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Analyzing Silhouette Curve Options: Loop Selection

The Loop Selection option enables you to control the location of curve segments in reference to the part edges and specify which loops are included in the curve.
• Loop selection:
– Loops created at every shutoff location.
– Status options:
♦ Included
♦ Excluded
• Chain selection options:
– Upper
– Lower
– Single

Loop 1
Figure 1 – Included Versus Excluded Loops

Loop 2
Figure 2 – Upper Versus Lower Chains
Including and Excluding Silhouette Curve Loops
During silhouette curve creation, the system may create curves along edges that you do not want included. You can selectively remove curves along edges that you do not want curves created for using the Loop Selection option in the Silhouette Curve dialog box.
Selecting the Loop Selection option causes the Loop Selection dialog box to appear. The Loops tab in the Loop Selection dialog box lists the loops of curves which comprise the silhouette curve, and whether their status is Included or Excluded. When you select a loop in the dialog box, it highlights in the mold model.
Loops are typically created at every location in the mold model where there is a shutoff. A shutoff is any surface where the mold core and cavity contact.

When the mold closes the core and cavity it creates a seal that shuts off that area of the mold. One loop typically is created along the exterior of the reference model. Other loops are created at each interior hole or cut. Loops are also created at areas of undercut geometry.
Loops are, by default, included in the final silhouette curve, although you can exclude any loop from the final silhouette curve. The most common reason loops are excluded is because the shutoff at that specific location is being formed by a slider or saddle. In Figure 1, the two loops around the opening are excluded.
Another way to exclude loops created by undercuts is to use the Slides Silhouette Curve option.
Specifying Edges for Silhouette Curve Creation
When the system encounters a vertical surface or a surface that has no draft for which a silhouette curve loop is to be included, the system may select the wrong edge to create the silhouette curve along. In most cases you can change which edge to create the silhouette curve along. The following status options are available:
• Upper – The chain is currently located at the uppermost edges of a vertical surface. The upper edge is higher relative to the positive Z-axis, or pull direction, as shown in the left image of Figure 2. When the chain is specified as upper, the shutoff effectively causes the mold feature to occur in the core mold component.
• Lower – The chain is currently located at the lowermost edges of a vertical surface. The lower edge is lower relative to the positive Z-axis, or pull direction, as shown in the right image of Figure 2. When the chain is specified as lower, the shutoff effectively causes the mold feature to occur in the cavity mold component.
• Single – You cannot move the chain for a Single location because the edges that the chain lies on are associated with a drafted surface.
The Chains tab in the Loop Selection dialog box displays both the chain number, and its status. The chain number is displayed as A-B, where A is the corresponding loop number from the Loops tab that the chain belongs to, and B is an incremental number for multiple chains belonging to a single loop, starting with 0. For example, if there are three chains belonging to loop number 1, then the three chains are numbered 1-0, 1-1, and 1-2.

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