Drawing Interchange Format

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The Drawing Interchange File Format ( DXF ) is one of Autodesk specified file format for CAD - data exchange and was in the CAD program AutoCAD integrated. So from 1982 there were also AutoCAD versions for different operating systems (MacOS, MSDOS, etc.) and thus the requirement to exchange geometry data from AutoCAD between the different platforms. The data exchange format DXF was defined for this purpose.

The DXF format is described and openly documented by AutoDesk. Because of the well-documented, simple data structure, the DXF format is used almost exclusively for cross-program data exchange, even across different operating systems. Every CAD and CNC program of today masters the import and export of DXF, whereby DXF as an industrial standard forms the lowest common denominator of all CAD systems. All elements that are useful and implementable for technical drawings are supported in DXF.

term

The derivation of the designation DXF from “Data eXchange Format” is obvious and common, but incorrect. Autodesk founder John Walker said on September 18, 1982: "The file type of the Drawing Interchange File Format was changed from DIF to DXF so that some gonzo would not try to load a drawing into Visicalc ."

General

Many elements of technical drawings are supported in DXF.

DXF is dimensionless, so the recipient of a DXF file must know the unit used.

A DXF file is mainly divided into the four main parts head, tables, blocks and the geometric part of the drawing.

head

The head is used to define the basic properties:

  • Specifications about the associativity of dimensions
  • Attributes for dimensional chains
  • Settings for roundings
  • global parameters for hatches etc.
  • Pin assignments of the output devices
  • Position of the local and global coordinate systems

Tables

The table section contains information about the display of various elements such as colors, line widths, etc., the displays on the screen, paper areas and the like.

blocks

Block definitions contain information about elements that are grouped into blocks. The blocks are often resolved during the import, which increases the memory requirement if the block is referenced often.

geometry

Lines, polygons, circles, arcs, texts and all other basic elements with different attributes such as levels, color, line width or line type are saved in the geometric part. Some programs only import this section, which causes a lot of information to be lost.

DXF versions

The DXF versions have version numbers and are colloquially assigned to the corresponding AutoCAD version with which the version can be generated for the first time. DXF data can be imported into AutoCAD from its own version or from an earlier AutoCAD version. At the beginning of a complete DXF file is the version number (ACnnn) of the DXF version. This can be used to determine the required version of AutoCAD. DXF is always fully downwardly compatible.

Autocad version DXF version
Release 5 / Version 2.0 AC1.50
Release 6 / Version 2.1 AC2.10
Release 7 / Version 2.5 AC1002
Release 8 / Version 2.6 AC1003
Release 9 AC1004
Release 10 AC1006
Release 11/12 AC1009
Release 13 AC1012
Release 14 AC1014
Release 2000 / 0i / 2 AC1015
Release 2004/5/6 AC1018
Release 2007/8/9 AC1021
Release 2010/11/12 AC1024
Release 2013/14 AC1027
Release 2018 AC1032

Supported geometry elements

Supported geometry elements are all elements required and used by vector programs such as points, lines, arcs, circles, splines , text, external symbols and fonts, blocks, dimensions, ruled surfaces, simple freeform surfaces, solids and solids trimmed with surfaces.

Problematic geometry objects during CAD data exchange

DXF only supports graphic primitives very well if it is used as a CAD exchange format across systems.

Geometric elements that are not graphic primitives are often not fully supported, as in any CAD format, but can be represented as blocks or grouped individual elements using graphic primitives.

If CAD objects are used in DXF that the target system does not know, they will be ignored as long as the DXF standard is adhered to, or the import will fail. However, since many programs improperly implement the current DXF standard, special programs have been on the market for a long time that can repair such unclean files and make them readable.

  • Fonts are only supported to a limited extent; when exporting, it is usually unknown which fonts are on the target system. For this reason, Autodesk provides plotter fonts that can easily be reduced to geometric primitives without changing the typeface. Due to the principle, such resolved fonts are then no longer available in the target system as fonts, but as grouped basic elements. This problem cannot be avoided because there are no font definitions that are supported by all CAD systems. TTF and similar fonts can be integrated, but only work satisfactorily if they are also available in the target system.
  • Hatching causes problems similar to fonts. Autodesk and DXF are based on the US American standard ANSI, hatchings are only properly transferred as such, if the target system also supports this standard, here too the explosion of the elements offers a possible solution, which, however, makes subsequent changes very difficult.
  • In principle, dimensions can only be transferred unsatisfactorily because there are too many standards for their formatting. They can also be transferred optically clean by breaking them down into basic elements, but the associativity is lost.

The above-mentioned restrictions are inherent in the system and are now largely regarded as unsolvable. The data exchange between CAD systems is only possible in a few cases without rework.

For historical reasons, the “line width” attribute of an object could not be transferred directly with DXF. Here the information “color” of an object was used as a substitute for assigning a certain line thickness. Only in modern AutoCAD versions is it possible to assign lines and other geometric objects to their own line thickness when creating them and to transfer this information directly in the DXF.

Other formats

Other formats for exchanging CAD data are IFC , STEP and IGES , but these are less common than DXF and the VDA -IS, which is now considered out of date.

literature

  • Dietmar Rudolph, Thomas Stürznickel, Leo Weissenberger .: DXF internal. 3rd edition. Essen 2000, ISBN 3-9805108-1-6 .

Web links

Footnotes

  1. ↑ DXF internal , ISBN 3-9805108-1-6 .
  2. ↑ Generalidad de Catalunya: Estàndard d'intercanvi de dades urbanístiques en format CAD ( Memento of December 3, 2013 in the Internet Archive ) (cat .; PDF; 402 kB)
  3. ↑ Scan of a report in c't issue 24 of November 24, 2005, p. 56. ( Memento of December 3, 2013 in the Internet Archive )
  4. ↑ Gerhard Pülz, Bauhaus University Weimar, DXF data exchange (PDF; 343 kB)
  5. ↑ международная стандарт обмена данными International standard for data exchange (Russian)
  6. ↑ DXF internal (printed version from 05/1998)
  7. ↑ Gerhard Pülz, Bauhaus University Weimar, DXF data exchange (PDF; 343 kB)
  8. ↑ Autodesk Exchange: Saving drawings in earlier drawing file formats ( Memento of the original from May 4, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / exchange.autodesk.com
  9. ↑ Формат IGES Формат DXF Формат STEP Comparison of the formats IGES, DXF and STEP (Russian)
  10. ↑ Fritz-Nikolai Rudolph, Jürgen R. Dietrich: Practical Use of CAD and EDM / PDM Systems, Part III . In: CAD-CAM Report . No. 6 , 2003 ( fh-trier.de [PDF; 520 kB ]).