High Volumes, Sharp Edges
When people think of agricultural machinery, they rarely consider the expertise embedded in these machines or who develops and manufactures them. With a high level of in-house production and state-of-the-art quality management, Stemplinger KVF GmbH in Jahrdorf near Passau has earned a strong reputation in this market segment. The stringent quality requirements for their own products are now paying off, as the company has been producing its first customer series component for over a year after expanding its focus beyond prototype production.
Strengthening Its Market Position Through Agricultural Engineering Expertise
Stemplinger Konstruktion, Verzahnungs- und Fertigungstechnik GmbH, founded in 1982 as Stemplinger Maschinenbau by Johann Stemplinger in the southern Bavarian Forest, initially specialized in the development and production of front power lifts and their gearboxes for use on agricultural machinery. Even then, quality standards were high, leading to the goal of developing and manufacturing as many components as possible in-house.
This strategy proved successful, and in 1990 the new facilities were opened at the current location, and the new production site was put into operation. Further investments followed in CNC machines and gear manufacturing equipment, enabling a significant expansion of the in-house manufacturing capabilities.
Additional expansions took place in 1999 and 2012, so that Stemplinger finally had approximately 6,000 m² of production space, providing ample room not only to continue producing front systems but also to establish a foothold in prototype construction and contract manufacturing using state-of-the-art Zeiss metrology technology.
Image: Inside surface of the hydraulic component to be deburred at the Stemplinger user site. A single KEMPF ibex tool removes secondary burrs from the walls and bore exits and also machines the external flat surfaces.
Absolutely #burrfree Components Posed a Challenge
In the market segment where Stemplinger operates, expertise and manufacturing quality play a decisive role, as the customers—mostly from the automotive sector—have high quality demands. Whether complex components for drivetrains and all-wheel-drive systems or smaller parts such as gearing components and aluminum housings—because all machining steps like turning, milling, and gear cutting are performed in-house, continuous quality assurance is required and is ensured at Stemplinger.
These factors are extremely important for the customers of the 50-employee company and led in October 2021, for the first time in the company’s history, to the awarding of a large series order for a production component with approximately 20,000 pieces per year.
The hydraulic component, initially developed as a prototype and milled from a saw-cut section of an aluminum extruded profile, must be delivered completely burr-free to the customer due to its intended application. What sounds simple, however, posed a major challenge for the responsible staff, since manual deburring, which had often been done previously, was no longer an option for series production.
Image: A KEMPF ibex deburring system consists of a compensating holder and here a forward and reverse cutter with special CrossCut gearing. A high-strength, specially sealed aluminum sleeve prevents the ingress of dust and chips.
KEMPF Also Created the NC Programs
Many different tooling solutions on the market were tested to deburr both the contour and surfaces on the outside as well as the milled pockets and bores without leaving residual burrs. However, none of the tools proved satisfactory. This led to customer complaints, as the components simply did not meet the requirement of being completely burr-free. Prompted by a recommendation, the Stemplinger team eventually became aware of the deburring specialists at Kempf from Reichenbach-Fils. Markus Götzelmann, who leads the Technical Internal Sales for this area, took on the project and initially conducted internal trials. For the deburring operations on the milled outer contour, the entire outside, and the complex inner surfaces, two tooling systems proved to be the right solution, for which Kempf also took over the creation of the NC programs. This allowed the automated deburring processes with a ceramic fiber surface brush and the ibex deburring system to be integrated into the existing workflow on-site by KEMPF field service technician Waldemar Freund into the existing workflow.
Image: The 40 mm ceramic fiber surface brush ‘BÜA11-CB40M’ used here. Its red ceramic fibers are highly flexible and therefore suitable for fine deburring of aluminum, copper, or brass.
When the brush is worn, it is removed from the aluminum sleeve and replaced.
Ceramic Fiber Brushes Prevent Metal Contamination
To clean and deburr the interior surfaces of the component as well as to machine the exterior surfaces, steel and brass brushes could not be used due to the risk of metallic residue or contamination. Initially, plastic brushes were used for deburring. However, they fell far short of the desired results. Kempf therefore turned to the better-suited ceramic fiber brushes, which, as emphasized by Kempf, offer clear advantages over conventional brush materials and ultimately solved this problem.
The brushes used here consist of individual ceramic fibers, which in turn are made up of eighty percent technical ceramic (aluminum oxide or Al2O3), with only 20 percent binder content. This ceramic is especially suitable when workpieces require a special surface finish or, as in this case, when no adhesion can be tolerated that might later detach in the oil circuit.
Successful applications in aerospace confirm the unique properties that far exceed those of conventional wire or nylon brushes. The “oxide ceramic” is, for example, harder than steel and therefore excellent as a cutting material in machining. Because the ceramic fiber rods are very flexible despite their high hardness, they conform well to the workpiece surface and provide a consistent grinding effect during the manufacturing process. Additionally, this type of ceramic is highly heat resistant, dimensionally stable, and very wear-resistant in deburring or polishing operations.
Image: These “Xebec” ceramic fiber rods spread out due to centrifugal force during deburring and remove fine burrs from the component. Each rod consists of approximately 1,000 bonded micrometer-thin ceramic fibers, whose tips simultaneously form the cutting edges. Due to the special ceramic material properties, the rods withstand temperatures up to 150 °C.
The Ibex Deburring System Ensures Clean Contours on the Cast Component
The deburring of the component’s outer contour was performed by the Ibex deburring system from Kempf. The system, consisting of an axial compensating holder and a special CrossCut cutter, is particularly well suited for machining undefined contours, such as those on cast components with significant dimensional variation. Due to its high flexibility and the ability to compensate up to 10 mm in both axial directions, the clamped cutter adapts to any component geometry, deburring even undefined edges cleanly, with process reliability and uniformity.
Image: Part of the outer contour of the hydraulic component before deburring (left) and after (right). The saw cut of the aluminum profile results in an undefined outer contour due to manufacturing; therefore, the tolerances are too large for conventional deburring cutters. The Ibex deburring system compensates for these tolerances.
Process time per component reduced by over 30 percent
Two deburring solutions based on this principle ultimately led to a reduction of the total process time per component at Stemplinger by approximately 30 percent. This also laid the foundation for the complex hydraulic component to be fully machined. A random sample inspection of the parts is sufficient, and personnel previously tied up in this task can now take on more productive roles within the company. The outcome: Despite tool use in three-shift operation over five working days per week, the Ibex compensating holder has not needed replacement so far; only the ceramic fiber brush was replaced twice within six months of use. This investment has more than paid off in the form of freed-up capacity, faster yet more reliable production processes, and a significant reduction in customer complaints.
Image: Another segment of the component in question. Due to the additional use of the ceramic fiber surface brush, the saw-cut surface is also smoothed, and the edges/contours are additionally rounded. This results in a clean deburring pattern along the contour.