SolidWorks 2011 Assemblies Bible - Matt Lombard [104]
When one part drives another part in this way, the assembly must also be open to drive the relationship. If just the two parts are open individually, then changing the driving part does not update the driven part; because the relationship was created in the context of the assembly, the assembly must also be open to facilitate the change.
Cross-Reference
Chapter 10 offers more in-depth information on general in-context situations and external references.
Renaming documents referenced by equations
Equations update with new part names regardless of how the parts are renamed. Names of subassemblies also update when assembly files are renamed. This includes renaming a document using the Save As command, using SolidWorks Explorer, or using Windows Explorer. It also includes redirecting the assembly to the new part name, as well as renaming the assembly using each of these techniques. If the assembly can find the part and recognizes the part as the one that it is looking for, then the equation works.
Of the previously mentioned methods, SolidWorks Explorer is the most highly recommended. Save As methods can work properly if you use them in a disciplined way. Windows Explorer is never a recommended method for file management, at least not for name changing.
Caution
You may have unexpected results if a single dimension is controlled from more than one location. For example, if you have a part-level equation and an assembly-level equation, then one of the equations will be automatically set to Read Only and will not be used.
Sharing equations
In addition to the use of equations in an assembly, you can also share equations between parts or assemblies using linked text files. This is a great method for when multiple parts need to use the same equation, and the equation may change frequently. You only need to change the equations in one place, and it updates for all linked documents. This method effectively links equations between parts without using an assembly at all.
When you share equations between parts, you have to make sure you have given the dimensions, sketches, and features the same name in both parts. To start sharing equations, first build an equation in a part, and then click the Export button in the Equations dialog box, as shown in Figure 12.2.
FIGURE 12.2
To share an equation between two parts, you must first export the equation.
The Equation Export dialog box enables you to select which equation(s) you would like to export, by using the Active column check boxes. When you click the Save button, the equations are saved to an external text file. To link the current file to the external file, make sure the Link To File option at the bottom of the Equation Export dialog box is selected.
When a part is linked to an external equation text file, you are not able to edit the equations in the Equations dialog box. You can add more equations, and you can use the new equations either linked or unlinked. The linked equation file is listed at the bottom of the Equations dialog box, but there is no link to access the text file. You have to browse to the file and open it manually.
If you want to change the equation, you must do this in the external text file. To update the equation in the part file, just close and reopen the Equations dialog box, and the equation edits appear updated.
Note
You cannot use external equation files to share link values or global variables.
To share equations saved out from another part, again open the Equations dialog box, but this time click the Import button, and browse to the location where you saved the exported text equation file. When equations are imported and linked, you cannot edit them in the Equations dialog box, only in the external