Sometimes I think the Synchronous message gets a little bit garbled. We get so caught up in stressing the strengths of Synchronous Technology and dinging history-based modeling that we tend to forget what we are really promoting is not one method, but a combination of the two. It’s true. History-based modeling has strengths, although they might not be strengths you recognize. To me, the most important strength of history-based modeling is the ability to remember topology that gets eliminated by subsequent features. The most limiting weaknesses of history-based modeling are that the design intent is hard to change and that parent/child relationships make feature failures common, and force the concept of “rebuild time” which users of direct editing methods haven’t even heard of.
Synchronous Technology belongs to the direct edit family of CAD tools. Synchronous is really direct edit plus several other tools (driving dimensions on the model, live rules, face relations, procedural features, features as face selections, selection methods, and other stuff). Synchronous Technology’s main strengths are the tools that allow you to determine design intent at the time of the edit, and the ability to make changes directly to the model without working indirectly through a series of sketches and dialog boxes. The main weakness of direct edit methods is that they cannot remember topology that has been removed from the model.
What do you notice about these strengths and weaknesses? That’s right: they line up. The weaknesses of one are the strengths of the other.
Now if you had to pick one method or the other, you’d be kind of up the creek, so to speak. But the lucky thing is that by using the two methods together, each method counterbalances the weaknesses of the other. This makes it easy to determine when to use which method. To avoid parent/child entanglements, use Synchronous. To avoid problems with topological changes, use history.
Here’s a practical example.
Prismatic/analytical model faces can be broken up into several types, as shown below.
Using faces with identifiable topological forms make it easy to edit and extend those faces. Complex faces cannot be extended because they are made from splines that are not predictable – the form of the spline can be any shape the user wants to make them, so the software is not able to predict what the user wants. The word “topology” means the type, number and connections between the faces in a model. A cube has 6 planar faces connected at linear edges. A sphere has a single spherical face. A cylinder has one cylindrical and two planar faces. These are all descriptions of topology.
Sometimes, an edit may remove a face from a model.
Notice that the boss on the left has a couple of fillets that cover over the planar and cylindrical faces of the original. The faces shown in the green image are removed from the gray image. This is where direct edit methods, including Synchronous Technology fall short. This demonstrates the problem, now let’s demonstrate the solution by bringing Synchronous Technology together with history-based modeling.
In this screenshot, you can see the Solid Edge Pathfinder, which is the equivalent of the Works FeatureManager. Notice there is a Synchronous section that lists the synchronous features, which to a Works user is going to just look like a selection of faces for each feature. And you also have an Ordered section of the tree. The Ordered section is really history-based in the same way that your SolidWorks FeatureManager is history-based. A Works user will think of the Synchronous section of the tree as an imported body, although it is more than that, we can work with that definition to get you rolling.
If any of the fillets were to totally consume any face, you would not be able to use Synchronous to make an edit and get the missing face back, as shown in the 3 images above, but if the fillets are ordered you can.
This is what I consider to be the best way to use the strengths of both Synchronous and Ordered modeling methods in a single Solid Edge model. The most common source of failures in Synchronous edits is fillets/rounds. So by making those Ordered features, you eliminate that weakness. The adaptability of fillets is a strength of history-based modeling. So for this part, you can edit the overall prismatic part using Synchronous/direct methods, and you edit the fillets using history/ordered methods.