Surface Modeling with SOLIDWORKS
SOLIDWORKS, as you might gather from its name, is primarily a solid modeler. It is parametric, which means you assign dimensions to your geometry that tell it how to behave. In this way, you can capture design intent. Why would you want to do that? Repeatability and changeability. It’s very rare that you design something and get it right the first time. You usually need to make countless small changes—no matter how great the concept. That’s just how it is. Design is a messy business. But SOLIDWORKS helps you with that by giving you tools that are easy to use and very powerful.
There are many ways to arrive at your ideal design destination. You can do everything on a napkin sketch. Easy to do and valuable for initial concept work, but not very versatile or informative. (You can’t really measure it accurately.) You can build your design with surfaces. This is somewhat tedious because you generally must build one face of the model at a time, trimming and manipulating as you go. You can create any shape you can imagine (given enough time and practice). But a surface model defines only surfaces, so it is hollow.
Or you can use solid modeling. Solids have many benefits, but there are inherent limitations there, too. They are really great at capturing manufacturing data (like mass, weight, etc.) but they can also be fairly restrictive in what you can create. Often your models will appear somewhat boxy and dull. The best way to use SOLIDWORKS is to use surfaces and solids to achieve truly marvelous models. You have a box of tools; use them wisely. Solid modeling is really, really good at getting a lot done, quickly. Surface modeling produces super-high-quality models, but can take time. Use both methods to achieve great models, fast, and with greater flexibility.
Figure 1. Extruding gives you control of your model from one end to the other.
Figure 2. Revolving gives you greater versatility to shape your model, but its basic shape will always be cylindrical.
Whether surface or solid, your SOLIDWORKS models will begin with a sketch. You must really think about the overall shape you wish your model to achieve. Reduce it to its most basic shape—the lowest common denominator. That’s what you start with. For instance, a mighty space rocket is, at its heart, a cylinder. The next decision is a little more daunting. Should you extrude the cylinder or revolve it? This is very important to decide. If you extrude it, you can control the diameter and height as well as the shape perpendicular to the direction of the extrusion (see Figure 1). If you revolve it, you can control the diameter, height and axial shape (see Figure 2). Neither tool is superior to the other as both find their value in their application.
Figure 3. A sketch is normally two dimensional, occupying a plane of the X and Y axes.
Figure 4. A 3D sketch occupies space, with parameters along the X and Y as well as the Z axes.
The sketch is usually planar or in other words, flat or 2D (see Figure 3). This type of sketch is easiest to make and control. But for sketches that cannot be confined to a plane, SOLIDWORKS also offers 3D sketches (see Figure 4). Both have advantages and both have limitations.
Figure 5. A boundary surface can have any kind or number of sides, but its edges must form a fully-closed boundary.
Figure 6. A lofted surface uses its sketches to establish its shape.
There are basic surfaces, such as boundary and loft. These are very powerful. A boundary surface uses curves that fully enclose a single shape: say, a rectangle or an octagon. You can either use a single sketch or a combination of multiple sketches to describe a closed boundary—hence the name. (That doesn’t mean it has to be 2D either.) Each of the bounding entities can dance all around, just as long as their ends coincide with the ends of another sketch to make a closed loop (see Figure 5). A lofted surface usually, but not necessarily, uses multiple parallel sketches to build a shape. Picture the rafters in a house, or the ribs of a skeleton. Each sketch represents a shape the surface will be stretched across, thus describing the model’s shape (see Figure 6).
Figure 7. You can use the Deform command to add grip features.
Once you have your surface, or, in this case, a sweep, you can use various techniques to tweak it into just the right shape. First, identify your profile sketch, then the sweep path. That gives you the basic shape. Now, select Deform. There are various options available to you. One of the most powerful (and easiest to use) is the Curve To Curve option. It works much like “go from here to there.” Choose as your Initial Curves the sketch representing the current geometry. Then, click in the Target Curves box and select the sketch that represents the geometry you want. Last, choose the geometry you wish deformed. Deform will alter the geometry to match (see Figure 7).
Figure 8. After you are done modeling your features, you can knit them together to form a solid body.
You have many options within Curve To Curve. You can fix edges and/or curves so they don’t move during the Deform. You can adjust the accuracy of the shape so that it exactly matches the curves you specified. When you are done, if you so choose, you can knit your surfaces into one surface. If you have created a completely enclosed volume, SOLIDWORKS will recognize it as a solid body (see Figure 8).
Once you have mastered a few simple surface types and how to use them, your models will begin to take on new and more interesting shapes. Form versus function? No. Form is function. How something is used dictates its most optimal shape. And with the right tools, any shape is possible. That’s what makes SOLIDWORKS so powerful—and fun! So, don’t just be a surface modeler or a solid modeler. Be a modeler and explore all the tools that you have. See what they’ll do and discover when you might want to use them. Then, you’ll be prepared to not only take on the big jobs, but also excel!
More information on advanced surface design can be found here.
About the Author
Michael Hudspeth has been a designer for two decades, a lifelong artist, an avid model builder and author (specializing in science fiction). He, his wife, two daughters and one too many cats thrive in the great American heartland, just outside of St. Louis, Missouri.