DXF inside AutoCAD
DXF After Conversion


The DXF Format:

DXF stands for Drawing Exchange Format, and it is a format for transferring drawings between Computer Aided Design systems.  DXF is widely used as the de facto standard in the engineering and construction industries.  The DXF format is a tagged data representation of all the information contained in an AutoCAD® drawing file. Tagged data means that each data element in the file is preceded by an integer number that is called a group code. A group code's value indicates what type of data element follows. This value also indicates the meaning of a data element for a given object (or record) type. Virtually all user-specified information in a drawing file can be represented in DXF format.

The DWG Format:

Similar to the DXF format except it's a binary file.  Typically conversions are more reliable with DWG and are the preferred format (compared to DXF). 

The Problem - DXF / DWG files can be Tricky to Handle:

DXF data is probably the most extensive and difficult format to work with, especially when converting to other EDA formats; however it is the de facto standard file format among most engineering CAD tools.

Here is a list of some common difficulties found inside DXF \ DWG files:

* Entities found in a Block that are drawn on layer '0', usually need to be moved to the blocks new inserted layer. If the block is inserted onto multiple layers, the '0' layer entities from that block must be moved each time.

* A solid hatch with internal geometries, does not explicitly define the polarity of the internal geometries.

* Non-Manhattan geometries, angles, and non-uniform scaling are permitted.

* Invalid, self-intersecting polygons are permitted.

* Identical, overlapping entities on the same layer can be stacked on top of each other. These identical entities are impossible to see, and can cause problems during conversions, etc.

* The DXF format specifications change almost every year, with the latest releases of AutoCAD.

* Nested Non-Manhattan transformations.

* Tapered polylines with non-uniform widths are permitted.

* Some boundaries may appear closed, but internally are still open.

* Filled pads are drawn as outlines of circles, donuts, or rectangular.

* Extraneous data such as UCS, and 3D object extrusions can be fond in many files.

* AutoCAD will not display filled areas on-screen, such as polygons, and other closed boundaries (only solid hatch). Making it tough to determine the final results.

* Fonts can be difficult to handle, especially MText (Multi-line text)

Note:  Most vendors, and mask houses stay away from accepting DXF files as input, because they have a hard time dealing with this data, and there are only a few decent software products on the market today, that can reliably handle DXF.


Here's a list of important features every DXF or DWG translator should include:

* Block entities drawn on layer '0', are automatically handled by the option: ByBlock/ByLayer.

* Polygon De-Embedding is used to process entity polarity for solid hatches with internal geometries.

* All angles, and non-uniform scaling are supported.

* Invalid, self-intersecting polygons are either automatically corrected or may be fixed using the editor.

* Identical overlapping entities are either automatically deleted, or may be fixed using the editor.

* Every year the DXF Plug-In is updated to supported the latest versions of DXF.

* Unlimited nested transforms are supported.

* Outlines are generated for tapered polylines with non-uniform width.

* Open boundaries will be automatically closed when it is possible.

* Recognizes outlined pads: round, donut & rectangular; When requested these pads are automatically filled & flashed.

* Most extraneous 3D data is ignored.

* Direct support for TrueType fonts


Important Links:

* DXF/DWG Conversion Secrets for Gerber, GDS-II, ODB++, etc.