The attempts at Onshape on a raspberry pi failed but there are native linux cad tools available. With a few CNC projects out there opportunities for making use of 2D CAD data exist. One of the more accessible CAD programs, from an install and setup standpoint, is LibreCAD. It is open source, lacks a little in the UI, but is a fairly intuitive drafting tool.
# sudo apt-get install librecad
That is all it took. Within minutes I was able to pull up the software and begin sketching. The UI for LibreCAD is very similar to other 2D drafting packages, that is to say it could use some updating. Still for CNC work or even layer profiles of 3D printing this is fine.
Surprisingly there is very little CPU or GPU usage while running the LibreCAD software. That is not a real surprise given that the graphics are so bare, but even it did strike me that the CPU usage was a fraction of what the system uses to run even the barest of webpages in a browser.
To get things started a simple template helps to provide some context. Importing an image can be done from the left side menu. Tracing the print is a good way to get practice in the sketching and drafting tools function.
The file types are limited for saving, the default format is .dxf which can be used by AutoCAD or imported into Solidworks or Onshape. Most major CAD programs will accept the incoming design files and for CNC or 3D printer control there are file conversion tools that are relatively easy to access.
Coupled with OctoPi, or some CNC control projects, the possibility of driving useful prototyping and manufacturing tools from a Pi really start to open up.
There are also other online tools, like the easle app by instructables, that can be used through a chromium browser. TinkerCAD offers a similar in browser design tool and though the functionality is not the best it is plenty to get something started. I am sure too that over time Onshape will start to become an option. At this point it seems to be a limitation on the support for the Chromium browser, which is just getting started in WebGL with some of the more recent builds. Rather than troubleshooting to make it work I prefer to jump over onto a mac or PC with native Chrome or Firefox where the in browser design experience is still much more stable.
Surely there are other programs that could help to round out the tool kit. A few tutorials show that it is possible to get Blender, the open source sculpting and animation tool, up and running on the Pi 3. Personally it feels like pushing the limits on some of these does not make sense if you have access to another more stable machine. Waiting for heavy programs to load or process is a pain often associated with CAD system pushing the limits of the hardware. Still it is a unique way to get access to some very powerful tools, all for under $100 in hardware.
If anyone knows of other CAD tools available for the Pi that helps to extend capabilities feel free to drop a line here.