High Optimization Potential in Smoothing for Series Production
With a simple yet innovative diamond burnishing tool from Kempf, Buro GmbH in Winden was able to optimize a previously complex machining operation in series production. The positive result ensured consistent quality of the produced eccentrics.
Between Cycle Time and Precision
When it comes to "smoothing" surfaces, there are various approaches to executing this seemingly simple operation. In series production, however, the wheat is separated from the chaff: “The individual processes must be performed as quickly as possible—meaning automated—and consistently maintain quality over many machining cycles without the need for constant tool changes or adjustments,” explains Thomas Welte from the Technical Field Service at Kempf in Reichenbach Fils. “Especially when high requirements for the component’s surface condition are involved, selecting the right tool and approach is often challenging—and many manufacturers face significant hurdles.”
Small Component, Big Impact
At Buro, a manufacturer and developer of mechatronic components and systems, the extensive machine park enables the implementation of all machining processes. This allows the various departments specializing in milling, gear cutting, turning, and grinding to cover the majority of machining operations in-house and offer a wide range of manufacturing capabilities. Customers appreciate this advantage—combined with high manufacturing quality and delivery reliability—and have been commissioning parts production in Winden for decades.
Buro produces a compact eccentric component used in pumps and ventilators. The component, available in length variants from 20 to 50 mm and diameters from 16 to 38 mm, was until recently manufactured from lead-containing free-machining steel. The turning process was already fully automated. However, to achieve the required surface finish, extensive grinding operations were necessary, consisting of several separate machining steps. The parts had to be removed from the lathe, inspected, and then finished in a subsequent grinding process. This was followed by a washing step and another (dimensional) inspection, resulting in the complete machining of the eccentric parts being associated with high costs, increased error rates, and significant time expenditure.
The diamond burnishing tool UDBTM-R-16 is used. At a cutting speed of 100 m/min and a feed rate of 0.05 mm/rev, it takes less than six seconds to burnish the approximately 10 mm long surface smooth, drastically improving surface finish and cylindricity. A tolerance of +7 to 12 μm is maintained in the process.
Completely machined on the lathe: Thanks to the compact design of the diamond burnishing tool and the ability to swivel the diamond head 180°, the tool can be used even in tight spaces. At BURO, this eliminated the need for a second setup on another machine.
Optimized Complete Machining
With the change of workpiece material to C45 steel, Buro aimed to optimize the complete machining process. Initial tests were conducted using different indexable inserts and various radii to achieve the required surface finish of less than 0.4 µm Ra. While this approach appeared to work for a small number of components, the tool life of the inserts was insufficient for series production—the wear on the indexable inserts was too high.
Mandatory random surface measurements are performed. The component without burnishing shows a surface finish of 0.72 μm Ra and 3.8 μm Rz after turning operations. After burnishing, a surface finish of Ra = 0.12 μm and Rz = 1.2 μm is achieved. The customer-required Ra value of 0.4 μm is thus clearly exceeded.
A Small, Innovative Diamond Burnishing Tool Is the Solution
The solution to this challenge was found by Buro at Kempf: the diamond burnishing tool UDBTM-R-16, measuring just 97 mm from the diamond tip to the shank end, already proved convincing in initial tests. With the ability to rotate the diamond tip up to 180° from left to right, the tool offers great flexibility: this not only allows the desired lead angle to be set relative to the component contour but also enables the diamond burnishing tool to be used in tight spaces on CNC lathes. As a result, the tool could be integrated into the turning process, eliminating the previously required grinding operation. Compared to the previously used turning tools, wear on the diamond tip is practically undetectable even after many thousands of parts, significantly increasing both the tool life and the workpiece quality.
The component before and after machining with the KEMPF diamond burnishing tool
Buro is thus able to manufacture nearly 200,000 eccentric parts per year with process reliability and full automation while simultaneously guaranteeing uniform surface quality. “Due to the various advantages offered by the UDBTM-R-16 in terms of tool life and surface quality, several of these diamond burnishing tools are now in use on multiple lathes in Winden,” emphasizes Thomas Welte. “After all, these Kempf tools are highly versatile and flexible thanks to their design and the ability to adjust the angle while clamped.”
Tested and rated very good.
From left to right: Lead setup technician and group leader, Marco Berblinger. KEMPF technical field service, Thomas Welte. Setup technician, Michael Kern.
The Tool Used
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 approach angle to the component contour to be set.