By Bill Fane

AutoCAD can both import and export drawing files from several brands of CAD software. However, there are a few things you need to consider about the compatibility of your files.

No translation is perfect, whether of computer file formats or of human languages. Neither of them have exact equivalencies for certain items or terms. The first test of any translation is to do a round trip out and back into the original format, and then look for the differences.

For example, legend has it that programmers did a round-trip test when they were writing the first human-language translators. What went in was “The spirit is willing but the flesh is weak.” What came back was “The booze is okay but the meat’s gone bad.” Even rolling an AutoCAD DWG file back to an earlier release can cause loss of things such as parametrics or 3D objects that didn’t exist in the earlier release.

You have probably guessed by now that AutoCAD isn’t the only CAD program on the market, nor is it even the only one that can process files with the DWG format. A number of programs, ranging from lower-cost to free, claim to be AutoCAD compatible.

Varying degrees of “compatible” exist, and compatibility isn’t necessarily a function of price. Degrees of compatibility range from AutoCAD object types that don’t exist in the compatible programs but can still be displayed to objects that can be damaged or destroyed by a round trip.

Examples of some of the varying degrees of compatibility include the following:

  • 3D: Other CAD programs may not be able to create or edit 3D solids and surfaces, may not be able to display them, and might even strip them out of an incoming DWG file.
  • Self-scaling annotations: Other CAD programs may not be able to create or edit self-scaling annotations or display more than the first scaled variant applied to an object. Some programs might strip out the other scales, so they don’t survive a round trip.
  • Parametrics: Other CAD programs may not support editing of parametric values. Some programs might strip out the parametrics so that they don’t survive a round trip.
  • Tables: Tables are basically spreadsheets that can be inserted into an AutoCAD drawing. They can then do such things as read values from AutoCAD objects or external Excel spreadsheets into individual cells and extract cell values out to linked Excel spreadsheets. Earlier releases of AutoCAD, and some other CAD programs, don’t support these features. At best, the tables will be translated into simple line elements and text objects that display the current cell value. Connectivity will be lost. At worst, the table may disappear entirely.

The bottom line is that you should conduct round-trip cycles on test files before committing hard data.