Maintaining tight tolerances How fine boring heads deliver precision for spindle manufacturer

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Jongen Werkzeugtechnik GmbH

BIG KAISER Präzisionswerkzeuge AG

Focusing on the production of components for machine tools as well as main spindles, SPL Präzisionsfertigung in Germany demands the utmost in precision. This is why it invests in boring and tooling technology from Big Kaiser.

In 2007, SPL Präzisionsfertigung started with just 14 workers and today employs 30 highly skilled employees. The manufacturer produces all manner of parts for turning, milling and grinding spindles as well as special spindles and test bench spindles.

The production of main spindles requires the utmost precision, accuracy and care, so from the very beginning, SPL has regularly invested significant resources into employee training and state-of-the-art technology. In 2019, SPL took the decision to build a brand new, air-conditioned production hall, purchasing a high-precision machining centre from Hermle together with all the necessary tools and accessories. This investment enabled the company to stay on top of precision manufacturing, enabling the production of spindle housings, which are now an essential segment in its product portfolio.

For the task of finish machining prismatic parts or spindle housings, SPL has also purchased a Hermle C62U 5-axis machining centre. “We made the decision to invest in a state-of-the-art machine and I remember writing to various machine manufacturers, but Hermle was the only supplier not discouraged by our demanding specifications and strict accuracy requirements,” explains Managing Director Andreas Pilz.

“This cutting-edge 5-axis milling machine meets the most stringent demands in terms of machine kinematics and positioning accuracies, which are necessary for our production in the ≤ 0.005 mm range,” Pilz adds. SPL utilises fine boring heads from Big Kaiser to ensure that the bearing bores in the spindle housings also meet their tight precision tolerances.

Partners for the highest precision requirements

It was while machining a test workpiece at the headquarters of the machine manufacturer Hermle in Gosheim, that Pilz first saw the fine boring heads from Big Kaiser in action. The quality of the bores convinced him from the very outset that these tools are the optimal choice. “We would not only be purchasing a high-precision tool but also gaining access to expert technical support and assistance from Jochen Renz, Technical Manager of Customer Service at Big Daishowa, the sister company of Big Kaiser in Germany. This was extremely important for us, particularly concerning our strict parameters such as rotational speeds, cutting and feed rates,” explained Andreas Pilz.

Digital fine boring heads — the first choice

SPL relies heavily on the digital EWE fine boring heads from Big Kaiser. “The industrial components that SPL produces are very expensive. So, it makes logical sense to rely on the proven quality provided by Big Kaiser’s digital fine boring heads. We would use them regardless, even if only to eliminate reading errors in the very tight tolerance ranges under which we operate,” points out Enrico Müller, Application Engineer at Big Daishowa.

Another advantage of digital fine boring heads is their ultra-fine handling accuracy. High-precision machining requires the utmost care and cleanliness. When manufacturing in the micron range, the machine, as well as the tool, must also ideally be in the micron range.

Big Kaiser has a modular system that covers all diameters and lengths. Fine boring heads can be adapted in a modular fashion to diameters and boring depths with various adaptations. The HSK-A 100 tool interface and the solid extensions provide high stability during spindling even at greater depths. Due to the system's vertical tool infeed design, errors caused by tool deflection are prevented and the achieved cylindrical shape of the bores is less than or equal to 0.005 mm.

Impressive bore lengths to 800 mm

The EWE fine boring heads feature high-precision insert holder diameter adjustment. Since SPL spindle diameters range from Ø60 to Ø400 mm and bore lengths can reach up to 800 mm, bridge tools from the 318 series are also used. The 318 series is suitable for various applications such as roughing, finishing, tenoning and face grooving. It is based on aluminium bridges of varying lengths that can be combined with a variety of aluminium and steel components for roughing and finishing configurations. The tool components are plugged onto the bridges at specific points and bolted in place. The precise positioning of the components on the bridges together with setting scales for the fine boring heads allows for fast and easy diameter setting.

80 percent time-saving in roughing operations

At SPL, Big Kaiser spindle tools are also used for roughing operations on an MTE milling machine. However, in this application, two cutting edges are utilised on the tool, not just one as is the case with finishing. “Mr. Müller, who has worked together with us on the project from the very beginning, came up with the great idea, right on-site, that we could try roughing using a two-flute cutter on our MTE. As a result, our machining speed is now five times greater than before with the milling tool. This is important, we're talking about an 80 percent time improvement, not to mention a better surface finish and reduced costs,” explains Pilz. Now, 15 fine boring heads from Big Kaiser are in use at SPL — for fine boring of bearing bores and for roughing during re-boring.

A long-term successful partnership

“We could not be more satisfied with the results. The tools, the service as well as the advice are all top-notch, there is simply no other way to put it. Our industry places the highest possible demands on us in terms of precision, accuracy and quality. Nevertheless, with the tools from Big Kaiser, coupled with their consulting competence and on-site support, success is practically guaranteed. In this case, we are also a little proud that we've earned our place in the ≤ 5µ range,” Pilz concludes.

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