set up for machining parameters. Current records show that the initial parameters have been set up using trial and error approach or simulation data; and there is still ongoing effort to find a better solution to set up the initial parameters. The electrode-electrolyte interface was recognised as one of the main effective parameters on µECM machining performance. The complex nature of the reaction which happens at this interface, in addition to the electrode-electrolyte structure need further investigation and analysis in order to improve the µECM machining performance. Finally, the ever increasing demand to optimise all manufacturing processes and products, has increased the need to assess the sustainability of the machining process including new developed technologies; but there is very little information available in the area of micro and nano machining sustainability assessment including µECM. Therefore, in this research it has been tried to address these three knowledge gaps and to suggest new methodologies to overcome them using a new practice consisting of laboratory experiments, mathematical analysis and simulation to investigate the initial machining parameters’ values, explore the electrode-electrolyte interface structure for stainless steel workpiece and tungsten and nickel tool electrodes. Also, to introduce a series of indicators and measures to assess the sustainability of the µECM process to justify its initial high cost in comparison with any other machining process. Laboratory experiments carried out using potentiostat (iviumstat) and mathematical analysis and simulation took place using Matlab and Simulink; and a few experiments carried out using in house built µECM machine to examine the obtained results through the laboratory and simulation works. The results suggested that combination of 6.5 to 7.5 volts, electrolyte concentration between 0.4 and 0.7 mole/L and inter-electrode gap between 22 and 27 µm generates optimum process results. Additionally, electrode-electrolyte interface structure is a useful parameter to set up the pulse on time. Finally, introduced sustainability assessment indicators and measures provides the opportunity to assess the µECM process for further optimisation. As a result, µECM is a valuable process and in claim for current manufacturing industries especially in micro and nano products which demand higher accuracy and quality, better production life cycle and lower cost. So, it is very worthy to invest for further development to bring this technology to the industrial level.