SolidWorks 2011 Parts Bible - Matt Lombard [319]
This basic analysis is good for visualizing changes in draft angle, but it also has some less desirable properties, which will become apparent as you study the other types of draft.
Gradual Transition
Although the Basic draft analysis is able to show a transitioning draft, the Gradual Transition draft analysis takes it a step further. With the Gradual Transition, you can specify the colors. It is also useful because it can distinguish drafts of different amounts by color. It may be difficult to tell in the grayscale image in Figure 24.22, but the ribs, which were created at one degree, have a slightly different color than the floor of the part, and the walls also have a different color. Notice that cavity and core directions have different colors, as well (called Positive and Negative draft in the Draft Analysis). You may want to open this part in SolidWorks, re-create the settings, and run the analysis so that you can see the actual colors.
FIGURE 24.22
The Gradual Transition draft analysis
Some problems arise when you use this display mode, the first being the flat, non-OpenGL face shading that is used to achieve the transitioning colors. This often makes it difficult to distinguish curved faces, and faces that face different directions. The second problem is that you cannot tell that the boss on top of the dome has absolutely no draft. In fact, there is no way to distinguish between faces that lean slightly toward the cavity and faces that lean slightly toward the core. The third problem is the strange effect that appears on the filleted corners. The corners were filleted after you applied the draft and before the shell, and so the filleted corners should have exactly the same draft as the sides; however, from the color plot, it looks to be a few degrees more.
Caution
Software can sometimes interpret things differently from the way that a person does. As a result, any computer analysis must be interpreted with common sense.
Due to this and some of the other problems that I mentioned earlier, I recommend using the Gradual Transition draft analysis in conjunction with one of the other tests. Gradual Transition gives an interesting effect, but it is not a reliable tool for determining on its own whether or not a part can be manufactured.
Face Classification
Face Classification draft analysis groups the faces into classifications using solid, non-transitioning colors. You will notice a big difference between the coloration of the Face Classification draft analysis faces and of the Basic or Gradual Transition faces. Face Classification uses OpenGL face shading, which is the same as that used by SolidWorks by default. This allows for better shading and differentiation between faces that face different directions. The Basic Analysis coloration looks like all the faces are painted the same flat hue, regardless of which direction they are facing, which makes shapes more difficult to identify. The non-OpenGL alternate shading method makes it possible to display a transition in color. SolidWorks OpenGL shading cannot do this.
Another advantage of using the OpenGL shading is that the face colors can remain on the part after you have closed the Draft Analysis PropertyManager.
Face Classification draft analysis also adds a classification that is not used by the Basic draft analysis. Straddle faces refer to faces that straddle the parting line, or faces that, due to their curvature, pull from both directions of the mold. These are faces that need to be split. On this part, a straddle face is shown in Figure 24.23.
FIGURE 24.23
Face Classification draft analysis and a straddle face
The light bulb icons to the left of the color swatches enable you to hide faces by classification. This is useful when you are trying to isolate certain faces, or visualize a group of faces in a certain way. This can be an extremely useful feature, especially when you have a very complex part with a large number of faces, some of which may be small and easily lost