Injection Molding: Gate

Before the molten material is injected into the mold cavities, there's a "Gate" as an opening in a mold, it is between the scrap and plastic part.

What influence the size of the gate

  1. Weight of plastic part
  2. Material feature of plastic part
  3. Shape of the gate

Unsuitable gate size may cause defect, so it is important to consider above condition and measure the requirement carefully, the last but not least, we should mind the molding efficiency and requirement of plastic part, below we list out the defect which may occur:

A. If the gate is under dimension

  1. Short shot
  2. Sink mark
  3. Weld line

B. If the gate is over dimension

  1. Residual stress around the gate causes deformation and torsion
  2. Cracking
  3. Increasingly difficult to remove the gate

● Gate Type

Gate can be classified into two main types: Unlimited Gate and Limited Gate, Direct Gate represents Unlimited Gate, and there're four types included in Limited Gate, please check below:

A. Side Gate: including Side Gate and Over Lap Gate

B. Tab Gate: including Tab Gate and Fan Gate

C. Film Gate: including Film Gate, Ring Gate, and Disk Gate

D. Point Gate: Point Gate and Submarine Gate (Tunnel Gate)



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