SolidWorks 2010 Bible

Chapter 32: Using Plastic Features and Mold Tools

Shut-off Surfaces

The screw holes that go through this housing require shut-off faces in order to create the mold cav-
ity and core. You can’t just seal off one end of the holes; you have to pay attention to which end of
the hole is where the draft in opposite directions meet. In this case, the counterbored holes from
the outside have to be drafted from the outside, so they must be sealed or shut off from the inside.

When you initiate the Shut-off Surfaces feature, SolidWorks identifies some of the necessary shut-

offs for you. Figure 32.23 shows this.

FIGURE 32.23

Creating Shut-offs

When all appropriate edges around all the holes and slots are selected, the Shut-off Surfaces

PropertyManager message window turns green and says “The mold is separable into core and cavity.”

The tags on the loops in the graphics window will say either “No Fill,” “Contact,” or “Tangent.” No

Fill means that you do not want SolidWorks to create the shut-off surfaces. You will do these man-

ually. Sometimes shut-off surfaces require complex or multi-feature shut-offs, which you have to

do manually. The Contact condition means that the shut-off surface just needs to touch the edges,

usually at a right angle. Tangent should be obvious.

Sometimes you need a combination of conditions in a single shut-off, in which case you will need

to finish the feature manually. When the parting line and shut-off surfaces are complete,

SolidWorks will automatically knit together all the surfaces in each Cavity and Core folder into a

single surface body.