The formation of a weld line region in SIGMASOFT is presented. The flow front is depicted in grey. The "tracer" particles in orange show clearly that the melt fronts do not collide in a flat region, but that this weld line has a complex 3D profile at the end of the filling and packaging phases.
Sigma Plastic Services presents a new functionality of its injection molding simulation software SIGMASOFT. The simulation of the cavity filling in injection molding allows identifying regions where weld lines are formed, not only on the surface but also through the part's thickness, with a completely 3D approach. With the interface SIGMALINK it is now possible to transfer this 3D information into FEA (Finite Element Analysis) software, to consider the drop in mechanical properties in these regions when performing structural design. A particular advantage of SIGMASOFT is the fully 3D prediction of the weld lines, which reproduces the weld regions not only on the surface, but also through the part's thickness, as it occurs in reality, the company said.
Weld lines occur as a consequence of the collision of two or more flow fronts in the cavity of a mold. This disruption in the homogeneity of the injection molded part causes optical defects, which compromise the surface quality, but also produces a weakening from the mechanical point of view and, under certain circumstances, weld lines can even act as stress concentrators. Therefore, there is a loss in the mechanical properties in the regions where weld lines appear.
Using the "tracer" technology, which has been available for years in SIGMASOFT, the appearance of weld lines can be reproduced during the filling stage. The location of the weld lines can be described precisely and an indication is given regarding how critical they are. The formation of the weld lines during the filling stage and the way they flow as the packing pressure is applied are predicted accurately in a 3D approach, the company said.
The interface SIGMALINK enables exporting (mapping) physical and flow-related properties into commercial software for FEA (such as Ansys, Abaqus, Radios, etc.). Factors such as flow and thermal induced stresses and fiber orientation can be considered in the FEA. With a further expansion of SIGMALINK it is now possible to export the information about the final position and 3D profile of the weld lines in the structural FEA. In this way, the drop in the mechanical properties produced by the apparition of weld lines can also be considered in the mechanical part design.
For more information contact:
SIGMA Plastic Services, Inc.
10 N. Martingale Road, Suite 425
Schaumburg, IL 60173