One blog reader asked this question…
Would you please give me the guidelines for runner and gate sizing with respect to nominal wall thickness?
Below are some common guidelines…
An edge gate should be approximately 1/3 of the part thickness at the mold cavity.
The fan and flash gate should taper down to approximately one-quarter of the part thickness.
Disc gates taper down to less than one-quarter of the part thickness at the mold cavity.
Pin gates are commonly machined to 1/8 of the part thickness.
3 plate pinpoint gates taper down to a diameter of approximately 1/3 of the part thickness as they approach the cavity.
The submarine gate diameter at the mold cavity should be approximately 1/3 of the part thickness. This gate should have at least a five-degree taper per side so it can be removed without complications.
Unfilled, semi-crystalline materials typically require smaller than average gates, while hard to process amorphous materials such as polycarbonate may require larger than average gates.