Generating Non-Circular Helixes
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| Figure 1. |
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| Figure 2 |
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| Figure 3. |
The helical sweep functionality allows springs with a circular trajectory to be created extremely easily. Creating a linear non-circular spring, however, is much more of a challenge.
The traditional approach would be to create two surfaces—an extruded surface whose cross-section represents the shape of the spring as viewed along the spring’s axis, and a second helical surface created using the variable section sweep form (Fig. 1). A datum curve is then created as the intersection of these two surfaces. This datum curve is used as the trajectory to create a solid swept protrusion to complete creation of the spring.
The problem with this approach is illustrated in Figure 2, which shows the results of performing a slope analysis of the top surface of a portion of the spring. While the pitch of the spring is constant, the slope of the spring varies greatly. This occurs because the distance from the center axis to the intersection point varies throughout the trajectory.
The following tip shows you how to use Pro/SHEETMETAL™ to easily generate the trajectory needed to create a spring such as the one in Figure 3, where both the pitch and slope of the spring remain constant.
