GMH Gruppe invests in quality management

The largest monoblock crankshafts in the world are manufactured for GMH Gruppe at WSK in Wildau. To be able to guarantee production work that is accurate to a hundredth of a millimetre with the purest steel qualities despite these dimensions, the company is investing in new measuring and testing equipment.

When energy generated in engines is converted into rotary motion, mobility is created. A key element of this is the crankshaft. In Wildau, particularly big and heavy crankshafts are produced which weigh up to 20 tonnes. The Wildauer Schmiede- und Kurbelwellentechnik (WSK) specialises in the production of crankshaft of up to 12 metres in length, such as those used in large engines for stationary power generation, or in marine propulsion systems, in compressors (for hydrogen production, LNG gases) or in large pumps on construction sites, or in mining (for dewatering, disposal of overburden sludge).

WSK has invested in two measuring and testing devices in order to be able to precisely verify the accuracy of fit and material resistance of these unique components that weigh several tonnes, and are manufactured individually according to the customer's requirements and specified dimensions:

A coordinate measuring machine: This CNC system can measure forged parts and crankshafts of up to 15 metres in length and two metres in height and width, with an accuracy of 0.005 mm. To achieve this very high accuracy, the measuring machine is mounted on a granite bed on an air cushion. This CNC-controlled process is carried out at a constant temperature of 20 degrees Celsius, in an air-conditioned cabin built separately around the measuring device. This guarantees the comparability and repeatability of the process. Components weighing up to 60 tonnes can be measured on the measuring table.

An ultrasonic inspection device (phased array): With the help of this compact and very powerful mobile ultrasonic device, WSK can detect the tiniest material defects. For this purpose, an ultrasonic transducer, with a total of 128 interconnected ultrasonic transmitters, moves in an automated process along the product and detects defects that correspond to a sound attenuation of a drill hole with a diameter of 0.3 mm. Depending on the size of the examined workpiece, this precise material inspection takes up to eight hours.

Both devices serve to increase quality assurance and the exact verifiability of the required quality characteristics. After extensive test runs, the measuring machine was put into regular operation in March of this year. The phased array system is currently undergoing final approval and is scheduled to go into operation in mid-July.

"Both our expectations and our customers' quality requirements for wear-resistant crankshafts have increased. The newly installed coordinate measuring machine, one of the largest in the world, guarantees to our customers that their individually manufactured forged products meet the tightest tolerance specifications," explains Dr David Biere, Plant Director at Wildauer Schmiede- und Kurbelwellentechnik GmbH.

Additionally, Dr Biere continues: "Particularly in the case of large crankshafts for combustion engines, the focus is increasingly on reducing emissions. New fuels have a different combustion process which leads to higher combustion pressures and therefore higher stress on the components. The crankshafts are often intended for decades of use. With our new ultrasonic testing method, we can reliably detect even the smallest impurities in the material. Our customers therefore receive crankshafts that meet their specifications by 100%."

Unlike the coordinate measuring machine, for which the company has built a base and a climate cabin in the factory building, the ultrasonic device is small and mobile. The testing device can therefore be made available to other GMH Gruppe companies at any time, including the accompanying test trolley and oscillating arm, to rule out material defects. The total investment for this WSK quality offensive amounts to two million euros.