In my youth, I used to work at a local car wash place. If you traveled trough Balkans you probably saw many of them, and they all use handheld pressure washers. When I saw this video it reminded me of that time and I thought you guys would enjoy and find something useful in this project.
Ben Krasnow used a very cheap pressure washer and attached a DIY abrasive sand container combined with AccuStream professional cutter head to make a low-cost DIY waterjet cutter.
It can cut thin aluminum, wood, and plastics. it looks like the cuts are very precise and controllable. In water only mode it cuts trough soft materials like foam.
Here is the full video with all the details.
Next step would probably be to mount this cutter on a CNC gantry and turn it into a fully computer controlled machine.
Since there are much more powerful pressure washers, like the Karchers I used, this could be made into a more capable device.
With right settings, it could potentially cut plastic 3d printed parts or use it as a sand blasting device for surface finishing.
Applied Science YouTube channel: