You can create sprues, runners, and gates to channel molten
plastic into the mold cavity.
• Create sprues using sketch-based
• Create runners and sometimes
gates using the Runner feature.
• Section shapes include:
– Half Round
– Round Trapezoid
Figure 2 – Core Showing
Runners and Gates
A sprue is the channel through which molten plastic is injected into the
mold. The sprue should be as short as possible to minimize material usage.
Typically, the sprue is tapered to ensure proper ejection from the mold cavity.
You can create sprues in the mold model using sketch-based features such
as extrudes, revolve, sweeps, and blends.
Creating Runners and Gates
You can create runners and gates in the mold model to transfer material
from the sprue to the mold cavity. The runner is the channel that guides
the molten plastic from the sprue into the mold cavity, and the gate is the
restricted entrance from the runner into the mold cavity that helps to simplify
the removal of the final molded parts from the runners.
You can use the Runner feature to create the runners in your mold model.
Depending upon the shape of your gates, you can also use the runner feature
to create them, or you can create them using sketch-based features such as
extrudes, revolves, sweeps, and blends.
You can create runners by sweeping a sketched section along a path or
trajectory. The following section shapes are available, and the dimensions
that define the shapes are shown:
• Round — Assigns a circle to the runner’s
• Half Round — Assigns a half circle to the
• Hexagon — Assigns a six-sided polygon to the
• Trapezoid — Assigns a quadrilateral to the
• Round Trapezoid — Assigns a trapezoid with
an arc base to the runner’s cross-section.
In addition to the shape, you must define the following items:
• Name — Enables you to specify the name of the Runner feature in the
model tree to be different than the default name applied by the system.
• Def Size — Enables you to specify the default size values for each of the
runner cross-section dimensions. The dimensions that you are prompted
to specify depend on the section shape specified.
• Flow Path — Enables you to either select or sketch the flow path for the
runner. If you select the flow path, you can select datum curves as the flow
path. If you sketch the flow path, you must specify the sketch plane and
reference plane and orientation. As you sketch the flow path in Sketcher,
a dashed line displays on either side of the sketch line. This dashed line
denotes the actual section diameter of the runner.
• Direction — Specifies the direction of runner creation.
• Intsct Parts — Enables you to select the mold components which the
runner intersects or cuts through. The same options available in the
Intersected Components dialog box for waterlines and ejector pin holes are
also available for runners.
Optionally, the Segment Sizes option enables you to define runners with
segments of varying size within the same runner feature. When you specify
a runner segment that you want to be of different size than the default
size, the system prompts you to specify new dimensions to define the
cross-section. Note that the runner shape specified cannot be changed for
You can create sprues and runners any time after the workpiece and
reference model are assembled. When the volumes are split, any previously
created sprues, runners, and gates are automatically subtracted from the
mold volumes along with the reference model.