DXF Made Easy

Preparing a DXF File from AutoCad

When creating a DXF file for use by a Macintosh user, it must be prepared somewhat differently than if it were for another PC user. There are a few major differences which must be kept in mind. First, Mac programs do not understand the concept of Paper Space. Second, the majority of Mac programs do not read attribute information attached to blocks. As with the Mac to PC translation process, it is always best to keep things as simple as possible.

PAPER SPACE

If you give a paper space DXF file to a Macintosh user, odds are that the program they are using will not recognize paper space, and will import the drawing with the paper space entities at the same scale as the model space entities.
Convert your drawing to an all model space drawing prior to exporting for best results. While in paper space, create a block with the "BLOCK" command. Call it something easy to remember, and give it an insertion point which you can readily find on the model space drawing. Toggle your tilemode with the "TILEMODE" command to 1. You may then need to zoom extents to see your model. Then insert the block containing all the paper space entities at the model space scale. You now have a model space drawing which should contain all your paper space entities.

ATTRIBUTES AND BLOCKS

Exploding blocks will give a better translation.
Unfortunately, b locks which have attribute information attached will return to their default values when exploded. The DXF (actually named DXX) files created with the ATTEXT (attribute extract) command are unreadable on any Macintosh Cad programs I have seen thus far.
Several lisp routines, for instance, MEX (available on-line), written by Steve Johnson of the Water Authority of Western Australia, or A2T can explode blocks and replace attributes to their proper text entity values. I have used MEX quite a lot, and found it highly helpful in creating a good DXF file.
Attribute definitions which are not bound to a block will not DXF out. The default value will be assumed, or they will be left blank.
Nested blocks will have a tendency to import at the wrong angle of insertion in MiniCad.
The long and short of it is that if you want your information to come across correctly, you need to explode the blocks.

XREFS

XREFS are not properly exported unless they are bound into the drawing. To bind them all, the command is XREF, press B for Bind when prompted, and * when asked to select objects. The MEX lisp routine mentioned earlier also does this automatically.

ZOOM EXTENTS PLEASE

One of the trickiest aspects of file transfer is making sure that the scale is right, and the way that the Macintosh Cad environment handles scale is slightly different than AutoCad does. Having objects outside the drawing area will make this difficult. If you Zoom Extents and delete any objects outside the normal drawing area, things will translate smoother.

SCALE BARS OR DIMENSIONS

You should be aware that the Macintosh does not draw all things at 1:1 scale like AutoCad does. Therefore, scaling the drawing becomes critical. To facilitate this, make sure that there are dimensions or a scale bar on your drawing so that the scale can be verified.

Importing a DXF file from MiniCad into AutoCad

On the whole, MiniCad writes a fairly clean DXF file. Problems which occur can be attributed to one of several things; naming conventions as noted elsewhere in this article, non-standard drawing prototype, or random program errors. The random program errors are rare.

NAMING ERRORS

The most common are duplicate block definitions, and undefined linetypes. To solve the duplicate block definitions, either edit the DXF file with a text editor and rename the blocks, or ask for a new DXF file with the symbols given more unique names. Undefined linetypes are easier, make note of the linetype name, and create a dummy linetype prior to DXFINing the file.

PROTOTYPE

Several third party products change the prototype ACAD.DWG. These can make it impossible to import a DXF file. In release 12 of AutoCad, you can specify in the dialog box to use the default prototype. In previous releases, if you create a new drawing and give it a filename which ends in an equal sign, it will use a factory default prototype. For example, create a new drawing, call it IMPORT= and you will have a clean slate to import your DXF file into.

RANDOM ERRORS

MiniCad allows you to create text strings of over 256 characters. When these long strings are DXFed, they create an unreadable DXF file. Sometimes people use control characters in their text blocks. These both create "premature end of file" errors in AutoCad.
You can get improper table name errors sometimes if the MiniCad operator exported classes as layers. The problem is that the layer name was not defined. Have the MiniCad operator create a new file, re-import their DXF file, and re-export it. This will solve the problem.
If there is any text which has been scaled on the drawing to a small size (under 1 point) the DXF file will be written so that the size is INF, and will not import. You can either tell the MiniCad operator to hunt down his small text, or go into the DXF file with a word processor and change the word INF to a number such as 12.
If all the information is not visible, it may be that the layer has not been mapped to a correct color. Go into the layers dialog, and assign it a color and it will show up.
If the file was sent as a ZIP file, and does not wish to extract, there is a good chance that it was created with MacBinary turned on. Tell the MiniCad operator to turn off MacBinary in his preferences in his Zipping program.