Design and application of a combined roller and plain bearing as a pivot and main bearing in a servo knuckle joint press
Forming technology is characterized by high output in mass production as well as high process forces while forming. Shifting from rigid and inflexible processes, which are typical for the field of forming, to technologies with higher flexibility, e.g., servo presses, the requirements on the capacity of machine parts are increasing. Especially bearing components are highly loaded and therefore critical. Trends are heading towards the developed of new technologies, which causes pure roller or plain bearings to not fulfil the given requirements anymore. Such a new technology is given by the 3D Servo Press, which was developed at PtU. Being equipped with three decoupled gear drives, the 3D Servo Press is able to perform both roll and pitch movements of the press ram in addition to the standard translation movement in vertical direction. This leads to higher requirements on the capacity of the press bearings and the application of combined roller and plain bearings (Figure ). By using a combination of both bearing types, a combination of the specific advantages can be realized, such as low friction and the lack of backlash of the roller components as well as the high capacity and good damping properties of the plain component.
The project aims for a further technological development of combined roller and plain bearings for an industrial applicability. In cooperation with an industrial partner, the bearings are adapted to industrial requirements before applying them into existing or newly developed presses. In addition, the effects of backlash free preloaded roller bearings on the controllability of presses are investigated. At least, a design methodology for combined bearings is developed and verified for an industrial applicability.
In terms of the project a test bearing is developed by PtU and investigated on a special test bench. A design methodology is developed based on the received information, which can be used by the industrial partner for developing the press bearings. Suitable bearing positions in existing or newly developed presses are selected in cooperation with the industrial partner, before the press bearings are dimensioned. The industrial partner takes on production and assembly of the bearings as well as an investigation of effects on the controllability of the modified press.
Within the scope of the project, a design methodology was developed which can be used to design combined bearing arrangements for industrial applications. The design methodology includes, among other things, a numerical simulation model based on an analytical calculation approach for plain bearings supplemented by rolling bearing components. A sensitivity analysis was used to determine the most important design parameters for combined bearings and a proposal was made to determine these parameters. Using the design methodology, bearings with different rolling bearing types (cylindrical roller bearings and angular contact ball bearings) could be designed and evaluated in terms of their operational safety. Investigations have shown that the stiffness behavior of combined roller and plain bearings differs mainly by the respective operating mode. In full circulation operation, a speed-dependent stiffness increase of up to 5 times could be shown. The use of cylindrical roller bearings or angular contact ball bearings has a significantly lower influence on the stiffness behavior of the combined bearing in relation to the rotational speed and the operation mode.
The research project is funded by the Central Innovation Programme for SMEs (ZIM) of the Federal Ministry for Economic Affairs and Energy (BMWi).