Abstract:
Plasma Electrolytic Polishing (PEP) is a subset of the processes known as Plasma Electrolytic Processes, which have applications ranging from cleaning to coating. The increasing popularity of additive manufacturing increases the need for polishing due to the very rough surface delivered by the 3D printing process. PEP is a quick process that uses environmentally safe electrolytes under high voltages in the range of 180-500 V.
In the present work, a plasma polishing setup is designed and fabricated with data logging capabilities to study the various parameters that influence the process with a focus on brass alloys. The influence of time, voltage, electrolyte concentration, insulation, initial roughness, grain size, and distance between the electrodes on polishing effectiveness is studied and characterized using citric acid as an electrolyte. A full factorial Design of Experiments (DoE) is carried out, and optimum voltage and pH to polish brass alloys in citric acid are identified. A novel method of identifying new electrolytes is proposed and tested by identifying sodium gluconate as an alternative. DoE is carried out to identify the optimum polishing parameters for sodium gluconate as well. The data collected during the various trials are analyzed to study the applicability of various mechanisms proposed in the literature to brass polishing. A mechanism is proposed to explain the phenomena observed during the PEP of brass alloys.