General Information

The first technical applications of waterjet technology date back more than 100 years. Around 1870, waterjets were first used to extract gold. Once suitable pumps had been developed, it was possible to increase water pressure far enough to be able to cut non-metallic materials.

Then, at the start of the eighties, solid particles were added, the most recent innovation in the evolution of waterjet technology. Today it's possible to cut practically any material with pure waterjet respectively abrasive waterjet.

Waterjet technology has a variety of advantages in terms of the specific process:

• It is a "cold" cutting process so the material being cut is not subject to any thermal influence.
• The extremely small cutting gap enables optimum material exploitation.
• The pure waterjet and abrasive waterjet can be started and stopped in the material.
• Reaction load is extremely low thus enabling simple handling.
• Two- and three-dimensional cutting is possible.
• The "waterjet" tool works independent of direction.

Essentially, we can distinguish between two different processes:

Cutting with the pure waterjet and abrasive waterjet cutting.

While pure waterjet cutting relies on the static pressure of the compact waterjet and the erosive effect of the droplets in order to cut the material, in abrasive waterjet applications there are the solid particles incorporated in the jet which cause micro-cutting action on the material – in this case the waterjet serves merely to accelerate the solid particles.

Essentially, both types of jet can be used for cutting materials as well as cleaning and removing, while cutting it is possible to obtain a variety of qualities of the cut edge depending on various parameters. Various quality zones are created on the cutting surface whose size will depend on the selection of cutting parameters.

Pure waterjet

As opposed to when used in cleaning applications, where the main objective is to achieve large surface, constant removal of material, waterjet cutting works on the principle of coherent jets. The jet diameter ranges from 0.1 mm to 0.5 mm (0.004" to 0.016"). In order to achieve the necessary energy density, the operating pressure is up to 420 MPa (60,000 psi), which corresponds to the pressure at the base of about 42 km (25 miles) water column.

Depending on the material pure waterjet is able to cut up a thickness of 300 mm (12").

The abrasive waterjet

In connection with many technical materials the energy density of pure waterjet is not sufficient to cut. This is why solid particles have to be added to the waterjet. In such cases far greater cutting performance are achievable.

Typical waterjet cutting applications are:

• Foodstuff portioning (frozen food, bread, cakes and pastries, chocolate, ice-cream)
• Paper product cutting (nappies, corrugated cardboard)
• Textile cutting (leather, furniture fabrics, carpets)
• Serialisation of mounted boards
• Trimming of plastic mouldings and carpet shapes for the automotive industry
• Prepregs and laminated material cutting for the aircraft and aerospace industries
• Cutting of insulation material
• Cutting of gasket and special components

The so-called abrasives are usually a sharp-edged mineral material such as garnet or olivine at a grain size of approx. 0.1 mm to 0.3 mm (0.004" to 0.012"). Depending on the specific cutting application, the amount of abrasives required varies between 100 and 500 g/min (0.22 and 1.10 lb/min).

The pressure used in abrasive waterjet cutting is the same as in pure waterjet cutting, i.e. up to 420 MPa (60,000 psi). The jet diameter is between 0.3 mm and 1.2 mm (0.024" and 0.047").

As a limit for thickness while cutting with abrasive waterjet we look at approx. 250 mm (10").

Typical applications are:

• Cutting high-grade steels, especially nickel-based alloys
• Glass cutting, bullet-proof glass and acrylic glass
• Decorative parts cut out of nature stone such as granite and marble
• Materials for the aircraft and aerospace industries such as thick fibre-reinforced plastics and titanium alloys
• Cutting high-tech ceramics
• Application on small series and job shop activities