PA66 GF30 car parts plastic injection molding

Filling is the first step in the entire injection molding cycle. Due  to the flow of the fountain, the plastic polymer chains in front of the  flowing waves are directed to the almost parallel flow wavefront. Therefore,  when the two plastic melts meet, the polymer chains of the contact  faces are parallel to each other; plus the two melts have different  properties (different residence time in the cavity, temperature and  pressure are different), resulting in the fusion zone of the melt. Microscopically, the structural strength is poor. When  the parts are placed at an appropriate angle under light, they are  visually observed, and it is found that a significant bonding line is  produced, which is the formation mechanism of the weld lines. The  weld line not only affects the appearance of the plastic part, but also  has a loose microstructure, which tends to cause stress concentration,  so that the strength of the part is lowered and fracture occurs.
In general, the strength of the weld line which is welded in the high temperature region is preferred. Because  of the high temperature, the polymer chain activity is relatively good,  and it can penetrate and entangle each other. In addition, the  temperature of the two melts in the high temperature region is  relatively close, and the thermal properties of the melt are almost the  same, which increases the strength of the welded region; In the low temperature region, the welding strength is poor.