Waterjet technology glossary.

Terms

Abrasive waterjetAWJ

Process in which an abrasive is metered into the water jet in the mixing chamber. The accelerated grit produces the material removal; the water jet is the energy carrier.

Operating point

Pair of values — operating pressure and flow rate — that results jointly from the pump and the nozzle configuration. A single pressure figure does not describe an operating point.

Discharge coefficientc_d

Ratio of actual to theoretical flow rate through an orifice. In practice between 0.60 and 0.80; falls with wear and an unfavourable inlet contour.

Direct drivecrankshaft pump

Plunger pump whose pistons are driven directly via a crankshaft. Higher efficiency than an intensifier, but generally more limited in the pressure it can reach.

Pressure-flow product

Product of the permitted operating gauge pressure in bar and the flow rate in l/min. From 10,000 bar·l/min, DGUV Rule 100-500, chapter 2.36 comes into scope.

Intensifierintensifier pump

Oil-hydraulically driven pressure generation with differing piston areas. The classic route to pressures above 4,000 bar in the cutting-machine market.

Focusing tubemixing tube

Wear part made of a hard-metal composite that focuses water and abrasive within the cutting head. Inside diameter is typically two to three times the water-orifice diameter.

Taper

Deviation of the cut edge from vertical across the workpiece thickness. Without compensation, typically 0.5° to 1.5°; cutting heads with controlled tilt reduce it considerably.

Mesh

Sieve mesh-size rating used to denote abrasive grit. A higher number means a finer grit; mesh 80 corresponds to roughly 0.18 mm and is the most widely used grit.

Pure waterjet cuttingpure waterjet

Cutting without added abrasive. Suited to soft and fibrous materials; produces very narrow kerfs at small orifice diameters.

Reaction force

Force to be absorbed at the tool, equal to twice the product of pressure and orifice cross-section. Operationally limited to 250 N, with additional requirements from 150 N.

Stand-off distancestand-off

Distance between the tool exit and the workpiece surface. Typically 1–3 mm in abrasive cutting; larger distances widen the kerf disproportionately.

UHPUltra High Pressure

Umbrella term for applications above roughly 1,000 bar. The boundary is not standardised and is drawn differently depending on the sub-market.

Orificewater orifice, jewel

Component containing the actual nozzle bore, made from sapphire, ruby, or diamond. Together with pressure, it determines flow rate.

Units and Conversions

Quotes from the US and UK markets often state pressure in kpsi. The most common value, 60 kpsi, corresponds to roughly 4,137 bar.