Waterjet & laser have cut through a small point that can follow any programmed 2D path and can start a hole in the middle of a sheet.
By contrast blades are often very restricted as far as shapes go. Imagine cutting a disk with a band saw. A wire saw can get closer, but you don't start a hole with one, and AIUI it's quite slow (a thin wire is fragile, you can't feed hard). Milling tools can likewise follow arbitrary paths but usually the tools are unnecessarily large for cutting a shape out of a sheet. So you have higher forces and need better clamping and waste more material. Tiny milling tools exist but again you run into issues with fragility & low feeds, high rpm requirements, coolant, tool wear, etc. And the depth of cut tends to be very limited. All of the said methods will leave burrs instead of a nice smooth cut.
The setup for laser cutting can be very very simple.
I was indeed picturing a mill setup. I guess the cost of the abrasive seems higher than the costs associated with material loss, coolant, etc at the hobbyist scale, but I'm also not particularly familiar with this domain.
Well, if waterjet works anything like laser (we had a big one at work), then you just barely need to clamp the work. Gravity does its part, and I imagine the cutting force would be aligned with gravity, pushing the work into the table. So the setup really is simple and easy, and you can cut parts off the sheet and let them just drop.
By contrast, milling tools will try to push the work in all directions depending on what kind of cuts you're taking at the moment. They will also try to pull the work (and if the work is loose, you can easily shatter tools). Of course the countering forces affect the tool and through it the rest of the machine, which needs to be rigid enough to take it. The workpiece and the part that will fall off must be clamped accordingly, and then you run into the issue of tool paths that would cross over your clamps, so you'll need the operator to re-clamp things in the middle of the job. And there are clearance issues when you try to operate small tools near clamps. It's definitely harder to set up, and more involving than a laser that just needs a path and then cuts it all up for you after you press play.
I don't know what exactly the state of the art of hobbyist scale machine tooling is right now, but I would be surprised if high speed (=> suitable for small tools and low forces) CNC mills were commonly available. Most hobbyist machines I've seen are neither rigid nor CNC, so you won't be easily cutting smooth & complicated shapes with them.
"Well, if waterjet works anything like laser (we had a big one at work), then you just barely need to clamp the work. Gravity does its part, and I imagine the cutting force would be aligned with gravity, pushing the work into the table. So the setup really is simple and easy, and you can cut parts off the sheet and let them just drop.
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Go hit part of something not flat to within a few microns with 75k psi of water and see if it vibrates :)
Also, unless your nozzle alignment is perfectly vertical, there is some sideways motion imparted.
(IE you are kinda right, but you still gotta do something)
Particularly for small pieces, it can be a pain in the ass. On the plus side, yeah, light clamping with c-clamps/etc works most of the time.
The waterjet is especially flexible compared to a milling machine. The small kerf means you can create smaller features. There's no need to change tools depending on the material type. Chips are automatically blasted into the catch tank, instead of accumulating on the workpiece. Waterjets also typically have a much larger workbed compared to a milling machine, so you can load an entire 4x8 foot sheet and cut a bunch of different parts, or one big part.
I think you're right, though. For occasional prototype parts you're probably better off either ordering waterjet cut parts from an online service, or running them in a small CNC milling machine.
By contrast blades are often very restricted as far as shapes go. Imagine cutting a disk with a band saw. A wire saw can get closer, but you don't start a hole with one, and AIUI it's quite slow (a thin wire is fragile, you can't feed hard). Milling tools can likewise follow arbitrary paths but usually the tools are unnecessarily large for cutting a shape out of a sheet. So you have higher forces and need better clamping and waste more material. Tiny milling tools exist but again you run into issues with fragility & low feeds, high rpm requirements, coolant, tool wear, etc. And the depth of cut tends to be very limited. All of the said methods will leave burrs instead of a nice smooth cut.
The setup for laser cutting can be very very simple.