The specifications of a modern caterpillar crane are impressive: the strongest one in the world with lattice jibs can lift 3,000 t. It is used in the manufacture of power stations, refineries and wind power plants. It reaches a maximum lifting height of 245 m and an outreach of 196 m. This combination of size and strength demands an exceptionally stable and light construction. This is achieved by the use of fine-grain structural steel.
The components for such XXL cranes are manufactured at Gothaer Fahrzeugtechnik GmbH in Gotha, Germany. The core competence of the family-managed company is the manufacture of lattice masts for mobile and caterpillar cranes. Numerous renowned crane manufacturers, such as Liebherr, have their lattice components produced at Gothaer Fahrzeugtechnik.
From material cutting and welding to mechanical machining and painting, each production step is handled by the 400 employees in Gotha. “The more precisely each single crane component fits, the faster a crane can be assembled on-site,” CEO Jens Schwabe explains. Mechanical machining therefore plays an important role in the company. After the welding process, an exact fit can only be achieved through mechanical machining. Compensating the inevitable welding distortion by means of heat would impair the stability of the crane components to a great degree. Absolute precision when boring and milling the workpieces is therefore paramount.
“The largest crane components we manufacture are 12 m long, 3.20 m high, 3.60 m wide and weigh 30 t,” Jens Schwabe says. The floor-type boring mill PCR 150 with a boring spindle diameter of 150 mm made by UnionChemnitz turned out to be the ideal solution for the machining of the crane components at Gothaer Fahrzeugtechnik. The machine, which is equipped with a 10 x 3 m floor plate and a 12 m X-axis, has been in operation in Gotha since 2009.
Its additional highlights: a hydrostatically guided RAM that can be extended 1 m, a fully automatic tool changer and an integrated rotary and traversing table. “The RAM and the boring spindle of the PCR 150 allow for machining up to a depth of 1,700 mm inside the workpiece, that is beyond the middle of the workpiece. The component is then flipped to machine the other side,” Frank Winter, head of work preparation at Gothaer Fahrzeugtechnik, explains. The precision required for these machining processes is guaranteed by the robust design of the PCR 150 with a strongly ribbed column, as well as the fully automatic RAM sag and column tilt compensation and the longitudinal compensation of the boring spindle.
Since the PCR 150 has been commissioned in 2009, the boring mill works in two or three-shift operation. “Investing in the PCR 150 has been the right decision,” says Frank Winter. “We are absolutely satisfied. The RAM design is great and a big advantage in terms of stability. The price-performance ratio is convincing, as well.”
The last step in the production of a lattice mast at Gothaer Fahrzeugtechnik is painting. After cutting the material, welding and mechanical machining, this step, too, is performed at the company itself. When the finished lattice mast components for mobile and caterpillar cranes leave Gothaer Fahrzeugtechnik, they become the foundation of the secure transport of parts that weigh up to 3,000 t at construction sites around the world – thanks to the united expertise of crane construction specialist Gothaer Fahrzeugtechnik and UnionChemnitz.