Finite element analysis of vertical injection molding machine before the template

Date：2014-08-19 09:58:24

        Vertical injection molding machine is a plastic injection molding for short, is a thermoplastic or thermosetting plastic molding plastic parts of the main processing equipment. After it is heated to melt the plastic particles, the high-pressure high-speed way molten plastic is injected into the mold cavity is closed, the pressure maintaining a predetermined time, after cooling and shaping the mold cavity to obtain the same plastic.
         Therefore, it has the following characteristics: a molding can create a complex shape, size, accuracy, or with inserts of plastic parts; strong adaptability to all kinds of plastic processing; machine production rate, as well as easy to automate production. Currently, the world's annual production of about injection molding machine more than 30 million units, the fastest-growing varieties, specifications, one of the largest number of models produced plastics machinery production.
         A finite element calculation
         FEM is a numerical method for the structure of discrete units. Finite element modeling is divided into a grid of cells and the formation of structural calculation model. Each unit (triangles or squares) are connected through a node, the unknown element is displaced on each node, the stiffness matrix of the units combined with each other to form the entire structure of the overall stiffness matrix, according to known forces and the boundary conditions used to solve stiffness matrix, to arrive at the unknown displacements, and calculate the stress in each cell. FEM calculation model can be attributed to the discrete linear equations: F = K δ where: F is force suffered vector; K for the calculation of the overall stiffness matrix model; δ for each node on the calculation model the displacement vector.
         Two vertical injection molding machine template
         Universal vertical injection molding machine mainly consists of the injection device, clamping device, the hydraulic drive system and electrical control systems. Clamping device (or clamping devices) is a key component of vertical injection molding machine, which is molded article working parts to ensure a reliable and achieve closure mold mold opening and closing movements, which mainly consists of a template, rod, clamping mechanism , the top of the device and security products, doors and other components. Templates are an important rigid vertical injection molding machine parts, a fixed mold and sports-oriented positioning reference function, by transfer molding templates, dynamic templates, the former template composed by connecting rod between the template. The mold is fixed on the movable platen, respectively, and the former template. Templates are fixed before bed, moving the template through the drive mechanism and toggle back and forth movement of the hydraulic system on the rack rails. Therefore, the template structure and rigidity directly determines the quality of the machine.
         Production practice templates designed mostly for the experience of using the traditional formula, mainly depends on the experience of designers. Usually will simplify the calculation of the specific design template into Charpy calculated based on the number of design parameters determined empirically, without taking into account various factors in the manufacturing process of each template and the impact of the work process, as well as the situation changes and differences in load affect the template functions. Indeed vertical injection molding machine template in the work process force the situation is very complicated, and different templates bear the load conditions vary. Thus, when the terms of design templates based on manual calculations, the results will inevitably lead to the design differences between the actual situation greatly. Either create a template quality tests, either too conservative design, greatly improving manufacturing costs.
         3 template structure analysis
         Clamping device is a closed system by force template, rod, toggle clamp mechanism and other components. Under the clamping force, the template is mainly exposed to bending work. From the standpoint of equal strength, the shape of the template is usually designed as a plate-like structure or box-type structure with ribs. Since the template is a reference fixed mold. Precision templates, structural strength and stiffness will affect the performance of vertical injection molding machine.
         Therefore, in the design template, stress analysis should be based on the actual stress situation, to meet the strength and stiffness of the condition, it has a reasonable structure shapes and sizes. Finite element analysis method can simulate the situation by force template to calculate the stress and strain analysis to determine the weak parts of the template.
         When applied finite element structural analysis template, note the key factor three aspects:
         (A) establish an appropriate geometry. Since the geometric model determines the accuracy of the finite element solution, the simulation accuracy and solving efficiency. So, try using a simple analytical model is reasonable; template model can be used symmetrical form; maximize the use of low-level units, etc.
         (2) the correct selection unit form and select the appropriate mesh density. Unit in the form of selection depends on the mechanical model, solution accuracy requirements, hardware and software systems. Should follow the "convergence curve test" principle, that is, when the stress or strain, deformation, etc. The results tend to converge with mesh refinement, only to confirm the results.
         (3) the right to determine the boundary conditions. Since the template that contained the actual situation is very complicated, if fully consider the actual situation, computational analysis is not possible. According to the actual work of the template, if the load boundary conditions and constraints on the boundary conditions appropriate to simplify, you can simplify the calculation and analysis, and can meet the required accuracy.
         4 Front template finite element analysis
         Before a single template for the study, finite element analysis. Vertical injection molding machine clamping force of 530 t, the former template material for QT440, the elastic modulus E = 164 GPa, Poisson's ratio μ = 0.27. Since before the template structure and force situation is complex, consider the impact of the actual working conditions of all possible nor necessary. Thus, the structure and the loading conditions of the template prior to the need for simplification.
         (1) Solid Modeling
         Before the template size: tonnage of 530 t; total height of 0.430 m; floor height of 0.350 m. Dredged block: Length 0.100 m, high 0.260 m, width 0.560 m; cavity height of 0.200 m; boss for the diameter 0.680 m, lower diameter of 0.970 m. Before the establishment of the CAD model templates quarter in UG, while ignoring the impact on the structure and properties of small detail structure, imported into ANSYS analysis environment, get the model shown.
         (2) Mesh
         Divided by hexahedral elements, can reduce the number of units to improve accuracy. For NA hexahedral elements divided body region, available tetrahedral unit division. ANSYS will automatically generate the transition unit between the two units, get the finite element mesh model.
         (3) boundary conditions and loads imposed symmetry plane of symmetry constraint template quarter of the previous model, adding to the constraints on the Z screw constraint circle. Clamping force 530 t, will be reduced to a quarter clamping force uniform load as shown in the cross-sectional area of the ring plane.
         5 Results Analysis
         Respectively, and Figure deformation stress distribution before the template of Figure. Higher stress occurs in the central region of the template and screw constraint area. Template central region a larger area to the stress, the maximum stress 74 MPa. Z template showing the deformation characteristics typical of bending deformation, deformation of the central region of the larger template, a maximum of 0.29 mm, gradually decreasing from the center outward, showing the approximate concentric distribution.

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