Micromachining Milling more accurately than you can measure

Editor: Alexander Stark

Austria — A Tyrolean precision parts manufacturer has recently purchased a Micro HD from Kern Microtechnik. As a result, the job shop could increase its productivity by 30 percent.

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With the Micro HD, Innerbichler increases productivity by more than 30 percent and achieves surfaces in polishing quality with Ra values in the low nanometer range.
With the Micro HD, Innerbichler increases productivity by more than 30 percent and achieves surfaces in polishing quality with Ra values in the low nanometer range.
(Source: Kern Microtechnik)

Micro-precision machining is the present and the future for Siegfried Innerbichler and his employees. Accordingly, he is investing in high-end technology — most recently in the five-axis precision machining center Micro HD from Kern. Innerbichler explains: “We use it to mill 100 percent, without any defective parts and with a perfect surface in series — from the first part on. Even polishing has been superfluous since then. "

At Innerbichler, some things are small — the size of the company with seven employees as well as the products to be manufactured. The tolerances and surface quality to be observed are in the single digit µm range. In other respects, however, the company proves its true size — in the range of products and services as well as in the qualifications of employees and the quality of suppliers, machines, and products. Business is therefore good even in economically difficult times. According to the company boss, further growth is currently only slowed down by an acute shortage of skilled workers.

“Of course, we have certain requirements in terms of qualifications and commitment,” explains founder and managing director Siegfried Innerbichler. But the employees are more than satisfied with their job, explains Sebastian Erler, project manager in production automation, on behalf of the workforce: “We work here in an environment that others can only enjoy on vacation, and at the same time we have all the freedom and scope for decision-making, to always react quickly to customer requests. We can also realise ourselves. For example, besides working for Innerbichler, I am currently studying environmental, process and energy technology and will then add a degree in business administration.”

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Customers expect highest quality

For company boss Siegfried Innerbichler, high quality and flexibility are important in every respect. Only in this way can he meet the requirements of his customers. All of these come from demanding industries such as toolmaking, analysis and medical technology, precision optics and the automotive industry.

The trained master toolmaker and technician originally started his business in 1998 with services for construction and trade: “I have worked in construction for well-known companies for years. This step made sense for me.” But Innerbichler quickly realised that he could offer his customers even more, so in 1999 he bought his first machine tool and hired his first employee, Jochen Fill (now authorized signatory).

More machines and employees followed and just five years later the small business invested in 5-axis technology. The component requests became more complex and the demands on precision increased.

We are living accuracy — Kern makes it possible

Jochen Fill

Micromachining was increasingly in demand and with that came the next investment. “In my career as a technician, I have remembered Kern machines for over 30 years,” explains the boss: “In 2016, the Kern Micro was able to make a long-awaited dream come true. With the Micro HD — which we now operate together with the Micro — I topped it off in 2020. We can now live accuracy - and Kern makes it possible.”

The combination of advice about the feasibility of parts and the high-precision implementation in small series is now widely known. Correspondingly, reliable repeatability with accuracies of less than 10 µm are usually required for the jobs. The current task is to manufacture hardened mold inserts for seals in series of up to 400 pieces, which are used, among other things, in massage seats for high-quality limousines. A precision of 2 µm and a polished surface are required.

For micro specialist Jochen Fill, this poses no problem at all with the Kern machines. He explains: “We achieve customer specifications one hundred percent reliably and with the Micro HD more than 30 percent faster than was previously possible.” It is not just the reliable repeatability that inspires the authorized signatory and his boss. The consistently achieved surface quality in polishing quality with Ra values in the low nanometer range also helps to save time. This creates additional capacities, because in the past we had to repeatedly assign employees to polish the components. “These colleagues can now turn to other, more productive things,” adds Siegfried Innerbichler.

With the Micro HD measuring is actually no longer necessary

To guarantee maximum productivity, the five-axis precision milling center runs around the clock, if necessary, and two shifts are without staff. This is possible because of the Erowa workpiece loading system that takes over the automated loading and unloading for both machines. Jochen Fill then just takes out the finished parts the next day and passes them on to the measuring department. “We could actually resolve this,” reports Innerbichler and adds with a smile: “because the Kern HD makes no mistakes and is more accurate than our measuring machine. But as long as our customers request the measurement protocol, we will of course do it. A proven reject of zero percent is also quite nice.

This reliable precision is possible due to the basic construction of the Kern machines, in which only high-quality components are installed that are vibration-decoupled or vibration-damped and are kept thermally stable by a sophisticated cooling management. The project team in charge of the Micro HD has made further leaps in development, based primarily on three innovations: the micro-gap hydrostatic, linear direct drives and the new temperature management.

Three innovations make all the difference

Microgap hydrostatics are not found anywhere else in machine tool construction. In combination with linear motors, it is extremely dynamic and requires around 80 percent less energy than conventional hydrostatic systems. At the same time, the small gap improves the rigidity and damping properties of the machine, which ensures the highest surface quality and accuracy on the workpiece.

Another highlight of the new Kern Micro HD, Peter Schöps, Kern regional sales manager for Austria, mentions are the large linear motors. They bring high accelerations of up to two Grams as well as rapid traverse speeds of 60 m / min in all axes and enable maximum control accuracy. Schöps cites the new type of temperature management as particularly important for the successful integration of the direct drives: “Our linear motors are actively temperature controlled and integrated into the hydrostatic system, which minimizes the heat input. In addition, the coolants of the HD are very precisely regulated by sending a volume flow of up to 200 l/min through the machine frame, rotary / swivel axes, linear axes and spindles. “The result: the temperature fluctuations in the machine room remain at just +/- 0.05 Kelvin. “This is perfect for the high-precision machining that we demand,” says Siegfried Innerbichler, summarizing these values.

Additional growth with sophisticated milling of ceramics

It doesn't matter which materials are to be milled, as the head of the Tyrolean company notes: ”We almost exclusively process demanding materials such as titanium, tool steels, powder-metallurgical steels and, recently, technical ceramics such as silicon carbide or aluminum oxide.“ Innerbichler can still see some potential. Because the advantages of these materials are manifold. They are extremely hard, extremely stiff, resistant to chemicals and heat, as well as thermally conductive.

The only disadvantage is the high brittleness of ceramics, which excludes a few applications and makes mechanical finishing expensive. However, a solution to the latter problem seems to be in sight, as Kern specialist Peter Schöps reveals: “Our Kern application engineers recently developed a ductile cutting mode. As a result, chips are now flying when milling ceramics. This multiplies the removal rates in a process-stable manner, as our extensive tests prove. "

Siegfried Innerbichler is really looking forward to the cutting mode. Because he knows that developments from Kern are always available quickly: “Like all customers of Kern — we are part of the Kern family and participate in all innovations,” explains the Tyrolean boss and adds: “In the past there have already been several further developments that Kern has initiated together with tool manufacturers and with which we have been able to increase our productivity. This was the case, for example, with a new tool with which lead-free copper can be processed very well. And the new ceramic cutting mode will certainly work perfectly too.”