Waterjet cutting of metal

Waterjet cutting has developed in recent years into one of the most versatile and precise processes in modern metalworking. Thanks to the fully cold, contact-free cutting process, almost all metallic materials can be separated – regardless of alloy, surface condition or material thickness. While thermal processes such as laser or plasma always introduce heat and thus affect the microstructure, the waterjet works without any thermal load. This characteristic makes it the ideal choice for high-quality metals, sensitive surfaces, coated or anodised components as well as alloys that are difficult to machine.

A key advantage lies in the extremely high geometric freedom: even complex contours, fine internal radii, very delicate cut-outs or sharp corners can be realised with high precision and repeatability – without tool changes and without restrictions imposed by tool geometry. Even large material thicknesses, which become problematic or uneconomical for lasers, can be cut reliably with the waterjet. The combination of dimensional accuracy, gentle processing and flexibility makes waterjet cutting a central building block in numerous industries, from mechanical and plant engineering through to medical technology.

How waterjet cutting works

Waterjet cutting uses the enormous energy of an extremely accelerated waterjet, which is forced through a very fine diamond nozzle at pressures of up to 6,000 bar. The water exits at extremely high speed – often over 800 m/s – which corresponds to a controlled erosion process. When the jet hits the metal, the smallest particles are removed from the surface until the contour is completely separated.

For metalworking, an abrasive granulate is additionally added to the water, usually high-quality garnet sand. This abrasive is introduced into the jet via a mixing chamber directly in front of the nozzle. The combination of water speed and abrasive action creates a high-energy but thermally neutral cutting process. The decisive factor is that no heat whatsoever is introduced into the material – the metal remains unchanged in its structure.

Abrasive vs. pure waterjet cutting

Waterjet cutting is based on a high-energy, contact-free separation process in which water is compressed to pressures of up to 6,000 bar and expelled at extremely high speed through a fine diamond nozzle. The jet speed is far above the speed of sound and removes the material through controlled erosion.

The CNC-controlled jet guidance enables complex contours, tight radii, delicate areas or large sheet thicknesses in a single operation. Since the process remains completely cold, no microstructural changes, temper colours or stresses occur in the material.

Suitable metals

Waterjet cutting is suitable for almost all metals:

• Stainless steel (e.g. 1.4301, 1.4571),
• Aluminium & aluminium alloys,
• Steel & tool steel,
• Titanium & titanium alloys,
• Copper, Brass, Bronze,
• Special alloys such as Inconel or Hastelloy.

Advantages over laser cutting

• No heat-affected zone: No temper colours, no distortion, no microstructural changes.
• Ideal for reflective metals: Copper, brass or aluminium can be cut without difficulty.
• Large material thicknesses: Even over 100 mm possible.
• Clean edges without oxidation: No melt residues or hardened zones.

Advantages over CNC milling

• Complex contours without tool changes.
• No tool costs, no tool breakage, no wear.
• No mechanical load: Ideal for thin sheets or sensitive materials.
• Fast and efficient for cut pieces, prototypes and small series.

Precision, tolerances & cut quality

The precision of waterjet cutting is one of the greatest technical advantages of the process. Depending on material thickness and the selected quality level, modern systems achieve tolerances of up to ±0.1 mm. The kerf is typically between 0.8 and 1.2 mm and enables very efficient material utilisation. The resulting cut surfaces are uniform, smooth and free from thermal influences, since no heat is introduced into the material.

As a result, no oxides, no hardened zones and no distortion occur – even with sensitive or high-strength alloys. The achievable surface roughness is usually in the range of Ra 3–6 µm, which means the edges are already ready for assembly in many cases and additional post-processing is rarely required.

Decision aid: When is waterjet cutting worthwhile?

Waterjet is particularly suitable when:

• heat-sensitive metals are being processed,
• complex contours or fine internal radii are required,
• thick sheets must be separated precisely,
• high-quality, burr-free edges are needed.

Laser or CNC make sense when:

• very high speed is decisive (laser),
• functional surfaces, threads or fits must be machined (CNC).

Comparison: Waterjet vs. laser vs. CNC milling

Process	Heat influence	Material thicknesses	Cut quality	Complex contours	Cost structure	Typical applications
Waterjet	none	up to >100 mm	very high, burr-free	excellent	variable	Cut pieces, complex contours
Laser	high	thin to medium	good, thermally affected	good	economical for series	thin sheets, mass production
CNC milling	low	variable	very high	tool-dependent	higher	functional surfaces, threads

Sustainability & ecological advantages

Waterjet cutting is one of the lowest-emission and most resource-efficient separation processes in industrial manufacturing. Since no thermal process takes place, significantly less energy is required compared with laser or plasma cutting. At the same time, neither flue gases nor toxic vapours are produced, so no complex air extraction or filter technology is necessary. The material is also not oxidised or thermally altered, so no environmentally critical melt residues are produced.

