SPL Präzisionsfertigung GmbH based in Fraureuth, Germany, was founded in 2007. The company focuses on the production of components for machine tools as well as main spindles. "We started with just 14 workers and today we employ 30 highly skilled employees. At our factory, we produce all manner of parts for turning, milling and grinding spindles as well as special spindles and test bench spindles," says Dipl.-Ing. Andreas Pilz, Managing Director of SPL Präzisionsfertigung GmbH.

The production of main spindles requires the utmost precision, accuracy and care. SPL has, from the very beginning, 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 center from Hermle together with all the necessary tools and accessories. This major investment has enabled the company to stay on top of precision manufacturing, for example, by enabling the production of spindle housings, which are now an essential segment in its product portfolio.

Tolerances starting at just ≤ 0.005 mm

For the task of finish machining prismatic parts or spindle housings, SPL has also purchased a Hermle C 62 U 5-axis machining center. The C 62 U is the flagship model from the Hermle High-Performance-Line, featuring a traverse path of 1,200 x 1,300 x 900 mm, and a 1,350 x 1,100 mm swivel rotary table with a max. load capacity of 2,500 kg. "Previously, we contracted third-party production on a DIXI jig boring machine. Following the closure of the DIXI-Machines plant, where continued service was put into question, we made the decision to invest into a brand-new state-of-the-art machine. I remember writing to various machine manufacturers but Hermle was the only supplier who was not discouraged by our demanding specifications and strict accuracy requirements," explains Pilz. The purchase of the Hermle machining center was the final building block that enabled high-precision production of the company's new spindle housing components. "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 concludes. SPL utilizes fine boring heads from BIG KAISER to ensure that the bearing bores in the spindle housings also meet their tight precision tolerances.

BIG KAISER & HERMLE - True partners for highest precision requirements

"It was while machining a test workpiece at the headquarters of the machine manufacturer Hermle in Gosheim, that we saw firsthand the fine boring heads from BIG KAISER in action. The quality of the bores was second to none and convinced us from the very outset that BIG KAISER was the optimal choice for our machining tool needs. A huge differentiating factor was that we would not only be purchasing a high precision tool but we also gained access to expert technological support and assistance, provided namely by Jochen Renz, Technical Manager Customer Service at BIG DAISHOWA, the sister company of BIG KAISER in Germany. This was extremely important for us, particularly with regard to our strict parameters such as rotational speeds, cutting and feed rates, etc.," explained Andreas Pilz.

Enrico Müller, Application Engineer at BIG DAISHOWA clarifies, "We have a very close working relationship with Hermle, especially in situations where highly complex tasks are on the table, so when it comes to maximum precision, we are the primary point of contact."

Digital fine boring heads; our clear 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 for the purpose of eliminating reading errors in the very tight tolerance ranges under which we operate," Müller points out. "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 µ range, the machine as well as the tool must also ideally be in the µ range. In our situation it is clear-cut case - no ifs, no buts, no room for compromises!", Pilz sternly stresses his conviction.

BIG KAISER has a modular system that covers all diameters and lengths, and fine boring heads can be adapted in 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. In addition to the diameter, the base surfaces, end faces and deeper face installations are all milled on this machine within a single setup. 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 of up 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 aluminum bridges of varying lengths that can be combined with a variety of aluminum 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% time saving in roughing operations

At SPL, spindle tools from BIG KAISER are also used for roughing operations on an MTE milling machine. However, in this application, two cutting edges are utilized 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. No sooner said than done! 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%-time improvement, not to mention a better surface finish and reduced costs," explains Pilz.

At present, 15 fine boring heads from BIG KAISER are in use at SPL - for fine boring of bearing bores and for roughing during reboring.

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 ≤ 5 µ range," Pilz concludes, and Müller adds, "What SPL is achieving here is the high art of spindling. To produce a cast component with such exacting precision requires a lot of skill and know-how, and as you can see, the technicians at SPL have both!