Curvature continuity in SOLIDWORKS refers to the smoothness between two adjacent curves or faces at the point where they meet. This blog discusses three types of continuity: C0, C1, and C2. Curvature combs are a good way to visually understand curvature continuity so they are turned on in the following images.

C0 continuity is where two entities touch each other, but that’s all.

C1 continuity is where two entities are tangent. It creates a smooth transition from one entity to another and is sufficient for many applications. However, even though it’s smooth, the radius could be completely different at that point which may affect the esthetics. Esthetics can be important in applications such as automotive parts or consumer products where how it looks and how it feels is critical.

C2 continuity is where the curvature is the same where the two entities meet. In applications like the ones mentioned above, this is the desired type of contact.

The fit spline command is an excellent way to generate C2 continuity because it replaces entities that just touch (C0 continuity) or are tangent (C1 continuity) with a single spline which will have continuous curvature (C2 continuity).

The fit spline command generates a single spline that lays over the top of selected entities. The underlying entities remain and are converted to construction geometry. A tolerance can be assigned which determines how closely the spline adheres to the underlying geometry.

Here’s an example of C1 continuity, where the arc is tangent to the two adjacent lines and the resulting revolved feature.

Here’s an example of C2 continuity, where the fit spline command was used to replace the arc and two lines with a single spline and the resulting revolved feature.

When esthetics are important and continuous curvature is desired, a fit spline can be an excellent way to accomplish that.

If you enjoyed learning about fit spline and curvature continuity in SOLIDWORKS, be sure to check out TriMech’s Tech Tips for more step-by-step tutorials.