Traditional Versus Synchronous

There continues to be a lot of discussion on merits of history free (Synchronous technology for Siemens PLM products) versus traditional history based modeling. There are many points at which you can make comparisons. The other day Doug Stainbrook put together an example that I thought would be interesting to share with you. It is done in Solid Edge but I think the same ideas would apply for other CAD systems as well. Here is what Doug said:

I want to share with you a very simple example of a Traditional vs. Synchronous Technology edit scenario that shows how powerful Synchronous Technology is and how it gives you the answer you expect without a lot of work.

I modeled this original part in Traditional Solid Edge. The edit scenario is that we want to simply change the angle of this very simple lever arm by modifying the angle dimension in the driving sketch.


The point to make here is that in a sketch driven system, the user has to be very careful about how the sketch is constrained and dimensioned in order to get the desired results. As I began to scroll the angle dimension, I could quickly see that my sketch elements were not constrained properly and found myself in a real mess.

Depending upon how many times the user scrolls the mouse to change the value, it is very easy to get this sketch to a point where they can’t even use UNDO to get back to the original profile. At this point the user typically closes the model file to start over.



When using Synchronous Technology, it does not matter how the part was created with a sketch. In fact, this part could have been imported from another CAD system and we could still modify this part exactly the same way, as we expected to. In this case I converted the traditional part to a synchronous part.



I then simply added the PMI dimension to the angle and modified its value. The Live Rules took effect, keeping the rest of the geometry in the correct relative position. “Now THIS is the answer I was expecting!”


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This article first appeared on the Siemens Digital Industries Software blog at