Waterjet cutting drives water at very high pressure through a small orifice, and for anything harder than foam it entrains an abrasive garnet on the way out. The stream erodes its way through material rather than melting it, which means it cuts anything, leaves no heat affected zone, and does neither of those things quickly.
What it cuts that nothing else does
Any material, conductive or not: metals, stone, glass, composites, ceramics, rubber, foam and laminated stacks of different materials at once. Very thick sections, far beyond laser and often beyond plasma. Hardened and heat treated material without altering its temper. And parts where any heat affected zone would be unacceptable, which is why aerospace and composites work uses it so heavily.
The edge and the taper
The stream loses energy as it goes down through the material, so the kerf is slightly wider at the top than the bottom. On thin material it is negligible; on thick material it is visible and must be allowed for. Modern machines tilt the head to compensate, which removes most of it. The cut edge itself is matte and slightly striated, cleaner near the top and rougher near the bottom.
Why it is slower and what that costs
Erosion is a slower removal mechanism than melting, so cut speeds are well below laser and plasma on material both can handle. Machine hours are therefore the dominant cost, along with abrasive consumption and the wear parts in the cutting head. It is priced by time, so a long intricate profile is expensive whatever the material.
Where to choose it
When the material cannot be laser or plasma cut. When thickness is beyond the alternatives. When heat would damage the part or its temper. When the part is a composite or a stack. And when the edge must be free of the recast and hardened layer that thermal processes leave, which matters if the edge is later machined or is fatigue critical.
Questions people ask about waterjet services
What can a waterjet cut?
Almost anything: metals, stone, glass, composites, ceramics, rubber and foam, conductive or not, and at thicknesses well beyond laser cutting.
Does waterjet cutting leave a heat affected zone?
No, which is its main advantage. The material is eroded rather than melted, so temper and microstructure at the edge are unchanged.
Why is waterjet expensive?
Because it is slow. Erosion removes material more slowly than melting, and the process is priced by machine time plus abrasive and wear parts.
What is kerf taper?
The kerf being slightly wider at the top than the bottom because the stream loses energy as it descends. Machines compensate by tilting the head.