In the German machining industry, precision and process reliability continue to be the main focus. The example of Weigel & Schwarz Präzisionstechnik GmbH in Wetzlar shows how the use of specialized deburring tools from KEMPF made it possible to automate and sustainably improve the deburring of highly complex components. The focus is on a safety-relevant component used by the hydraulics specialist Roemheld in foot pumps for the medical sector.
The company “Weigel & Schwarz Präzisionstechnik GmbH”, founded in 1957 by Richard Weigel, initially specialized in linear technology. With the takeover by the Wolni family in 2004, the company was gradually reoriented towards machining metals and plastics. Today, the second-generation owners Günter and Lana Wolni manage a modern machine park with 4- and 5-axis CNC machining centers and offer a wide range of services: from material procurement and precise machining to surface finishing and assembly. As a “contract manufacturer”, the company mainly produces demanding and high-quality milled parts in small and medium series from aluminum, stainless steel, titanium, brass, and plastic for customers in various industries, including cylinder housings, linear guides, lens and objective holders, as well as other components for the optics industry and general mechanical engineering.
Invisible burrs inside the component
The Roemheld Group, headquartered in Laubach, is one of the leading suppliers of clamping technology, assembly and drive solutions and is also known worldwide for hydraulic components. Driven by the goal of accelerating machine setup processes, many inventions have emerged, including the “foot pump” in a closed design, which ensures maximum efficiency without leakage points and is used in automation, mechanical engineering, medical technology, and care applications. As the global market leader in this field, Roemheld has worked closely with Weigel & Schwarz for years on the production of certain individual components. Thanks to the “direct neighborhood” and the shared mindset regarding quality, the high requirements can be implemented quickly and efficiently.
A safety-relevant pump piston housing made from an AlCuMg1 aluminum alloy—initially used in lifting devices for height-adjustable workstations and today, now in its fourth generation, also used in operating and instrument tables, therapy couches, and medical beds—comes with very specific quality requirements. Due to its use in the medical field, Roemheld performs continuous 100% inspections, as the highest standards apply to this component. For this reason, Weigel & Schwarz, with their expertise and strong quality awareness, were commissioned to manufacture it. The Roemheld-designed component, which boasts high mechanical fatigue strength, features ten bore holes and just as many intersections that previously had to be manually deburred at Weigel & Schwarz in separate process steps after machining. Since all relevant areas are located inside the housing (barely visible from the outside), this was a highly demanding and time-consuming task—an enormous challenge with an annual order volume of around 15,000 components. To meet increasing requirements and enable further development of the foot pump product line, an automated solution became necessary. Weigel & Schwarz therefore decided to integrate deburring directly into the machining process in order to increase productivity and process reliability. Trials with various tool solutions followed, but none delivered the desired results. Manual work remained necessary.
Achieving burr-free production with only three deburring solutions
Only after contacting Marcus Schneider, Field Sales Technician at KEMPF in Reichenbach an der Fils, did the project regain momentum. First, the machining process of the aluminum components was assessed as a whole, and a “deburring strategy” was developed considering the existing workflow. “When selecting suitable tools, it always matters why and how burrs form and where they are located within the component—such as whether burrs protrude into a main bore or are pressed from the main bore into a cross bore,” explains Marcus Schneider. Cutting parameters and the sequence of tools also play an important role in developing an implementable strategy.
The pump piston housing presented several geometry-related challenges: two deep-hole bores intersect at a defined, non-right angle with bore relationships of 1:1 on different levels. A cross bore meets a main bore at a 90° angle with a bore ratio of 1:2 (cross bore to main bore) at the cutting edge near the bore tip. Another cross bore meets a threaded bore at a bore ratio of about 1:2 (cross bore to main bore). Additionally, another deep-hole bore intersects two threaded bores outside the bore axes and “half-open” intersects the bottom of a cylindrical bore. The requirement: all contours and intersections must be absolutely #burr-free so that no burr can detach and enter the hydraulic system. Considering the machining steps and clamping situations, the corresponding deburring tools and strategies were selected. Within weeks, they enabled “series-ready complete machining,” ensuring that the components now leave the machine absolutely #burr-free as required. Markus Götzelmann, Technical Inside Sales Specialist at KEMPF, configured the tools based on drawings and 3D models. “Only three deburring solutions were required, which keeps tool change times extremely low,” says Lana Wolni.
The first of the three selected deburring tool types is the “Back-Burr Cutter & Path Deburring System”, consisting of a ball milling cutter (“lollipop”) with 290° freedom of movement and a path (NC dataset) for contour-tracking secondary burr-free deburring on the CNC machine. The optimum cutting angle is calculated in advance for each coordinate point through the NC dataset provided by KEMPF. This ensures that the milling cutter—unique on the market so far—is able to shift the cutting engagement point along the tool’s cutting edge during machining, thereby using the entire cutting edge instead of wearing it at a single point. This optimization prevents premature tool wear and significantly increases tool life.
Two deep-hole bores intersect at a defined, non-right angle with bore ratios of 1:1 on different levels.
This intersection was deburred using the Back-Burr Cutter & Path system. With the NC dataset supplied by KEMPF, the milling cutter precisely follows the contour and guarantees repeatable deburring results. The special-design ball cutter with reduced shank and 2.3 mm diameter, featuring a high heat-resistant AlTiCrN coating and stepped shank, is ideal for this type of deburring task.
The second tool solution is the HSD deburring tool (High Speed Deburring). The tool is pressurized internally with 6–8 bar coolant pressure, which “activates” the cutting blades on the tool head so that they extend at the desired locations inside the component. The internal coolant pressure ensures that the blades reach into all cavities such as cross bores and grooves and remove burrs with high process reliability.
Left breakout on the bottom surface: a deep-hole bore intersects the bottom surface in a half-open manner. This is reliably deburred through the deep-hole bore using the HSD deburring tool.
The third tool type consists of two ceramic fiber brushes used to ensure complete deburring of the component. These superior ceramic fiber brushes are made of individual ceramic fibers, containing approx. 80% engineered ceramic (Al2O3 – aluminum oxide) and only about 20% binder. This ceramic is particularly suitable when workpieces require a special surface finish or, as in this case, must not allow adhesion that could later detach and enter the oil circuit. The oxide ceramic has extremely high hardness (harder than steel), yet is flexible enough to adapt to the workpiece surface and create uniform abrasive action. The ceramic is also highly heat-resistant, dimensionally stable, and extremely wear-resistant for deburring and polishing tasks. Another advantage: the individual ceramic fibers return to their original shape after machining. For this reason, this tool type is often used as a “cross-hole brush” for deburring (cross-) bores. At approx. 6,000 rpm, the fibers spread out through centrifugal force and remove even the smallest burrs in relief cuts that would otherwise be unreachable deep inside the geometry.
Right breakout at the bore bottom: the deep-hole bore ends half-open in the bottom surface, and a burr forms in the relief groove that can only be removed using the ceramic fiber cross-hole brush type BÜCHA127M. Under rotation, the fibers spread through centrifugal force and gently remove micro-burrs.
Further application in the cylindrical step with relief groove:
The bore exit is first deburred using the HSD deburring tool with 3.3 mm diameter. This reliably removes burrs at all edges.
The final tool used is a second ceramic fiber brush applied to the bore exit in the cylindrical step. A small residual burr that forms after machining is removed completely using a small surface brush.
The residual burr that may form in the relief groove is removed as a precaution using a ceramic fiber surface brush type BÜA11CB06M with 6 mm diameter.
With this tool combination, all critical cross bores were reliably and completely deburred. All steps are now performed directly inside the machine—without additional manual work—allowing the CNC center to operate unattended during the second “ghost shift” without concerns about quality.
The result: reproducible, burr-free quality without rework – Made in Germany
The results speak for themselves: since the introduction of the KEMPF tools, Weigel & Schwarz has delivered the aluminum components to ROEMHELD in consistent, absolutely burr-free quality. During the 100% inspection by the Weigel & Schwarz and ROEMHELD quality assurance teams, not a single part has failed to meet the requirements. “With the block in this excellent quality, we go straight into our assembly,” adds Alexander Schul, Product Manager at the ROEMHELD Group. For Weigel & Schwarz, this means that the components can now be manufactured with high process reliability and repeatability. Additionally, 24/7 full production is now possible, providing significant economic advantages in series manufacturing and ensuring maximum efficiency.
From left to right: Alexander Schul, Product Manager of the ROEMHELD Group, with a ready-to-use foot pump mainly used in medical beds and therapy couches. Next to him is Lana Wolni, Managing Director of Weigel & Schwarz GmbH, holding the newly manufactured and burr-free pump piston housing directly from the machine. On the far right is Marcus Schneider, Technical Field Sales Technician at KEMPF GmbH, with the three tool types that now even enable unmanned production of the housing parts.
This project shows that even well-established production processes still offer significant optimization potential. By integrating deburring into the CNC process, Weigel & Schwarz was able to improve quality, increase process reliability, and use resources more efficiently. The combination of precision manufacturing at Weigel & Schwarz, the safety-critical requirements at Roemheld, and the tool solutions from KEMPF demonstrates the importance of burr-free, process-safe manufacturing. It not only delivers technical benefits but also reinforces the ambition to manufacture complex and highly precise components competitively in Germany—all in the spirit of “Made in Germany”.
View the project video here (in German):