Page 290 - Mastering SolidWorks

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262 CHAPTER 8 Selecting Secondary FeatureS

Split Line is another feature that can create edges on faces that can be used like curve features.
Split Lines can function as curves in some situations, so this section discusses the Split Line along
with the rest of the curve and other curve-like features.
Of these, the Projected and Helix curves are by far the most frequently used, but the others
may be important from time to time. Curve functions do not receive much attention from
SolidWorks. Updates to curve features are few, and in some cases the functions are buggy. The
usefulness of curve features is limited in the software, but in some cases there is no other good
way to achieve the same result.
TIP When you come across a function that does not work using a curve entity, but it works on a
sketch (for example, making a tangent spline), it may help to use the convert entities function.
converting a helix into a 3d sketch creates a spline that lies directly on top of the helix and enables
you to make another spline that is tangent to the new spline.

You can find all the curve functions on the Curves toolbar or by choosing Insert ➢ Curve from
the menu. Curve features, in general, have several limitations; some of them are serious. You
often have to be prepared with workaround techniques when using them.

Manipulating Curves
Curves cannot be mirrored, moved, patterned, or manipulated in any way. (A workaround for
this may be to use Convert Entities to create a sketch from the curve, or to create a surface using
the curve, and pattern or mirror the surface, using the edge of the surface in place of the
curve feature.)
Working with Helix Curve Features
The Helix curve types are all created from a sketch circle. The circle represents the starting plane,
center, and diameter of the helix. Figure 8.1 shows the PropertyManagers of the Constant Pitch
and Variable Pitch helix types.
You can create all the helical curve types by specifying some combination of total height,
pitch, and the number of revolutions. The start angle depends on the relation of the sketch plane
to the origin. The start angle can be controlled outside of the PropertyManager through dimen-
sions, design tables, equations, and so forth. The term pitch refers to the straight-line distance
along the axis between the rings of the helix. Pitch for the spiral is different and is described later.

Using the Taper Helix Panel
The Taper Helix panel in the Helix PropertyManager enables you to specify a taper angle for the
helix. The taper angle does not affect the pitch. If you need to affect both the taper and the pitch,
you can use a Variable Pitch helix. Figure 8.2 shows how the taper angle relates to the result-
ing geometry.

Using the Variable Pitch Helix
You can specify a Variable Pitch helix either in the chart or in the callouts that are shown in
Figure 8.3. Both the pitch and the diameter are variable. The diameter number in the first row
cannot be changed but is driven by the sketch. In the chart shown, the transition between 4 and
4.5 revolutions is where the pitch and diameter both change.