In recent years, due to rapid development of automobile industry and trend of lightweight automobiles, plastics account for an increasing proportion of automobiles. Rapid development of automotive industry has driven development of automotive injection molding industry. In actual injection molding production, molding defects of automobile injection parts have always plagued injection molding production. According to statistics from Japanese injection molding experts, 70% of injection molding defects are caused by unreasonable product structure design and mold design.

Adopt three-point latent glue feeding, 1+1 pieces, cold runner. as picture shows:

 

Material of upper part of car door panel is PP, and glue is injected from 3-point hot runner to cold runner, as shown in figure below.

 

Material of middle section of car door panel is PP, and glue is injected from 3-point hot runner to cold runner.

 

Material of lower section of car door panel is PP, with a 3-point sequential valve needle valve type hot runner to cold runner for glue, as shown in the figure below.

 

Rear cover material of front map pocket of car co-pilot is PP, and ordinary runner is glued, as shown in figure below.

 

Frame material of car door armrest is PP, side gate of ordinary runner is glued. As shown below.

 

This mold pouring system adopts hot runner to feed glue, and adopts 1-point open hot runner + cold runner + banana gate to feed glue. Material of plastic part is ABS.
Since plastic part is made of ABS material, material has good fluidity. When designing runner, runner design range is wider, but runner length from hot nozzle to edge of plastic part should be designed to be within 60mm as much as possible. If it is not possible, try to keep it within 100mm to avoid excessively long cold runners and large pressure loss. Position of hot runner gate of injection mold for mirror housing of automobile rearview mirror is shown in figure below.

 

This mold gating system adopts hot runner injection, a 1-point open hot runner + cold runner + side gate, and plastic part material is ASA. Position of hot runner gate of injection mold of automobile rearview mirror bracket is shown in Figure 8. Cold runner is designed on fixed mold core, and side gate is designed on movable mold push block. In this mold, panel and A plate need to be opened, and hot nozzle needs to be movable, so an insert is designed to prevent hot nozzle from wearing.

 

Front of rearview mirror holder is a leather-grained surface, so it is not possible to install a gate on appearance surface of plastic part, so gate is set on periphery of plastic part. Before general design, first determine approximate location of gate based on experience, then use MolFlow software to simulate and analyze gate, optimize shape and location of gate according to analysis results. Finally, it is determined that mold adopts gate plan of cold runner to side gate, the best gate position is shown in Figure 9. Setting of gate position can effectively avoid welding marks, and flow marks are generated in unimportant positions of plastic part, so as not to affect appearance quality of plastic part. Setting of gate also takes into account different shrinkage of plastic part in longitudinal direction and transverse direction. Temperature at which melt enters cavity from gate is same, which effectively ensures uniform shrinkage of plastic parts in cavity.

 

Through mold flow analysis, gating system adopts a 1-point open hot runner to feed plastic, hot runner + cold runner + latent gate is used to feed glue. Mold plastic parts have high requirements for appearance, and weld mark must be driven to non-appearance area during design. When designing mold, in hot nozzle area and movable mold area where hot nozzle is directly opposite, cooling water should be designed to enhance cooling of hot nozzle area to avoid hot nozzle from casting, drawing, and phenomenon of excessive gate residues.