Integrated Simulation of Fluid Flow and Heat Transfer in Injection Molding for the Prediction of Shrinkage and Warpage

Abstract

This work employs a coupled analysis of the fluid flow and heat transfer in the polymer melt during the filling and post-filling stages of the injection-molding process and of mold cooling/heating which occurs during the entire process. Polymer melt analysis (PMA) has been carried out through a unified theoretical model implemented using a hybrid finite-element/finite-difference/control-volume numerical solution of the generalized Hele-Shaw flow of a compressible viscous fluid under non-isothermal conditions. Further, mold-cooling analysis (MCA) has been carried out utilizing a periodic heat conduction model implemented using a modified three-dimensional boundary-element method. To faithfully accommodate the effects of mold cooling on the fluid flow and heat transfer in the polymer melt, PMA and MCA have been coupled for appropriate data exchange and iterations carried out until a convergent solution for mold temperatures and for flow, pressure and temperatures within the polymer melt is obtained. The results obtained from this integrated simulation for different test cases have been compared with experimental data and a favorable agreement has been noticed. Using an illustrative example, the results are discussed in detail.

Three-Dimensional Transient Mold Cooling Analysis Based on Galerkin Finite Element Formulation With a Matrix-Free Conjugate Gradient Technique

“…Heat exchange takes place by forced convection between coolant and cooling channel surface and natural convection between the ambient air and the exterior mold surface. Chiang et al 4 treated the exterior surface as adiabatic because the heat loss through the exterior surface is less than 5 per cent of overall loss in most injection molding applications. This approximation simplified the problem.…”

“…As explained, standard and modified BEM play a dominant role in mold cooling analysis. Chiang et al 4 pointed out that the standard BEM leads to numerical difficulties and convergence problems. Modifications have to be made to accommodate the thin mold cavities and long but small diameter cooling channels.…”

Approximate Model of Thermal Residual Stress in an Injection Molded Part

“…Conversely, when the stresses due to external loads are added to the residual stress, plastic yielding will begin at a lower load. An asymmetric mold wall temperature distribution will cause asymmetric residual stresses; and if the part is not sti enough, it will warp after its ejection from the mold [3].…”

Procesado, modelización y caracterización de mezclas industriales de SEBS con materiales con cambio de fase (PCM) para la mejora del confort térmico en aplicaciones de ortopedia y puericultura

“…Himasekhar [Himasekhar, et al, 1992] plantea una simulación tridimensional del enfriamiento del molde en inyección; Chiang [Chiang, et al, 1993] plantea una simulación integrada de la fluidez y la transferencia de calor en moldeo por inyección para la predicción de contracciones y deformaciones. Wolf [Wolf, 1994] prueba y desarrolla modelos experimentales para el paquete informático Moldflow® como software disponible para la simulación del llenado de la cavidad en moldes para inyección de plástico.…”

“…Las herramientas de simulación CAE (Computer Aided Engineering) permiten determinar las mejores condiciones de procesado por inyección de piezas en plástico [Potente, et al, 1993, Titomanlio, et al, 1995, Wang, et al, 2010, Wang, et al, 1988 ya que permiten predecir el comportamiento que va a presentar el polímero, optimizar el flujo del material en el proceso [ISO-868, 2003, Kennedy, 1995, Park, et al, 2006, Shen, 1984 , así como controlar la contracción y deformación [Chiang, et al,1993, Kolarik, et al, 2002, Ni, et al, 1993 y supervisar muchos otros parámetros del proceso.…”