Part II: Building Intelligence into Your Parts
FIGURE 9.7Triangles calculate the length of the helical edge.
From this point, you can calculate the flat pattern again, using SolidWorks’ sketch-solving
capabilities as the calculator. Think of the auger as being the cardboard tube inside a roll of paper
towels. If you examine one of these tubes closely, you see that it is simply a straight and flat strip of
cardboard that has been wound around a cylinder. What was the flat, straight edge of the original
board is wound into a helix. This method simply reverses that process.This example requires the little-used arc-length dimension to drive the size of the arc. The
hypotenuse dimensions are shown by driven or reference dimensions, and these are used to drive
the arc-length dimensions, as shown in Figure 9.8. Remember that you can create arc length
dimensions by using the Smart Dimension tool to click both endpoints of the arc and then the arc
itself.The reasoning behind this example may be a little difficult to grasp, but the equations and the
sketches are certainly simple.Caution
Using reference dimensions on the driving (independent or right) side of the equation can, and in some
situations, require more than one rebuild to arrive at a stable value (meaning a value that does not change
with the next rebuild). SolidWorks issues a warning when it sees that you are using a reference dimension in an
equation, but it does allow it. n