From Machine design to Consumer Product design, creating Fillet features is something that you quite like do when creating your models. There are basically six types of fillets you can apply in SolidWorks: Constant, Variable, Full-Round, Fillet via Hold Line, Setback or vertex fillets and Curve Continuous Fillets. Let’s review them quickly.
Even with the arsenal of six different ways to apply fillets, there can still be times when Fillets are difficult to apply to your model. There are a few common reasons why this might occur for your situation;
- Non-tangent intersection – The edges that you are specifying for the fillet are not tangent to one another, therefore the fillet stops and does not propagate along (default setting) the set of “seemingly” tangent edges. Sometimes fillets cannot find a geometry solution when the fillet stops at non-tangent intersection. In situations like these, sometimes you can apply your fillet solution by unchecking “Tangent propagation” and selecting each of the edges individually. In this way, the constant fillet solution is applied to each edge individually and therefore can sometimes find a total fillet solution.
- Self-intersection – in some cases when the designer is trying to apply a fillet to a set of continuous (tangent) edges, say the end face of a box which already has vertical fillets applied to it and when the fillet runs along the edge it encounters a rounded corner (existing vertical filleted edges) the fillet that is being applied is a larger value than the rounded edge that it needs to traverse. The SolidWorks Constant fillet can usually overcome this situation, but for anything other than a constant fillet (variable etc.) this situation will prevent the fillet from continuing around the edge. Good designers usually avoid this situation by the following rule-of-thumb: apply your largest fillets first to your design, and then apply progressively smaller fillets henceforth. This results in good aesthetics since fillets on products naturally want to “flow” along edges and self-intersection and sharp resultant apexes are a thing to avoid aesthetically.
- Fillet Run-out – Most fillet problems are caused by what I like to term “unresolvable fillet run-out condition.” It is in situations like these where the fillet “runs off” the edge of the part and literally there is no geometric solution that can be attained. There is a known solution to this problem which is known in the community as the “Atomic Bomb solution.” This technique, first invented by SW community icon Ed Eaton, applies a clever solution to this problem by simply temporarily eliminating the run-out problem before the fillet ever sees it.
When it is suspected that there is a run-out issue, the technique calls for the designer to “chop away” the end of the fillet edge (at the end vertices) by either extruding a cut over it or applying a split line around the vertex and deleting the resultant split-line face, turning the solid body into a surface body. At this point the fillet can be applied. Once applied a Fill Feature is applied to fill the hole at the end of the fillet and turn it back to a solid Body. The following example illustrates this solution:
There you have it. this technique usually solves those tricky filleting problems by creating a custom blend solution and resulting in an aesthetic and functional result.
Look to SolidWorks providing additional fillet functionality in the future. In fact a new fillet feature is being introduced and tested in Beta right now. If you have not already done so, please go check it out by signing up for SolidWorks 2014 Beta here.
A degreed Industrial Designer, Mark has worked in the product design industry for over 25 years for such companies as Atari, Hewlett Packard and IDEO. Joining SW in 2004 as a Product Manager, he currently is Senior Product Manager for Definition.