Precision machining Creating capacity for the new

| Author / Editor: Udo Hipp / Theresa Knell

Whoever wishes to meet the tough requirements of complex geometries and difficult-to-process materials must be equipped with a suitable machine park. This is why Andreas Bruns Zerspanungstechnik has for years seen itself as being well positioned with its Hermle machines.

Manufacturing complex products means the highest precision in difficult-to-machine materials.
Manufacturing complex products means the highest precision in difficult-to-machine materials.
(Source: maikgoering photography)

”A lot developed on its own,” recalls Andreas Bruns, CEO of the Andreas Bruns Zerspanungstechnik GmbH. He started in a garage in 1994. In the course of time, his firm developed into a much sought-after manufacturer of prototypes and small batches for the automobile industry, medical technology, and general machine and installation construction. Thanks to the good order situation, the firm moved into a 400 m² hall within only a few years of its founding.

After renting the hall for a total of ten years, Bruns built the firm’s current base in Isernhagen by Hannover eleven years ago. Not only the available space, but also the portfolio have changed – today there are 20 employees working on more than 1250 m². “It is the highly demanding components that attract my special interest,” explains Bruns. Besides the complex geometries and a high precision, he also appreciates the challenge presented by difficult-to-process materials such as Inconel, titanium and high-quality copper alloys.

Anyone wishing to meet such high requirements must have a corresponding machine park at his disposal. A glance into the production hall shows that, as far as quality and precision are concerned, Bruns has particular confidence in one manufacturer: alongside the installations for turning, eroding and sawing there are four CNC processing centres from Maschinenfabrik Berthold Hermle AG. “Our first Hermle is about 20 years old,” says Bruns, looking back. “We were convinced by its reliability.” The CEO likewise invested, in 2014, in the C 22 UP high-performance processing centre with pallet-changer system. “And that proved to be the right choice,” he confirms. For, as Bruns points out, it has been running smoothly since its commissioning.

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Greater precision and shorter tooling times

The more the firm concentrated on complex products, the more established working processes reached their limits where precision was concerned. “If a workpiece required not only processing on a turning machine, but also milling, we risked dimensional errors due to the re-clamping.” In order to avoid the continued necessity of working on two separate machines, Bruns decided in 2018 to purchase a C 42 U MT. The mill/turn version of the 5-axis processing centre provides, in addition to tandem drive on the A-axis, a torque motor for the C-axis. This offers a maximum rotating speed of 800 min-1 for turning workpieces weighing up to 700 kg. In pure milling operations, the table can even take loads up to 1400 kg. “Besides the higher precision, we profit from the enormous time-saving and the resulting reduction in tooling costs – that creates capacities for new tasks,” explains Bruns. He can now furthermore process parts with diameters up to 700 mm. The previous limit was no more than 300 mm. He currently manufactures small batches of rotationally symmetrical components with diameters up to 400 mm and heights up to 500 mm.

Mill/turn technology requires more familiarisation

The 5-axis mill/turn centre was delivered and commissioned in November 2018. “All of this went perfectly,” the CEO confirms. Accustomed to handling the C 22 U, the operators soon noticed, however, that mill/turn technology requires more familiarisation. Two spindles were promptly damaged, which is especially painful for the firm in this initial phase. “Fortunately, Hermle also lived up to its reputation when it came to service: they usually got a technician on site the same day,” Bruns tells us. One factor in the quick repair was the constructional principle of the spindle: the tool spindle, of slimline construction, has two parts and can be replaced quickly and simply. Equally direct and uncomplicated is Hermle’s help by telephone, as with programming problems, for example. This takes place mainly in the CAD/CAM department of this family firm. From the customer’s step files, the trained staff principally program 3D free-forms on a PC. In contrast, simpler processing steps, such as bores, can also be input directly via the C 42 U MT operating surface. Bruns is confident that the learning curve will rise steeply after the first difficulties. In the meantime, the three relevant operators have gained deep respect for the machine’s sensitivity and enthusiasm for the Heidenhain controller. The greater the familiarity, the higher the productivity of processes on this high-performance machine.

The capacity question is important for Bruns. Like many other firms in his sector, he has noticed that it is increasingly difficult to find specialist staff. His strategy here is based on, alongside training on the firm’s premises, a worker-friendly single-shift working day. To avoid capacity losses, he needs machines guaranteeing reliable autarkic operation, even at night. In addition, his thoughts are moving towards automation: “We have already arranged for automation to be prepared for the C 42 U MT. At the moment, however, this is not yet cost-effective for us, since we still need to intervene with measurement processes carried out on a separate machine. Furthermore, our first task is to acquire intimate knowledge of the handling.”

This caution applies only to the milling/turning machine, however, for there are plans to install a C 400 U equipped with the flexible HS flex handling system before the end of this year. “The specifications of components, in particular concerning precision and availability, have risen steeply. This is where a Hermle is needed,” says the CEO, justifying the new investment. “This will replace another milling centre and likewise score points with its high precision and reliability,” Bruns states confidently.

At a glance

The more the Andreas Bruns Zerspanungstechnik GmbH concentrated on complex products, the more established working processes reached their limits where precision was concerned. They therefore decided on a C 42 U MT from Hermle. The mill/turn version of the 5-axis processing centre offers not only tandem drive on the A-axis, but also a torque motor for the C-axis. Besides the higher precision, the firm benefits from time saved and the resulting reduction in tooling costs.

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Udo Hipp is in charge of marketing at the Maschinenfabrik Berthold Hermle AG in 78559 Gosheim, tel. (0 74 26) 95 62 38, udo.hipp@hermle.de.

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