The analysis is performed on a hydraulic press which is intended for use in the automotive industry and is a part of a production line. The final phase of manufacture of interior and acoustic parts takes place in this press. These interior and acoustic parts are made of sandwich fabric which is inserted into the heated mould of the press and by treatment with a defined pressure (or, more precisely, a defined compression) and temperature, it is formed into its final shape. This press has a frame with four columns and it is not preloaded. Two double acting hydraulic cylinders placed on an upper cross beam exert the compressive force. Due to continuously increasing demands on the accuracy and quality of products not only in the automotive industry, it is necessary to ensure compliance with the accuracy of certain values of machine operation. Especially in this case, the value of accuracy substantially depends on the clamping plates of the press, for which a certain value of flatness is required, both at room temperature and at elevated temperatures. To achieve this accuracy, it is necessary to guarantee sufficient stiffness of the machine to resist the pressing force with the smallest deformation possible. Another crucial factor affecting the accuracy of the machine is heating of the heated clamping plates. Unequal heating of parts of the frame causes additional deformation that has to be quantified and eliminated. The main aim was to verify the design of the press by numerical computation and gather knowledge for modifying the topological design of the press so that it fulfils the required customer parameters of flatness and parallelism for different types of loading. A computational model of the press was created for the numerical solution of a coupled temperature-displacement numerical analysis. The analysis was performed using the finite element method in Abaqus software. The press is symmetrical in two orthogonal planes and the load of the press is considered to be centric. On the basis of these two factors it was possible to carry out the analysis by considering only a quarter of the press. The analysis was used to investigate the effects of static and combined loads from the pressing force and heat on the press. The influence of a cooling circuit located in the press frame for the reduction of frame deformation (and deformation of clamping plates) was investigated. Contacts were defined among individual parts to ensure the computational model had characteristics as close as possible to the real press. The analysis was solved as stationary, on the basis that the cooling of the tool between individual pressing cycles is negligible. The insulating plates are made of a particulate composite material which was considered to have isotropic properties depending on the temperature. For strength evaluation of composite materials all individual components of the stress tensor were examined according to the maximum stress criterion. Hook’s law was considered to be valid for the metallic materials. Von Mises criterion was used to evaluate the strength of the metallic materials. The geometry of the press was discretized using 3D linear thermally coupled brick elements with 8 nodes and full integration (C3D8T). There were approximately 174,000 elements in total. Design procedures for designing a press frame with higher work accuracy (flatness) were proposed with the example of the simplified model of the press table. With these methods it is possible to achieve times higher accuracy than is achieved with conventional method.
Abstract. The constantly increasing demands on product quality place higher requirements on production machines. The machine we investigated is a hydraulic press. Higher accuracy is required and measured on the clamping plates for the tool or on the press frame. The effect of additional cooling in the frame is investigated on a hydraulic press which is intended for production in an industrial production line. The shaping phase of fabric car parts takes place in the mould of this press. The press mould is heated for technological reasons and causes heating of the frame. Heating of the frame causes undesired additional deformation. This paper investigates a press design with additional cooling circuits and its influence on the press work accuracy.
A computer numerically controlled (CNC) milling center is a machine tool for the production of parts with planar, cylindrical and shaped surfaces. The milling center analyzed here includes an open frame -a structure resembling the shape of the letter C. The main cutting motion is performed by a tool clamped in the spindle. Secondary motion can be linear, rotary or a combination of these. Linear movements in three axes are performed by the tool by means of linear motion components (i.e. motion screws and linear guide rails). Rotary motion is performed only when the workpiece is clamped to the rotary table which is mounted on the mounting plate.The basic demands placed on the structure of a milling center include high static and dynamic stiffness during machining processes. This article is primarily aimed at evaluating the response of the frame of the CNC milling machine to the excitation caused by the fluctuation of cutting forces due to step changes in the number of engaged cutting edges. To ensure optimum machining conditions it is important to set suitable cutting conditions for a frame structure with sufficient stiffness. Unsuitable cutting conditions and low stiffness of the machine frame may lead to dimensional inaccuracies of the workpiece, to decreased quality of the machined surfaces or even to the destruction of the tool cutting edges.The aims of the study include the determination of the static deformation, modal analysis to assess the dynamic properties of the frame, and harmonic response analysis, taking into consideration the amplitudes of the loading forces specified in accordance with the recommended operating conditions of the individual tools.Finite element method (FEM) analyses of the frame were performed using MSC.Marc software. Due to the high structural complexity of the computer aided design (CAD) model, the
Abstract. This article is written for the purpose of pointing out the problem that is focusing on creation of the FEM analysis by simplification detailed CAD model. Each simplification brings an error into the calculation. If designer do not fully understand to the design and specific simplification method, he can create the error that can lead to serious consequences.The created computational model shows the simplifications of the CAD model. To analyze response of the frame of the CNC milling machine based on different definition of roller linear guides, through MSC Marc for simulation and analysis, a simplified FEM computational model was created. Four variants of the replacement of the linear guides with the final evaluation of the results of each variant were described.
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