Reproducible, Fast and Adjustable Surface Roughening of Stainless Steel using Pulse Electrochemical Machining

Abstract

Pulse Electrochemical Machining (PECM) is known to produce finished surfaces with a typical roughness in the region of conventional machining methods like grinding or lapping. Furthermore, the process characteristics support the leveling of a rough anodic surface by using an either smoother, equally rough or even rougher cathode. This research focuses on an empirical investigation of the contrary approach, since for some applications surfaces with a well-defined roughness within small tolerances are needed. Examples are forms for injection molding, medical implants and friction pairs. In this contribution the copying accuracy to specifically produce and reproduce a localized as well as adjustable rough surface structure in steel is analyzed under different process conditions. The surface structure and roughness of the used PECM cathodes are initially produced by Electrical Discharge Machining (EDM) using copper as electrode. This study will show how surface roughnesses can accurately be produced with PECM in a range of typical conventional and non-conventional machining methods. Furthermore, the possibility of adding a surface texture by PECM is pointed out which will create a similar result as an EDM process but without the disadvantages of heat affected zone, tool wear and long machining time for fine finishes. The changes of the surface roughness during the process chain - producing the electrodes by turning, machining the PECM cathodes with EDM and finally machining the parts with PECM - are measured in all stages and correlated to the process conditions and influencing parameters. For all PECM experiments a commercially available PEM Center8000 with sodium nitrate as electrolyte and for all EDM experiments a FORM 20 with IonoPlus IM E-MH as dielectric was used.