Page 263 - Mastering SolidWorks

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understanding Fillet tyPes 235

Using Tangent Propagation
By default, fillets have the Tangent Propagation option turned on. This is usually a good choice,
although there may be times when you want to experiment with turning it off. Tangent propaga-
tion simply means that if you select an edge to fillet, and this edge is tangent to other edges, then
the fillet keeps going along tangent edges until it forms a closed loop, the tangent edges stop, or
the fillet fails.
If you deselect Tangent Propagation, but there are still tangent edges, you may see different
results. One possible result is that it could fail. One of the tricks with Fillet features is to try to
envision what you are asking the software to do. For example, if one edge is filleted and the next
edge is not, then how is the fillet going to end? Figure 7.17 shows two of the potential results
when fillets are asked not to propagate. The fillet face may continue along its path until it runs
off the part or until the feature fails.

Figure 7.17
deselecting the tangent
Propagation option

TIP this may sound counterintuitive, but sometimes when Fillet features fail, it may be useful to
deselect propagation and make the fillet in multiple features. there are times when creating two fil-
lets like the one shown in Figure 7.17 will work and times when making the same geometry as a single
feature will not. this may be due to geometry problems where the sharp edges come together and are
eliminated by the fillet.

Best Practice
in general, fillets should be the last features applied to a model, particularly the small cosmetic or
edge break fillets. larger fillets that contribute to the structure or overall shape of the part may be
applied earlier.
Be careful of the rock-paper-scissors game that you inevitably are caught up in when modeling plas-
tic parts and deciding on the feature order of fillets, draft, and shell. Most fillets should come after
draft, and large fillets should come before the shell. draft may come either before or after the shell,
depending on the needs of the area that you are dealing with on the part. in short, there is no single
set of rules that you can consistently apply and that works best in all situations.