This paper deals with the aspects of die design in the gear forging process. It discusses also alternative tool designs that may be used on a press with only one moving slide and ejection system. Influences of different designs on metal flow and load requirements are examined through experiments and finite element simulation. Tool design of parts should be chosen with respect to the geometry to be forged as the relative movements of the element affect the flow of the workpiece and the manner in which filling occurs. This is more evident when a large frictional force exists in the tool-workpiece interface because the friction condition plays an important role in the tool design. When no friction exists in the interface, the relative movement of tools has no effect on the metal flow and the forces required to fill the cavity. For the examples of chamfered punches, both the punch and counter punch load are 12500 kN whether the die is either rigidly fixed or elastically attached to the machine bed. The metal flow pattern is also independent of the relative movements of the tools. The friction effects on the formation of the tooth were studied using a design in which the die is elastically attached to the machine bed and both the punch and counter punches are chamfered. The tooth formations at the final stages, where frictional factors of m=0, 0.1 and 0.2 were employed for FE simulations. When there is no friction, the mode of metal flow is close to a free upsetting process and the middle region of the tooth was formed prior to the top and bottom corners. As there is no frictional resistance in the vertical direction, the top and bottom corners were filled uniformly at the same time. When friction exists in the interface, the movement of the die will assist the metal flow downwards and the bottom corner was formed much earlier than the top corner. At the end of the process, the bottom is fully filled while a chamfer was formed at the top and the ends of gear can be easily faced off to obtain a perfectly formed gear. The non-uniformity increases with friction. It is shown that the top corner was formed at an even later stage when the frictional factor m=0.2. A slightly larger chamfer was also formed at the top corner.
Alternative die designs in net-shape forging of gears
2004
8 Seiten, 13 Bilder, 5 Quellen
Conference paper
English
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