SolidWorks 2011 Parts Bible - Matt Lombard [306]
In order to make this move, I had to select seven faces:
1. Top of ring
2. Bottom of ring on left
3. Bottom of ring on right
4. Top of boss
5. Bottom of boss
6. Full round on end of boss
7. Hole in the mounting boss
Notice how the Web now extends up the side of the barrel. This is the type of edit that would be clumsy in SolidWorks if it were what you wanted to do. In direct edit, it is the kind of edit that would be clumsy if it were not what you wanted to do.
This is one of the limitations of direct edit techniques in general — not a limitation of SolidWorks, but a limitation of the concept as implemented in SolidWorks. Direct edit cannot make new faces without adding another feature and has problems with the intelligent type of face creation that you find in history-based systems. Direct edit programs are certainly not more powerful than SolidWorks or any other history-based CAD program. They have weaknesses in different areas, and the weaknesses are more limiting than SolidWorks history-based weaknesses.
Figure 23.18 shows where the weakness of using the direct edit tools within SolidWorks begins to show up. The first feature in the part is a revolve that uses a sketch. The last feature in the part is a Move Face feature that moves the faces created by the revolve. So if you want to change the geometry of the barrel, it is controlled by two different features. If you make the sketch a specific size, the Move Face feature will change it. Move Face can only change relative to a starting point; it cannot make something a specific dimension, so it will always either add or subtract a given amount from the geometry created by the original feature.
FIGURE 23.18
Move Face features put some geometry in double jeopardy — it can be changed from two different places.
Some SolidWorks power users consider this double-jeopardy condition sloppy design or bad practice. You can make a strong case that the direct edit tools should not be used on native SolidWorks parts, and that you should edit the feature the way it was created. There is certainly a place for that argument. But I know from my own modeling work that sometimes changing a feature way back in the tree can have unintended repercussions later in the tree, so using a Move Face feature late in the tree avoids fixing a lot of propagated errors. Is that a cheap, sleazy cheat? You will have to decide that for yourself.
Combining direct editing with imported geometry
Regardless of any argument against using direct edit tools on native SolidWorks data, there can be no such argument against using them on imported data. Direct edit tools may have their limitations, but when dealing with imported geometry in SolidWorks, your choices are limited, as you see from the following:
• Direct edit tools
• Cut and add modeling
• Manual surfacing tools
• FeatureWorks deconstruction
When faced with these options, direct edit tools look like the safe choice. The big problem will be that if the part is covered with fillets, you may not be able to change much. In cases like that, you might use a combination of tools, such as FeatureWorks to remove fillets, and then direct edit to make changes.
Handling imported data with FeatureWorks
FeatureWorks is not part of the scope of this book because it is a part of SolidWorks Professional, and the book is limited to SolidWorks Standard. FeatureWorks is an add-in that rebuilds imported solid models as feature-based models. It can recognize and rebuild features automatically, or semi-automatically with you guiding it through the process.
FeatureWorks works by deconstructing, or “unbuilding,” the part, removing faces of features that would be applied last. For example, first it will try to recognize fillets, and removes them from the model. Then it recognizes other types of features, including holes, and then finally it recognizes the base extrude or revolve feature.
You can use this as part of your process, but only deconstructing the part partially,