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Saturday, 21 March 2020

External Reference "Attachment vs. Overlay"



What is the difference when you use overlay and attachment methods?


While adding an external reference to a CAD file you're presented with two options, either keep it as an attachment or keep it as an overlay. I was very confused with what difference do the two options make when you just get the Xref as in the background of the drawing by selecting on either of them.

Attachment 

When you add a file as an external reference an attachment, you make it a permanent pair. Now, whenever you attach the file with file another file you'll be able to see what attachments are made to that file and would be able to toggle them on or off from the other file. Let me explain this with an example, suppose you have a file name 'A' to which you attach an external file 'B' and save it. Then if you attach 'B' it is to any other file (let's call it 'C' here) then 'A' will automatically be attached to 'C' but not as a direct attachment, if in any case, you detach 'B', the 'A' file will automatically be detached.
The good part here is that you can control what attachments you want to load/unload in a drawing and that makes it really good.

Overlay

It is similar to the attachment method with a difference such that here when I xref a file 'A' to drawing 'B', it'll make no difference to the attachment but when you attach 'B' to another file 'C' you won't be able to see the other xrefs and it'll be only 'B' that is attached to 'C'. This method is generally preferred by many professionals as it removes confusion in many cases and also keeps the drawing clean.

Still, I don't know much about the two methods, while working on drawings I generally prefer to have it in the attachment mode as it saves my time of searching for files. I generally attach all the drawings to a single drawing and then use it wherever I need it. While submitting the drawings to third parties I generally detach all xrefs to maintain the confidentiality of the project.

This method helps me in getting my work done, would be glad to learn your opinion on the use of xrefs in the drawings.

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