It would seem to me that it would be easier to acquire a few
specialised parts (I'm thinking of the nozzle) and pumps that have an
adequate rating than it is to acquire high-power lasers that can cut
the more bulky types of materials.
Things that seem (!) easy:
The forces exerted to the Cartesian bot are not excessively high, in
the medium range of CNC or perhaps even lower?
Things that may make it difficult:
The pump should not wear out too quickly from the abrasives. Filter
and add new abrasives? Special types of pumps that are suitable for
Parts of the machine need to be well protected or be waterproof.
The machine needs a heavy frame to carry a lot of liquid and has a big
envelope if, say, you want to slice blocks of granite. Though that
might be out of the question due to high pressures needed.
Accurate control of the stream.
Wire EDM is probably a heck of a lot easier. This rather amusing video
made me believe it is probably a much better candidate for open
I made one myself but I probably need a specific material to get a