SolidWorks 2011 Parts Bible - Matt Lombard [125]
Using the Tapered Helix panel
The Tapered 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, then you can use a Variable Pitch helix. Figure 8.2 shows how the taper angle relates to the resulting geometry.
FIGURE 8.1
The Helix PropertyManager
FIGURE 8.2
The Tapered Helix panel
Using the Variable Pitch helix
You can specify the 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.
SolidWorks 2011 adds functionality that allows you to double-click a Helix feature and it displays the dimensions on the screen, which you can then double-click and change, rather than going back through the Helix PropertyManager interface. These dimensions can also be configured, which is a new function for helix features. This makes the Helix feature more standardized with other SolidWorks features. Figure 8.4 shows the variable helix with dimensions displayed from double-click. Simpler helix features have fewer dimensions on the screen.
FIGURE 8.3
The Variable Pitch helix
FIGURE 8.4
Double-click dimensions on a helix feature
Workflow
The workflow for all of the Helix type curves is as follows:
1. Draw a circle, or select an existing circle.
2. Start the Helix command.
3. Set the options.
4. Click the green check to accept the feature.
Using the Spiral
A spiral is a flattened (planar) tapered helix. The pitch value on a spiral is the radial distance between revolutions of the curve.
Creating projected curves
The two types of projected curves are:
• Sketch On Faces
• Sketch On Sketch
These names can be misleading if you do not already know what they mean. In both cases, the word sketch is used as a noun, not a verb, so you are not actively sketching on a surface; instead, you are creating a curve by projecting a sketch onto a face.
Using Sketch On Faces
The Sketch On Faces option is the easiest to explain, so I will describe this one first. With this option set, the projected curve is created by projecting a 2D sketch onto a face. The sketch is projected normal (perpendicular) to the sketch plane. This is like extruding the sketch and using the Up To Surface end condition. The edge at the end of the surface would be the projected curve. The sketch can be an open or closed loop, but it may not be multiple open or closed loops, nor can it be self-intersecting. Figure 8.5 shows an example of projecting a sketch onto a face to create a projected curve.
FIGURE 8.5
A projected curve using the Sketch On Faces option
Using Sketch Onto Sketch
This is the concept that most frequently causes difficulty for users. The Sketch Onto Sketch Projected Curve option can be visualized in a few different ways.
Picturing reverse 2D drawing visualization method
One way to visualize Sketch Onto Sketch projection is to think of it as being the reverse of a 2D drawing. In a 2D drawing, 3D edges (you can think of the edges as curves) are projected onto orthogonal planes to represent the edge from the Front or Top planes. The Sketch Onto Sketch projection takes the two orthogonal views, placed on perpendicular planes, and projects them back to make the 3D edge or curve. This is part of the attraction of the projected curve, because making 3D curves accurately is difficult if you do it directly by using a tool such as a 3D sketch spline; however, if you know what the curve looks like from two different