With a simple but innovative diamond roller burnishing tool from Kempf, Buro GmbH in Winden was able to optimize a previously complex machining step in series production. With the positive result of being able to guarantee the consistent quality of the eccentrics produced.
When it comes to ‘smoothing’ surfaces, there are various approaches to implementing this simple work step. In series production, however, the wheat is separated from the chaff: “On the one hand, the individual processes must be carried out as quickly as possible, i.e. by machine, and on the other hand, they must be produced in consistent quality over many processing cycles without having to constantly change or correct the tool,” explains Thomas Welte from Kempf's Technical Field Service in Reichenbach Fils. “The right tool selection and procedure are often problematic, especially when there are high specifications for the quality of the component - and many manufacturers are faced with major challenges.”
The last tool to be used is the UDBTM-R-16 diamond roller burnishing tool. At a vc of 100 m/min and a feed rate of 0.05 mm/rev, it takes less than six seconds to smooth the approximately 10 mm long surface and drastically improve the surface quality and cylindricity. A tolerance of +7 to 12 μm is maintained.
Thanks to its diverse range of machinery, the manufacturer and developer of mechatronic components and systems Buro is able to implement all machining processes, meaning that the various departments for milling, gear cutting, turning and grinding can cover the majority of machining processes themselves and offer a wide range of manufacturing options. Customers appreciate this advantage - coupled with the high production quality and delivery reliability - and have therefore had components produced in Winden for decades.
Small component, big impact
For example, Buro produces a compact eccentric component that is used in pumps and ventilators. Until recently, the component with lengths of 20 to 50 mm and diameters of 16 to 38 mm was made from leaded automatic turning steel. The turning process was already fully automated. However, in order to achieve the required surface quality, complex grinding work was necessary, which in turn consisted of several separate work steps. The components had to be removed from the lathe, checked and finally finished in a downstream grinding process. This was followed by a washing process and a further (dimensional) check, meaning that the complete machining of the eccentric parts was associated with high costs, a higher error rate and a considerable amount of time.
Completely machined from the lathe: The compact design of the diamond roller burnishing tool and the ability to swivel the diamond head through 180° means that the tool can even be used in confined spaces. This meant that BURO did not require a second clamping in another machine.
Optimized complete processing
By changing the material to C45 steel, Buro aimed to optimize the complete machining process. Tests were initially carried out with different indexable inserts and different radii to ensure that the required surface quality of less than 0.4 µm Ra was achieved. This seemed to work for a small number of components, but the tool life was not long enough for series production - the wear on the indexable inserts was too great.
Random sample measurements of the surface are mandatory. The non-smooth-rolled component has a surface quality of 0.72 μm Ra or 3.8 μm Rz after the turning operations. After roller burnishing, a surface quality of Ra = 0.12 μm and Rz = 1.2 μm is achieved. The Ra value of 0.4 μm required by the customer is thus clearly exceeded.
A small, innovative diamond roller burnishing tool is the solution
Buro found the solution to this problem at Kempf: The UDBTM-R-16 diamond burnishing tool, which measures just 97 mm from the diamond tip to the end of the shank, was already convincing in initial tests. The ability to rotate the diamond tip by up to 180° from left to right means that the tool can be used very flexibly: not only can the desired angle of attack to the component contour be set, but it is also possible to use the diamond burnishing tool in confined spaces on automatic lathes. As a result, the tool could be implemented in the turning process and the grinding process previously required could be eliminated. Compared to the previously used turning tools, wear on the diamond tip is virtually undetectable even after many thousands of parts, meaning that the service life of the tool and the quality of the workpiece have also increased many times over.
The component before and after machining with the KEMPF diamond burnishing tool
This enables Buro to produce almost 200,000 eccentric parts per year in a reliable and fully automated process while guaranteeing the uniformity of the surfaces. “Due to the various advantages resulting from the use of the UDBTM-R-16 when it comes to tool life and surface quality, several of these diamond roller burnishing tools are now in use in various lathes in Winden,” emphasizes Thomas Welte. “After all, these Kempf tools can be used very variably and flexibly thanks to their design and the ability to change the angle when clamped.”
Tested and found to be very good. From left: Main installer and group leader, Marco Berblinger. Technical sales representative of KEMPF, Thomas Welte. Setter, Michael Kern.
The small diamond burnishing tool UDBT-R-16 with a 12 mm shank and a diamond head that can be rotated 180°, allowing the desired contact angle to be set in relation to the component contour.
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