Jetting (injection moulding defect)

Jetting is an moulding defect that can occur in the manufacturing process of injection muolding. Jetting is a snake-like stream which occurs when polymer melt is pushed at a high velocity through restrictive areas.[1]

Jetting

Effect
  • Surface blemishes
  • Part weakness

Prevention methods
  • Design a feed system to direct the melt against the metal surface of mould (see example of edge gate and overlap gate)
  • Use an optimized ram speed profile so that melt front velocity is initially slow. [2]

References
  1. "The Importance of Gate Geometry".
  2. "Mitsubishi Engineering Plastics Guide" (PDF).
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