Manufacturing Valve Housings with Cross-Holes #burrfree Straight Out of the Machine Using "High Speed Deburring"
Wherever absolute reliability is required from hydraulic systems and safety-critical components are controlled under high pressure, a single chip can mean the proverbial "technical knockout" for the entire system and, in extreme cases, endanger lives. The "human factor" plays a crucial role here, as manual (deburring) work can result in inconsistent quality and potential deviations from specifications. To eliminate this source of error and to enable fully automated machining including deburring even for smaller production runs, Weidemann Hydraulik GmbH is taking unconventional approaches. The specialist in hydraulic block manufacturing is integrating two machine deburring solutions into the production process on the CNC machine, including the High-Speed Deburring "HSD" tool.
Founded in 1974 by Hans Weidemann in Straubenhardt near Pforzheim, the original focus of the sole proprietorship was on developing and distributing valves for hydraulic systems. It was only when Franz Reher joined the company a year later that in-house production began, with Mr. Reher himself operating the machines at that time. The subsequent high demand for hydraulic valves also fueled demand for valve housings and control blocks, which were then manufactured in-house as well. The quality was convincing, and the resulting strong reputation, along with the focus on “custom solutions,” was so well received that 48 years later, six warehouse and production buildings stand at the same location. Today, 42 employees continue to be engaged in the manufacturing and distribution of valve housings, control blocks, connection plates, manifold connection plates, and other valve components.
The range of applications for the components from Straubenhardt is as diverse as the bores in a valve housing. Weidemann hydraulic components are used in start and brake systems for chain carousels, marine gearboxes, theater technology including the Bregenz Festival, rolling mills, and even in the Rethe bascule bridge in Hamburg—essentially wherever top quality, reliability, and safety are required.
Deburred Components Are the Key to Success
What makes the difference is—who would have thought—deburring. Wherever multiple bores intersect and cross-holes or cross bores are created, burr formation almost always occurs as a result of the production process, which can have critical consequences in hydraulic components. Often, deburring is still performed manually because the expertise for these delicate machining operations is frequently lacking in CNC machining, or there is reluctance to alter the cycle time of the machining center.
The valve housings machined in the first setup are temporarily stored and then all completed in the second setup. The numerous bores, which intersect with the lateral and rear bores, are clearly visible, resulting in burr formation at the intersections.
Eliminating Manual Deburring
Weidemann is taking a different approach here, aiming to achieve 100% machine deburring and meet their self-imposed quality standards. After contacting the deburring specialist KEMPF at last year’s Deburring Expo 2021 in Karlsruhe and a subsequent machining analysis by field service technician Dominik Messaros, two machine tooling solutions were initially integrated into the machining process of one machine. Although these tools are primarily designed for series production, Weidemann even uses them for small batch production—simply to eliminate manual deburring and achieve the desired (machine) quality.
Tooling Solution for Precise Deburring
One solution used for this purpose is the “High-Speed-Deburring” (HSD) tool, which is designed to reliably deburr cross-holes through the main bore. The unique feature of this tooling solution is that the cutting edges removing the burr inside the bore can be precisely actuated using the internal coolant pressure, enabling accurately positioned deburring. This deburring solution allows burrs to be removed exactly where they form, with absolute process reliability and speed.
The HSD tool in operation. The tool, designed for cross-holes, is usually customized for the respective bore diameter. Since many bores in the valve blocks are dimensioned at ¼ inch diameter, the HSD tools are used independently of the component. The folded cutting edges are clearly visible. The tool enters the bore in this state.
The HSD tool with a diameter of 11.30 mm used at Weidemann is not only employed for machining a single component but is also suitable for nearly all valve housings produced on various machines due to its standard bore diameter of ¼ inch. When larger bore diameters require deburring, the same HSD tool is used to machine the area to be deburred with a circular helical motion, ensuring reliable burr removal in the process.
One of the many cross-holes in close-up: clearly visible is the bore coming from the backside as well as the third bore intersecting vertically. The burr at these intersection edges was completely removed by the specially designed High-Speed Deburring tool (HSD). Weidemann uses this tool for all occurring ¼ inch bores.
Ceramic Fiber Brush for Surfaces
Since the valve housings are milled entirely from a solid block, the tools used leave milling marks as well as burrs on workpiece edges, bore entries, and countersinks, which must also be removed. Ideal for this machining is the so-called ceramic fiber surface brush, whose brush fibers consist of 80% technical ceramic (Al2O3 aluminum oxide) and only 20% binder content. This ceramic is especially suitable when workpieces require a special surface finish. Successful applications in aerospace and automotive industries demonstrates the unique properties that far surpass those of conventional wire brushes or nylon brushes.
The “oxide ceramic” features, for example, a high hardness (harder than steel) and is therefore ideally suited as a cutting material in metal cutting operations. Because ceramic is very hard, yet the fiber rods are flexible enough to conform to the workpiece surface, the use of ceramic fiber brushes produces a uniform grinding effect, resulting in consistent and excellent polishing and grinding characteristics, thereby generating uniform surfaces. Additionally, this type of ceramic is highly heat-resistant, dimensionally stable, and very wear-resistant during deburring and polishing operations.
Minimizing Manual Deburring Tasks – Maximizing Quality and Process Reliability
At Weidemann GmbH, the ceramic fiber brush type BÜA21-CB60M with a diameter of 60 mm is the second machine-applied deburring tool used, and the only solution capable of meeting the customer’s stringent requirements. In combination with the HSD tool, this provides a comprehensive machine deburring process for internal bore intersections as well as all burrs and milling marks on the surface.
The surface is treated with the white ceramic fiber brush of type BÜA21-CB60M. These fibers are particularly stiff, providing higher abrasive performance than, for example, red or pink fibers, which are also available. This allows for process-reliable removal of burrs up to approximately 0.2 mm thick.
Despite the wide range of products and bore sizes deviating from standard dimensions, machine deburring operations are highly efficient, even though they initially require additional programming effort. At the specialist for high-quality hydraulic solutions, the goal is to establish a complete machining process that already includes full deburring and can be applied to other machines and additional components. This approach ensures the consistent production of high-quality valve housings that meet internal quality standards and can be used in highly sensitive and safety-critical applications.
On the left, the component, machined from a single piece of 11SMn30+C steel, after the first setup. Five of the six surfaces are fully machined at this stage. In the second setup (right), an additional five bores and a flat countersink are produced. The component is then fully finished, including bore deburring and surface finishing.
The Best Solution Even for Small Production Runs
Due to the high demand for custom solutions, Weidemann GmbH primarily operates with smaller order quantities. There are no off-the-shelf mass-produced products. Nevertheless, the company has chosen to collaborate with deburring specialist KEMPF to apply their expertise and corresponding tooling solutions, thereby gaining an additional competitive advantage.
Components that were previously deburred manually now come completely finished straight out of the machine, freeing up resources that can be used to optimize their own production. This is an advantage that Weidemann’s customers appreciate, as burr-free valve blocks and increased quality awareness also lead to significantly fewer complaints and stronger customer loyalty. An investment that pays off!