SolidWorks 2010 Bible

Part II: Building Intelligence into Your Parts

To make the transition from r = ∞ to r = 2 smoothly, you would need to use a variable radius arc if

such a thing existed. There are several types of sketch geometry that have variable curvature, such

as ellipses, parabolas, and splines. Ellipses and parabolas follow specific mathematical formulas to

create the shape, but the spline is a general curve that can take on any shape that you want, and

you can control its curvature to change smoothly or continuously. Splines, by their very definition,

have continuous curvature within the spline, although you cannot control the specific curvature or

radius values directly.

All this means that continuous curvature Face Fillets use a spline-based variable-radius section for the

fillet, rather than an arc-based constant radius. Figure 7.44 illustrates the difference between continu-

ous curvature and constant curvature. The spikes on top of the curves represent the curvature (1/r,

and so the smaller the radius, the taller the spike). These spikes are called a curvature comb.

FIGURE 7.44

Using curvature combs to evaluate transitions

Lines and arc
non-continuous curvature

Lines and spline

continuous curvature

In Comparison to Figure 7.45, notice how the curvature comb immediately jumps from no curva-

ture to the constant arc radius, but the spline image ramps up to a curvature that varies.

Face Fillets with Help Point ...........................................................................

The Help Point in the Face Fillet PropertyManager is a fairly obscure option. However, it is useful

in cases where the selection of two faces does not uniquely identify an edge to fillet. For example,

Figure 7.45 shows a situation where the selection of two faces could result in either one edge or

the other being filleted (normally, I would hope that both edges would be filleted). The fillet will

default to one edge or the other, but you can force it to a definite edge using the Help Point.