Whether optical or functional properties - surface treatment faces many challenges. On the one hand, higher requirements must be met in terms of surface roughness and geometric accuracy of the component, but at the same time the process must meet 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. Processes such as manual processing or traditional electropolishing with liquid electrolytes cannot meet these requirements, or only to a limited extent. The innovative DryLyte technology from GPA Innova, a partner of Rösler Oberflächentechnik, represents an innovative solution for the reproducible processing of sophisticated and geometrically complex components made of conductive metals.
From deburring to high-gloss polishing - sustainable and efficient
The automated process simplifies and standardizes various surface treatments from deburring, smoothing and grinding to polishing with a mirror finish as well as the post-processing 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 mass finishing, blasting and other pre-grinding processes or on its own.
DryLyte technology is based on the principle of electrochemical surface removal. However, liquid electrolytes are not used for metal removal, but a large number of polymer beads of different sizes with an integrated electrolyte medium adapted to the application. In contrast to conventional electropolishing, no harmful vapors are produced by electroplating baths, which require energy-intensive extraction and special protective equipment for personnel. As 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 processing result is achieved over the entire service life of the electrolyte medium. Replacement is only necessary when the dry electrolyte is saturated due to the metal ingress, for which it is then disposed of in a similar professional manner to abrasives. In conjunction with the polishing machines required for this process, the degree of saturation of the electrolyte is recorded by the machine and the operating personnel are constantly informed about the condition and the remaining useful life. This ensures that reproducible results are always achieved on the component and that the electrolyte is utilized optimally. This reduces labor and disposal costs. At the same time, theCO2 footprint of the products is reduced due to the high resource efficiency.
Precise, gentle and geometry-preserving processing
"Dry" electropolishing takes place in polymer beads of different sizes with an integrated electrolyte medium adapted to the application (Photo: Rösler Oberflächentechnik GmbH)In dry electropolishing, the components, which are fixed to special suspensions, move slowly through the electrolyte medium, whereby a homogeneous flow takes place. Depending on the component, internal processing can also take place, which is made possible by special (auxiliary) electrodes. Due to the process, material is mainly removed from the roughness peaks on the surface. Material removal is therefore comparatively low and gentle. The machined components have a homogeneous surface without marks, pattern formation or orange peel effects. Even with delicate and complex geometries, no micro-scratches or cracks occur during processing.
On the one hand, the targeted and "controlled" processing ensures that the component geometry of precision parts, such as machine tools and tools for the pharmaceutical industry, is not altered and edges are not rounded off. On the other hand, the effective smoothing of the surface minimizes the formation of cracks and craters. As with conventional (electro)polishing, this results in improved corrosion and fatigue resistance and therefore a longer component service life. Compared to conventionally electropolished workpieces, however, dry-polished parts corrode 4 to 15 times slower (the corrosion tests were carried out in a salt water solution with 30 g/L NaCL). For workpieces such as gear wheels used in mechanical systems, the treatment improves the sliding properties at the same time due to the rapid increase in contact ratio and an optimum distribution of lubricants on the surface is achieved. Component wear and noise emissions are also significantly improved thanks to better surface quality.
The process times are comparatively short, ranging from a few minutes to 1.5 hours, depending on the application, initial roughness and desired result. 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 using an additional abrasive vibratory finishing process.
Adaptable to many applications
The new and patented process was originally developed for processing model castings and crowns made of cobalt-chrome and titanium in the dental industry. GPA Innova's dry electropolishing process is now 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, such as aerospace, pharmaceuticals, mechanical engineering and the consumer and luxury goods industry. Due to its proven biocompatibility, it is also used in medical technology in the manufacture of implants and instruments.
The process design and definition of the process parameters are tailored to the components and application in Rösler's Customer Experience Center. Various systems for an automated process are available for implementation. This ensures that all parts are processed with defined or validated parameters.
Surface finishing is becoming increasingly important due to rising demands on surface quality combined with higher requirements for reproducibility, traceability and resource efficiency of the processes. This requires adapted processes and innovative solutions for surface finishing. With the DryLyte process, Rösler Oberflächentechnik offers an alternative, innovative technology for electropolishing demanding metallic components. In contrast to conventional electrochemical polishing processes, automated processing with electrolyte-containing, solid particles takes place in a primarily dry environment.
