SolidWorks 2011 Parts Bible - Matt Lombard [274]
Using the Base Flange Sheet Metal method tutorial
SolidWorks contains two completely separate methods for working in sheet metal. In one method you can use dedicated sheet metal features from the start, and in the other method you build a part using thin features and other generic modeling tools, and then tell SolidWorks it is sheet metal so you can flatten it.
The reason for two methods is that the generic modeling method came first, and then SolidWorks introduced a more powerful set of dedicated sheet metal features. You can use these tools together or separately, and either way you get an accurately flattened part at the end. Situations where you might want to use one or the other are covered in this chapter.
Sheet metal tools do not always represent real-world sheet metal manufacturing processes 100 percent accurately because some shapes that result from bending processes are too complex to easily represent in a CAD model. So there are times when you still have to use your imagination a little bit, particularly where bends intersect or overlap. The main point is that the Flat Patterns are always accurate because sheet metal is usually fabricated using 2D data.
Using the Base Flange Features
The features used in the Base Flange method are easy to grasp conceptually, and they have many individual controls. These are the tools that represent the newer method of building sheet metal parts from dedicated sheet metal features. You can edit many of the features by pulling handles, by using spin arrows, or by typing in specific numbers or dimensions. Maybe best of all, SolidWorks knows to change the thickness for the entire part at once.
The SolidWorks sheet metal Base Flange method works on a straight brake-press basis. This means that you can place straight bends of a constant radius. The software does not behave well when bends intersect, and does not allow bends to cross. SolidWorks does not flatten anything where the material deforms or does anything other than a straight bend. The exceptions to this are the Lofted Bends and Edge Flange on a curved edge. You should use these two features sparingly, and you should always verify the results before depending on the flat patterns you get from these features.
You will most often design a part in 3D and then flatten it for manufacturing, but SolidWorks also offers a workflow where you start with a flat pattern and add bend lines to it. Both methods work, but designing in 3D is most effective when you are trying to make a sheet metal part fit together with other parts.
Understanding sheet metal manufacturing processes is very helpful for using SolidWorks sheet metal tools to design functional and manufacturable parts. SolidWorks helps you by not allowing you to create a part that cannot be flattened, but it is still easy enough to model a part that cannot be manufactured, or cannot be manufactured economically. You may find it useful to rely on the expertise of either designers with experience or shop personnel to help you learn how to design for sheet metal processes.
You can access the Sheet Metal features by clicking the tool you need in the Sheet Metal toolbar or by choosing Insert⇒Sheet Metal from the menus and selecting the appropriate tool.
Using the Base Flange/Tab feature
The first feature you add to a sheet metal part is the Base Flange feature. In addition to letting SolidWorks know that the part is a dedicated sheet metal part, the Base Flange/Tab tool has three functions:
• By drawing an open contour in the first feature, the Base Flange creates a thin feature-like extrusion that includes the rounded corners of the bends.
• By drawing a closed contour in the first feature, the Base Flange creates a flat pattern sheet that is shaped like your sketch for you to start from.
• When the Base Flange is used at any time other than the first feature, it functions as a tab.
Figure 21.1 shows these three functions of the Base Flange/Tab feature.
Notice that the sketch of the part shown in preview