The Drawing Interchange File Format ( DXF) is a specified by the Autodesk file format for CAD data exchange, and was integrated into the CAD program AutoCAD. The DXF format was led next to the DWG format to ensure an external interpretable data exchange between AutoCAD systems.
The DXF format is described by AutoDesk and openly documented. Because of the well-documented, simple data structure, the DXF format is used almost exclusively for cross-program data exchange across different operating systems also. Each of today's CAD and CNC program controls the import and export of DXF, DXF which is the industry standard for the lowest common denominator of all CAD systems. All items that are meaningful and implementable for technical drawings, are supported in DXF.
A DXF -like format is DXX. This is used by Autodesk block related to the exchange of attribute values.
The development of the DXF format is determined by Autodesk as a developer of the CAD program AutoCAD. With each new AutoCAD release a new, enhanced DXF version may be. DXF is always only expanded, there will be no elements removed from the default.
The derivation of the name of DXF "Data eXchange Format " is indeed obvious and common, but wrong. The founder of Autodesk, John Walker said on September 18, 1982: " The file type of Drawing Interchange File format was changed from DIF to DXF, lest any Gonzo tries to load a drawing in VisiCalc. "
The first DXF version came with the first Autocad version 1.0 release in December 1982. The then typical PC had one or two floppy drives with 100-360 kB memory capacity. The former versions of AutoCAD were designed to be run on a PC with two floppy disk drives without hard drive. The space was perfectly adequate for the former data traffic. So there was at that time also AutoCAD versions for different operating systems ( MacOS, MSDOS, etc.) and thus the need to exchange geometry data from AutoCAD between the different platforms with each other. For this purpose, the data exchange format DXF defined.
DXF files are divided among other elements, mainly in the four main parts of the head, tables, blocks and geometric part of the drawing. These are marked with the corresponding English name. It far more than the geometric content is stored.
The head is used to define the working environment. Here basic properties are stored:
- Determinations about the associativity of dimensions
- Attributes for dimensional chains
- Settings for rounding
- Global parameters for hatches etc.
- Pinouts for the Output Devices
- Position of the local and global coordinate systems
The table section contains the information about the representation of various elements such as color, line thickness, etc., the representations on screen, paper and similar areas.
The block definition contains information about items that are grouped together to form blocks. In addition to hatching or dimensional chains which may also include user-defined geometry elements. For problems with the DXF Blocks are often easily blown up and made into normal elements which, although requires more memory and more difficult fiddling with the elements, but eliminates the vast majority of problems.
In geometric partial lines, polygons, circles, arcs, text, and all other basic elements with different attributes such as layers, color, line thickness, or line type to be stored. Some programs only import this section, which lost a lot of information problems are largely avoided.
The DXF versions have their own version numbers and the corresponding version of AutoCAD are often colloquially associated with this version can be produced for the first time. In AutoCAD DXF data can be from their own version or an earlier version of AutoCAD read. At the beginning of a full DXF file is the version number ( ACnnn ) the DXF version. Based on this, the required version of AutoCAD can be determined. DXF is always fully backward compatible.
It is possible by simple means, such as text editors, and almost all programming languages to create DXF files to analyze or manipulate. These opportunities are particularly suitable for geometric and geometric -based calculations of CAD models, for example, to optimize space. Known DXF conversion programs are DXFKONV and CADconv of Kazmierczak Software.
Supported geometric elements
Supported geometric elements are all required of vector programs, using elements such as point, line, arc, circle, spline, text, external symbols and fonts, blocks, dimensions, ruled surfaces, simple free-form surfaces, solids, and trimmed with surfaces solids. DXF import is fully backward compatible, in the export unknown from older versions of the program objects are ignored, allowing the use of basic and new files in very old versions of the program.
Problematic geometry objects in the CAD data exchange
DXF supports only graphical primitives very good when it is used as a CAD exchange format across systems.
Geometric elements that are no graphical primitives are often not fully supported as in any CAD format, but can be represented as blocks or grouped individual elements by graphical primitives.
Be used to DXF CAD objects that do not know the target system, they will be ignored as long as the DXF standard is complied with, or the import fails. However, since many programs implement unclean the current DXF standard, are on the market that can make legible the repair such unclean files and has long specialized programs.
- Fonts are only partially supported when exporting is usually unknown, which fonts reside on the target system. For this reason, Plotter provided by Autodesk, which can be easily reduced to geometrical primitives without changing the typeface. Due to the principle such writings are then blasted in the target system is not more than writing but as grouped primitives available. This problem can not be avoided, since there are no font definitions that are supported by all CAD systems. TTF and related writings can be incorporated, but only work satisfactorily if they are also present in the target system.
- Hatching prepare similar problems such as text. Autodesk DXF and are based on the U.S. Standard ANSI, hatches are only properly passed as such, even if the target system supports this standard also provides the blowing up of the elements of a possible solution, however, which greatly complicates subsequent changes.
- Dimensions can be transferred only unsatisfactory in principle, since there are too many standards for their formatting. They can also be transmitted optically clean by dissolution in basic elements, associativity is lost, however.
The above restrictions are due to the system and are now regarded as largely intractable. The data exchange between CAD systems is possible only in a few cases without amendments.
For historical reasons, the attribute " line thickness " of an object could not be transferred directly to DXF. Here is the information "color " of an object was alternatively used to assign a specific line thickness. Only in modern versions of AutoCAD, it is possible to assign lines and other geometric objects directly when creating their own line strength and to transmit this information directly in the DXF with.