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that other design or manufacturing people might not be familiar with. Shut-offs, in mold lingo, are just locations inside the mold where the two sides of the mold dies touch one another. Shut-offs in the mold usually create holes within a plastic part. The shut-off surface – where the steel from one side of the mold touches the steel from the other side of the mold - is usually flat. Shut-off faces touch each other with significant pressure, so they are usually flat and perpendicular to the clamp force so they don't induce sliding. However, angled shut-offs can exist, and passing shut-offs are highly angled – as much as 80 degrees or so.

The screw holes that go through the plastic part require shut-off faces in order to create the mold cavity and core. You can't just seal off any end of the holes; you have to pay attention to which end of the hole is where the drafts 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, as shown in Figure 21.10.

To use the Shut-off Surfaces feature, follow these steps:

1. Click the Shut-Off Surfaces toolbar icon on the Mold Tools toolbar. SolidWorks should automatically select the inside edges of the seven screw holes. If not, then select these edges manually.

2. Locate the slanted ventilation slots in the plastic part, right-click the edge of one of them, and choose Select Tangency from the RMB menu. Four edges are added to the list box for each slot, and there are five slots.

When all 27 edges are selected, the message box at the top of the Shut-Off Surface PropertyManager turns green, as shown in Figure 21.11.

FIGURE 21.10

Creating shut-offs

FIGURE 21.11

Sealing the shut-offs with surfaces

3. Ensure that the center option (All Contact) is selected in the Reset All Patch Types section before you finish.

4. When you are satisfied with the results, make sure the settings match those in Figure 21.11, and click the green check mark icon to accept the feature.

Note

If the feature does not work, and displays an error message stating that it cannot knit, then deselect the Knit option. While this isn't ideal, you will be able to troubleshoot later, as the automated Shut-Off feature does not allow you to troubleshoot in the middle of the command.

If you have to disable the Knit option, and the feature works, you may notice that some of the shut-off surfaces turn red and some turn green. This is just because SolidWorks actually creates one red and one green shut-off surface for each location. The red surfaces are knit together into the Cavity Surface body and the green surfaces are knit together into the Core Surface body.

When all appropriate edges around all the holes and slots are selected, the Shut-off Surfaces PropertyManager message window turns green and displays the message, “The mold is separable into core and cavity.”

The tags on the loops in the graphics window display the text “No Fill,” “Contact,” or “Tangent.” The No Fill condition means that you do not want SolidWorks to create the shut-off surfaces. You will do these manually. 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. The Tangent option creates a surface that is tangent to the surrounding faces all the way around.

Sometimes you need a combination of conditions in a single shut-off, in which case you need to finish the feature manually. When the parting line and shut-off surfaces are complete, SolidWorks automatically knits together all the surfaces in each Cavity and Core folder into a single surface body.

Parting surface

The Parting Surface feature in SolidWorks Mold Tools works best on planar parting lines that are convex all the way around. On the sample medical device part used in this