It can also be due to the manufacturer’s handling of the material before production. Type 2: Injection Molding Defects Related to Storage or Materials UsedĪsides from the molding process, injection molding defects can also occur due to the plastic resin itself. Add exhaust systems (gates and gas vents).Reduce the melting and molding temperature.High-speed cast screw or excessive injection speeds.Delay in removing the air in the cavity.However, it becomes a problem when the part gets burned to a level of degradation. Burn marks do not generally affect the integrity of parts. The molded plastic part may also appear to be rust-colored. This injection molding defect appears as a black discoloration on the surface of the molded part. Adjust the position of the gate and include a venting slot.Increase the fluidity of the molten material.Inserts, holes, and multi-gate features on fabricated parts.A too low or too high temperature of molten material.The weak bonding further lowers the part’s strength. This defect usually occurs due to weak material bonding. The molten material initially splits off into two or more areas in the mold. Weld lines are plastic molded part defects that cause a convergence of molten material on the surface of your part. Reduce the thick wall size of the mold material and control the adjacent wall thickness.Improper structural design of the intended molded component.Very high melting or molding temperatures.Too short cooling or holding time and pressure.Very low holding or injection pressure.This causes the material to pull inward from the outside. Sink marks usually occur when there’s a shrinking of a molded component’s inner part. These features occur on flat and consistent surfaces of molded parts. This type of injection plastic defect occurs as small depressions or recesses. Switch to a hot runner or reduce the size of the main channel.Add some more distance between the mold gates and the mold coolants.Increase the injection pressure, speed, and material temperature.Variation in the material’s cooling speed as it flows in different directions.The small size of the gate and flow channel.Low mold temperature and material temperature.While flow lines may not impact your parts’ integrity, they may be unacceptable in some consumer products. They are also usually close to the mold’s entry points. These bands may occur on your product’s surface. You can also see flow lines as ring-shaped bands. Flow lines usually come in a slightly different color than other areas around them. These are wavy-like patterns that appear on the narrow section of molded parts. However, you can easily prevent such defects by simply adjusting the temperature, flow rate, or other mold parameters. The molding process is the leading cause of defects in injection molding parts. Type 1: Injection Molding Defects Caused by Molding ProcessĬertain injection molding processes may not be effective for the production of some parts. Let’s check out the several injection molding defects and causes, as well as the solutions. It could also help to replace production equipment or redesign mold tooling. Preventing plastic molded part defects can be as easy as adjusting the injection molding process. It could be a result of the molding process, materials used, maintenance, or storage conditions. These defects can be caused by several reasons. Some injection molding defects can be very difficult to address. VII FAQ – Injection Molding Defects Injection Molding Defects, Causes, and Solutions
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