Equations and external relations leading to out of date light weight?

I have noticed that when I open a top level assembly most of the components are out of date light weight and I know that I have not made changes to those items. I have started thinking that possibly this being caused by how we are using equations and external references.

Here is a typical scenerio, we have an assembly that goes four levels deep (assy A contains assy B, B contains assy C and assy C contains multiple instances of part D). Assembly B contains planes that are defined in context of assy A. Assembly C contains planes that are defined in context of assy B (the planes in C are 0" offset from the planes in B, which in turn are defined by being 0" offset from some entity in assy A). Assembly C has a 3dsketch that has entities related to these planes and some driven dimensions. Those diven dimensions are then in turn used in some equations, the results of the equations are used to drive other dimensions to locate the components in assy C. So my theory is that since the equations are dependent on these planes and the planes have external relations I think that sw thinks the document is in a constant state of needing to be rebuilt.

Does anyone have any experience with this type of scenerio? Someone had suggested that I just set my option for out of date lightweight components to Don't Check but I think that is just a cover up for this problem, the problem is still there but I just dont know it.

Thanks, Sam

I'm no expert on external references, but we do see similar things happening on our assemblies. We also think that the problem lies in our use of in-context features.

It seems like you should be using a "skeleton" or "master" part to establish your references. Make a part that has the necessary planes and possibly your

3D sketch. Put an instance of that part in each of your assemblies where you need it, then use it and your equations to drive the placement of the components. Now you just have external relations to the skeleton part, not to multiple layers of assemblies. This might get rid of your out of date parts. (It seems like SW doesn't burrow down into the layers when it rebuilds, but just goes one layer deep, leaving the deeper relations "out of date".)

Jerry Steiger Tripod Data Systems "take the garbage out, dear"