Numerical analysis of the power train and the guidance system of a servo-screw-press

The servo technology was implemented in screw presses to produce high press forces for stamping and forming applications. Instead of the usual flywheel, a powerful servo motor directly drives the screw which is used to transform the rotational into the linear movement of the press ram. Nowadays stamping and forming processes can be designed more dynamic and flexible because the drive system can be accelerated faster due to the lower moment of inertia. Nevertheless, new strategies must be developed to ensure an efficient projection process and to reach a high project quality. The static, dynamic and thermal behavior of the servo-press has a great importance as it may result in unwanted behavior during process. Apart from the static loads, machine tools are subjected to constantly changing dynamic forces and the machine tool structure will deform according to the amplitude and frequency of the dynamic excitation. Both the static and dynamic stiffness of the machine tool structure determine the machine's accuracy and productivity. At first, a previously studied FE model of the servo-screw-press is evaluated and analyzed in a static and dynamic analysis using the Finite Element Method (FEM). Then, an extraction of modal parameters from experimental results and correlation between the Finite Element Analysis (FEA) and the Experimental Modal Analysis (EMA) is performed. A numerical study of the uncertainty in stiffness and damping properties for the power train and guiding system of the servo-screw-press is performed with an addition of some other uncertainties in the model such as mass and stiffness distribution in the FE model. This is done by applying a statistical probability distribution to physical properties and randomly sample of many physical properties. Implementing the powerful tool of sensitivity analysis and model update is not yet to be performed on such a large FE model as the servo-screw-press, therefore, evaluation of this tool using the commercial software FEMtools v.3.6 is carried out. The second focus in this study is to define a FE model of the servo-screw-press for modeling of transient thermal analysis and structural analysis from the resulting new temperature distribution. Results from the thermal-stress analysis were validated experimentally relating the temperature distribution and the strains at the power train and guiding system.