Equations and external relations leading to out of date light weight?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components are out of date light weight and I know that I have not made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suggested that I just set my option for out of date lightweight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 This might get rid of your out of date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rebuilds, but just goes one layer deep, leaving the deeper relations "out of
date".)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"