November 2024 Volume 6

EQUIPMENT & TECHNOLOGY

horizontal reference state. This significant drop in torsional stiffness compared to the stiffened horizontal axial forming machine results from the omission of support for the upper and lower base plates of the machine frame (Figure 4). Whereas the mounting points of both base plates via the common machine base counteracts the torsion of the horizontal press frame, further optimization steps are required for the vertical machine design. Due to the solid ram design and the installation of four or optionally eight recir culating ball-bearing carriages, a significant stiffening could be achieved. This results in a stiffness improvement of the vertical axial forming machines of approx. 70% compared to the reference state, so the torsion angle amounts to only 0.17 degrees. Machine torsion occurs from insufficient tool guidance. There fore, the new simplified vertical machine frame was developed for a complete machine concept based on the data obtained from the numerical investigation. The main focus was on implementing the greatest possible machine stiffness so that acceptable gear quality within the production of greater helical gears in the future could also be achievable. The optimized design of the machine frame and the ram unit is shown in Figure 5. According to the simulation model. Thus, the ram unit consists of a solid ram plate (yellow) axially supported by eight recirculating ball-bearing carriages along the guide rails. The bearing package for absorbing the axial forming forces during the turning of the forming tool is situated inside this ram plate. It has been designed for a minimum space requirement. In this design, the driven tool carrier has been extended by a second servo motor in order to generate greater torques with simultaneously higher positioning accuracy and, thus, to improve the achievable gear tolerances. Moreover, the forming tool can now be decoupled from the driven tool carrier by a short-stroke cylinder. Therefore, damage of the already formed gearing during the ejection by the uninhibited torsion of the forming tool can be completely prevented. Further more, a direct measuring system can be installed on the rotary bearing at a later date in order to be able to track the actual posi

Figure 4: Simulated deformation of the loaded axial forming machine with a) the stiffened design with 4 guide elements and b) with the optimized machine design

tions and actual velocity of the driven tool carrier during the axial forming process with maximum precision. Although the optimized design of the ram unit results in a significant dimension increase, the maximum ram stroke remains constant or is even longer due to the simultaneous extension of the press frame. Therefore, this new machine concept can manufacture longer helical gears in the future. This new machine concept for the manufacture of high-precision helical gears was developed on the basis of investigations by struc tural-mechanical FEM simulations and designed for high rigidity, especially with regard to torsional loads. In the future, this machine concept will be applied to manufacture a wide range of helical gears according to the achievable gearing parameters, component dimen sions, and the corresponding tolerances. In order to get the newly developed machine concept ready for series production, the simula tion results concerning numerically determined torsion angle will be evaluated by carrying out experimental trials. An overview of the achieved simulation accuracy as well as the influence of the new machine concept on the gear qualities and tolerances will be repre sented in a further publication after completion of the experimental trial. Conclusion The Felss axial forming is not only capable of manufacturing simple spur gears but is also suitable for the production of helical gears due to the modified machine design. In order to achieve gearing quali

ties of IT5-6 and to comply with marketable gearing tolerances, the conventional axial forming machine had to be extended by a driven tool carrier and stiffened to support the occurring torque. By a complex synchro nization of the turning drive and the recur sive stroke, the manufacturing of external helical gears with a helix angle of up to 22° has already been achieved with process stability. Through additional stiffening of a horizontal axial forming machine, the reduc tion of the previously high total helix devia tion up to 10 μm could be realized, which makes an economical application of axial

Figure 5: Optimized design of the vertical axial forming machine

FIA MAGAZINE | NOVEMBER 2024 13