As I start work on the pattern for etching, there is good news and bad news.
First the good news: it appears that OnShape have improved the compatibility with Inkscape, and so, now I can take flat patterns from OnShape and import them directly into Inkscape without traversing through QCadCam. Someone is still resizing the part along the way, but I suspect it is Inkscape, and that is still easy to fix.
Now the bad news: the part coming from OnShape consists of many individual paths, rather than a single connected path. This means I can’t simply select an area and fill it with colour until all the coincident but unconnected nodes have been connected together to make a closed path. That’s a lot of labour; granted, it’s just about the most complex shape I have, but hooking up the half frame above took over half an hour. There has to be a better way!