The arrows on the drawing here represent the plastic flow from the feed runner into and around the periphery of the long, hollow tube. Then it flows radially across the ring gate and uniformly down the length of the tube. The material flows easily on long, hollow, cylindrical parts. Ring gates prevent weld marks, trapped air, or stress concentration around the gate.
Almost any resin/filler may be used with this style of gate because of the large radial flow area of the gate. Although gate thickness would be a key factor, there should be no problem with viscosity or filled resins in the most common materials.
This drawing represents the hollow plastic tube with the ring gate/runner system removed. Since a scar or blemish remains it is desirable to gate into a non-cosmetic or non-function surface. If the tube inside diameter is large enough a disc gate (reverse of a ring gate) may be used. This will keep the gate scar off of the outside part surface.
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