IMM 7/97

What is the advantage of using a subgate design that completely flows into the cavity area (A), versus one that has the diameter partially intersect the cavity area (B)?

Subgate B changes the direction of flow to help avoid jetting that can occur when using subgate A-especially on curved surfaces. Remember that you will need a larger diameter to get the same area as the gate.
-S. Baldwin,Canplas Ind. Ltd., Barrie, ON, (705) 721-8727.

Subgate A gives a directional flow with less turbulence just inside the gate. Subgate B creates more turbulence. (These gates both snap off on ejection, but B would snap easier.) Turbulence can't affect splay, weldlines, and surface of the part. Some color concentrates can be better dispersed.
-J. Goad, Calsak Corp., Norcross, GA, (770) 441-1234.

Use subgate design A. Different materials will do better with different sized gates. For polycarbonate, the orifice should be at least .040 inch to start on a medium-sized part, and might have to be opened up from there. Subgate B design would cause flow problems in some shear-sensitive materials. It might be okay for PP or PE, but I see no real advantage, and some disadvantages.
-W.E. Foster, Tessy Plastics Corp., Elbridge, NY, (315) 689-3924.