Excellent finish for deep-drawn precision medical components

Die Prozessentwicklung einer Kantenverrundung erfolgte an einem 20 mm großen Baugruppengehäuse aus Edelstahl, das in der Medizintechnik eingesetzt wird. (Foto: Hubert Stüken GmbH & Co. KG) / In this project, an edge radiusing process had to be developed for a 20 mm large stainless steel housing used in a medical device. (Photo: Hubert Stüken GmbH & Co. KG)

„Die Herausforderung bei diesem filigranen Gehäuse lag in seiner großen Oberfläche bei extrem dünner Wandstärke. Für den Materialabtrag an den Kanten sind hohe Kräfte erforderlich, die gleichzeitig so gut beherrscht werden müssen, dass keine Formänderung auftritt“, beschreibt Dirk Schulz, Projektingenieur bei Stüken, die Aufgabenstellung. (Foto: Hubert Stüken GmbH & Co. KG) / Dirk Schulz, project engineer at Stüken, explains the finishing task as follows: „With this delicate housing the main challenge was a large surface area in combination with extremely thin walls. To remove sufficient material at the edges requires a high processing intensity. But the intensity must be tightly controlled to prevent any deformation”. (Photo: Hubert Stüken GmbH & Co. KG)

Deep-drawn functional components are increasingly being utilized in the production of medical and pharmaceutical products. To also meet the strict standards for manufacturing and quality management in the field of surface finishing, Stüken Medical relies on mass finishing solutions and consumables from Rösler.

In order to meet the increasing demand for deep-drawn metal components in the field of medical and pharmaceutical engineering, a few years ago the Hubert Stüken GmbH & Co. KG, founded in 1931, established the business division “Stüken Medical”. The product range of this family-owned company includes also stamped and bent parts, plastic-coated components and complex assemblies. The company maintains manufacturing operations at fivelocations in Europe, Asia and the United States.

Andreas Hellman, manager of the ISO 13485 certified business division,explains: „Components used in the field of medical and pharmaceutical engineering must meet strict quality standards. The same strict standards apply also to the actual production operations. For this reason, we have pooled the required knowhow for the development and production of such precision components at Stüken Medical”. Among other items, this division produces complex housings and assemblies, valves, extremely precise micro parts and primary packaging. These components are made from metals suitable for deep drawing, such as stainless steel, aluminum and titanium. To meet the strict quality standards in the medical and pharmaceutical industry, the company utilizes multi-stage cleaning systems and operates two class 7 cleanrooms. The company’s R&D and development department, located at the corporate headquarter in Rinteln, Germany, is continuously exploring the possibilities to expand the range of processes and materials.

A team approach for innovative solutions

„For many of our customers we are a development partner. To perfectly adapt new products to their intended use, we are not only working with our customers but are also cooperating with partners from various technological sectors”, continues Andreas Hellmann. When it comes to issues around surface finishing that can be resolved by mass finishing, for 30 years the company has been relying on the experience and knowhow of the Rösler Oberflächentechnik GmbH. Andreas Heilmann explains further: „Our long partnership is based on the excellent quality and reliability of the Rösler equipment and consumables. This helps us to ensure that the required results are achieved in a consistent manner”. Dirk Schulz, project engineer at Stüken, adds: „When it comes to the joint development of finishing processes, we value especially the flexibility and expertise of Rösler. In this respect, our access to the Customer Experience Center in Untermerzbach is extremely valuable. Rösler supports us also with documentations and equipment details, required for machinery and processes that must be qualified and validated in line with ISO 13485. At its manufacturing locations around the world this deepdrawing specialist is using around 15 rotary vibrators and 10 centrifugal disk finishing machines for its finishing operations. The company is also operating 18 centrifuges for the eco-friendly and reliable cleaning and recycling of the process water.

Strict requirements for the finishing results

The deep-drawn components are generally characterized by an extensive degree of material shaping, complex geometries and extremely small dimensions requiring a high dimensional accuracy. This results in especially demanding specifications for deburring, edge radiusing and polishing of external and internal work piece areas. Equally challenging are the surface
roughness and surface quality requirements. Dirk Schulz explains: „On the one hand we must ensure that all pieces within a work piece batch receive the same high-quality surface finish. On the other hand, the work pieces must not be damaged or deformed. Last-but-not-least, after completion of the finishing process the work pieces and media must be reliably separated. A carry-over of the work pieces and/or media into the next batch must be prevented at all costs”. In conjunction with polishing jobs, the work piece surface must frequently be marked with an UDI code. To fully meet these specifications requires not only finishing processes that are precisely tailored to the respective work pieces. Likewise, the equipment and consumables must also be adapted. Frequently, this requires conducting special feasibility studies.

A process for finishing medical components

The process for radiusing the edges on a 20 mm large stainless steel housing for a medical device was developed in close cooperation with Stüken. The project engineer explains the finishing task as follows: „With this delicate housing the main challenge was a large surface area in combination with extremely thin walls. To remove sufficient material at the edges requires a high processing intensity. But the intensity must be tightly controlled to prevent any deformation”. The Customer Experience Center at Rösler is equipped with ultra-modern machines for running a wide variety of different finishing processes. This allows conducting processing trials for defining the most suitable equipment technology under actual production conditions. During such development processes, the processing bowl of standard machines must be frequently modified, sometimes involving substantial engineering changes. For this project, the comprehensive mass finishing experience at Stüken was a valuable source of ideas. To guarantee a reliable and complete separation of the finished work pieces from the media the finishing equipment for Stüken Medical required a few changes in the separation process. Another goal of the processing trials is the determination of the optimal media shape and type (ceramic or plastic) for the finishing task at hand. In order to achieve consistently good surface finishes, very often the media must have extremely tight dimensional tolerances. All ceramic and plastic media are produced at Rösler in compliance with the highest ecological standards. With over 15,000 different products the media, together with the compounds and process water cleaning agents, represents the by far largest range of mass finishing consumables in the world. Key factor for the development of successful
finishing processes is the perfect interplay between the right equipment technology and the right consumables (media and compound). Generally, the best results are achieved by close cooperation with the customer.