By Dennis Collin
External reference files seem to give AutoCAD users all kinds of issues when issuing files to clients. They are frequently used on larger files as they can enable multiple users to work on multiple sections of the project at once and due to the nature of Xrefs, changes in referenced files apply to the main container file. Therein lies the problem as External references (Xrefs) are not part of the drawing. Rather, they are links to an externally referenced file. To provide a copy of a drawing containing external references to someone else, you must also provide all the external reference files. In addition, the person receiving the drawings must either re-create the same paths you used when linking the external references, or change the paths for the external references so that these reference files can be found.
To mitigate path issues, relative pathing can be used, however even if doing this the recipient will require all the files, both the container drawing and all its references to see the complete picture and avoid the error messages and dialogues shown above.
Since an AutoCAD project that uses Xref attachments contains many files, it is practical to embed all the Xrefs into the container drawings, reducing the number of files to send, and reducing the risk of files being omitted from transmittal or not being displayed correctly.
The embedding process is referred to as Binding Xrefs. The bind process comes in two forms, Bind>Bind and Bind>Insert.
Bind, embeds the external reference and creates a unique name for each named entity, such as a layer or block, that is located within the external reference. For example, a layer named HVAC in the external reference will be named Xref$0$HVAC in the current drawing. If the current drawing already has a layer or block with the same name, the name is changed incrementally, for example, Xref$1$HVAC. The bind option should be strongly considered when working with blocks, due to the fact blocks work with names and potentially can change their appearance when being redefined to the incumbent block style i.e. a double door block called door may change to a single door appearance if the resident block name is also door.
Insert, embeds the external reference but does not change the names of any named entities in the external reference. For example, a layer named HVAC in the external reference will have the same name, HVAC, in the current drawing. If the current drawing has a layer or block with the same name, the named entity in the external reference takes on the properties of the named entity within the current drawing. The advantage of insert option is that it reduces the number of layer and style names, but there is a risk of blocks being redefined and changing appearance if the block names are the same.
The Bind command can be accessed in several ways, but typically can be accessed through the reference mangers right -click menu. When bind the Xref the element is converted to a block, embedding it within the container file. The difference between using the bind or insert option can be seen below. If in doubt use the Bind/Bind option to ensure display fidelity!
It should be noted that not all reference files can be bound, for elements like Point clouds and images these files will have to be included manually in the transmittal. If there are many files, users should consider the Etransmit function which bundles all relevant files into a convenient transmittable package. This process will be covered in future post.