The injection molding factory analyzes the reasons for the welding marks of plastic molds


Author: MULAN -Plastic Molding Manufacturer

What is the reason for the welding traces of plastic molds? Recently, many friends have asked us why there are welding traces in plastic mold processing. Causes and treatment methods of traces Weld traces are caused by the cooling of the front end of the molten resin from different directions. Not fully fused at the junction. Fusion occurs at resin junctions.

The two streams of resin fuse when they meet. The injection molding factory Xingye tells you that the lower the temperature, the more obvious the fusion. Since the two streams of resin at the fusion do not mix with each other (because they advance while solidifying during the injection process), if the temperature is lower, the surface will thicken, the lines will be obvious, and the strength will be reduced.

This is because the bond between the two is weakened. Conversely, if the temperature of the two resin streams is higher, the adhesion will be enhanced and the appearance will be less obvious. The two molten resins are extruded at the fusion, where the bonding state depends on the pressure applied here.

The lower the holding pressure, the more obvious the fusion and the lower the strength. If not only the holding pressure setting is to be considered, but also the actual pressure applied at the fusion will reduce this condition. This is because pressure transfer becomes more difficult as curing progresses.

In addition, if the gate size becomes smaller, the gate position becomes worse, and the appearance and strength of the fusion deteriorate. The fusion is the confluence point of the resin, and it may also be the end of the stream. At this time, if a vent is not provided at this position to discharge the gas, the appearance and strength of the fusion will deteriorate.

In general, it mainly affects the appearance, coating and electroplating. In severe cases, it will affect the product strength (especially when fiber reinforced resin). Treatment methods for welding traces on plastic molds: 1. Adjust molding conditions to improve fluidity.

For example, increase resin temperature, increase mold temperature, increase injection pressure and speed. 2. Adding exhaust slots and setting push rods where welding traces are produced is also conducive to exhausting. 3. Minimize the use of release agents.

4. Set the process overflow as the place where the weld line is generated, and cut it off after forming. 5. According to the injection molding factory, if it only affects the appearance, you can change the four burning positions and change the position of the weld line. Or treat the part where the weld line occurs into a dark glossy surface for modification.

For more information about plastic molds, please visit Xingye's official website:

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