For a company to become and remain a leader in its respective industry demands that it constantly reviews and improves its products and the underlying manufacturing processes. With its competence and knowhow in materials for drive trains, chassis and automobile manufacturing equipment the automotive division of the world renowned thyssenkrupp AG is a significant contributor towards the technical progress and efficiency of motor vehicles. The thyssenkrupp Gerlach GmbH plant in Homburg, Germany, is a leading partner for the development of automobile engine components and offers a full service package ranging from the design of specific components, the fabrication of prototypes to full-scale production. To improve the cost efficiency at its Homburg plant and to meet all the customer requirements, in 2016 the company installed its high-tech “production line 19” for forged crankshafts for engines with 1 to 4 cylinders. For this line the engineers of the surface refinement specialist Rösler developed an innovative shot blast equipment concept that was so convincing that the thyssenkrupp management placed an order for the new Rösler “RKWS” crankshaft shot blasting system.
The fastest crankshaft forge shop in the world
At the beginning of the manufacturing sequence the bar blanks are cut to length. Before being shaped in a 6,500 ton press, they are heated in an induction oven. In a last step the crankshafts undergo a blast cleaning process in a shot blast machine. For the last operation the Rösler engineers developed a unique equipment concept that allows the handling of different work piece sizes without time-consuming retooling of the work piece holders. This helped reduce the cycle time to less than 10 seconds, which in turn allowed the manufacturing operation to be run in continuous flow. The result of the comprehensive cooperation of thyssenkrupp with Rösler and all the other partners was the fastest, most modern crankshaft forge shop in the world that produces a finished component for its customers every 7.5 seconds.
The “RKWS” system – designed for long life and easy maintenance
The three blast chambers and the work piece load/unload chamber are arranged in a circle around a rotary drive equipped with an asynchronous servo motor with an extremely high overload reserve. The blast media is accelerated and thrown by Rösler Gamma blast turbines equipped with the worldwide unique “Y” design of the throwing blades. The critical wear components of the Gamma turbines are not made of chilled iron castings, typically used in conventional turbines, but of forged tool steel. This results in a much longer uptime of, for example, the throwing blades. The blade curvature produces a much higher throwing speed than straight throwing blades. In addition, the symmetrical “Y” design allows the use of both blade sides. The combination of more wear resistant material and the blade geometry result in an up to 3 times longer usable blade life.
Another feature of the Gamma turbines is their easy maintenance. Turning the blades around or exchanging them can be done from the top of the turbine housing without having to dismount impeller, control cage and the media inlet tube required with conventional turbines. The RKWS is equipped with 12 Gamma turbines, each with an installed power of 22 kW. The turbines, evenly placed on the three blast chambers, are throwing the large steel shot onto the entire surface area of the crankshafts with a speed of 80 meters pe second. This results in a complete removal of forging scale and other surface contaminants.
By utilizing highly wear resistant material for all components exposed to the large cast steel shot and the removed forging scale, the Rösler engineers ensured that the RKWS shot blast system was not exposed to excessive wear. The three blast chambers were lined with wear resistant hardened steel. The media augers were made from special steel that is predominantly utilized in the mining industry. Technical characteristics of this material are its extreme toughness and its remarkable hardness of 600 Vickers providing it with a considerable structural strength.
Smart maintenance concept
The entire volume of customer orders is handled by the new “production line 19” within 21 shifts per week. This poses a considerable organizational challenge for the thyssenkrupp Gerlach GmbH maintenance department. For managing the time for the equipment upkeep the maintenance team, led by Markus Kania, decided to introduce a TBM system (time based maintenance). Within a pre-determined time span a recurring time window is defined for all inspection and maintenance activities as well as any required repairs including the replacement of spare parts. The time management allows requisitioning all repair materials in advance and facilitates the effective assignment of the maintenance personnel at thyssenkrupp Gerlach GmbH in Homburg.
Adequate spare parts stock allows sustainable long-term planning
Planning certainty for the entire manufacturing line, along with a constant high product quality, is a high priority at thyssenkrupp Gerlach GmbH. For this reason, the project leader, Markus Kania, made sure that besides a forward looking preventive maintenance the essential wear and spare parts for all machines were determined jointly with the equipment suppliers and stocked on site in Homburg. To define the specific requirements for the crankshaft shot blast machine the customer relied on the experience of the Rösler service department. Based on the customer specifications the service experts at Rösler conducted a risk and wear analysis. For this purpose they utilized a ultra-modern simulation of the blast media recycling process that allowed them to determine the wear intensity for every single component. Based on the results of the analysis a comprehensive list of recommended spare parts was prepared including wear parts such as protective wear plates, etc. „The professionalism displayed during the preparation and presentation of the list of recommended spare parts with assembly drawings and 3D models was so impressive that after a brief internal discussion at thyssenkrupp we placed an order for the recommended wear and spare parts”, explains Markus Kania. He continues “With the maintenance and spare parts concept we minimize the risk of downtimes and save time and money during the procurement process. This will be a significant contribution towards strengthening our competitive advantage at our Homburg location”. For special situations the maintenance team of the “PL 19” can rely on the quick response by the Rösler service department. The Rösler manufacturing depth with short production times and express delivery of practically all spare parts is no doubt a great advantage.
The excellent cooperation with Rösler during the entire project was the main reason that thyssenkrupp Gerlach GmbH decided to work again with the surface refinement specialist from Memmelsdorf for a new investment project at the Homburg location. This time the customer plans to establish a new production line for the manufacture of axles and crankshafts for heavy-duty transport vehicles.