PSI - Issue 77

Vasco Gomes et al. / Procedia Structural Integrity 77 (2026) 559–566 Gomes et al./ Structural Integrity Procedia 00 (2026) 000–000

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2. 3D Model 2.1. Kinematic chain

The 3D rigid body model, as previously mentioned, used the 3D CAD model of the servo press. This model was then simplified, with its major components, such as the input shaft, gears, crankshafts, rods, slide, contact guides, tool and structure, being isolated and exported to the SimulationX® software as rigid bodies, where they were connected by linear, rotational and spherical joints. The servo press (Fig. 1) system starts with an external source, which is followed by the inertia and transmission ratio of the reducer. The resulting output is then connected to the rotational joint of the drive shaft. As the drive shaft rotates, a spur pinion (located at its end) engages the two separate gears: the right gear and the intermediate gear, with the latter further engaging the left gear. To model this transmission system, a total of three tooth contact elements were used to represent the interactions between the gears. This allowed the transmission for each of the two crankshafts, to which are associated the two rods (two-point system), whose purpose is to transmit the force to the slide and to maintain parallelism between the slide and the bolster (since, for a large slide area, single connecting rods may not be sufficient) (SCHULER GmbH, 1998). The gear-crankshaft-rod sequence was achieved via revolute joints, and each rod was linked to its respective HOLP using a spherical joint. Both HOLPs were constrained to the slide, thereby merging the two kinematic branches into a single system. The slide is allowed to move through a combination of a linear joint (in the vertical direction) and a rotational joint. Contact interactions between the slide and the press structure were then introduced. The structure is supported by spring-damper elements. Finally, the tool was included with its upper punch fixed to the slide and the bottom die to the press’s structure. Besides the kinematic chain previously explained, the 3D model also included additional features that increase the accuracy of the model, such as an FMU block, stamping forces, a pneumatic counterbalance system and contact elements.

Fig. 1. (a) 3D rigid body model of the servo press; (b) resulting 3D representation of the rigid body model.

2.2. FMU block The FMU block is a common addition to SimulationX® models, serving as mean to import, directly to the model, another external model or system, which has a group of inputs and parameters that will generate a group of predefined outputs. In this particular scenario, this unit was developed by Baumüller and is intended to control the movement of the servo press, replicating therefore the function of the motor and servo drive of the real press. To establish this control, three alternative methods can be employed: target position, target angle of the motor’s shaft or target speed for that same shaft. The output provided by this element, the motor torque, is connected to the external source.