Something missing?

This may be another one of those "How do I approacht this?" issues.
In doing some assembly work with SW one thing that irritated me was just how
easy it is to break mates when editing parts. It would be quite useful to
have the ability to have more absolute mate references (or truly smart
ones).
One example of this is a part that you'd want to mate with another by always
using the highest surface in the Y direction. I don't think that there's a
way to embed this kind of intelligence into parts at the moment. Having
this degree of intelligence would allow you to edit and experiment with a
part and not destroy a million mates in an assembly.
I haven't looked into the internals of Mates, however, on a superficial
first-inspection they seem to be tied to the names of features, edges,
points or planes rather than the feature itself. There seems to be little
intelligence. Which means that, if you were to model exactly the same part
without a single geometric difference except for the modeling sequence, a
"Replace Component" would result in lots of errors.
It is far too easy to blow-up a complex assembly by making an innocent
change in a part. The more I use it the more I understand why in-context
relations and features regarded as problems. The sad part is that such
abilities as defining in-context geometry is one of the big reasons many of
use have looked towards the use of programs such as SW.
-Martin
Reply to
Martin
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Martin,
You are absolutely correct, creating in context relationships between parts is easy, too easy. It takes a fair bit of experience and forthought to make parts and assemblies that work well and retain in context relationships but IT CAN BE DONE, and too good effect There is a defnite heirachy of suitable mating geometry. Model vertices are the least desirable geometry for mating, followed by model edged, then faces, the reason being is that these geometry types are easily deleted or supressed. Adding a fillet to a part can "delete" several vertices / faces in the context of an assembly. Using planes or axis as primary mating picks can help however planes and or axis that rely on other model geometry for their existence are just as vulnerable.
Layout assemblies or "Skeleton" parts /
assemblies can be used to great effect when doing this kind of modelling, Greg Jankowski of SolidWorks has an excellent presentation covering this topic, your VAR should be able to provide you with this.
Mates are specific to the assembly in which they are created, if you replace one part with another in an assembly then the mates will inevitably be broken, however SolidWorks does a great job of helping you fix the "dangling" mates with a fairly simple UI.
Reply to
Wry&Dry
Look into Ed Eaton's Trees of Blood presentation which can be found elsewhere on the newsgroup.
Mart> This may be another one of those "How do I approacht this?" issues. >
Reply to
P.
"One example of this is a part that you'd want to mate with another by always using the highest surface in the Y direction. I don't think that there's a way to embed this kind of intelligence into parts at the moment. Having this degree of intelligence would allow you to edit and experiment with a part and not destroy a million mates in an assembly"
For this specific example you could try: -extruding a body from the xz plane "through all" in the desired y direction without "merge results" checked. Maintain this as your last feature by re-ordering as required. -mate to the surface of this place-holding part, then hide it -prior to sw2004 or if otherwise desired, the same could be accomplished with surface bodies
This would only work well if both mating entities were planer. If there were not, the same general process could be used with reference geometry like planes and sketches with pierce-points, but the exact method would have to be examined on a case-by-case basis.
Reply to
Brian
IIRC, "through all" extrudes to the internally defined bounding box, which is not precisely the furthest extent of the model. Anyhow, it's limited to the 6 basic dierections.
I think a macro feature would be necessary to get this precisely. There is a macro for obtaining a precise position of a models extents in a given direction. That macro could be rolled into a macro feature.
Without that, I think the user is stuck manually maintaining the mate plane's definition according to the furthest entity in the desired direction.
Reply to
Dale Dunn
Dale Dunn wrote in news:Xns961961E9C3064daledunnatjamestoolc@65.24.7.50:
Scratch that. It does work, and pretty well at that. This could be adapted into a pretty decent library feature for extracting finished stock size (which we just gave up on maintaining).
Reply to
Dale Dunn

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