A Microscopic Wall Slip Model Establishment Method for Injection Molding

Abstract

The invention discloses a method for establishing a microscopic wall slip model for injection molding. Based on the macroscopic viscosity model, the length of the molecular segment and the characteristic size of the micro-parts, the following steps are sequentially performed: 1) introducing a microscopic correction factor to the macroscopic viscosity model. Correction; 2) Set the ratio of the molecular segment length le reflecting the polymer flow characteristics to the micro-part characteristic size d as the minimum macroscopic size of the microstructure as the microcosmic influence factor; 3) establish the relationship between the microcosmic correction factor and the microcosmic influence factor , and use the least squares method to fit its parameter values; 4) Introduce the relationship between the microscopic correction factor and the microscopic influence factor into the macroscopic wall slip model relational expression, and obtain the microscopic Wall slip model relations. The establishment method of the invention considers the microscopic viscosity change and the characteristic size factors of the micro parts which affect the slippage of the wall surface, and significantly improves the accuracy of the prediction of the flow characteristics of the polymer melt.

Description

technical field [0001] The invention relates to injection molding, in particular to a method for establishing a microscopic wall slip model for injection molding. Background technique [0002] The feature size of micro-injection molded parts has reached the micron level. Affected by the micro-size effect, the degree of influence of micro-factors such as roughness and wetness on the filling behavior becomes correspondingly greater. When the shear stress of the polymer melt on the part wall is greater than a certain critical value, the polymer melt will slide along the wall. The existing microscopic wall slip models mainly include the following four types: the first is the generalized Navier wall slip model based on the entanglement-disentanglement mechanism, which is generally used for macroscopic deformation, and does not consider the size effect caused by the small size of micro-injection molded parts; The second is a wall slip model based on the relationship between the ...

AI Technical Summary

Problems solved by technology

The existing microscopic wall slip models mainly include the following four types: the first is the generalized Navier wall slip model based on the entanglement-disentanglement mechanism, which is generally used for macroscopic deformation, and does not consider the size effect caused by the small size of micro-injection molded parts; The second is a wall slip model based on the relationship between the melt slip velocity and the wall shear stress; the third is a wall slip model that considers the critical wall shear stress established on the basis of the second, and the second, All three are under the assumption that the viscosity of the polymer melt is constant, and the size of the micro-injection parts is not considered. However, affected by the micro-size effect, the viscosity of the polymer melt increases with the decrease of the characteristic size of the part. reduced; the fourth is a microscopic wall slip model based on the effect of microscale effects on polymer melt wall slip, and does not consider the feature size of micro-injection molding parts

The pressure difference simulation error value and filling rate simulation error value of the above four microscopic wall slip models are relatively large, which cannot accurately simulate the flow characteristics of polymer materials

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