Auto-crane manufacturer manitowoc invests in future technology

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WILHELMSHAVEN  – the Manitowoc Group is one of the world's leading crane manufacturers. The US Group produces its GROVE brand auto-cranes at the Wilhelmshaven site. To increase competitiveness, the company is currently investing in state-of-the-art production technology and optimised material flow in the traditional manufacturing shops. Its heart is a 60 m-long CLOOS laser welding/cutting system around which the production of the telescopic booms flows.

Where Krupp once manufactured harbour cranes, today around 500 yellow and black GROVE auto-cranes leave the traditional factory in Wilhelmshaven every year. The applications of the current range of vehicles are diverse. 16 current types from 4 to 7 axes lift loads of 50 to 450 tonnes to heights of 135 m, e.g. for installation of large-scale wind energy plants.

The performance capacities of the Manitowoc mobile cranes depend to a great extent on the boom.  A boom comprises a main element and up to 6 six telescopic sections, each of which can measure up to 14 m. "To optimise the manufacture of our crane booms, we have changed a few things in the conversion to the laser welding system" says Michael Hüneke, the production manager and welding expert at Manitowoc. The lower half is made of a thicker sheet than the upper half. "The abutting elements thus provide the laser with a precise fillet weld path along which it can travel cleanly." High-strength fine-grained steels with material thicknesses from 4 to 15 mm are used to produce the boom sections.

With the new CLOOS robot laser welding system Manitowoc moves into state-of-the-art production technology. The top and bottom of the auto crane boom sections which measure up to 14 m (max. 19 m) are welded and drilled on the system.

Compared to previous production processes increased welding speed are not the only benefit of the new laser system. "On the old system we could only weld under powder in the PA position. We had to rotate each part through 180 degrees for the second weld" recalls Hüneke. In the CLOOS system a 7-axis QIROX robot on a mobile 4 m high gantry moves the laser hybrid torch precisely to the left and right along the boom in the PC position, i.e. at 3 and 9 o'clock. At the same time the new process has considerably increased the welding speed from 60 cm/min formerly to 150 cm/min.