WANTED!

MACHINE FOR SOPHISTICATED
FINISHING OF PLASTICS

When the long-established company Krüger Aviation needed a machine for finishing plastics at short notice, satisfying the high demands was therefore a very big challenge. For it is no accident that Krüger Aviation GmbH from Barsbüttel near Hamburg boasts a list of references that reads like a who’s who of the aviation industry: The long-established Hanseatic company supplies more than 300 companies in the industry – from Airbus, Lufthansa Technik, Safran through to ZIM Flugsitz. Customers like these definitely expect their suppliers to use the very best machinery and processes – including when finishing plastics.

The supreme quality that Krüger Aviation GmbH provides is of course not just down to the machines that are used but also the 40 employees who apply processes including thermoforming, CNC machining and 3D printing to manufacture semi-finished products as well as complex finished parts and assemblies from plastic. “We also help our customers to design and certify components or even switch from one production process to another,” explains Florian Ehinger, Head of Customer Service. “But increasingly customers are coming to us with an aluminium component and asking: Could you suggest to us a plastic that we could maybe use instead of aluminium here?”

The company’s particular specialities include high-quality mirrors made from special plastic. The firm from northern Germany is one of the world’s leading suppliers of this product and has already received multiple awards such as the Crystal Cabin Award. The factory in Barsbüttel also uses thermoforming to make light and seat fitting covers as well as other components for use in cabin and toilet areas from materials including polycarbonate (PC), polyamide (PA 66) or polyphenylsulfone (PPSU).

But all components have one thing in common: They are visible parts without any supporting function. Ehinger: “Visual quality plays an important role with all our components. This is why we make a very big effort here.”

Just-in-time delivery is another requirement: The aviation industry insists on extremely short delivery times even for the components that are usually customised and made in small batches. This is why Krüger Aviation optimises all processes from development and production through to handling.

The phrase “minor adjustments” probably reflects Hanseatic understatement because Krüger Aviation had a specific request: The workpiece holder which the northern German company developed was a vacuum clamping table which, together with semi-finished products, can even hold complex shaped components at a high milling speed securely and without any vibrations. The vacuum clamping table which was developed in-house was previously made of wood or Ureol. HG Grimme was now given the task of producing a solid aluminium version. The desire to have an even more robust clamping table is understandable given that the new gantry design machines in the X/Y axis at a speed of up to 80 metres per minute.

An unusual sight for experts in metalworking is the very compact milling head which can rotate up to a maximum of 540 degrees and can tilt up to 365 degrees. “As the sort of high forces that are common in metalworking do not occur here, we can operate with a milling head mounted on one side,” explains Horster. “We can also use it to mill the typically intricate workpieces very dynamically because we can now tilt the head down a very long way without running the risk of the milling head colliding with the table or the holders.” The risk of collision is now much lower than it was with the previous machine.

The results with the first milled components were very good. Krüger Aviation started off with semi-finished thermoformed parts made from the plastic Ureol and is now also testing components made from other plastics for the aviation industry for which the first article inspection by the customers is now pending.