Waterjet Basics

The Basics

The concept of waterjet cutting is quite simple. Here’s how it works:

1. Generate Pressure

An ultrahigh-pressure pump generates a stream of water with pressure rated at 94,000 psi (6,480 bar).

To put it into perspective, a fire hose contains a pressure of 390 to 1,200 psi (20 to 84 bar).

2. Convert Pressure into Velocity

This pressure is converted into velocity via a tiny diamond orifice (0.381mm diameter), creating a stream as small as a human hair which can cut soft materials.

3. Introduce Garnet

To increase cutting power by 1,000 times, garnet is pulled into the supersonic waterjet stream.

Water and garnet exit the cutting head at nearly four times the speed of sound, capable of cutting steel over one foot thick.

Pure & Abrasive Waterjet

There are two types of waterjet: pure and abrasive. Combined, these two technologies can cut virtually any material, any shape, at any thickness.

Pure Waterjet

Pure waterjet cuts soft materials like gasket, foam, plastic, paper, disposable diapers, insulation, cement board, automotive interiors, carpet, food.

Abrasive Waterjet

Abrasive waterjet is similar to a pure waterjet, except that after the pure waterjet is created, garnet abrasive is pulled into the head via a venturi vacuum, mixed with the water, and then the resulting abrasive waterjet stream can cut hard materials like metal, ceramic, stone, glass and composite.

Stream Velocity

Waterjets cut with stream velocity.

How do you get velocity? With ultrahigh-pressure water.

Ordinary tap water is filtered and fed into a waterjet pump rated to pressures of 94,000 psi (6400 bar). The pressurized water runs to the cutting head safely contained within the plumbing to maintain pressure. At the cutting head, the water then passes through the diamond orifice and the supersonic waterjet stream is created.

All the pressure is exchanged for velocity when the water passes out of the diamond orifice. The higher the pressure, the higher the stream velocity.

Waterjet vs. Other Technologies

ProcessSecondary ProcessingMaterialsThicknessPart Accuracy (Overall Tolerances) Capital InvestmentMachine Setup
Erosion using high speed liquid sandpaperUsually none. Waterjet is a cold-cutting process that leaves a satin smooth edgeVirtually any material Up to 24 inches, virtually any material. Z-axis constraint is only limit to thicknessUp to +/- 0.025mm (Typically 0.25mm though) £45,000 – £350,000+Same setup for all materials
Using a high temperature ionised gas arc
Typically yes. Slag grinding for removal of HAZ (heat affected zone) & flattening to eliminate distortion from heat. Assist gas used impacts depth of HAZPrimarily steel, stainless steel and aluminumUp to 2–3 inches, depending on the materialUp to +/-0.25mm (Typically lower though)£45,000 – £250,000+Different setup for different jobs
LaserMelting using a concentrated laser light beamSometimes yes. Removal of oxidised edge and HAZ. Gases used impact depth of HAZA variety of materials, but primarily steel, stainless steel and aluminumGenerally 1 inch or less, depending on the materialUp to +/-0.025mm (Typically 0.2mm)£155,000 – £800,000+Different gases and parameters for different jobs
EDMErosion using an electrical dischargeUsually none. Very shallow HAZ impartedConductive materialsGenerally 12 inches or lessUp to +/-0.025mm £80,000 – £300,000+Different wire types for different jobs

Edge Comparison

With waterjet, you get a satin smooth edge right off the table. With other cutting technologies there’s often secondary processing required to get that same satin smooth edge that waterjet produces.


Cut Speed Range

There are clear benefits to each cutting method below, waterjet in comparison with laser, plasma, and edm is an incredibly versatile process that allows you to cut thick or thin materials with ease. With waterjet, you get a satin smooth edge right off of the table – no secondary processing required.