Double face grinding in high-end precision with maximized throughput

Precision disks for automotive manufacturers are manufactured by a supplier in series production using double surface grinding. For maximum throughput and highest precision, the company relies on the equipment and know-how of a specialist.

Rudolf Rafflenbeul Stahlwarenfabrik GmbH & Co. KG in Hagen, North Rhine-Westphalia, manufactures a wide range of products with more than 4,000 articles made of spring steel. These are developed and produced for numerous customers in the automotive, supplier and electrical industries as well as for mechanical and plant engineering and the trade. In addition to standard parts such as dowel pins and thin-shaft screws as well as various spring washers, contact washers and spring washers, this also includes special stamped and formed parts according to customer-specific requirements.

For example, Rafflenbeul supplies many well-known automobile manufacturers with precision washers used in shock absorber systems. In order to be able to guarantee the highest precision requirements despite high quantities, a great deal of experience and competence is required, as well as process-stable manufacturing technologies and a high-performance machine park.

For high-precision series production, the company relies on the latest generation of machines from the manufacturer Supfina Grieshaber from Wolfach in the Black Forest for double surface grinding. "We have been using the Supfina Planet V4 system for a good six years and use it to produce precision disks with diameters between 6 and 85 mm and material thicknesses from 0.6 to 40 mm using the double surface grinding process. Before making the investment decision at the time, we had initially rented the very space-saving machine from Supfina for one year," recalls Carsten Dietze, who, as a technical employee in the tool shop at Rafflenbeul, has been familiar with the machine and the associated processes from the very beginning. "Very quickly, the very reliable, consistently high precision became apparent, which is decisive for us with regard to the high demands of the automotive industry."

"With the system, we achieve straightness below 8 µm - with a very flat, homogeneous surface finish," adds Carsten Dietze. In the two-sided grinding process, the stamped discs are ground simultaneously from above and below in a transport disc, with the upper grinding disc slightly angled, enabling very high, reproducible accuracy - in just one process, without any upstream or downstream fine grinding.

"In addition to reliable high quality, efficiency and cost-effectiveness naturally also play an important role for us, especially against the background of increasing automation in our series production," emphasizes Carsten Dietze. "With the Supfina Planet V4 alone, our most powerful double surface grinding system, we now produce around 25 million workpieces per year. Whereby we have been able to continuously optimize cycle times in recent years and significantly increase throughput." This is where Carsten Dietze brings the close cooperation with Supfina Grieshaber and the lubricant manufacturer Oest into play.

"With the acquisition and integration of the Planet V4 system into our production process, we were in close contact with Manfred Welle from Supfina Grieshaber from the very beginning, who still supports us in maintenance today. Despite very good results from day one, it is always our aim to exploit the performance potential of our machines to the full and to continuously optimize production processes. The intensive exchange of information and experience with Manfred Welle was ultimately the impetus for a changeover to cooling lubricants, which has brought us another significant step forward," reports Carsten Dietze. And Manfred Welle from Supfina Grieshaber adds: "With the delivery and installation of new machines, we do not consider our work to be finished by any means. For us, individual personal support means constantly working together with the customer on process optimization, with the focus on high throughput, fast setup times, smooth processes and maximum consistency in quality. The goal and the aspiration to work together on optimal solutions unites us with our customer Rafflenbeul in a special way."

And Manfred Welle looks back: "Since abnormalities with the cooling lubricant occurred relatively frequently in the early days, we naturally also discussed this topic. The high foam formation, constant re-conservation and the maintenance effort with defoamers, as well as the relatively short service lives, were not something I had experienced with our machines. I therefore referred to our lubricant partner Oest, a manufacturer with more than 100 years of experience, who offers customized cooling lubricants through its application technology, research and development and ensures very competent personal all-round support on site."

Stephan Tippmann from Oest remembers: "As the area sales manager for NRW, I was of course always approached by Rafflenbeul, especially since we were already supplying the company with corrosion protection from the Oest Antiko series. Through Supfina Grieshaber as a reference and the personal recommendation of Manfred Welle, the already existing contact was intensified. Initial detailed consultations took place, together with our application engineering department, and finally the Supfina system was switched to our semi-synthetic water-miscible cooling lubricant from the Oest Colometa ecoT series."

"The Supfina Planet V4 has undoubtedly taken double face grinding to a new level. The sophisticated technology with the built-in patented titling navigation system (TNS) not only ensures reproducible results in top quality at all times, but also enables fast changeover and reliable process stability," says a satisfied Carsten Dietze. "In practice, however, it is evident that the right cooling lubricant is also an important success factor for the efficiency and stability of the system. In this respect, the close cooperation in the three-man team with Oest and Supfina Grieshaber has proven itself in every respect," emphasizes Carsten Dietze. "By working together, all conceivable parameters that contribute to result optimization and process efficiency are included. This is the basis for our high throughput with the Supfina Planet V4 and the cycle speed achieved with up to 300 parts per minute - with consistently high quality, low setup times, less tool wear and reduced costs in the use of cooling lubricant."

The partially synthetic cooling lubricant from the Colometa ecoT series used as a concentrate produces a finely dispersed, low-foaming emulsion with many advantageous properties when mixed with water. These include not only low consumption. Oest Colometa ecoT is free of FAD, MIT, boric acid and other restricted substances. The cooling lubricant thus ensures a consistent formulation with reliable occupational, environmental and health protection in the long term. At the same time, it is characterized by high biostability and enables long service lives, which Manfred Welle also confirms when using Supfina machines: "Due to the low susceptibility to germs, I usually observe disproportionately long service lives. High cleanliness in the machine without sticking in the system ensures low care and maintenance requirements."

The weekly cooling lubricant check and documentation in accordance with TRGS 611, which is carried out at Rafflenbeul by trained employees, is nevertheless important in order to be able to react at an early stage in the event of any abnormalities. In addition to the control data collected, Stephan Tippmann also regularly sends samples to the Oest laboratory. "Like Manfred Welle, who is available to us for machine-specific questions and concerns, we can rely on the expertise of Stephan Tippmann and the Oest application technology department when it comes to fluid management. This close cooperation is very important for us and offers the best conditions for us to develop further together and to be able to optimize processes," sums up Carsten Dietz. (OM-05/23)