Transitory electrochemical masking for precision jet processing techniques

Abstract

a b s t r a c tElectrochemical jet processing techniques provide an efficient method for large area surface structuring and micro-milling, where the metallurgy of the near-surface is assured and not adversely affected by thermal loading. Here, doped electrolytes are specifically developed for jet techniques to exploit the Gaussian energy distribution as found in energy beam processes. This allows up to 26% reduction in dissolution kerf and enhancements of the defined precision metric of up to 284% when compared to standard electrolytes. This is achieved through the filtering of low energy at discrete points within the energy distribution curve. Two fundamental mechanisms of current filtering and refresh rate are proposed and investigated in order to underpin the performance enhancements found using this methodology. This study aims to demonstrate that a step change in process fidelity and flexibility can be achieved through optimisation of the electrochemistry specific to jet processes.

A review of physical experimental research in jet electrochemical machining

“…Mitchell-Smith et al [34] built upon a previous study of nozzle geometry, introducing sodium iodide (NaI)-doped electrolytes and including the concept of current filtering and re-fresh rate at varying machining parameters. Material removal associated with NaCl-, NaNO 3 -and NaI-doped electrolytes are compared and analysed.…”

“…However, with the inclusion of the doped electrolyte, precision with the use of the complex nozzles is improved but at the cost of lower current efficiencies with increasingly doped electrolytes. Overall, dimensional accuracy improvements and 'superior surface intersection' are achieved with iodide-enhanced electrolytes; however, there is a decrease in material removal rates with increased doping [34].…”

“…For this study, striations were produced with two passes over a coincident toolpath, using various combinations of the electrolytes. The electrolytes used were NaNO 3 , NaCl and NaI, or more specifically a mixed sodium nitrate and sodium iodide solution with 20% NaI referred to as NaI20 as previously used by Mitchell-Smith et al [34], with all electrolytes kept at the same temperature and concentration. It was found the best combination took advantage of the high removal rate of NaCl followed by the better surface finish produced by NaI2O.…”

“…Changes to the nozzle geometries have been shown to alter the machined profiles, with the ability to produce more complex structures with nozzle combinations [31,34]. Changing the angle of address of the nozzles can significantly enhance the precision of cuts [31] as well as increasing the depth of cuts [32].…”

“…Iodide-doped electrolytes have been shown to increase precision [31] and dimensional accuracy [34] as well as improved surface finish in some cases over neutral electrolytes such as sodium chloride [35]. Combinations of electrolytes can be used to further improve the Jet-ECM process [35].…”