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Editing Engineering and Production Models with Solid Edge

By Chris McAndrew, January 18, 2013

(See Pt 1)

It is likely that many engineers, designers, and vendors will want to have input throughout the design process. Each member of the team has to be able to work with the design and its related CAD files. I cannot keep track of the number of hours I spent rebuilding parts in SolidWorks, mostly when preparing a part for manufacturing on behalf of a client. This is because my design intent does not necessarily match that of others on the team.

For instance, in the early stage of prototyping, designers might be working with the intention of machining the part, but then the intent changes when it moves to the injection molding stage. One of the benefits of Solid Edge is that its Synchronous Technology removes some of the design intent from a model’s history, making it easier to manipulate.

Synchronous Technology (ST) is what allows us to push, pull, and turn existing models without linking the actions to an ordered set of features. This is a big draw of Solid Edge, and as a SolidWorks user was something I was eager to try out.

For instance, in SolidWorks and in the "ordered" design setting of Solid Edge, each new feature builds on the last. This means that if I change one feature, then every other one following must be rebuilt. Over time, I was forced to learn many kinds of best practices to ensure models would be rebuilt by SolidWorks in an efficient manner - ones that helped me eliminate rebuild time but have no relation to design intent. These practices include things like placing fillets at the end of the feature tree, keeping dimensioning reference planes off the part coordinate system, and fully defining sketches.

Unfortunately, our industry has no governing body for best practices!

This is why eliminating feature order can have a dramatic effect on the ability of team members to work with designs. The old way of working with designs has more to do with helping the software solve equations than it does with how designers like to think about parts. Because the "how" of part creation is no longer a concern with Solid Edge, it becomes easy to pull in an existing part and start working with it - and hence make changes to the "why."

The Change in Sketching

Working with Synchronous Technology, I found I no longer needed to consider many of the old ways of doing things. For instance, figure 1 shows a sample part built solely with Synchronous Technology in Solid Edge. Say the previous designer built the file such that the handle and slot (R5.24) were the first two features, and that the hole (circled in red) was the last feature. Changing the slot radius to R6 would require rules-based software like SolidWorks to reevaluate the highlighted hole, even though it has nothing to do with the item being changed.

With Synchronous Technology, there is no feature that created any portion: the handle and hole are simply there in the model. When I edit them, there is no time spent fixing references or features that might be rebuilt incorrectly; construction sketches don’t lose relationships, because there are no construction sketches.

Figure 1: Synchronous Technology editing

Sketches are still used, however, for procedural features, as well as initial sketches, but instead of being the framework of the design, they are simply tools in the process. I found this out after creating a few sketches for extrudes, revolves, and other features, and then deleting the sketches. It is fine to leave sketches in place when there is a reason to keep them; otherwise, erase them, because sketches are no longer associated to anything. (In SolidWorks this would create panic, dozens of lost relations, multiple errors on child feature rebuilds, and a mountain of headaches.) Instead of a bunch of red features and errors, deleting sketches in Solid Edge actually cleans up the feature tree.

The Change in Dimensioning

In my first CAD modeling class, the professor drilled into us that sketching was king, that dimensioning was only slightly less critical, and that both were critical when passing files to others. He explained that if a sketch was wrong, or undefined, or sloppy then it would cause problems during editing. Always.

Problem is, having being taught this makes taking the leap to Synchronous Technology not trivial, for it requires more of a change in the thought process, than it is just a change in software application. Of course dimensioning is in Solid Edge but nearly all dimensions and relations are linked to the solid and not the underlying 2D sketch.

The refreshing part of Synchronous Technology is that I can make changes to the base geometry relationships that normally would be in one of the primary sketches. Figures 2 and 3 show an example of these relations in Solid Edge.

Figure 2: Synchronous Technology relations: Live Rules are inactive

Now I still had to define and lock relations in Solid Edge, but many of these were handled by Live Rules. (Check out the selection bar on the right side of figure 2.) Live Rules looks for obvious relations by reading the model and then identifying items that are tangent, concentric, and coplanar - even if they are not as such defined though dimensions. In figure 2, I am pushing and pulling the left-hand bracket; the live rules I turned off are highlighted in red on the selection bar.

With the rules off, the bracket is being edited by itself; in figure 3, I turned the rules back on, and so the opposing bracket also changes. All this means that even if a designer forgets to fully define a relation, the software will make the connection and highlight it.

Figure 3: Synchronous Technology relations: Live Rules are active

Nothing makes it easy to edit a CAD model, but I found Synchronous Technology does reduce the complexity. Synchronous Technology also frees up my time to focus on the function of the model, rather than the order in which it is built. Some ordered features still exist, and but overall I am happy to see that making edits to a part of a model in Solid Edge only affects the part I am editing.

This seems like a simple thing, but I can imagine it relieving a lot of headaches when dealing with design edits, iterations and engineering change orders.

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About the Author

Christopher McAndrew develops and markets toys and children's products. He has a bachelors degree in mechanical engineering from Tulane University. Chris writes the 3 Dimensional Engineer blog. More...

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