Waterjet Basics

The Basics

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

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

	Process	Secondary Processing	Materials	Thickness	Part Accuracy (Overall Tolerances)	Capital Investment	Machine Setup
Waterjet	Erosion using high speed liquid sandpaper	Usually none. Waterjet is a cold-cutting process that leaves a satin smooth edge	Virtually any material	Up to 24 inches, virtually any material. Z-axis constraint is only limit to thickness	Up to +/- 0.025mm (Typically 0.25mm though)	£45,000 – £350,000+	Same setup for all materials
Plasma	Burning/melting 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 HAZ	Primarily steel, stainless steel and aluminum	Up to 2–3 inches, depending on the material	Up to +/-0.25mm (Typically lower though)	£45,000 – £250,000+	Different setup for different jobs
Laser	Melting using a concentrated laser light beam	Sometimes yes. Removal of oxidised edge and HAZ. Gases used impact depth of HAZ	A variety of materials, but primarily steel, stainless steel and aluminum	Generally 1 inch or less, depending on the material	Up to +/-0.025mm (Typically 0.2mm)	£155,000 – £800,000+	Different gases and parameters for different jobs
EDM	Erosion using an electrical discharge	Usually none. Very shallow HAZ imparted	Conductive materials	Generally 12 inches or less	Up 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