Waterjet Cutting - Process, Features, Application and Prospects

Basic principles of waterjet cutting

Waterjet cutting uses a high-pressure stream of water mixed with an abrasive material to cut a wide range of materials.

A high-pressure water pump pressurises the water. This water flows through high-pressure tubing into the cutting head. In the cutting head, the water flows through a nozzle, turning it into an extremely fine stream. This stream cuts whatever material is placed in front of it.

A waterjet cutting machine can produce pressures as high as 100,000 psi or about 6900 bars. To put it into perspective, fire hoses generally deliver pressures between 8 to 20 bars. The waterjet nozzle is assisted by a vision system to facilitate the precise and efficient cutting of the part.

It is easy to manipulate the nozzle to accommodate the cutting of different materials. Depending on whether an abrasive substance is used or not, there are two types of waterjet cutting methods: Abrasive waterjet cutting and Pure waterjet cutting.

Abrasive waterjet cutting
When cutting harder materials, abrasive agents are mixed with the water. This occurs in a mixing chamber located in the cutting head just before the abrasive jet exits the system.

Popular agents for abrasive waterjet cutting are suspended grit, garnet and aluminium oxide. As the material thickness/hardness increases, so should the hardness of the abrasives in use.

With the right abrasives, various material types can be cut. Common materials cut with abrasives are ceramics, metals, stones and thick plastics. There are, however, certain exceptions such as tempered glass and diamonds that cannot be cut with abrasive water. Tempered glass shatters when cut with a water jet.

Pure waterjet cutting
Water jet cutters also work without the addition of abrasives, mainly to cut soft materials. A waterjet cutter designed only for this purpose does not have a mixing chamber or a nozzle. A high-pressure pump forces pressurised water out of an orifice to create precise cuts on the workpiece. Although most industrial cutting devices using waterjet technology enable the use of both methods.

Pure waterjet cutting process is less invasive compared to abrasive waterjet cutting. The jet stream is also exceptionally fine and does not impart any additional pressure on the workpiece.

Pure waterjet cutting is ideal for softer materials like foam, felt, wood, rubber, food and thin plastics.

Waterjet Cutting Materials

Waterjet cutting can cut almost all materials. The process is compatible with a wide range of materials like:

Metals
The high velocity and pressures in waterjet systems make them capable of cutting thin and thick metals with relative ease. This process is capable of cutting extremely hard materials such as titanium and inconel along with common metals such as aluminium and mild steel.

The process is mainly used to cut thicker workpieces that can’t be cut with laser or plasma. For thinner metals, laser cutting has an edge over waterjet in terms of cutting speed. A waterjet cutter with a 30 HP pump can cut 12 mm titanium at a rate of 180 mm/min.

For metals, waterjet provides the advantage of no HAZ formation which improves the final quality of a part significantly. There is also no need for secondary finishing in most cases as this process provides satin-smooth edges.

Waterjet cutting metal parts have high quality and are thus used in the most demanding sectors such as the aerospace industry that have no margin of error.

Wood
A decent waterjet cutting machine can effectively cut wood up to 125 mm in thickness at a rate of up to 15 m/min. It can be used to split wood as well as to carve intricate shapes. Moreover, the stream passes the wood at such a high speed that it causes virtually no surface wetness. This prevents the wood from absorbing the water. The high pressure also causes minimal delamination.

However, the machine may have to be recalibrated if there are knots in the wood. Either we can use a higher pressure that can cut through the knots along with non-knotted areas or use different pressures for different areas. Using either option can affect the final quality of the part.

Rubber
Waterjet technology is also increasingly used to cut rubber with varying thicknesses. A key advantage of a waterjet cutter is that it does not create concave edges, unlike die-cutting.

The technology is also not limited by the thickness of the rubber. The abrasive waterjet machine can cut rubber of varying hardness and thickness to the desired final quality.

In many cases, pure water jet cutting may be enough to meet product specifications for rubber products. Pure water jet cutting can easily cut sponge rubber of up to 50 mm thickness and hard rubber greater than 25 mm thickness up to a bidirectional tolerance of 0.25 mm.

Ceramics
Waterjet technology is commonly used in industrial cutting devices for ceramics. Ceramics are hard and brittle and difficult to machine. They cannot withstand the excessive pressure that a workpiece is subjected to in other mechanical cutting methods.

In waterjet cutting, no excessive pressure is applied to the workpiece except at the cutting point. This makes it ideal for cutting ceramics. The cutter can pierce its own starting hole and precisely cut complex shapes.

CNC (computer numerical control) technology is used in conjunction with abrasive waterjet cutting to ensure repeatable accuracy and good edge quality.

Glass
Waterjet cutting can cut a variety of glass with incredible detail. It can cut the most delicate glass without cracks or craters on it. On the other end of the spectrum, you may use it to cut stained glass.

Cutting with a water jet does not require etching or breaking. But starting holes are pierced at a lower pressure due to the tendency to crack. A waterjet can cut up to 50 mm of bulletproof glass, this number is even greater for other types of glass.

