Turned Parts Contractor Adopts 'Complete Machining'

July 5, 2018
Producing a new part in a specialty alloy offered a growth opportunity, and a new mill/turn center provided process reliability, as well as precision and finished product quality.

Heinrich GmbH was a turned-parts contract machine shop -- but one with a higher objective. Recently, the Berlin, Germany, manufacturer acquired and installed a Bumotec s181 mill/turn machining center from the Starrag Group, in its task of producing high-precision components for respiratory protective devices. Although more affordable machine tools were available for the task, precision was not the only reason that managing partner Christian Pooch selected the Starrag machine. Process reliability was another decisive factor.

The Bumotec s181 is a five-axis simultaneous mill/turn center with a total of nine CNC axes, for complete machining of complex and high-precision workpieces. It is fitted with a CNC FANUC 31i panel and machine-tending unit.

Heinrich’s aim was to use the machine to break new ground. A regular customer inquired if the shop would be willing to produce a "distributor" for a respiratory protective device. "It is a component that has extremely high demands with regard to tolerances and the absence of burrs," explained Christian Pooch, CEO, "because it is not acceptable for a fireman to inhale small pieces of burrs during use."

The component connects an oxygen bottle to a respirator mask. It starts as a blank, a forging made from a special silicon-containing aluminum alloy (AlSi05). One example of the precision that the new machine offers is the H7 opening, which is cut to exactly 14 µm.

"It's astonishing that a drilled hole can be cut so precisely – with absolute roundness and a high level of surface quality," observed Christian Pooch.

According to Michael Paulus, product sales manager at the Starrag-TechCenter for Medical Technology and Precision Mechanics, Oberhausen, Germany, the greater challenge lies in ensuring that "there are no burrs in the many interconnecting channels."

Heinrich’s new machine also impresses in terms of ergonomics: Pooch finds the machine’s main spindle to be very "smart," because it makes it easier for operators to transition from a standalone lathe to the machining center. With its HSK-40 tool spindle (30,000 rpm), very small components can be machined precisely to 1.5 µm — either bespoke or off the shelf (maximum diameter: 32 mm).

"On its own, our former core business of lathing nuts and screws has not been enough to sustain us for a long time," said production engineer and general manager Tobias Pooch. "But now, with the Bumotec, we can position ourselves even better than before with high-precision components, and also establish ourselves internationally."

The response from Heinrich’s customers has been notable too, because the Bumotec has opened a path to new markets and new project, meaning "growth."

"What's special about this is that the machine cuts not only bar parts but also inserts," according to Starrag’s Paulus. "The Bumotec inserts the blank automatically, processes all six sides and then automatically transports it onward." A complicating factor here was that the initial part is a pressed piece with very high tolerances; these parts can be cut precisely, not least thanks to a specifically designed clamping system adapted to the machine.

"We developed and ran-in the clamping system specifically for this component and this machine," Paulus noted.

In all, the new mill/turn machine lives up to Starrag’s claim, "Engineering precisely what you value" in many different ways. Heinrich put a special emphasis on profitability, reliability and growth, and already achieved one of those goals: since its start-up, the s181 has run reliably and without any tolerance deviations. "With this process reliability, we can capture a new customer base," CEO Pooch maintained.