Documenting

CAD is a way to communicate but most people are not familiar with reading drawings and probably want something more visible. And how about illustrations for service manuals and flyers? It is not that hard to create material as a post stream and there are good tools to help you.

Summary

With some open source tools and non free BricsCAD it is possible to create a flow to paper, pdf and the web. Most tools work on OS-X, Windows and Linux. The basic programs are BricsCAD, Inkscape and LibreOffice. In addition more programs can be of help, such as Cygwin to create a OS-X/Unix style command line or ImageMagick to convert and edit graphical formats. This page helps you solving problems in order to get the best results and overcome some problems you may hit. The most basic flow is: Make a drawing in CAD, export to SVG. Post-edit the SVG in Inkscape. Export SVG and embed in in your web pages and or import it in LibreOffice from where you can publish to PDF or print to paper. Since SVG is scalable, you will get the best possible graphics.

Introduction

File formats

  • DXF, Drawing eXchange Format, does it need an introduction? Okay, CAD-data are contained in DXF as ASCII - plain - data (binary is less usual). Many programs can handle this format. DXF is a proprietary format from Autodesk.
  • SVG, Scalable Vector Graphics. This format can be directly viewed with all major web browsers. SVG can be embedded in HTML. Many popular illustration programs read and write it. Inkscape even saves native in SVG (with some enrichment in the files). Developed by the World Wide Web Consortium (W3C). Files have a high precision if needed. Modern, straight forward, easy to understand and platform independent format for vector and meta graphics. Limited entity set, a polyline from CAD (arc-line compound) becomes a b-spline for example. Preferred over closed source formats like emf and wmf.
  • HTML, HyperText Markup Language, the language of web pages. Developed by the World Wide Web Consortium (W3C).

  • PDF, Portable Document Format, a page describing language, popular for document distribution. Developed by Adobe, published by ISO. Very popular for document distribution. Not and never intended as exchange format or image format. Something to think about. You'd better use SVG as image format and DXF as exchange format.
  • (E)PS, PostScript, like PDF, still populair with illustrators. AutoCAD has a command PSOUT to generate PS. It is intended for paper and lacks precision as high quality exchange format. Mature. Just as PDF a page describing code, meaning that SVG is better for images.

Software Tools

  • LibreOffice is a great program for writing service manuals. If you define your styles properly you'll find out that is does a better job than MS-Office when doing bulky documents. It exports PDF natively - with easy hyper-linking from a table of contents - and can handle SVG very well. It does have some caveats but you can work around them.

  • CorelDraw, a very universal program. In particular PSOUT-output from AutoCAD can be re-used in a neat way.

  • Inkscape, the free, open source, alternative for Corel. Very good at making SVG's from DXF's or even better, use BricsCAD to generate SVG and feed them to Inkscape. Produces content everybody can view and edit.

CAD to vector

Some general points to consider:

  • Closed polylines consisting of lines and arcs give good results if you need to fill them with colours.
  • In CAD, export to:
    • PS if you want to go from AutoCAD to Corel
    • DXF if you go from BricsCAD and AutoCAD to Inkscape
    • Best results so far: Use BricsCAD to export to SVG and use Inkscape for post-processing.
  • All other formats may seem to do the job too but if you take a close view, you'll find out that arcs are converted to way more amounts of nodes.
  • If your CAD model contains splines you need to trace them to polylines.
    • Best result: Do it manual.
    • Alternative: Export to DXF rel. 12 to create polylines frome splines.

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