Surfacing in SolidWorks

A few days ago I had a conversation on Twitter with SolidWorks blogger Gabi Jack about surfacing in SolidWorks and how it sometimes can be a challenge. I usually find myself fiddling with models created by customers or prospects. Creating models from scratch is not something I do regularly. But when I do, my favorite tool of choice for creating mechanical models is SolidWorks. However, when I need to create a non-prismatic model I simply fire up Rhino, draw curves whichever way pleases me, use them to create surfaces and later join them to create solids. I do that because Rhino lets me design the way I think. I have done a bit of surfacing in SolidWorks, but just enough to conclude that it is not as easy as doing it in Rhino.

My conversation with Gabi made me want to take a closer look at surfacing in SolidWorks. So today after I finished putting up the last of the Christmas decorations in the house, I fired up SolidWorks 2010 and began to do some surfacing. I came up with this.

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As you can see I am very much in the Christmas mood. Now that may look like a lot of surfaces. But it is actually just one surface that has been mirrored and arrayed over and over again. This is the sub-assembly for each holly sprig that has been arrayed around the ring of the wreath.

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When I look at it more closely, surfacing in SolidWorks is not that complicated after all. What can sometimes be a bit difficult is the act of creating the curves that are used to cook up the surface. In a CAD system like Rhino you simply draw curves in no particular order and without really having to think a few steps ahead. In SolidWorks the situation gets a bit complicated since you need to deal with 3D Sketches, impose constraints and assign relationships between various geometric objects. Before you do anything in SolidWorks you need to formulate a strategy because you are in effect solving a problem, not just wandering around the place clicking away. Once your brain is programmed to think differently, I guess surfacing in SolidWorks does not become that difficult a task.

To create a leaf of the sprig I created this 3D Sketch describing the edges of one half of the leaf.

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I use the Filled Surface command to create half of the leaf surface.

Next I mirrored the surface to get the other half of the leaf.

Now here is something worth mentioning. When you model a symmetric part, such as this leaf, the normal practice is to completely model one half and then simply mirror everything over to the other side using a single mirror feature. In surfacing this may not always be possible. For example, in this case, after getting one half of the surface I thickened it to give it a volume and then tried to mirror. The mirror operation failed. This is because after I thickened the surface, part of the resulting solid spilled over to the other side due to the surface curvature at the ridge of the leaf. Most probably that threw the modeling kernel into a spin. So without any other option at hand, I first mirrored the surface and then stitched both halves into a single surface using a Knit Surface command. When I tried to thicken the united surface it worked and I got a solid leaf.

Maybe creating sexy surfaces in a surface modeler like Rhino is easier than doing the same in a history based parametric modeling system like SolidWorks. But once you get it done, you end up with a powerful model with a lot of intelligence in it. Of course, modifying a history based parametric model has its own challenges and that is where Direct Modeling can come handy. Especially the type which maintains the history tree which is what Inventor Fusion is trying to do. But that’s a different story altogether.

All said and done, I think I need to spend more time using SolidWorks for surfacing tasks. If you are interested you can download a zip file containing the SolidWorks 2010 part and assembly files of the wreath from here. I have also thrown in a Parasolid file in case you don’t have SolidWorks 2010.

Here’s wishing you a Merry Christmas and a Prosperous New Year.