Live Rules Primer

The Live Rules panel in Solid Edge ST4. Yellow indicates the active rules for the current selection.

One of the main components behind Synchronous Technology is Live Rules. Live Rules, from my understanding, is a couple of things:

  1. It works like sketch relations in SW, except that it is applied to the faces and edges of 3D geometry
  2. it is applied automatically and on the fly by default, instead of ahead of time. This is what allows Solid Edge to change design intent so quickly, without extensive redesign.
  3. It uses some concepts from feature recognition. So it can recognize faces as fillets, and uses special rules to deal with them. It recognizes things like faces coincident to the base planes, perpendicularity, coplanar edges, patterns

And the thing is that to a SW user, SE can do all of this on “dumb” geometry. In SW, the intelligence is built into the part file. In Solid Edge, the intelligence exists in the software. Solid Edge does allow you to create “persistent” relations, for example a relation that may not be automatically assigned by Live Rules can be manually assigned, and will persist until you delete it or suppress it.

This may not be something that you will just “get” immediately, although the concept is intuitive. Sometimes I think SW users have been brainwashed. I know that in writing books and doing training for years, I’ve been a part of that brainwashing. But now I’m seeing that so much of the “best practice dogma” that we so rigidly cling to is completely unnecessary. Solid Edge users do not get all uptight about relating parts to the origin, or about fully defining sketches. Why is that? Because your part is not going to change on its own. In SW, your part has the potential to change every time there is a Rebuild, because the intelligence is in the part. There is no such concept as “rebuild” in Solid Edge (except when working with ordered features). It doesn’t need it. If the parts themselves are “dumb”, they can’t change on their own or due to some change in the software. What do you do in SW if you are desperate, and really don’t want something to change? Translate it out and reimport, to remove the intelligence from the part – make it “dumb”. How much better would you sleep at night knowing that your parts and assemblies wouldn’t just decide to automatically change the next time you opened SW?

Anyway, here is a little video with a really quick demo of live rules. After my homemade demo is another video put up by Solid Edge showing more involved Live Rules options and scenarios.


Add a Comment
  1. Wow, a breath of fresh air over here, especially after the comments by Andy from CATIA on the Designstuff blog.

    Solid Edge looks great, thanks for the posting.

    Devon Sowell

  2. Hi Matt,

    Here is a video about the brain of the ST4. This is funny, but useful! :-)



  3. Here are some answers to the question about the functions I didn’t understand:

    1. nice functionality shown on that video

  4. Matt the Live Rules is interesting, But i think what your readers will probably like to see is the

    Rigid  command

    Makes all faces in the select set rigid with respect to each other. For example, when you apply a rigid relationship between two faces, the two faces maintain the same spatial orientation if either face moves or rotates.

    Ground Command

    Grounds the seed face in model space. Grounded faces cannot move or rotate outside of their current position in space, but they can resize. For example, if you ground a planar face, then move an adjacent face later, the grounded face maintains it position, but can be made larger or smaller when you move the adjacent face. If more than one face is in the select set, all the faces are grounded.

    Use correctly it will give the freeze feature SW users are waiting :-). or freeze the design intent for an area while you play with the rest of the model

    For the detach faces, once faces are detach, use the contextual menu to attach the face back to the model.


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