(View All Videos) Toggle Members Videos
View Other Content
Categories See All →
Surfacing in Solid Edge - a twisted perspective!
I don't pretend to understand the mathematical complexities of NURBS (Non-Uniform Rational B-Spline) surfaces, but I have spent several thousand hours creating a wide variety of surfaced shapes in Solid Edge with varying degrees of success. Rarely does the Customer look at the first attempt and say 'Great! That's EXACTLY what I want' ... more often, the first reaction is lukewarm at best, but hey - you have to start SOMEwhere, and often the Customer him/herself isn't sure what they actually want and sure as heck doesn't understand how the software creates & edits surfaces! Sometimes you are working from pencil sketches, sometimes air sketches, sometimes a vague verbal description or a blurry image of someone else's product or perhaps a hand-made prototype. It takes hundreds of hours to build up your skills AND to learn the limitations and strengths of the software when creating aesthetic shapes and I'm not going to try to impart all of that knowledge in one article, but here are a few hints/tips to help you along the path to 'Type 1' surfaces (ones the Customer likes!)
* Think of freeform surfaces as thin sheets of rubber. Imagine (or even try this at home) that you have cut a piece of rubber from the cuff of a domestic rubber glove or even a surgical glove. Stretching it between your hands or over a solid object changes the shape, but it's INCREDIBLY difficult to create a smooth, uniform shape from the entire piece. How COULD you achieve this? Maybe hold down the perimeter with a ring or frame of some sort, then apply gentle air pressure behind the rubber? This is actually a very helpful concept, because successful surfacing combines smooth, uniform boundary constraints with a uniform stress distribution throughout the surface itself. Poking your finger or a pencil etc. against the rubber introduces localised distortions and stresses, but applying gentle pressure uniformly allows a smooth, manageable shape IF we have set up the boundary conditions correctly.
* Start with a simple exercise. Create 2 Keypoint curves (NOT just planar Sketches - you need to get REALLY good at creating & editing Keypoint curves, so start now!) and create a Bluesurf between them. Solid Edge will take the simplest option first and create a Ruled Surface, where corresponding points on the 2 curves are joined by straight lines. You will see that the connecting edges of the surface are straight, and remain so even if you alter one or both curves. The surface probably looks quite unattractive at this point - certainly not something you would want to see in a finished consumer product!
* From this simple beginning, investigate the following options in turn: a] Changing the start/end conditions b] Adding edge curves and finally c] Adding one or more intermediate curves to modify the shape of the surface. Just playing with different options and observing the results is invaluable in developing your surfacing skills, and you will soon learn that some tweaks will make the shape smoother and more attractive, whereas some will create folds/ridges/ripples which are highly detrimental. Above all, remember the rubber glove analogy: the smoother & more-uniform the perimeter constraints and 'pressure' on the surface patch, the smoother the result.
* Select a common household object with some aesthetic or ergonomic shape (kitchen knife handles are good examples) and think how you might model portions of the shape. It's rare that the entire grip can be modeled as a single feature, and how you approach breaking-up the shape into manageable portions is part of the skill. Modelling the end portions then allowing the power of the software to create the middle portion smoothly and seamlessly is often a good approach, whereas creating many complex cross-section curves in an effort to create a single highly-complex surface rarely works.
It's all about compromise. Often you will have to modify your technique to work around limitations in the software, but on the other hand you need to work out the best techniques to take advantage of the power of the software to create amazingly complex and pleasing shapes given the right inputs. Doing all this whilst maintaining correct draft angles, wall-thicknesses etc. for moulding is one of the most difficult challenges in 3D design and requires a LOT of patience and a critical eye but don't be discouraged if your early attempts aren't as successful as you hoped. Persevere!
If any of you are interested in reading more or have specific problem areas in surfacing which you would like to see covered, let me know. I will also post some images of surfaced parts from the MASCO archives in the Gallery when time permits.
- Community Administrator, Sean Cresswell and imics13 like this