Page 270 - Mastering SolidWorks

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242 CHAPTER 7 Modeling with PriMary Features

The Circular profile is the normal type of fillet specified with a single radius. This is what we
think of as a default fillet.
The Elliptic profile is available only when specifying asymmetric fillets. The two radius values
determine an ellipse, which is used to round the selected edge instead of the usual arc.
The Conic rho profile is driven by rho (ρ). Conic in the name refers to the conic sections from
classical geometry–circle, ellipse, hyperbola, parabola—but as driven by the parameter rho in
many other CAD systems. Rho runs between 0 and 1. Figure 7.26 shows the effect of the range of

Figure 7.26
The effect of parameter
rho on conic rho
profile fillets

rho = .8
rho = .15

rho values on the profile of the fillet. If you want to experiment with this, the file used to create
this screen capture is in the download materials under the filename Conic rho fillet.sldprt.
The Conic radius profile is specified by the main radius value and a conic radius value, which
can be any positive number. The Conic radius value is the radius of the conic section curve at the
shoulder, which in this case means the middle of the curve. This works in a way similar to the rho
value, and the range of effects is similar to what you see in Figure 7.26.
Curvature Continuous profile is available on edge-selected fillets. This is new. Previously,
curvature continuity was available only on face fillets, as discussed next. Curvature Continuity
(c2) is a spline-based profile that matches the curvature of the faces on either side of the selected
edge. This edge-selected c2 fillet is a big convenience over needing to select faces. Any old c2 face
fillets you have should still work, but going forward in most cases, the edge-selected fillets will
be easier to create.

Using Continuous Curvature Face Fillets
Curvature continuity refers to the quality of a transition between two curves or faces, where the
curvature is the same or continuous at and around the transition. The best way to convey this
concept is with simple 2D sketch elements. When a line transitions to an arc, you have noncon-
tinuous curvature. The line has no curvature, and there is an abrupt change because the arc has a
specific radius.
NOTE radius is the inverse of curvature, so r= 1 . For a straight line, r= ∞—in which case, c =0.
c
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 curva-
ture, 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 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 fillets use a spline-based profile for the fillet, rather
than circular or elliptical. Figure 7.27 illustrates the difference between continuous curvature and