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Plastic Knowledge: Common Defects In Injection Moulding
Jun 05, 2018

Core Tip: We all know that the injection mold often has some defects after molding. This time has seriously affected the normal use of the workpiece, and even led to the production of the workpiece can not be used, which will seriously affect the cost of manufacturing the workpiece, work efficiency. Therefore, we must do a good job in preparing the mold before molding, and identify the specific causes of these defects.

    Injection Molding Common Defects

 

    1, lack of plastic

 

    (1) If one of the multiple mold cavities lacks glue, there may be a difference in the size of the water entry point or the length of the flow path in each cavity.

 

    (2) Poor mold exhaust can also cause lack of glue, but it is often accompanied by burning.

 

    2, shrink

 

    (1) Shrinkage caused by non-uniform wall thickness.

 

    (2) Shrinkage caused by uniform product wall thickness.

 

    Phenomenon: Waves on the surface of the product Cause: (1) There may be no or insufficient CUSHION VOLUME for the injection molding machine. (2) It may be that the backflow prevention valve does not move smoothly.

 

    3, burnt

 

    Advice: Wear exhaust gas on the mold, or change the water level to facilitate the exhaust.

 

    4, black bars

 

    Phenomenon: The product extends from the black bar from the water inlet position.

 

    5, the surface of the product is poorly shiny and cloudy.

 

    6, silver stripes: In the plastic material flow direction appears a color line.

 

    7. Flow mark: The wave shape is formed centering on the inlet of the product.

 

    8, weld marks:

 

    The resulting fusion line at the product cavity.

 

    (1) Complete elimination of weld marks is difficult.

 

    (2) The number of water inlets also affects the number of weld lines.

 

    (3) Other ways to consider improvement:

 

    a: Change the water entry method.

 

    b: Increase the exhaust equipment.

 

    c: add bone where welding marks appear.

 

    9, jet: In the water part of the formation of 蚯蚓-like lines.

 

    (1) Other improvement methods:

 

    The blocking needle can be added where the incoming glue flows in.

 

    10, impurities: impurities mixed with the product

 

    Other reasons: The flow channel COLDSLUGWELL does not save light. When debris is ejected, it will remain in the cold well. Impurities appear on the surface of the product (even more PC material).