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Case Study: Machining Equipment Successful quest for the missing µm

Editor: Steffen Donath

“To be more innovative than others” - a guideline that Hannes Fuchshofer adopted during his apprenticeship in the 80s. As an independent entrepreneur, he has been living this for over 25 years.

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In the new production hall of Fuchshofer Präzisionstechnik, the Kern Micro HD not only occupies visually a special position – right in the center and a bright red color. Technically, it also represents the extreme of high-precision five-axis milling of small parts.
In the new production hall of Fuchshofer Präzisionstechnik, the Kern Micro HD not only occupies visually a special position – right in the center and a bright red color. Technically, it also represents the extreme of high-precision five-axis milling of small parts.
(Source: Kern Microtechnik)

The latest indication: the investment in a Kern Micro HD. With this high-end five-axis machine, Fuchshofer is fulfilling customer requirements for highest precision with repeatability in the µm range and surface qualities of Ra = 0.05 µm in series.

When Hannes Fuchshofer talks about his professional career, it sounds like a textbook on a manufacturing career: vocational training in 1987, master craftsman in 1991, then production manager in a mechanical engineering company until 1994. In this year he was looking for and found a new challenge in self-employment. Fuchshofer started a one-man business in the garage of his parents' farm in Eibiswald, Austria, and explains: “At the beginning I wanted to keep the investments as manageable as possible, because I saw other small businesses that went bankrupt in the first few years due to high running costs. "

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Through extreme hard work — 16-hour days were and still are not uncommon for him — and with the full support of his wife, the production engineer continuously developed his skills and the possibilities for his company. At the same time, he built up an excellent reputation for quality and reliability. Features that still characterise the company Fuchshofer Präzisionstechnik GmbH with around 100 employees and 33 CNC machining centers today. But this does not make Fuchshofer stand out from others, as the managing director and shareholder confirms: “I see these properties as an essential basis for every company. We complement this with the highest level of innovation. This is our not so secret strategy for success.”

What the entrepreneur means by this becomes clear on a tour of the company. Various machines for ultrasonic processing are discovered. They have expanded the regular customer base for several years to include optics, watch making and medical technology. Also in the portfolio: systems for additive manufacturing. They offer completely new possibilities, especially for the production of prototypes.

Top of the high-precision five-axis milling

As a third highlight, Fuchshofer is presenting a machine that is assigned to the important core business of classic machining: the new ‘Micro HD’ from Kern Microtechnik GmbH, based in Eschenlohe, Bavaria, Germany. In the new production hall built a few years ago, it not only occupies a special position visually — in a central position and red color. Technically, it also represents the excellency of high-precision five-axis milling of small parts.

The Austrian contract manufacturer has been practicing simultaneous five-axis milling for more than15 years, and precision in the hundredths-range has also been a matter of course for him for a long time. According to the managing director, however, some customers, especially from the optics and semiconductor industries, expressed their desire for even higher precision: “There was talk of a permanent accuracy of 2 to 4 µm. This could not be done with our previous machines — without a relatively high reject rate.”

So a new, even more precise milling center had to be found. According to Fuchshofer, the selection in this segment is manageable, “and those who manufacture with high precision naturally know Kern. We performed a test cut in Eschenlohe, Germany and quickly decided for simply the best in terms of maximum accuracy, the Kern Micro HD.” The data alone are impressive: The HD achieves seamless accuracy of less than 1 µm in circular measurements and surface quality in the low single-digit range with a Nanometer range of Ra = 0.05 µm, which can otherwise only be achieved by grinding — all in series.

No difference detectable, not even one µm

The communicated values not only sound good, according to Hannes Fuchshofer they are also achievable in practice. He demonstrates it clearly with the sample parts: “With the HD, we manufacture various ceramic and titanium parts, and some of them twelve times faster than before. A compensation plate made of invar and titanium for camera sensors is currently particularly tricky. In a small series of around 80 pieces, we make elongated holes and drills for which we have to guarantee an accuracy of +/- 2 µm. In the past, we required extensive preparations and various additional measurements, and my calculation included around 20 percent rejects. With the Micro HD, we manage the job much faster and in terms of repeatability there was no µm difference in the end. So zero rejects!“

Several technical highlights are decisive for the extreme precision and productivity: For example, the micro-gap hydrostatics, for which a patent is pending, is a novelty in mechanical engineering. The small gap of <10 µm improves the rigidity and damping properties of the Kern Micro HD. In combination with a fast spindle (42,000 min-1) and high-quality tools it ensures highest surface quality and accuracy on the part. In addition, the design of the integrated micro-gap hydrostatic and large linear motors in all axes enables high rapid traverse speeds of 60 m/min and accelerations of up to 2 g.

Another highlight of the HD is its temperature management, as Peter Schöps, Kern Sales Manager for Austria, explains: “Our engineers are constantly working on it and have now taken it to a higher level. This is important because temperature influences are responsible for around 70 percent of all accuracy errors in the high-precision range. This has been proven by different studies.” Because of this, coolants are being managed very precisely in the Kern machine. The coolants run with a volume flow rate of 200 l/min through the machine base, rotary / swivel axes, linear axes and spindle. In addition, the linear motors are actively tempered. The result: In the thermal stress test, the temperature fluctuations in the machining chamber remain at just +/- 0.05 Kelvin.

Integrated automation

For Hannes Fuchshofer there is no substitute for accuracy and productivity. This is not primarily about one-time achievable values for the production of individual parts. Rather, it is important to him to achieve these values permanently. He explains: “We are not a large-scale manufacturer. Most customers expect between 10 and 100 parts, sometimes a few hundred. This has to run fully automated and with a guaranteed constant quality. I can rely on this with the HD.”

Fuchshofer has his Micro HD currently equipped with an internal workpiece and tool changer. An interface for an external Erowa automation system is integrated. With this, he can adapt the machine to growing needs. He is convinced that with the new machining center he will soon be able to win new customers who were out of reach before.

The performance of the machine naturally contributed the largest part to the decision-making. Hannes Fuchshofer emphasises the outstanding support from the first contact all the way through to consultation, installation and process integration: “Kern thinks like us, and I have an extremely good relationship with all of the Kern employees I have met so far. First and foremost, of course, our personal Sales Manager Peter Schöps. The same is true for the service crew and Kern management. We became a member of the Kern family. If there is any kind of question, we will receive qualified support that will help us immediately. These are not just empty words, this is awesome.”

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