Defining Pipe Relationships
Pipe Relationships can be defined between two objects that have positional and directional information. Typically, this means lines, cylinders, or planes. The particular type of object does not matter—as long as the object properly describes the pipe’s position and orientation. When a pipe relationship is created, a tube representing the allowable cut region and ID/OD appears in the graphical view, and the Pipe to Pipe Relationship dialog is displayed.
The first step is to define the properties of each pipe segment:
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Inner. The inside diameter of the pipe.
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Outer. The outside diameter of the pipe.
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Begin. The start of the permissible cut region, as a distance along the pipe axis from its origin. This value should typically be less than the End value.
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End. The end of the permissible cut region, as a distance along the pipe axis from its origin. This value should typically be greater than the Begin value.
A pipe relationship will supply several forcing functions to an optimization:
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It will try to make the pipe segments coaxial.
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It will try to make the pipe ends parallel.
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It will try to overlap the cut regions evenly.
After defining the characteristics of the pipe segments, the weighting factors for the relationship may be modified, if desired. Typically, the default values are sufficient:
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Overall Weight. The weight of the pipe relationship as a whole, which determines the influence of the pipe relationship in the overall optimization scheme.
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Axis Offset. The importance of minimizing the mutual per- pendicular midpoint between the two pipe segments (i.e. how “coaxial” the two pipe segments are). Larger values attempt to bring the segments closer together.
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Axis Alignment. The importance of minimizing the angle be- tween the two pipe segments. Larger values will force the pipe segments to be more parallel.
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Center Pull. The importance of overlapping the center of each pipe segment’s cut region (along the axis direction). Larger val- ues assign more importance.
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Weight. The importance of having sufficient material for the weld. A value of zero implies that the solution does not care if there is sufficient material for the weld.
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Static Offset. A value that controls “how bad” the solution gets when there is insufficient material for the weld. Higher values assign a larger penalty to having insufficient material, effec- tively ensuring that material requirement is more crucial in the eyes of the solution.
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Constrain Cut to Region at OD. If checked, ensures that the cut angle at the outer diameter does not cause the cut plane to exceed the defined region. If unchecked, this restriction is ignored.
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Constrain Cut so ID/OD overlap. If enabled, the inner diameter/outer diameter values for the pipes are used to ensure that there is sufficient material based on the angle of alignment.
To Solve a Pipe Relationship:
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First take a moment to think about the assembly. If there is more than one pipe segment that will be assembled (that is, if there will be more than one independently moving object in the optimization), then each moving object (pipe segment) should be placed into its own collection. This includes the objects defining the pipe endpoint, the pipe surface/cylinder, and anything else you want to rigidly move with that pipe segment. In this situation, you must use Relationships > Move Col- lections by Minimizing Relationships in step 7 below.
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Create a primitive SA object with directionality (circles, lines, cylinders, or planes—but circles are preferred) to represent the end of each pipe opening in the assembly. Each object’s normal direction must face the mating pipe segment as depicted below.
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From the menu, select Relationships > Pipe Fitting.
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Select the object (i.e. circle) describing the first pipe segment, then the second.
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In the Pipe to Pipe Relationship dialog, click the Edit button for each pipe segment and define the ID, OD, and begin/end values for the allowable cut region.
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If any pipe ends are already cut, create a frame representing that pipe end (usually Construct > Frame > On an Object is appropriate) and then click the Force CUT to Frame button.
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Create any other conventional relationships governing the alignment, if applicable.
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Solve the relationship using Alignments > Relationship Fit > Move Objects by Minimizing Relationships or > Move Collections by Minimizing Relationships, as applicable. Enable/disable and adjust the weights on all relationships as desired.