Dry electropolishing: More sustainable surface finishing

Dry electropolishing ensures more sustainability in surface finishing. In contrast to classic electrochemical polishing processes, processing with electrolyte-containing, solid particles takes place in a dry environment.

Increasing demands on surface quality with simultaneously higher requirements on reproducibility, traceability as well as resource efficiency of the processes require adapted processes for surface finishing. With the DryLyte process, Rösler Oberflächentechnik offers an innovative solution for electropolishing demanding metallic components. In contrast to classic electrochemical polishing processes, automated processing with solid particles containing electrolytes takes place in a dry environment. Acid baths or process fluids are completely eliminated. In addition to high geometric fidelity and an overall improved surface finish, benefits include a reduced carbon footprint and reduced disposal costs. The costly and complex reprocessing of spent process fluids is completely eliminated and the workpieces come out of the machining process clean.

Whether optical or functional properties - surface processing faces many challenges. On the one hand, higher requirements have to be met in terms of surface roughness as well as geometric fidelity of the component, but at the same time the process has to fulfill economic and ecological criteria. Issues such as energy requirements and resource consumption as well as the avoidance of potentially hazardous substances and waste are increasingly coming into focus. In many cases, reproducible and fully traceable processes are also required. These requirements cannot be met, or only to a limited extent, with processes such as manual machining or classic electropolishing with liquid electrolytes. An innovative solution for the reproducible processing of demanding and geometrically complex components made of conductive metals is the innovative DryLyte technology from GPA Innova, a partner of Rösler Oberflächentechnik.

The automated process simplifies and standardizes various surface treatments from deburring, smoothing and grinding to polishing with mirror finish as well as the finishing of additively manufactured components. Depending on the initial condition of the surface and the required processing result, dry electropolishing can be used as a finishing process in combination with known vibratory finishing, blasting and other pre-grinding processes or on its own.

DryLyte technology is based on the principle of electrochemical surface removal. However, instead of liquid electrolytes, a large number of polymer beads of different sizes with an integrated electrolyte medium adapted to the application are used for metal removal. In contrast to conventional electropolishing, therefore, no health-endangering vapors are produced that require energy-intensive extraction and special protective equipment for the personnel. Since material removed from the surface is absorbed by the electrolyte medium, no dust or metal particles are released into the environment, as is the case with manual grinding and polishing processes. A stable machining result is achieved over the entire service life of the electrolyte medium. Replacement is only necessary when the dry electrolyte is saturated due to metal ingress, for which a similar disposal process then takes place as for the abrasives. The degree of saturation of the electrolyte is recorded by the machine and the operating personnel are permanently informed about the condition and the remaining useful life. This always ensures that reproducible results are achieved on the component and that the electrolyte is optimally utilized. This reduces the labor and disposal costs incurred. In parallel, the CO2 footprint of the products is reduced due to the high resource efficiency.

In dry electropolishing, the fixed components move slowly through the electrolyte medium, with a homogeneous flow around them. Depending on the component, internal machining can also be performed, which is made possible by special electrodes. Due to the process, material is mainly removed from the roughness peaks on the surface. Material removal is therefore comparatively low and very gentle. The machined components have a homogeneous surface without imprints, pattern formation or orange peel effects. Even with filigree and complex geometries, no micro-scratches or fractures occur as a result of the machining process.

On the one hand, the targeted and "controlled" machining ensures that the component geometry of precision parts, such as machine tools as well as tools for the pharmaceutical industry, is not changed and edges are not rounded. On the other hand, the effective smoothing of the surface minimizes the formation of cracks and craters. Among other things, this results in improved corrosion and fatigue resistance and thus an extended service life of the components. Compared with conventionally electropolished workpieces, dry-polished parts corrode 4 to 15 times more slowly (the corrosion tests were carried out in a salt water solution containing 30 g/L NaCL). For workpieces such as gears used in mechanical systems, the treatment simultaneously improves sliding properties due to the rapid increase in load-carrying capacity, and optimum distribution of lubricants on the surface is achieved. Component wear and noise emission are also significantly improved by better surface quality.

Another advantage of DryLyte technology is the comparatively short process times. Depending on the application, initial roughness and desired result, they range from a few minutes to 1.5 hours. The surfaces can not only be smoothed, but also polished to a high gloss in a single production step. Very rough surfaces, for example of additively manufactured components, are usually prepared by an abrasive vibratory grinding process.

The unrivaled and patented process was originally developed for the treatment of model castings and crowns made of cobalt-chrome and titanium in the dental industry. In the meantime, GPA Innova's dry electropolishing is also used for the treatment of stainless steel, steel, carbide, nickel, aluminum and copper alloys, as well as other conductive metals in other industries where high demands are placed on surface quality, for example in the aerospace, pharmaceutical, mechanical engineering and consumer and luxury goods industries. Furthermore, due to its proven biocompatibility, it is also used in medical technology for the manufacture of implants and instruments.

The process design and definition of the process parameters are adapted to the components and application in Rösler's Customer Experience Center. For the implementation, different systems are available for an automated process. This ensures that all parts are processed with defined or validated parameters. (OM-10/23)