Adverse Consequences Caused By Improper Gate Location Selection

Because the gate often leaves obvious traces, it cannot be installed in areas with high requirements on the appearance of the surface. High stress (shear) will be generated in any gate area, which will significantly reduce the performance of the plastic resin. The weld line quality of plastics without reinforcements is significantly higher than that of plastics with reinforcements. The mass attenuation factor in the fusion line area has a great relationship with the type and content of fillers and reinforcing materials. Additives such as processing aids and flame retardants have adverse effects on the quality of the fusion line. Thus, it is difficult to assess how much these factors affect the final strength of the part. Also, the fact that the weld line region has a high load-carrying capacity under tension does not mean that it has good impact or fatigue resistance.

Due to the inclusion of fiber reinforcement, the alignment direction of the fibers in the fusion line region is perpendicular to the flow direction. This will significantly degrade the mechanical properties of the part at this point

It is impossible for a complex mold to have no fusion line. If the number of weld lines cannot be reduced, they should be placed in unimportant positions of the mold in terms of surface quality and mechanical strength. This can be accomplished by changing the gate location or increasing/decreasing the wall thickness of the part. Basic design principles:

1.Do not place gates in high pressure areas

2.Minimize or avoid fusion lines  Keep fusion lines away from high stress areas as much as possible

3.For reinforced plastics, gate location determines part warpage behavior

4.Provide adequate venting to avoid air traps