Assembly drawings seem like they should be quick to throw together, because all that needs to be done is to copy and paste the drawings of various parts together. However, the drawings for all the parts are all either done in a variety of different drawing tools or have to be found from vendors, many of whom aren't just giving out free DXF files. So a big wad of different software is needed to put everything together. Here's the list:
Main drawing tool: I would use AutoCAD but it's bloated plus it's expensive and nobody wants to buy it for me. So I'm using DoubleCAD XT which is free for some reason.
To convert front panel drawings: All our front panels are done in Front Panel Designer, which exports to DXF. Astonishingly though, FPD is exporting 3D DXFs, which cause me problems because I am making 2D views and DoubleCAD XT unhelpfully goes nuts trying to render holes that are 3D. The solution is to explode the 3D drawings multiple times in Model Space in DoubleCAD, then select the entire mess and scale Z=0 to flatten the parts. The downside of this is that this results in the tops and bottoms of holes and edges being rendered twice. There's probably a more elegant solution but I haven't had time to figure it out.
To convert board silkscreens to DXF: GerbView is a tool that you can get a trial version of online, but it has proven to be so useful that I had to just buy it. It can be bought from here: http://www.gerbview.com/download.html GerbView can output any layer as PDF, DXF, or other formats. The downside is that the scaling gets mangled; I think that it is outputting the DXF in metric units but I am reading it as English units in DoubleCAD. So to read the DXF that GerbView produces into DoubleCAD requires rescaling before the image can be pasted into my assembly drawing. While searching for tools to view and convert Gerber drawings, I also found GBR2DXF here, and it seemed to be free, but the download process required registering for a password and it seemed like too much information to give out so I didn't try it.
To convert part drawings from PDF to DXF: Many manufacturers will release PDFs of their part drawings, or sometimes just line drawings of their parts. To paste these into my assembly drawing, I have a couple of techniques. The main one is to use a PDF to DXF converter program called Aide PDF to DWG Converter. It uses some kind of algorithm to trace PDFs, and the result is often shaky and poorly aligned if you zoom in but it is possible to then import the DXF and trace it with regular shapes. It has a free trial version but I'm probably also going to buy it. For really clean PDFs of things that were mechanical drawings to begin with, I can just give it the PDF file name, do the conversion, then import the resulting DXF and do cleaning up. It also produces results that are at an incredibly huge scale, so downscaling to convert to 1:1 is also necessary. For drawings where all I have is a JPG or other raster image, I first convert the image to PDF using PrimoPDF or CutePDF.
Some PDFs are shaded or have other features that make them not convert to DXF well. Sometimes I have to make a drawing from a photograph. In those cases, I can feed the drawing into an online tool that produces a black and white raster drawing that looks close enough to a line drawing that I can convert it to PDF and then feed it into the Aide converter. That online tool, oddly enough, is a service for quilters, it is called RapidResizer Stencil Maker. Again, the results of this tool are just approximate enough to produce a DXF that can be cleaned up and traced.
