Search Results

Injection molding tools are expensive and the fatigue failure during production would result in very costly rework on the tool and downtime. Currently, mold designs are mostly based on expert experience without a careful stress analysis and the mold tool life cycle relies largely on rough estimates. The industry state of the art applies averaged temperature change and peak pressure load on the mold tool. The static analysis is then performed. Mold temperature history and thermal shock are not considered in the durability analysis. In this paper, a transient thermal analysis of the tool is performed in conjunction with the injection molding process simulation. The spatial and temporal variation of temperature, pressure and clamping forces are exported from Moldflow simulation. These histories of temperature and pressure are converted to appropriate loading curves and mapped into Abaqus FEA model.

Weld lines occur when melt flow fronts meet during the injection molding of plastic parts. It is important to investigate the weld line because the weld line area can induce potential failure of structural application. In this paper, a weld line factor (W-L factor) was adopted to describe the strength reduction to the ultimate strength due to the appearance of weld line. There were two engineering thermoplastics involved in this study, including one neat PP and one of talc filled PP plastics. The experimental design was used to investigate four main injection molding parameters (melt temperature, mold temperature, injection speed and packing pressure). Both the tensile bar samples with/without weld lines were molded at each process settings. The sample strength was obtained by the tensile tests under two levels of testing speed (5mm/min and 200mm/min) and testing temperatures (room temperature and -30°C). The results showed that different materials had various values of W-L factor.