Using and Modifying External References in AutoCAD
Jaiprakash Pandey posted on June 17, 2016 |

In AutoCAD, you can import drawings in a way that keeps imported drawings independent of current drawings. This type of file is called an external reference or Xref. The Xref file does not become part of a drawing database and it is loaded simultaneously with other drawings in which it is imported.

You can import not only DWG, but also image, DGN, point cloud and PDF files as Xref. Since an Xref does not become part of drawing database, it helps in keeping the file size of the current drawing small as well.


Inserting an Xref in aDrawing

To insert an Xref in a drawing, go to the Reference panel of the Insert tab and click on the Attach icon—you can also use its command equivalent, ATTACH. After clicking the Attach icon, the Select Reference File window will appear.

Locate your reference file in the local or network drive and click on the Open button. A new Attach External Reference window will appear with a preview of your Xref in the Preview panel. If you want to select an external reference file and all its nested files, then select Attachment from the Reference Type panel. If you want to ignore the nested files of the selected Xref, then select the Overlay radio button as shown in Figure 1 below.

Figure 1. Attach External Reference window.
Figure 1. Attach External Reference window.
Keep other default settings selected in this window and click on OK. Click on a point in the drawing area to specify a base and the Xref will be loaded in the current drawing. In this case, I am attaching a DWG file in a completely blank drawing as an Xref. Xrefs and blocks can’t have the same name in a drawing, so make sure you rename any conflicting Xrefs or blocks before attaching.

When the Xref file is attached, you will notice that its transparency is faded to 50 percent of its original value. This change is automatically applied to the attached Xrefs to distinguish them from other parts of the drawing. To change the amount of fading applied to Xref, expand the Reference panel on the Insert tab and change the value in the Xref fading slider.

In a drawing with an Xref, you will also see an Xref icon on the lower right side of the status bar. This icon can be used to identify drawings containing Xrefs and it can also be used to open the External References palette.

 

Modifying External References

An attached Xref remains independent of the currently open drawing; to modify an Xref, you can directly open an attached drawing and make changes in it. Once you are done with the changes, save your drawing. On saving the attachment drawing, a balloon will pop up in the current drawing, indicating a change has been made in the Xref file. You can click on the Reload link in the balloon to make changes to the Xref visible in the current drawing.

Figure 2. Reload Xref balloon.
Figure 2. Reload Xref balloon.
When modifying an Xref, it is not always necessary to open the reference drawing. You can also open an Xref in the open drawing in which it is attached. Click on the Xref that you want to modify and you will notice that a new External Reference tab will appear.Click on the Edit Reference In-Place icon on the Edit panel of the External Reference tab.

This will open the Reference Edit window, which will show a preview of the Xref  that you have selected for editing and a hierarchical tree containing a list of all nested Xrefs and blocks. Select your Xref file and click on OK to open the reference in the current session of the drawing.

Now the transparency of the drawing will change to the normal value, indicating that the reference drawing is open in the current session of AutoCAD. Make the required modifications in the drawing and click on the Save Changes icon of the Edit Reference panel on the External Reference tab.

To open the Xref file in another AutoCAD window, select it from the drawing area and click on the Open Reference icon on the Edit panel of the External Reference tab.

Figure 3. External Reference tab.
Figure 3. External Reference tab.
This will open the Xref in a new window, in which you can directly modify the Xref drawing. Once you have made all changes, save the Xref drawing and close it. You will see a balloon in the open drawing letting you know that an Xref file has changed. Reload it to make changes visible in the open drawing as well.

 

Importing Named Objects from Xref

Design Center and Content Explorer are great tools for importing named entities from a drawing, but by using the XBIND command, you can directly import named objects like blocks and line types from an attached Xref.

Let’s assume that we want to import a block from an attached Xref in our drawing—for that, type “XBIND” and press Enter. The Xbind window will appear with the name of all the attached Xrefs in the left panel. Click on the“+” icon next to the Xref from which you want to import the block. The drawing tree will expand, listing all of the named objects under the drawing name.

Click on the “+” icon next to Block—this will reveal all of the blocks contained in the drawing. Select the required block from this tree and click on the Add button. The block will be added to the right panel of the Xbind window. Select more blocks or named objects from the left panel in a similar way and click on OK when your selections are complete.

Figure 4. Xbind window.
Figure 4. Xbind window.
All blocks and named objects will now be added to the drawing as well.

 

Organizing Xref with Clipping

Clipping an Xref will help you organize drawings on a sheet more efficiently by hiding unnecessary parts and details.

Let’s assume that we want to clip an Xref in such a way that only a portion of the drawing remains visible. For that, you can select the Clip option from the Reference panel of the Insert tab or you can also use its command equivalent, CLIP.

After invoking the clip command, select the Xref that you want to clip from the drawing area. Your cursor will change into a point selection cursor and the command line will prompt you to make a clipping boundary.

Press Enter and select Polygonal from the command line as shown in Figure 5 below. Now create a polygon around the Xref and press Enter when you are done making the clipping boundary.

Figure 5. Polygonal option in the CLIP command.
Figure 5. Polygonal option in the CLIP command.
In order to avoid selection of unnecessary snap points in the clipping boundary, you can turn off OSANP by pressing the F3 key.

The clipped geometry will become visible in the drawing area and the remaining portion of the Xref will hide from view. In many cases, you may need to reverse the order of clipping. For example, if you want to hide the Xref drawing inside the boundary and want to keep part of the Xref outside the boundary, then select the Xref clipping boundary and click on the Invert X-clip boundary grip as shown in Figure 6. This will reverse the direction of the Xref clipping.

Figure 6. Clipped Xref with Invert X-clip grip highlighted in red circle.
Figure 6. Clipped Xref with Invert X-clip grip highlighted in red circle.
If you also want to hide the clip frame, then type “FRAME” and change the value of this system variable to 0. To completely remove clipping from the Xref, select the clipping boundary or Xref and click on the Remove Clipping option on the Clipping panel of the External Reference tab as shown in Figure 6 above.

 

External References Palette

Type “XREF”on the command line and press Enter to open the External References palette. This palette will contain a list of all attached Xrefs and enables you to attach more Xrefs. This palette can also be used to control many Xref settings, such as attaching an Xref as a block and deleting an Xref. When you select an Xref in this palette, its details, such as the saved path and file size, appear in the Details panel.

Figure 7. External References palette.
Figure 7. External References palette.
To attach an Xref as a block in a current drawing, right-click on the name of the Xref that you want to use, select Bind from the contextual menu and click on OK in the next prompt window. You will notice that the selected Xref will be removed from the list of Xrefs and it will be converted into a block with the same name.

In order to temporarily hide an Xref from the drawing, select Unload from the contextual menu of the External References palette. To make it visible again, select Reload. To delete an Xref completely from your drawing, select Detach from the contextual menu of the External References palette.

External references are very helpful in work-group projects where several people are working on different parts of a drawing and these drawings are attached in other files. In these situations, several files are updated simultaneously and the changes are instantly reflected in the main drawing by simply reloading all of the reference files. Xref also helps in keeping drawings organized and free of unnecessary details.

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