However, the development of the "Turningator 6000C" is also a story of people who repeatedly find innovative solutions to extraordinary challenges. While the Swiss company Wysshus was responsible for the entire project planning and organization, Bunorm, also based in Switzerland, took on all design tasks, production and assembly through to commissioning. The two companies previously developed the standard sizes of the Turningator: 2000, 4000 and 6000, and Schaeffler also supervised these projects in the past. The current Turningator 6000C, with a machining diameter of up to 8,000 mm, surpasses the previous machines and was to be completed in just under a year. However, the design of the Turningator had to be fundamentally adapted to the new dimensions and calculated.

Bearing design using the Bearinx calculation program from Schaeffler.

Werner Locher, Head of Field Sales at Schaeffler in Switzerland, recalls the initial concepts: "We discussed and calculated various bearing designs for the main axis. The starting point was YRT bearings, double direction thrust bearings with radial guide bearings, which have been used successfully for years in the two smaller machines, Turningator 2000 and 4000. However, these bearings were not available in the size of over 1,200 mm shaft diameter. In the end, we opted for the crossed roller bearing with an inner diameter of 1,270 mm." These bearings have a very small cross-section in relation to their load capacity. This was important because the main shaft and two ball screw drives had to be guided through the inner ring of the upper main bearing.

The electronically synchronized ball screws encapsulated in black bellows support and position the 20 t Z-axis. Locher explains: "With normal solutions for the axial bearing of the ball screw spindles of the suspended axis, you don't get very far with these forces. We have had good experience with double-row axial spherical roller bearings in projects with similarly high forces and therefore recommended them to the Bunorm designers." A special feature of this mobile processing machine compared to its stationary siblings is that the Turningator can be used with both vertical and horizontal main shafts. This has consequences for the bearing load: In the vertical position, the lead screws and double-row axial bearings of the Z-axis have to transmit the centrifugal forces and the cutting forces.

With the main axis horizontal, the weights of the Z-axis slides are superimposed on these forces: The double-row axial bearings of the threaded spindles are loaded once in tension and once in compression with each revolution by the weight of the axis. The challenge is to ensure by design that there is no play in the axial bearings under all load conditions and therefore no slippage or backlash. This is the only way to achieve precise machining in the meter range with H7 tolerance. "This requires a great deal of expertise," the specialists from Bunorm and Schaeffler agree.

Markus Havrda emphasizes: "Right from the start, our aim was to appoint a partner and expert who would help develop and manage all issues relating to the bearings. According to the motto 'Go for it, we rely on it to work'. And it did. Regardless of whether it was a question of the design and selection of bearing types and sizes, the layout, the structural design or the bearing fits. Werner Locher and Gil Schuhmacher from Schaeffler's calculation department also provided us with excellent support when it came to detailed questions about the optimum amount of grease, sealing solutions or the mounting process for the main bearing."

Bearing torque adjusted with calculation program

The driving forces behind the team in front of the Turningator 6000C: (from left) Werner Locher, Schaeffler Switzerland, Stefan Gygax from Bunorm and Markus Havrda from Wysshus.

Schaeffler engineers do not just use their own Bearinx calculation program to design individual bearing positions. It can also be used to model complex bearing systems and vary their parameters automatically. This played a decisive role in the development of the Turningator 6000C, as Werner Locher explains: "After the initial assembly of the main shaft, the torque of the main bearing was too high. It was preloaded too far. The question now was how far the preload on the two-part inner ring had to be reduced using shims in order to achieve the desired torque. I called my colleague Gil Schuhmacher and asked him to carry out a parameter analysis in Bearinx. He did this straight away, as the machine had already been modeled in Bearinx. We were able to determine the necessary dimensions over the phone. Bunorm pulled the bearing, ground the corresponding shim to size, and after assembly it ran with the required torque. The whole thing was completed in just under four hours. It's that simple."

Markus Havrda continues: "You won't find this service in any catalog. Acting quickly and unbureaucratically is crucial in our project business, where there is enormous time pressure. The Turningator 6000C was completed as planned and we are already thinking about a follow-up project. We can very well imagine working together again."

Hall 2, Stand E21