Why You Should Use Conics in SolidWorks 2013

March 11, 2013

While there have been many incremental changes to SolidWorks over the years, the 2013 version offers a new feature that will make a big change: the conic section sketch entity. Since sketches are the building blocks for features, they are the foundation of our 3-D models and the products that are born from them. Pro/E users may be familiar with conics, but for the large portion of CAD users who are only accustomed to SolidWorks this is an entirely new tool. Up until 2012, Industrial Designers using SolidWorks have had to rely on using splines to sculpt products when arcs would not suffice. While splines have been the foundation of many designers’ surfaces for years, they have the following disadvantages:

• Difficult to dimension logically
• Prone to lumpiness
• Can flip/invert 180° to the entity to which they are constrained tangent.
• Doesn’t maintain smoothness after modification, even if there are no mid-curve control points.
• Mid -curve control points (when required) require complex dimensioning schemes.

Since most engineers prefer the simplest, most straightforward method of building their models, they have often opposed the use of splines in CAD models (“Couldn’t you just use an arc instead? It would make things a lot easier…”). Designers, while frustrated with the difficulties of splines themselves, have been willing tolerate them in order to fine-tune the aesthetics. The addition of conics in SolidWorks 2013 should be a welcome addition to both designers and engineers for the following reasons:

• Easier to dimension (a single “rho” value locks in the desired curvature)
• Naturally smooth and elegant curves can be maintained with a rho value near .5
• Can be constrained tangent to outside entities
• Robust

The image below compares a conic (top) with spline (bottom) and how they each react to dimensional changes.

Both curves are constrained tangent to vertical (left) and horizontal (right). The initial conic curve (in blue) had its right end-point dimensioned 2” off its ground plane. A corresponding spline was sketched (and fully constrained) over a mirrored reference of the above conic, creating a smooth, nearly-identical mirrored curve. However, once the 2” value is modified, the advantage of the conic is apparent—it maintains it smoothness at every dimension, while the spline starts to lose it. Conics allow a designer to dial in the right curvature and have the confidence to pass the CAD downstream to an engineer without much concern about degradation in aesthetics due to overall dimensional changes.

For more information on conics, check out the SolidWorks blog: Rho, Rho, Rho Your Boat: Conics in SolidWorks 2013.

Written by: Chris Kulujian, Manager of Product Development

Up Down