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 curing press is used in the final phase of tire manufacture. A tire semi product is placed into the curing press mold and a specific pressure and temperature gives it its final shape and final mechanical properties. There are many types of curing presses; this particular press is mechanical and the pressing force is exerted by an eccentric mechanism. The size of this press allows production of tires for trucks and medium-sized tractors. The basic demands placed on this type of press include tightness of the parts which are exposed to pressure from the heating medium. This paper mainly focuses on the tightness of the vulcanizing chamber and the tightness of the mold in which the semi product of the tire is inserted. Leakage of the vulcanizing chamber may cause leakage of the heating medium which could result in injury to the machine operator. Leakage of the mold causes an overflow of rubber into the parting plane, which may result in the production of rejects. To ensure the tightness of both these components, it is necessary to create sufficient pressure between the individual components. The value of the compressive force depends on the setting of the overlap of these parts, which depends on the stiffness of the individual parts and on the force exerted from the pressure of the heating medium that acts on these parts. Finite element method (FEM) analysis of this problem was performed using Abaqus software. A computational model of the curing press was created for this numerical analysis. The geometry of the press is symmetrical and the load is centric, therefore, only half of the press was modelled. The aim of this analysis was to find the most suitable settings for the overlap of the mold (independent variable) and the overlap of the chamber (dependent variable) which ensure the smallest possible leakage of the mold and an uninterrupted contact surface between the sealing and the upper part of the chamber. The sealing of the chamber is made from rubber which was modelled for the analysis as a five term generalized Mooney-Rivlin model, also known as the James-Green-Simpson model. This model assumes hyperelastic behavior with incompressibility. The insulating plates are made of a particulate composite which was considered to be linear with isotropic properties. For strength evaluation of the composite materials, all individual components of the stress tensor were investigated according to the maximum stress criterion. Hook’s law was considered to be valid for all the metallic materials. The Von Mises criterion was used to evaluate the strength of the metallic materials. The geometry of the press was discretized using 3D linear elements with 8 nodes and with reduced integration (C3D8R). The geometry of the rubber sealing was discretized using hybrid 3D linear elements with 8 nodes and with reduced integration (C3D8RH). The overall number of elements was approximately 97,000. Calculation model enabled to compute the best overlap setting of the chamber and the mold. This setting ensures their tightness. Effect of the setting to a stress in a press was also studied and the values of the stress were in a permitted range.
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