With digitized surf finishing Rösler paves the way towards the smart factory

All over the world joint replacement surgeries are rapidly increasing. Experts expect that until 2030 in the United States alone around 3.5 million artificial knees will be implanted. In comparison: In the year 2020 the total number of knee implants amounted to around 600,000.  Yet, to a large extent orthopedic implants still receive their final surface finish by manual operations, even though these are very time consuming, require a lot of personnel and are characterized by substantial quality fluctuations.  „The implant industry faces a huge challenge, namely, to produce ever increasing implant quantities in a cost-efficient manner and in a consistently high quality”, explains Michael Striebe. Michael looks back at over 25 years of experience in the field of mass finishing. And as  Global Sales and Process Expert for medical engineering at Rösler Oberflächentechnik GmbH he is the main contact for customers active in the medical engineering industry. „At the same time, the demands for a longer usable life and compatibility with the human body are continuously increasing. The manufacturers react to these challenges by making the artificial joints from materials like titanium, ceramics or ceramic-like coatings. However, the latter, because of their hardness, no longer allow manual surface finishing.“

Surf finishing allows precise surface treatment of complex shapes and tough materials

With the surf finishing technology Rösler offers a system that allows a particularly efficient treatment of orthopedic implants, even if they are made from extremely hard materials. Compared to typical vibratory machines, surf finishing is up to 40 times more intensive. As a matter of fact, it is the most intensive mass finishing method currently available in the market. Surf finishing machines consist of a carousel containing a number of rotating workstations. These are equipped with multiple spindles, onto which the work pieces are mounted. The carousel is then lowered into a rotating processing bowl filled with grinding or polishing media. Depending on the carousel design, up to 16 work pieces can be treated simultaneously. Exposure of the work pieces to the media stream in the processing bowl, combined with the targeted motion of the spindles, permits precise treatment of specific surface areas. Therefore, surf finishing is ideal for treating components with complex shapes. For example, the “joint box” on femoral knee components can be mechanically finished without requiring any manual post polishing operations. The Rösler surf finish machines even allow processing implants made from aluminum oxide ceramic with a finishing quality that is unmatched in the world. 

Smart process development and digital data exchange 

The digitization of the entire finishing process is another breakthrough. Special simulation software permits the complete evaluation of mass finishing processes with 3D models. For example, process parameters like immersion depth, treatment angle or possible shadowing can already be  analyzed during the planning phase. This helps accelerate the process development and saves costs. Up to 90 percent of the entire process can be defined digitally. The remaining 10 percent are verified by indispensable processing trials conducted in surf-finishers under actual operating conditions.

Another benefit of digitization, namely the direct data exchange between CNC machining centers and surf-finishers opens completely new possibilities. If the machines can be supplied with 3D data such as work piece dimensions and dimensional tolerances, the processing times can be automatically adjusted.  This helps increase the work piece throughput and saves costs by decreasing the consumption of media and compounds. The digital linking of the machines during the various process stages increases the efficiency of the entire value-added chain. Above all, the quality of orthopedic implants can be improved to an entirely new level.

Process control with Rösler Smart Solutions

The patented software module Rösler Smart Solutions (RSS) Comfort ensures complete process documentation and operational stability. This software monitors the process water quality generated by a cleaning and recycling centrifuge connected to the mass finishing equipment. As such it allows a realistic assessment of the quality of the achieved surface finish.  „We even go one step further. In the near future we will collect and analyze the consumption of all consumable items (media, compound, etc.) with the RSS module. This will then allow our customers to review and control the costs of their finishing process “, explains Michael Striebe.

At the center of this software expansion is a continuous information exchange between centrifuge, mass finishing machine(s) and software. By automatically measuring and collecting key process data, the contamination of the process water, the pH value and the electrical conductivity are continuously controlled. In case of deviations from preset values the system automatically adjusts the dosing rate of the process water cleaning additives. This helps maintain a high process water quality without the need for any intervention by the machine operator. All process adjustments are documented and can be retraced at any time. Rösler is the only company that can supply such a unique, innovative digital control system.

A path to the smart factory

The trend towards total digitization of surface finishing processes is an important milestone for creating a smart factory environment.  The digitization of production processes permits not only the implementation of more efficient and economical production methods but also increases the precision of the manufacturing operations. With digital simulation modules, intelligent data exchange systems and state-of-the art process monitoring software, Rösler provides valuable tools to its customers allowing them to transform the industrial challenges into opportunities.