November 2024 Volume 6

EQUIPMENT & TECHNOLOGY

offers very constant forming conditions due to the complete contact between the component and the forming die. In the remaining forming area at the end of the gearing, the forces drop again by reducing the contact between the component and the forming die. In order to reduce the dependence of the gear quality on the unavoid able load changes of the forming process, a study was carried out on the economic realization of the greatest possible torsional stiffness of different axial forming machines and their tool guidance design concepts. A FEM-based software Meshparts was used for this study. This offers the possibility to efficiently analyze the deformation of various machine designs via structural-mechanical simulations under the forming load and to evaluate their potential influence on the gear quality. Due to the complex and component-intensive machine design, the simulation model is reduced to the main supports of the machine frame within the forming process (Figure 2). For the simulation, unnecessary construction elements, such as smaller radii and bores, were neglected. The reduction of the simulation model and the simplification of the contours made a drastic reduction of the calcu lation effort possibly due to the lower number of required meshing elements of approx. 1.2 million without any significant influence on the investigated result. In accordance to the standard machine design, the bearing and contact surfaces were respectively defined, and the machine frame was preloaded via the tension rods. The other specified boundary conditions describe the maximum machine load during the forming process of a helical gear. This is represented by the application of a constant torsional force by the driven tool carrier corresponding to 9000 Nm and the application of the asso ciated reaction torque to the clamping device for component fixing. Moreover, the axial load of the forming process is also calculated by 400 kN, which is applied through the connecting surfaces of the hydraulic feed cylinder and the clamping device.

to a torsion angle of 0.05588 degrees, whereby approx. 98% of the total torsion occurs due to the torsion of the driven tool carrier and its guides. The first optimization stage of the horizontal axial forming machine was the installation of two additional guide elements, each with two recirculating ball-bearing carriages. The addition of the guide elements now stabilizes the forming tool on four posts of the machine frame preventing displacement due to torsion. This modi fication already resulted in an improvement of the torsional machine stiffness of approx. 41% compared to the reference condition and corresponds to a torsional angle of only 0.033 degrees. Based on the calculated results concerning increased machine stiff ness and its potential positive influence on gear quality, the 4-element guide concept was implemented on the Aximus H02 axial forming machine. After the upgrade was completed, the previous experi mental test was repeated. Compared to the gear results from (Figure 3a) of the conventional guiding concept, the low machine torsional stiffness against torsional forming loads could be verified as the main influence on the gear quality. Due to the new stiffened machine concept, the reduction of the previously insufficient total helix devia tions F β from over 20 μm to below 10 μm (Figure 3b) was achieved to be within the specified tolerance limits.

Figure 3: Helix corrected measurements of the gearing produced by a) the conventional forming machine, b) the stiffened forming machine (Helix angle of 10°) After additional validation tests, the actual torsion angle of 0.052 degrees in the reference condition of the axial forming machine at an applied torque of 9000 Nm was measured. There is a deviation of 5% between the calculated value and the actual value to deter mine the torsion angle. So, the simulation model provides a realistic representation of the determined torsional stiffness. After validation of the simulation model, the correlation between the new stiffened machine concepts and gear quality by the production of helical gears on vertical axial forming machines was evaluated. As both horizontal and vertical axial forming machines must be applied for the production of helical gears, a numerical investi gation of the machine frame's resilience under identical load and boundary conditions had to be carried out for the vertical machine design, as described above. The investigation of the already stiffened machine concept by integrating the previously optimized tool guid ance showed a torsional angle of 0.0407 degrees. This represents an improvement in torsional stiffness of only 27% compared to the

Figure 2: Simulation model of the horizontal forming machine with applied forces and torques The standard design of the die guidance system of a conventional, horizontal axial forming machine, which was installed to produce the first helical gears shown in Figure 3a, was defined as the refer ence condition for this investigation. This die guide consists of four recirculating ball-bearing carriages which guide the forming tool in the press space by two diagonally positioned guide elements. The numerically determined total torsion of this machine type amounts

FIA MAGAZINE | NOVEMBER 2024 12