Papers by Author: Reimund Neugebauer

Abstract: The paper points out a novel design methodology for electromechanical linear axis. It is based on common process parameters and an automated iterative solution algorithm. For the first time ever, different types of electromechanical linear axes can be compared. Furthermore, an optimum solution aiming a low moment of inertia ratio is the result of the design process. Using the example of a machining center, simulation and experimental results are shown. The performance of the process-oriented design methodology relating to additional design objectives is shown in this context.

Abstract: The paper points out a minimum variance based performance index for restricted controller structure, known in literature and applied in process industries. The theory is introduced briefly. As core of the paper adaption to the topic of speed control for electromechanical drives is shown. Simulational and experimental results for various single and dual-mass systems show good sensitivity to relevant parameters. As main drawback, the index prefers tough controller settings.

Abstract: The cascaded position control structure is state of the art in modern production machines and machine tools. Since an adequate controller performance of the electromechanical axes is still a key aspect for a resource efficient and high-quality production, this topic is addressed by the paper. An overall approach/framework to monitor and ensure an improved controller performance over time, comprising five tangible approaches is presented. All methodologies were developed in the department for control and feedback control technologies of the Technische Universitaet Chemnitz. They will be demonstrated and also be discussed based on experimental results.

Abstract: Monitoring functions of machine tools are of increasing importance to enhance their productivity. They can also be complemented by several system identification approaches which provide additional information. To utilize these approaches, special requirements, e. g. adequate reactions to variant process excitations during the regular process have to be fulfilled. The paper deals with the identification of velocity loop parameters of numerical controlled (NC) axes on a state of the art machine tool and gives an insight on how to correspond to the given requirements. Mainly, this is done by implementing extending modules, of which the model error estimation is pointed out in particular. Experiments with data for a turning operation show the practicability.

Abstract: To make the advantages of electromagnetic forming applicable for industrial manufacturing, a three step tool design strategy is suggested. At first, simplified decoupled electromagnetic and structural mechanical simulations are used for creating a preliminary design via a systematic iterative optimization process. The selected design is verified in more accurate coupled simulations. A prototypic realization serves for further optimization, if necessary. The applicability of the approach is proved on the basis of an inductor system for magnetic pulse welding of tubes.

Abstract: The presented study applied the state of the art in roller hemming simulation on a car body assembly. Corner areas with changing flange lengths are always challenging in case of reaching the quality demands. Thus, the numerical results like e.g. springback, hem thickness, roll-in and hemming geometry are compared to experimental results. It is shown that the quality of prediction depends on the system stiffness of the roller hemming device, the geometrical contour of the car body assembly and the consideration of steps in the process chain like stamping and flanging. Finally, the gained cognitions point out challenges for future research in this topic.

Abstract: Cylinder bore finishing requirements are defined by quality features such as roundness and cylindricity as well as by the manifestation of the surface profile. Honing is a proven manufacturing method s to achieve this. Undesirable distortions of the cylinder shape occur under operating conditions in a reciprocating internal combustion engine. These negatively affect the tribological system of piston, piston ring, and cylinder bore. As a result, efficiency deteriorates and oil consumption rises. The cylinder crank cases are finished in a defined tensioned state to compensate for distortions. This results in a highly complex manufacturing process and is only suited for compensating static distortions. Further increasing machining requirements resulting from strategies such as lightweight construction, downsizing, and friction reduction are pushing conventional honing methods to their technological limits.Adaptronic form honing constitutes a production engineering approach to manufacturing a free form in the cylinder bore. The objective is to keep inverse distortion geometries in store as macro shapes. These will then represent ideal cylinder shapes under the influence of distortion mechanisms in a defined engine operating range. Tool and process development and the analysis of machining results with respect to productivity, shape accuracy, and surface topography are presented and viewed as potential options for optimizing the tribological system of piston, piston ring, and cylinder bore. Other options such as shortening the process chain will be derived.

Abstract: State-of-art models for mechanical joints in large scale structures typically consider only the linear behavior of the joint zones with lower complex approaches, such as rigid or elastic beams or a merge of opposite sheet metal nodes. In the present study several feasible methods to model nonlinear joint behavior and the connection between sheets and joint are investigated and evaluated. A preferred combination based on nonlinear springs was chosen, which meets the requirements for application in large scale structure models: low computation time, mesh independence and availability in several FEM software packages. For the calibration of the joint zone models a 2-point-tension-specimen was used. Five different joint types and the two sheet material combinations aluminium/aluminium as well as steel/steel were investigated. With the calibrated models a more complex 5-point-tension-specimen was used to consider the local interoperation of the joints. Some deviations were determined especially for highly stressed joint zones. Hence an average function was defined to consider both, the local deformations in the joint zone and additionally the more global sheet deformations. Finally, the simplified joint models were used in a complex specimen model with 22 joints. The comparisons between experimentally and numerically determined results show a good accordance. The nonlinear joint behavior is captured very well. A method is presented, which uses 2-point-specimens to calibrate simplified joint models with nonlinear deformation characteristics. The efficient application in large scale structure models is possible due to simplicity, stability, low computation times and mesh independent implementation.

Abstract: Laser welding of complex aluminum add-on body parts such as vehicle doors, is a common joining technology in the automotive industry. Besides the many advantages (e.g. high processing speed) laser welding provides, temperature induced distortions are an important task to deal with. In the last twenty years, several simplified FE methods, which predict welding distortion (weld seams, spot welds) of large assemblies, were presented. In order to simulate the distortion of large car body components properly, realistic clamping conditions need to be considered [1, 2, 3]. Furthermore, the calibration process of simplified models has to be examined systematically, to find out their limits and achieve optimal simulation results [4]. In this paper, a new FE model is presented to predict distortion of laser welded structures, based on a shrinkage volume approach. Effective surface based clamping conditions (derived of the real clamping device) and effects of previous forming processes are considered. The simplified model was examined due to an extensive design of experiments. Not only simple, but even complex simulated specimens match with the experimental results very well.

Abstract: Machine tools for small work pieces are characterized by an extensive disproportion between workspace and cross section. This is mainly caused by limitations in the miniaturization of drives and guidance elements. Due to their high specific workloads and relatively small spatial requirements, Thermal Shape-Memory-Alloys (SMA) possess an outstanding potential to serve as miniaturized drives in small machines. However, most of the known SMA drive applications necessitate additional guidance elements to realize a certain mechanical stiffness. In this paper we present a novel SMA actuator design, which does rather not require an additional guidance. The stiffness in directions different from the actuators moving direction is realized by a specific arrangement of the SMA elements. Those are designed regarding geometry, applied load, and control aspects. Furthermore, a sample actuator is built to investigate the capabilities to serve as miniaturized feed axis in small machines.