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EspañolWhat are flow lines and knitting lines in Plastic Injection Mold?
Streamlines are defects that appear on the surface of a plastic part in wavy patterns of slightly different colors. They can also be implemented as a ring pattern close to the die entry point. Bond lines, on the other hand, usually appear as lines where two streams intersect. While in some cases these defects may just be an unsightly mark, if severe enough, they can threaten the mechanical reliability and structure of the part. Both of these defects are caused by many of the same reasons, such as fluctuations in cooling rates or the fact that plastic materials are kept at different temperatures.
Prevents flow lines and braided lines during injection molding
Time and temperature are important factors when it comes to flow and bonding defects. Here are some ways to avoid quality problems during injection molding:
Insufficient injection/packing pressure: If the injection and packing pressures are not sufficient to force the plastic against the mold surface, lines will appear along the direction of melt flow.
Incorrect residence time: If the plastic stays in the barrel for too short a time, it will not be compacted effectively during the holding process, leaving lines in the flow direction.
Improper cycle time: The cycle time is too short to adequately heat the barrel and the melt temperature is still too low. This creates a further problem of compacting the material into the mold.
Low barrel/nozzle temperature: Melt temperature is a critical factor in the injection molding process, if the barrel and nozzle temperatures are too low, the material temperature will drop rapidly, resulting in part defects.
Operator attention to detail is also important to avoid costly defects, which is why you should make sure you are working with the right supplier.
