LESSON 4-7

LESSON 4-1		AUTOCAD TEMPLATE FILES
LESSON 4-2		USING OSNAPS IN AUTOCAD
LESSON 4-3		LINETYPES AND LINETYPE SCALE
LESSON 4-4		AUTOCAD FILE FORMATS
LESSON 4-5		GRIP EDITING
LESSON 4-6		AUTOCAD'S INQUIRY TOOLS
LESSON 4-7		XREF'S (EXTERNAL REFERENCES)
LESSON 4-8		SYSTEM VARIABLES
LESSON 4-9		TABLES
LESSON 4-10		INTRODUCTION TO SHEET SETS
LESSON 4-11		MODIFYING AND CREATING DIMENSIONS
LESSON 4-11a		TYPES OF DIMENSIONS
LESSON 4-12		INTRODUCTION TO CUSTOMIZING AUTOCAD

Topics covered in this Lesson:

Xrefs

An X-ref is an ‘external reference' to another AutoCAD drawing file. One file can reference many other files and display them as if they were one. These are used in larger projects for many reasons: They keep the file sizes down. They allow many users to work on individual components of a project. Every time an X-ref is loaded, it is the most recent version of the drawing. X-ref's can be updated, added, or unattached from the main drawing at any time. You can X-ref drawings that they themselves X-ref other drawings (nesting). In these days of networks and the Internet, many projects are produced this way. People from anywhere in the world can collaborate on a project in real time. The first thing to do is to ATTACHthe X-ref. This means that you are linking another drawing to your current one. Do this by starting theXFEF (XR) command. When you start the command, you will see the palette shown on the left. To attach an Xref,click on the "Attach DWG" button on the top left. (Note that you can also Xref Image files and DWF's) The "Select Reference File" window will open: select a file and press Open. When you do this, you will see another dialog box appear. Once you find the file, decide whether you want it to be an attachment or an overlay. An overlay will not include any of the nested X-ref's that the file may contain. Below that section are the insertion parameters. You have a choice of either defining them on-screen, or using standard defaults in the dialog box. Once you make you decisions, press OK. Finish the Attachment by following the prompts on the command. You'll see that it is similar to inserting a block. After inserting the Xref, you will see that the Xref Palette is updated with the new Xref. Now that you have an X-ref, there are more options for you if you right-click the filename of the Xref. ATTACH – Attaches another X-ref. DETATCH – Detaches the selected X-ref. RELOAD – Updates the selected X-ref - use this if the Xref was changed. UNLOAD – Removes the X-ref, but retains the reference for future use. BIND – Permanently attaches a loaded X-ref, so that it is part of the drawing. Working with X-ref's is usually quite straightforward, but there are some things to keep in mind. The insertion point is very important. Everyone on a project must be working on the same set of coordinates and insert points.. When you attach and X-ref, you insert that file's layers and blocks. AutoCAD creates new layer names based on the filename and layer name of the X-ref. In AutoCAD R14, you have a limit of 31 characters for these names. If you exceed that number, your X-ref will not load. When you print, AutoCAD will automatically reload the attached X-refs. If a file is moved from a location that AutoCAD expects to find it, you can browse for a new path, without having to re-attach the X-ref. Recent versions have added more functionality to Xrefs. You can edit them in the drawing (as opposed to having to open the original file). To do this, just select the Xref in the drawing and right-click. As you can see, there are other options to Open the Xref, Clip it (crop it down) or open the Xref Manager. One problem in the past was the if a co-worker changed an Xref that was attached to your drawing, you didn't know and could keep working on the wrong information. Later versions of AutoCAD alert you when an Xref in your drawing has been modified by someone else. Keep in mind that Xrefs are important and used in any major project. Practice working with them by attaching some of your previous drawings.