At times in sketcher mode, you may need to control the pitch between multiple loops in a sketch with a single dimension. You can use multiple dimensions and sketcher relations to control the pitch between loops, but if the sketch is redefined and the driving dimension lost, the sketcher relation is also lost. Patterning the feature may not be desirable because of increased feature count and possible differences in loop geometry.

To overcome this, you can place construction lines (regular geometry lines that have been toggled to “construction”) from the center of one loop to the center of another. Simply select an entity mid-point from the first loop and then the mid-point of an entity in all other loops. To keep the pitch constant between loops, explicitly constrain all construction lines to be of equal length (Fig. 1). Since the geometry isn't patterned, the geometry of the loops doesn't have to be similar.

Figure 1.

Another application of this technique is to add or remove a specific amount of material based on the existing material. In other words, you can create “smart” geometry without using sketcher relations or dimensions that aren't required to capture design intent. For instance, to break a single roll form for a continuous hinge into equal sections to allow assembly, you can create a cut with multiple loops that are controlled by the existing geometry and a dimension for the width of the cut.

This means no more calculating the pitch value for a patterned cut in order to get the last one to line up exactly with the end of the part. This happens automatically in one feature (Fig. 2).

Figure 2.

Again, you can control feature geometry via part thickness without using sketcher relations, part relations or dimensions. Just create a construction line with a length equal to the part thickness. This will be the reference line. Then create a construction line to locate your sketched geometry, and constrain the two construction lines to have equal lengths in the constraint menu (Figs. 3a and 3b).

Figure 3a.

Figure 3b.

To have the geometry offset more than one material thickness, create a series of lines—all the same length as the reference line—that are end-to-end (Fig. 3c).

Figure 3c.

Jason Mastry is a mechanical engineer at NCR Retail Solutions Division in Atlanta, Georgia, USA. He can be reached by e-mail at Jason.Mastry@NCR.com.