extrenal references - please help me understand

In my continuous mission to explore far galaxies, I stumbled on the top-down
assembly construction method explanation on the sw2006 help documentation.
so please correct me if I'm wrong:
"external references on parts can be created only in the top-down modeling
technique by referencing a new feature or sketch in a new part to an
old/already-existing one which is open simultaneously on the same assembly
(part modeling within assembly modeling)."
is this statement true or false?
please help me remove the dust in front of my eyes!
thanks,
Gil
Reply to
Gil Alsberg
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Forget what they wrote and say to yourself, "Well, duh, how else would one do it?!".
If one part has entities that are constrained to another part, where would these constraints be made? In an assembly, of course. You can not convert (another part's) edges in a sketch or extrude to (another part's) surface or plane unless the two parts are residing in the same assembly.
As far as the new part-old part thing, basically SW is trying to tell you that if part "A" references part "B", then you shouldn't also have part "B" reference part "A".
Reply to
That70sTick
sorry, but I still don't understand:
is it possible to reference a part in an assembly externally using regular assembling by entering existing parts? (traditional bottom-up assembling) or is it only possible when creating a new part inside an assembly which already has at least one part? (top-down assembling)
Reply to
Gil Alsberg
Of course, after placing the previously made parts in the assy, you can then make external references to them from other parts in the assy.
Reply to
JEB Davis
The statement is false, but contains some truth. It is false insofar as external references on parts can be created through splitting a part, deriving a part or mirroring a part as well as through an assembly. If the context of the statement was within assemblies then it is true.
Thinking back to the days of tracing paper, an external reference is like making a drawing of a part by placing tracing paper over the layout and getting key features through the tracing paper. The part getting external references can be an existing part or a new part. See the post a day or so ago about removing external references.
Reply to
TOP
Forget "top-donw" and "bottom-up". An external reference is simply when a feature or sketch in one part is dependent on an entity in another part. In nearly all cases, this dependence happens in an assembly, with one component referencing another.
Reply to
That70sTick
thanks, TOP, that clarifies allot. good point on part splitting/mirroring.
Reply to
Gil Alsberg
Jeb, thank you for your reply. it helps me get a better picture on this subject which I'm awfully unfamiliar with.
Reply to
Gil Alsberg
let me rephrase: how do one create external references within bottom-up assembly? (I know how to do it on top-down but not on bottom-up)
thanks, Gil
Reply to
Gil Alsberg
Any part mated in an assembly can have external references created WRT other parts in the assembly. In fact when a part is created in an assembly a special inplace mate is created to hold it still while references are made. So for example, when doing bottom up modeling, mate a piece of "precut" sheet metal into an assembly. Locate some matching holes and cut them while editing the part in the assembly. Then open the part outside the assembly and remove references and create dimensions automagically.
Reply to
TOP
Please check the SW help file under.
Searching for Referenced Documents
This helped me a lot.
Kind regards,
Jan Jurjen
T> Any part mated in an assembly can have external references created WRT
Reply to
JJ

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