SPLINES! You say that too loud in a room full of structural engineers and you’ll either have 5 different types of guns pointed at you and a stapler in your forehead or… just… some very strange looks.
Nonetheless, you love Splines, or at the very least have a mild curiosity about them. A curiosity that has led you here. We can’t keep you from upsetting your co-workers with curviness, but we can show you how to control the curves and give you a little better understanding of how these sucka’s work.
Splines, Splines, Splines.
Generally speaking, if you don’t use splines, you hate them. If you do use them, you wish they were easier to control. Plus, if you’ve come from the realm of AutoCAD, you pretty much, automatically loath anything having to do with curved lines.
Splines in SolidWorks, however, have come a long way. They can be used for anything from cake molds to car design, tubing to turbo-props. It’s easy to plop down a few points and create a nice, curvy spline. The next step beyond that is controlling how those curves act. Here are six common and not so common ways to whip them into shape, literally.
Click to super-size all the screenshots below.
- Use Tangent Relations
The first and most useful way of controlling splines. Create a Tangent relation by selecting the Spline and another sketch line or feature.
- Use an Existing Axis
Make your Temporary Axes visible (View, Temporary Axes) then use those to create tangent relations.
- Use Construction Lines
Besides using existing reference geometry like the axis, it’s very easy to control 3-dimensional Spline and the space they use with a simple set of construction lines. - Use Existing Curvature
If you already have curved geometry, you’ll have the option of adding an Equal Curvature relation.
- Use Dimensions on Spline Controls
You can add dimensions to Spline Handles. If you don’t see the handles, select the dimension tool, click the Spline point, then select one of the the handles.
- Use Offset Planes
My favorite approach. You can set planes up in a grid like layout, then use combinations of the above to help define your shape.
Have more? How do you control your curves?
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I am a big fan of using the control polygon for minor adjustments, in fact, the control polygon never stops moving. When you're moving edit points around it's actually guessing where to move the control polygon to accommodate for your edit point drag.
Manipulating the control polygon can be more predictable and smoother, less jerky.
The downside is, it's less intuitive at first.
That's a great hint, Kevin. I've been missing that feature from Alias, and turns out it was there all along. Too bad the control polygons can't be mated like regular sketches.
Hey Kevin. Thanks. One thing I wish I could do is adjust control polygons along an axis. Could be with a relation to a line, grid snap, or just by holding down Alt or Shift when dragging them. but yeah, once you get them down, much smoother.
What about selecting handles and just giving them Horizontal and Vertical relations? Beats putting in construction geometry and a tangent relation.
You can also dimension the “length” of the handle, but it's a number that doesn't seem to relate to anything – and it doesn't really serve to lock the spline entirely.
Apart from being able to actually dimension/relate to the control polygon, other functionality I would like would be to drive a spline by defining its curvature, through curvature combs or something…
The biggest benefit of dimensioning the “length” and angle of a control spline is the ability to make adjustments to the spline by changing those dimensions without reentering the sketch. This gives a much finer control than continuously entering and reentering a sketch to get the feature to look perfect.
What about curvature combs, tangent weighting, control frames and sketch-on-surface? Come on man, these things do some pretty boss stuff.
True, johnburrill.
That reminds me when I used spline-on-surface for a lot of manual blending work (woo! fun…)
I would start, clicking on an edge and then clicking on the other edge, this often made the spline go red and fail. However, starting on an edge then clicking once (or twice) on the surface itself and only then clicking on the other edge, worked.
Sometimes splines just need more points to go through, mathematically.
That's a nice little trick to try, if you're having trouble with your splines-on-surface.
I use splines all the time! I love the taste of Mechanical Engineer tears. And yes, adding relations and dimensions can help you control things a lot more. However, SolidWorks hates splines and often, after adding a lot of relations to a spline, SW will tell you there's a conflict in your sketch, even though you know full well there isn't. SolidWorks is ca-razy like that.
I don't lock down splines all the time. Usually add just enough constraints to get them where I need them. Save having to redo a lot of relations/dimensions.
Ooo, yeah, spine-on-surface is really nice. I didn't list all these because they are the commands that help, instead of a process. But still, very valid and very useful. Thanks!
I don't lock down splines all the time. Usually add just enough constraints to get them where I need them. Save having to redo a lot of relations/dimensions.
Ooo, yeah, spine-on-surface is really nice. I didn't list all these because they are the commands that help, instead of a process. But still, very valid and very useful. Thanks!
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