Additive manufacturing (AM) offers unprecedented design freedom and the possibility to produce lightweight optimised components that are impossible to make with traditional techniques. Despite the significant progress made in AM, the surface roughness of metal parts produced by this method continues to be an issue. As a result, the application of AM parts in industry is being constricted, particularly in the aerospace and medical industries, where the surface finish of components is highly critical. We have developed PALMS, an innovative cost-effective macro-polishing solution based on novel electrochemical plasma technology. AM parts are rapidly treated in a highly controlled manner in less than 60 minutes, leaving a uniform, smooth micro-finish (<0.1μm), resulting in considerably improved aesthetics and mechanical performance.
PALMS macro-finishing technology relies upon intensification of conventional electrolytic alkaline cleaning by a plasma discharge that is initiated at the surface of an anodically polarised work-piece due to abundant gas liberation and electrolyte evaporation at high voltages. The PALMS concept applies cutting edge innovation to existing electrochemical plasma technology, revolutionising its use from basic micro-polishing of parts with surface roughness <2μm, and enabling it to be used on macroscopic surfaces (2-100μm), such as those encountered on AM produced parts
PALMS technology first removes the roughness peaks and then progresses to the flatter features on the surface. Hence the smoothing rate/roughness decrease is significantly faster than for a competitive technique such as electro polishing. For the same reason PALMS maintains the edges and the overall geometrical shape more effectively than other polishing techniques. Furthermore, unlike other finishing processes, our specially developed electrolytes are environmentally friendly, non-toxic, easily disposable and re-usable, with the main constituent being water.
The most important objectives for the project were:
• design, refine and building the PALMS industrial scale pilot plant
• refine the process for the two most common AM materials; titanium and stainless steel
• achieve TRL8 status by the end of the project
• validate the PALMS process and the PALMS job-shop service business mode
through successfully applying it to end-user partner components
and demonstration trials with at least 10 prime customers,
• secure two commercial contracts.
The PALMS project has been highly successful in meeting all these objectives, thereby placing partners in a very strong position to drive commercialisation forward.
