【正文】 also to be considered is the time required for changing the part as well as for auxiliary operations in line with the priority of a short cycle time. 2 Pressing Machine Requirements One manufacturing cycle, which corresponds to one stroke of the press goes through three stages: loading,forming and removing the part. Instead of the loading and removal stages we often find feeding the sheet, especially in sheer cutting. For this, the press ram must have a minimum height for a certain time. During the forming period the ram should have a particular velocity curve,which will be gone into below. The transitions between the periods should take place as quickly as possible to ensure short cycle time. The requirement of a short cycle time is for business reasons, to ensure low parts costs via high output. For this reason stroke numbers of about 24/min for the deep drawing of large automotive body sheets and 1200/min for automatic punching machines are standard the number of strokes in order to reduce cycle times without design changes to the pressing machine results in increasing strain rates, however. This has a clear effect on the forming process, which makes it necessary to consider the parameters which determine the process and are effected by it. In deep drawing operations, the velocity of impact when striking the sheet should be as low as possible to avoid the impact. On the one hand, velocity during forming must be sufficient for lubrication. On the other hand, we have to consider the rise in the yield stress corresponding to an increase in the strain rate which creates greater forces and which may cause fractures at the transition from the punch radius to the side wall of the part. In fing, short pressure dwell time is desirable. As the pressure dwell time drops the die surface temperature goes down and as a result the thermal wear This is counteracted by the enhanced mechanical wear due to the greater forming force, but the increase due to the strain rate is pensated by lower yield stress because of the lower cooling of the part. The optimal short pressure dwell can nowadays be determined quantitatively using the finite element method [3]. In addition to cost avoidance due to reduction in wear, short pressure dwell time is also an important technological requirement for the precision fing of near shape parts, which has a promising future. The requirements of high part quality and high output will only be met by a machine technology which takes into account the demands of the metal forming process in equal measure to the goal of decreasing work production costs. Previous press designs have not simultaneously met these technological and economical requirements to a sufficient extent, or they are very costly to design and manufacture, such as presses with link drives [6]. This makes it necessary to look for innovative solutions for the design of the press. Its design should be largely standardized and modularized in order to reduce costs [6]. Fig 1. Prototype press 3 Press Drive with Noncircular Gears Principle The use of noncircular gears in the drive of mechanical crank presses offers a new way of meeting the technological and economic demands on the kinematics of the press ram. A pair of noncircular gears with a constant center distance is thus powered by the electric motor, or by the fly wheel, and drives the crank mechanism uniform drive speed is transmitted cyclically and nonuniformly to the eccentric shaft by the pair of noncircular gears. If the noncircular gear wheels are suitably designed, the nonuniform drive of the driven gear leads to the desired stroketime behaviour of the ram. Investigations at the Institute for Metal Forming and Metal Forming Machine Tools (IFUM) of Hanover University have shown that in this simple manner all the relevant uninterrupted motions of the ram can be achieved for various forming processes [2]. Apart from, the advantages of the new drive, which result from the kinematics and the shortened cycle time, the drive concept is distinguished by the following favorable Propertius. Because it is a mechanical press, high reliability and low maintenance may be expected. In panion to linkage presses the number of parts and bearings is clearly reduced. Above all, a basic press type can be varied without further design changes by installing different pairs of gears, designed according to the demands of the customer. Unlike link drives, bearing locations and installations do not change within one load class as a result of different kinematics. Thus the above mentioned requirement of popularization and standardization is taken into account Reductions in time and costs are possible for the design and press manufacture. Prototype At the Institute for Metal Forming and Metal Forming Machine Tools (IFUM) a Cframe press has been remodeled and a pair of noncircular gears was installed. The previous back gears were replaced by a plaary gear set for this purpose. The work carried out shows that remodeling of existing presses for the new drive is possible. The state of the press at the end of the modelli is shown in figure 1. The press is designed for a nominal ram force of 1,000 N and 200 N of the die cushion. The center distance of the noncircular gears is 600 mm. The pair of noncircular gears has an average transmission ratio of gear wheel has 59 gear teeth, straighttoothed,module 10 mm (fiacre 2). The face width is 150 mm. The gears have involute gear teeth. We assume a noncircular base curve for the design of the flank geometry. As a result the tooth geometry of a noncircular gear varies along the circumference. In spite of this, it can be derived from the wellknown trapezium rack, however [4, 51. An algorithm for the putation, which takes the addendum