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What is the Best Way to Use Synchronous Technology


Picture1.pngWith this blog post, I’m really aiming at three audiences: 1) long-time Solid Edge users who are comfortable with traditional history-based modeling and haven’t yet incorporated Synchronous methods, 2) users of other history-based software who are curious about what life can be like without dependence on history, and 3) 2D users who are trying to make the switch to 3D.


It seems to me that the 2D crowd will be the people who warm up to Synchronous the fastest. It has been a long time since I was a 2D-only CAD guy, but the way you make changes in a 2D drafting tool are very similar to how you make changes in ST. You change dimensions, drag lines around, or snap one item to another. In 2D, you have to select which lines get moved, and that selection becomes your “design intent”. You can lock down certain lines, and allow others to move.


In 2D drafting, there is no such concept as dependency based on order of creation. If you remember back to when you learned how to manage history-based modeling, this concept took a while to warm up to. And now, with Synchronous Technology, you’re going to have to take some time to un-learn what is a fairly un-natural way of working.


First of all, what actually IS Synchronous Technology?  Here’s the definition that I use for myself: Synchronous Technology is the ability to decide design intent at the time of the change using dimensions and relations directly connected to the 3D model, along with automatic rules without the burden of history-based parent-child relationships. I’m sure we can improve on that compact definition, but it’s a start. Don’t let anyone tell you Synchronous Technology is not parametric. The use of dimensions and relations is the same as other parametric systems.


For those of you who have already seen ST, when you think of Synchronous Technology, what comes to mind? Steering Wheel? Live Rules?


If you have tried Synchronous and thought it seemed intimidating or confusing, there are probably two things going on. The first thing is understanding just what ST is, which is why I wrote the compact definition above. The second thing is that you might be starting at the wrong end of Synchronous. The Steering Wheel is the most obvious poster child for Synchronous Technology, and with the Steering Wheel comes Live Rules. Live Rules are very powerful, but probably a more advanced technique than what you should start out using.



In my opinion, the best way to start with Synchronous is dimensions. This is fun to demonstrate, and shows some stuff you can’t do easily with history-based systems.


dim1.PNGThe dimension shown here was just placed on the edge of the solid model. The dimension arrows show an arrow on one end and a dot on the other end. This means that when the dimension changes, the side with the arrow is going to move, the dot is going to stay where it is. This is design intent at the dimension level. You don’t have to set up sketch relations or use the part origin, you just look at the arrows. The dialog box where you change the dimension also has arrows. Left, right, and both directions. These arrows in the dialog allow you to change the arrows on the dimension itself. So this allows you to change the design intent at the time when you make the change. It’s SOOoo much easier than making a sketch with dim2.PNGconstruction geometry and a bunch of unrelated sketch relations to create a rectangle that changes symmetrically. The lock symbol allows you to change the dimension from driving to driven in a single click.


You can also make changes like the one shown here, where the overall dimension (97.96) is changed to a stacked dimension (35.3) by selecting the dimension line (the one with the arrow), then Alt-dragging the red dot on the extension line to the new dim3.PNGedge. You can do all of this without getting into and out of sketches or features. The dimensions are connected directly to the geometry.


I think dimensions are the easiest way to control design intent in Solid Edge.


Face Relations

The next level up, in my opinion, is Face Relations. If you need more control than simple dimensions can give you, then I recommend graduating up to applying relations between faces. If you’re coming from another system like SolidWorks, applying Face Relations to the model is like applying sketch relations between sketch entities in a sketch. Except that it’s more direct – you’re directly taking control of the geometry of the part, rather than indirectly controlling the part by controlling a facerelate.PNGsketch. Fewer layers of nonsense, in my way of looking at it.


Face Relations can be a one-time thing, or persistent. For example, you may want to make sure that two cylindrical bosses remain concentric, so you apply the Concentric relation and make it persistent so that the bosses remain concentric through other changes. But then at some point, the design changes, and one of the bosses has to be made off-center. Just remove the Concentric relation, and now you can move one boss off center.


Live Rules

Once you have a good grasp on Face Relations, the next step is Live Rules. And I recommend that you start with all the rules turned off, rather than all the rules turned on, the way it works by default. Live Rules is just automatic Face Relations that work with a set of rules. You can turn the rules on or off as you work. For example, using the previous example, if you have the Live Rule called Concentric turned on, any change that moves one item that is concentric with something else will also move whatever it is concentric with. Turn off the rule, and you can move the items independently. If you have several concentric things and only want to break the relation with one of them, turn off the rule, and apply face relations where you need them.



