sprues and runners

Ted Larson

I found some webpages that will help illustrate the difference between
a sprue and a runner.

shows a phantom view of an injection mold. The bright green ring at
the top of the mold is where the plastic is injected into the mold.
The two RED objects are molded plastic parts.

There is a vertical channel that brings the melted plastic from the
opening down to the level of the parts. This is the sprue.
This can be seen at Figure 1;
it is the tapered red component in the center of the drawing.

In Figure 1, there are a number of objects labeled "flow 1" or "flow
2". These represent the molded plastic parts. The round channel
connecting the vertical sprue to the molded parts is the runner.
Usually the sprue is removed at the molding plant, so that the modeler
only sees the parts attached to the runner. In a few cases, the sprue
runs directly to the molded plastic parts, but it will still look like
the sprue in Figure 1, it will not look like a runner.

Hope this helps.

Ted Larson

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