One of the potential solutions to the chassis issue for my 3D printed locos was to make frames from something else, with spacers - one of the materials tried is this laser cut Delrin - stable, low friction and pretty strong, and relatively cheap. However, it hasn't cut particularly well and is susceptible to warping, so I think this is a non-starter. Definitely worth an experiment though, and it provided the inspiration to try another method, which I think has worked well.
There's also a set of gears cut in the Delrin - nice, but not quite perfect geometry, so they don't run quietly. I think this would work really well for bigger gears, where the kerf of the laser isn't proportionally as large.
The conrod shown is cut in plywood and is very fragile. I'm planning to try and reinforce it with something (wire? superglue?) and use them. Hopefully will be fine with some careful handling, certainly better than 3D printed efforts.
I don't mean to sound ungrateful to my laser cutting friend! It's definitely a great technique that has a lot of applications, but I think the super-precise mechanical parts are maybe not the place for it.