I think people trying out Synchronous Technology try to use the Live Rules first thing, because it’s sexy, and it’s what happens when you tug on the Steering Wheel, which people also want to try out. Maybe we at Solid Edge need to change our approach to stop throwing new users into the deep end right away. I know the whole system made a lot more sense to me when I started from dimensions, worked up to Face Relations, and then approached Live Rules when I had some experience


With every release, the Live Rules scenarios get better and better. And I think the user community’s understanding of the philosophy of Live Rules keeps improving as well.


So if you’ve tried it, and something didn’t make sense, or you haven’t tried it because you think history is “good enough”, I’d encourage you to try the Synchronous side of things again, using a new approach, with Dimensions first, then Face Relations, and then Live Rules.

Valued Contributor
Hi Matt, Another thing I have found that helps someone coming from a strictly history based background is that you can work with just dimensions and turn off live rules until you begin to figure your way around. just as you applied dimensions to drive sketches in History based scenarios you can do so in ST. And with dimensions applied to the shape itself these can be used to drive the solid. Biggest problem seems to be learning to check what has been locked down and what should be locked down when to allow for edits that will only effect what you want effected. It seeems to make more sense to a lot of them until they can get their minds wrapped around the idea of working with faces and live rules.

This blog entry should be mandatory reading for everyone new to Solid Edge.


I came from SolidWorks, and was used to sketch based geometry cascading to the 3d model. It's easy to understand and is very rigid.


I was very upset with how fluid SE models seemed. I'd set a dimension and then all of a sudden, WHOA WATCH IT GO! ...where I don't want it to go.


Now I realize that with simple steps, this fluidity is extremely powerful and makes SE an incredible tool.


I'm glad I saw this post, it helped me get over a lot of my basic frustrations with SE.




Thanks, I'm glad to hear that another "SW refugee" found this helpful.






Yeah, turning off the Live Rules helps you learn, I think.


Now that I've opened this can of worms, I'm going to have to write something about Live Rules...

PLM World Member Genius



Once you get more familiar with the system, you will realize you can use four modeling method.


Pure synch

Pure Traditional (feature modeling)

Trad + Synch skeleton (SW appoach)

Trad + ordered skeleton (SW approach)


If you want to try something, start in synch, draw a rectangle any where on any of the three base plane, switch to ordered and create a feature using existing sketch....




Have fun


As a long time user of Solid Edge (previously I-DEAS) I have to confess that I have not got to grips with Synchronous modelling.  I think that Matt's blog post is helpful in that it gives some insight into the philosophy of synchronous modelling.  I feel that an overview of the philosophy of Synchronous Technology would be very useful.  I would personally find helpful further insight into how Synchronous Technology is intended to work.  I have some specific questions:


  1. Do relationships applied to 2D sketches still have a role in Synchronous modelling?  Or is rigour at this stage no longer required to give predictable edits?
  2. Face Relations can be applied manually to a part. e.g. Parallel makes the selected faces parallel.  With given Live Rules switched ON are the corresponding Face Relations applied automatically based on the underlying 2D relationships or on its reading of existing face orientations? 
  3. Matt recommends starting with all the Live Rules switched OFF.  The Live Rules can each be toggled OFF individually and there is also a Suspend Live Rules switch to suspend all live rules.  What is the difference and which was Matt referring to?
  4. When one applies a persistent Face Relation to two faces, is there any visual indication that it has been applied?  
  5. Matt stated, "Live Rules is just automatic Face Relations that work with a set of rules."  Do Live Rules automatically create Face Relations or do they make Face Relations work?

That's enough for now!


Thanks in anticipation of answers.



Gears Esteemed Contributor


1.  2D relationships have no role in the net 3D solid.

2. Live Rules analyze the faces anytime you modify the solid and dynamically apply relationships for the given modification.

3.  Suspend Live Rules turns them all off.  The ability to suspend individual items is to allow you to tailor the modification you want to make.

4. Not 100% on this but believe only if you use the relationship assistant and right click on the face to list it's relationships.

5.  Live Rules are the automatic dynamic relationships that are found on each edit.  Face Relationships are persistent and do not rely on Live Rules.




1. While the sketch relations don't get added to the 3D model, the sketch dimensions do. This is pretty cool, once you get used to the idea of essentially discarding the sketch.


3. I was recommending using Suspend Live Rules. When I get more into this later on, I'll be more detailed about this. It's probably best to use some live rules, but without really getting into it, it's easiest for now just to turn them all off.


9-11-2013 8-55-30 PM.png4. Persistent face relations are kept in the Pathfinder. You can click on them and they highlight, but there is no symbol on face pairs that are related. It would complicate the display if all the persistent face relations showed up at the same time. Viewing the highlighted faces pair by pair seems to work pretty well for me.


5. Live Rules just make temporary relations that the user never sees. The temporary relationships are part of the beauty of Synchronous - you are never saddled with design intent that you don't need/want.