Determination of the transition temperature at different cooling rates and its influence on prediction of shrinkage and warpage in injection molding simulation

Abstract

In injection molding simulation the phase change from melt to solid state is usually simplified by using a so called transition temperature. In the present work, the transition temperatures of several amorphous and semicrystalline polymers were determined using DSCruns at different cooling rates. The transition temperature was described as a function of cooling rate. The obtained transition temperatures of the semicrystalline polymers were used in injection molding simulations with the commercial software package Autodesk Moldflow Insight 2010 to calculate the shrinkage and warpage of box-shaped test parts. The simulation results were compared with the experimental values of optically measured injection-molded boxes. The results showed a strong influence of the transition temperatures on the simulation results of a 3D model and a very low influence for a 2.5D model. Transition temperatures obtained at higher cooling rates improved the 3D simulation results for several dimensions.

Simulation of shrinkage and warpage of semi-crystalline thermoplastics

“…The boundary conditions of the manufacturing process, such as injection speed and holding time, have been considered in the simulation. Although the geometry is quite simple, the prediction of the warpage shows a significant difference to the measurement (see figure 3 These results are in agreement to the results of other groups such as [1] and [8]. This is an indicator, that the assumption of homogenous material properties is already violated for a simple box geometry.…”

Study on the solidification kinetics of high-density polyethylene during thin-walled injection molding process

“…Altan and Yurci [34] found that the mold temperature is the most important parameter for residual stresses on the surface layer of injection-molded HDPE articles, which was also reported by Wang and Young [26] . In our recent studies [17, 35 -39] , the cooling stage of IM was numerically investigated using the enthalpy transformation methodology (ETM) [10,40] , which is a useful way to handle the multidimensional phase-change issues [39,41] . Our findings suggested that the mold temperature exerts more significant influence on the cooling rate compared with the melt temperature [35,42] .…”

The Elastic Mold Deformation During the Filling and Packing Stage of the Injection Molding Process

“…[12] Due to the complexity of the phase change especially when considering semi crystalline polymers, this simple approach is still state of the art in commercial software. [21][22][23] Lucyshyn et al [24] investigated the influence of the cooling rate on the transition temperature. He found, that a higher cooling rate causes a decrease in transition temperature for semi crystalline materials while no significant change was observed for amorphous materials.…”