Another key advantage lies in the handling of water and abrasive. The cutting water can be reused several times through filtration, which considerably reduces consumption. Likewise, the abrasive used – usually natural garnet sand – is free from toxic components and can be disposed of in an environmentally compatible way or partially reprocessed. Since the kerf is very narrow, significantly less waste is also produced, which reduces material consumption and further improves the sustainability of production.

Practical examples from industry from industry

Mechanical engineering: precise stainless steel and aluminium sheets, brackets, covers. Medical technology: titanium and special alloys without microstructural changes. Vehicle construction: aluminium and steel components with burr-free edges.

Extended aspects: kerf, surface roughness & environmental aspects

The kerf of waterjet cutting is exceptionally narrow compared with other separation processes. With typical values between 0.8 and 1.2 mm, it enables particularly efficient material utilisation – a decisive advantage with high-priced materials such as titanium, stainless steel or special alloys. The precise jet guidance ensures that hardly any waste is produced even with complex contours and that the components can be cut exactly from the raw material.

Surface quality is also one of the strengths of the waterjet. Since no heat is introduced into the material, the cut surfaces remain homogeneous and without thermally affected zones. Depending on the selected quality level, very smooth cut surfaces can be achieved that can be assembled or further processed directly in many applications. Particularly in mechanical engineering or medical technology, where tight tolerances and defined surfaces are essential, the high repeat precision plays an important role.

In conclusion

Waterjet cutting impresses with an remarkable combination of precision, material preservation and flexibility. As a fully cold, contact-free separation process, it avoids thermal influences that can lead to distortion, microstructural changes or surface impairment in laser or plasma processes. The ability to cut practically all metals – from aluminium through stainless steel to titanium and special alloys – in high quality makes the waterjet a universal tool for demanding industrial applications.

The process shows its strengths particularly with complex geometries, sensitive surfaces or large material thicknesses. The burr-free, uniform cut surfaces reduce the need for rework and enable efficient further processing. At the same time, waterjet cutting scores with its ecological balance: no smoke, no thermal pollutants, reusable water and low energy consumption. It is therefore one of the most modern and sustainable metalworking techniques and represents a technically and economically first-class solution for many companies.

FAQ – Frequently asked questions about waterjet cutting of metal

How thick can metal be cut? Modern high-pressure systems enable the precise machining of metal thicknesses well over 100 mm. Even at very large thicknesses, the cut quality remains constant, since no thermal effect occurs.

Which metals can be cut? Almost all metals can be separated reliably – including stainless steel, aluminium, titanium, brass, copper, bronze, tool steels and heat-sensitive special alloys.

How precise is waterjet cutting really? Depending on material and quality level, tolerances of up to ±0.1 mm are achievable. The edges are smooth, burr-free and without thermally affected zones, which often enables direct further processing.

Do burrs, distortion or heat influence occur? No. The process is completely cold and contact-free. Neither burrs, oxides nor thermally induced distortion occur.

Do waterjet-cut parts require post-processing? In most cases not. The cut surfaces are clean, uniform and directly usable for many applications. Only with extremely high requirements can fine machining be worthwhile.

Is waterjet cutting more expensive than laser or CNC milling? With thin sheets, the laser can be more economical, but with thick sheets, complex geometries or sensitive metals, waterjet cutting is often more cost-efficient – above all because no post-processing is necessary.

How fast is the process? The speed depends on material, thickness, desired cut quality and abrasive quantity. For cut pieces and small series with many variants, waterjet is often significantly faster than milling.

How clean is the cut compared with laser? Since no melting process takes place, the edges are metallically pure, without oxides or hardened zones. This is particularly advantageous for welding, coating or anodising.

How loud and how clean is the process? Waterjet cutting does not produce toxic vapours. Noise development is moderate and depends heavily on the enclosure. Many systems can be encapsulated and enable comparatively quiet operation.

Can waterjet also cut very small details? Yes, the fine jet enables very delicate contours and small radii. The accuracy depends on nozzle quality, distance and feed rate.

What about environmental compatibility? The cutting water is filtered and reused, abrasive is free from harmful substances, and neither flue gases nor heat are produced. Waterjet cutting is therefore one of the ecologically cleanest cutting processes.

Is waterjet suitable for series production? Yes, particularly for small and medium series as well as parts with changing geometries, since no tools wear out or need to be changed.