Generally speaking the preferred default option is to use overlays, because this prevents the possibility of having a reference loop, and is generally the more lightweight option. So which do you use? Well, like most things it depends what you're doing. So in the example above, if Outline.dwg were inserted as an overlay, it would not be shown when Model.dwg is XREFed into Drawing1.dwg. If Drawing1.dwg then XREFs Model.dwg in, Outline.dwg will also be shown as a part of Model.dwg.Ĭonversely, overlays allow you to insert as many XREFs as you want, but prevents them from being nested. For example, Model.dwg contains the XREF Outline.dwg as an attachment. If you insert an XREF as an attachment, this means that any other drawings that XREF the current drawing will also show the nested XREF as well. While both may appear to achieve the same thing, there is a subtle difference between them. XREFs can be inserted as two different types an attachment or an overlay. These should ALWAYS be an XREF, unless you actually want AutoCAD® to crash :-) Attachments vs Overlays While these are of course essential, avoid putting these directly into your drawings like the plague. Sometimes this is not practical, but mostly it is.Īlso, be careful of surveys and other mapping information such as Ordnance Survey maps. As such I try to keep individual drawings to below 5mb. I work under the premise that the bigger the drawing file size, the higher the chance that it'll crash my PC. This is a great way to add some structure to you drawings, and minimise any headaches you might face later with discrepancies between drawings.īreaking your modelspace down into smaller XREFs is also a great way to reduce file size. You can also logically separate aspects of the model so that each XREF has its own distinct purpose. Essentially, XREFs can become a kind of external modelspace for your drawings, saved in a central location. Put all the information in the one drawing and insert that XREF into all the drawings that require it. Ok, you can copy easily enough from one drawing to the other, but you have to remember to do that every single time you make any change to either drawing. Having multiple copies of the same thing is just a pain to deal with. XREFs should be used for content that could potentially be displayed on many drawings. Using the XATTACH command, you can invoke the command that would be used by clicking the DWG button on the XREF dialog. While the External References dialog can be convenient, for simply inserting an XREF you do not need to open this dialog. If this is the case you'll need to edit the path within the first XREF, and then refresh that XREF within the current drawing. In other words, it is an XREF within an XREF. This means that the drawing is actually an XREF within another drawing, and has not been directly referenced to this drawing. If you seem to be unable to edit this, it is likely that the reference you are trying to edit is a nested reference. You can update the XREF paths from here by overwriting the "found at" path, or by selecting the ellipsis (.) in this field and browsing to the drawing. Here is a good place to look to find any problems with your XREFs, such as XREF paths that might have changed. The External References dialog lists the currently loaded XREFs and displays details for each. The insertion point for the XREF will always use the coordinate 0,0 in the XREF as the base-point in a similar fashion to how blocks work. Click this button, and you will be prompted to select a DWG file to insert. In the top left there is a button for attaching a DWG file. This brings up the the External References dialog box. We can insert an XREF by simply entering XREF into the command line. If you want to edit the geometry of the XREF, you'll need to open the referenced file and edit that. The external file is inserted into the current drawing as a reference. No matter what the name, the concept is the same. Other names for XREFs include references, overlays, attachments and model files. As such, these are drawing files that are used as external references in our drawing. If it wasn't already obvious to you, XREF stands for external reference. Also I'll talk about some common pit-falls that often cause problems. In this article I am going to go through how to use XREFs and talk about some best practice tips to get the most out of your XREFs. However when used badly they can be a nightmare. XREFs can be an extremely helpful tool at your disposal when used well.
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