Papers by Keyword: Machine Tool

Abstract: PID parameters of machine tool for micro-defect mitigation of KDP crystal had been optimized, after which the velocity fluctuation frequency and amplitude variation of motion axis under different spindle speeds were studied. It is evident that the stability and following errors of the system run better under the velocity&acceleration feed forward PID control algorithm and Notch filters. The velocity fluctuation frequency of motion axis varies with spindle speeds significantly when the tool system is stable, while the fluctuation amplitude variation is slightly changed. To be conclude, the optimal working spindle speed is verified to be 4.78×104 rpm based on comparative experiments, at which damage pits can be mitigated by micro-machining successfully with roughness value of 34.4nm.

Abstract: The article deals with diagnostics of machine tool precision and necessity to train basic routines of measurement and its preparation. Such training is essential for efficiency of diagnostic processes as preparation is usually the most time-consuming and skill-demanding part of overall measurement. The article roughly describes simulation of machine tool errors on proposed experimental device and its implementation into the training process in order to gain experiences with measurement on machine tools in wide scale of conditions. Described device is designed to simulate several geometrical errors, inaccuracies and environmental impacts on precision of positioning which affects not only machine precision but also effectivity of measurement itself.

Abstract: The electric base load of milling machine tools has a high share of the machine’s total energy consumption. An approach to decrease the energy demand per workpiece is to shorten the machining time by raising the material removal rate. The maximum feed depends on the tool’s wear resistance while the maximum depth of cut is often limited by the chatter stability of the machine. In this paper active damping is used to damp chatter vibrations, which leads to a higher depth of cut. To evaluate the decrease of energy consumption for any workpiece, a modeling methodology for the energy demand of machine tools was developed, which is presented in this paper. The methodology is able to estimate the energy requirements of the spindle during cutting, of the feed drives, of the auxiliary equipment and of the base load. The numerical results were experimentally validated by different 2.5D machining processes, with good agreement between the simulation model and the experimental results. Therefore, the proposed methodology can be used effectively for calculating the total energy required for the machining of any workpiece. In addition, the structural dynamics of the machine tool, the active damping system and the cutting process were modeled in order to simulate the chatter stability. This enables a straightforward determination of the optimum cutting parameters as well as a comparison of different milling part programs, both in terms of the energy demand. Furthermore, it is possible to evaluate the energy conservation by active damping and to point out for which cutting processes active damping is useful.

Abstract: This study has developed a model in order to show the relationship between deflection of the low-rigidity processing system such like thin-walled component and the flexible milling force. The new model takes the deflection of cutter-workpiece system into account. The cutting force is analyzed simulatively by utilizing modified Newton–Raphson iterative algorithm. The simulative results show that the total normal deflection of workpiece–cutter system is the main factor affecting the change of cutting force.

Abstract: Chatter vibrations and tool deflection are common challenges in metal cutting processes. In roughing operations, it is often the occurrence of chatter vibrations which limits the productivity. While finishing, when tolerances are small, the tool deflection can lead to violating tolerances and thus producing scrap parts. Beside the tool and tool holder, it is also the guidance system, especially in the z-axis, which influences the aforementioned phenomena. In this paper the influence of an electromagnetic guided z-axis is presented. It is focused on the influence of the high damping and the high static stiffness of the guide. Further benefits of this technology are outlined.

Abstract: Heat resulting from motors, moved contacts as well as cutting processes, causes time-dependent deformation of machine structures that reduces the precision of machine tools. For design optimization and especially for correction of thermal induced displacements, it is necessary to have compact models, which allow fast simulation of the thermo-elastic behaviour of the entire moving machine tool during the process. This paper presents an innovative simulation technology that permits, starting from CAD geometry through FE modelling, to come to a time-saving thermo-elastic calculation model of entire moved machine tools. Thereby, calculated temperature and deformation fields are of high geometrical resolution. Results and potentials of the new approach are demonstrated on example of a Hexapod machine tool.

Abstract: This paper gives a description of the challenges in the development of a generalized approach for the structure model based correction of thermoelastic errors of machine tools. The correction approach can be divided in modules. The challenges are described on the requirements of the modules.

Abstract: The measures taken to improve the thermal behaviour of machine tools are based on thermal models. The models are applied to support the design process and to correct the machine tool operation in a control-based way. Especially the models for correction purposes include uncertain parameters that cannot be estimated with sufficient accuracy. Thus these parameters have to be adjusted by means of measurements. During the adjustment process, a broad diversity of machine behaviour and model characteristics has to be taken in to account. Therefore, substantial time, effort and expert knowledge are required. To identify the key expenses, a generalized and systematic analysis of the adjustment process was carried out. First, the typical design of the models, the parameters of the sub models and the current adjustment procedure were investigated. Based on the results of the analysis, support requirements were identified. Afterwards first methods and software tools for efficient support were developed. This strategy is demonstrated using the example of a hexapod strut model.

Abstract: The numerous different possibilities to influence the thermal behaviour of machine tools preclude a generally agreed upon evaluation that considers their effectivity and energetic-economic efficiency. This is caused by their different modes of action and non-linearity in their interrelations. A variance-based sensitivity analysis makes possible a comparison of different factors regarding their impact on changes in relevant characteristics. Its functionality is explained and exemplified by a simple thermal problem.

Abstract: In this paper, a synchronous approach for dynamic simulation of machine tools is described. Computer Aided Engineering (CAE) method models and analyzes a dynamical parameter prototype of machine tools. In which, the flexible structure, interactive movement, non-linear factor effects as well as characteristics of resonance frequencies and mechanical transfer function are considered. The integrating Finite Element Method (FEM), Multi-Body Dynamics (MBD) and control carries out a solution of machine tools simulation for predicting dynamic machine behaviors. The static analysis and modal analysis of components are presented with sample examples. Cybernetic characteristics like Bode diagram and such a controller are implemented for movement tailors. The synchronous approach deduces a practically technical method for machines tools.