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Example: Creating a Dimension Pattern Using Relations
This example shows using pattern parameters, such as MEMB_V and MEMB_I, to control the location of pattern members. When you are including other pattern parameters, such as the number of instances (p#) in the relation, you must build the relation in two steps. When you first define the pattern, you do not know the symbol that the system is going to assign to the number of pattern instances (in this example, p9). You can include the p9 parameter in the relation only after the pattern is created. Therefore, you can use a placeholder, such as 10 in the example below, and then redefine the pattern and change the relation to include p9.
The original part, with all dimension symbols, is shown in the following illustration. 1. Select the Hole feature and click Model > Pattern.
2. Select dimension d5 in the graphics window, which controls the distance from the hole axis to the left edge of the part. Accept the default value of the dimension increment.
3. Click the Dimensions tab and click the increment cell for the dimension.
4. Select the Define increment by relation check box below the collector. The dimension increment value changes to Relation.
5. Click Edit. The Relations dialog box opens.
memb_i = (d1-(2*d5))/10
7. Click OK in the Relations dialog box to close it.
8. Hold down the CTRL key and select dimension d4, which controls the distance from the hole axis to the front edge of the part. Repeat steps 3–5 to define the dimension increment by relation. Add the following relations:
incr=10
memb_v = lead_v + 5 * sin(incr*idx1)
9. Click OK in the Relations dialog box to close it.
10. Click on the Pattern tab to create the pattern.
11. To view the pattern dimensions, place your cursor over the dimension that controls the number of pattern members (2 HOLES), the dimension symbol appears in the pop-up balloon. In this example, it is p9.
12. Edit the pattern definition and modify the relation for d5 as follows:
memb_i = (d1-(2*d5))/(p9-1)
Modify the first line of the relation for d4 as follows:
incr = 180/(p9-1)
13. Change the number of pattern members to 10.
14. Click . The resulting pattern for these relations is shown in the next illustration. The pattern maintains the same relationship to the part, regardless of the change in the length d1, or the change to the number of instances in the pattern. If you modify the number of pattern members to 5, the resulting pattern is shown in the following illustration. 