Stone and tiles
Stone and tiles are other common applications for waterjet cutters. With the right technical settings, we can use a waterjet cutter for cement, ceramic, glass, granite, limestone, mosaic, metal, porcelain, travertine and quarry tiles.

Features of waterjet cutting:

Water cutting mainly has the following features:

• 1. Cold cutting: Because water and abrasive cutting are used, there is basically no thermal effect during processing, and the workpiece will not be deformed by heat and will not change its physical and chemical properties. It is especially suitable for materials that are greatly affected by heat, such as titanium.
• 2. Wide cutting range: It can cut almost all metal or non-metal materials, such as stainless steel, copper, aluminum, various alloys, ceramics, glass, composite materials, etc., and is not limited by thickness.
• 3. High cutting precision: the cutting surface is neat and smooth, and will not cause any damage to the object to be cut during the cutting process, and can complete cutting operations that many cutting tools cannot achieve; the slit is extremely small, which can reduce the material waste rate.
• 4. Good adaptability: high production efficiency, cutting can start from any point on the workpiece and proceed in any direction. Combining with CNC technology, CNC can realize mass production of workpieces with complex shapes. Moreover, one nozzle can process different types of materials and shapes without changing tools, which saves time and cost and improves production efficiency.
• 5. High safety and environmental protection: No toxic fumes are produced during the cutting process, and there is no spark, no thermal effect, and small vibration. It is a safe and environmentally friendly cutting process, especially suitable for dangerous working environments with special requirements.

Applications of waterjet cutting technology

Waterjet equipment and technology are research hotspots in the waterjet industry in various countries in recent years. According to previous international waterjet conferences, with the commercialization of waterjet equipment and technology, waterjet has been widely used in many industries.

• 1. Aerospace industry, such as titanium alloy, carbon fiber, special laminated thick glass, plexiglass, honeycomb panel, ceramic insulation layer, special rubber, metal matrix and ceramic matrix composite materials, rocket solid fuel cutting, instrument panel processing, etc.
• 2. In the military industry, it is used for cutting high-strength steel plates, armor plates, various special decoration materials, armor plates, tracks, turrets, bumpers, artillery, gun xie, bulletproof glass, car bodies, ammunition, etc. of various tanks. Clean up the mines and bombs left over from the war, deal with the explosives created by terrorism and separatist forces, peel off the adhesive layer and ice layer on the runway of military airports, cut nuclear reactors and waste, cut underwater structures and shipwrecks in military ports , military fortifications and engineering rock breaking, etc.
• 3. In the mining industry, the dust and friction sparks produced by the jet cutting rock are less, making it especially suitable for closed environments, such as underground rock mining. The reduction of dust improves the working environment, and the reduction of friction sparks greatly reduces the possibility of gas explosion during coal mining. The ultra-high pressure water jet reaming equipment for different hardness coal seams and different types of borehole reaming can increase the exposed area of coal around the borehole, increase the pressure relief range and influence radius of the borehole, thereby improving the drainage effect of the borehole .
• 4. In the automobile manufacturing industry, it is used for cutting instrument panels, interior and exterior decorations, door panels, and window glass without molds, which can improve the processing flexibility of the production line.
• 5. The building material industry and building decoration industry have technical advantages that other cutting technologies lack. It can be used to cut marble, granite, glass fiber, ceramics, asbestos and other materials, and can also cut complex-shaped stone mosaics. The cutting size is accurate and pollution-free. Water jet cutting technology can be used to remove aluminum oxide on the outside of the workpiece, molding sand and ceramic coating on the casting, and can also cut gray iron castings that are difficult to cut by conventional methods.
• 6. In the electronics industry, it is used for contour cutting of printed circuit boards, wafer cutting in integrated circuit chip manufacturing and cutting processes in ceramic mosaic technology, etc.
• 7. In the food industry, it is used to cut crispy food, vegetables, meat, etc., which can reduce the damage of cell tissue and increase the storage period. When cutting food, the "NC water jet" can control its cutting speed and route with a numerical control device, which can maintain the nutritional content of the cut object to the greatest extent, without causing the spread of bacteria and regular shape.
• 8. In the paper industry, it can be used for coiling and cutting of kraft paper, corrugated box board, etc., without dust pollution.
• 9. In the field of textile industry, it is used for cutting multi-layer fabrics, improving cutting efficiency and reducing edge damage. Waterjet cutting is also widely used in clothing cutting, shoe blanking, etc. Water jet cutting and effective nesting can save up to 18% of raw materials in shoe blanking.
• 10. Underwater cutting, the exploitation of seabed oil and solid mineral deposits, and the maintenance of ships and warships all inevitably require underwater cutting technology. Ultra-high-pressure water jet cutting can be used in various occasions such as underwater rescue and underwater repair, salvage operations, underwater demonstration sampling, oil drilling, offshore platform disassembly, wharf construction and maintenance, underwater operations of ships, and marine engineering. With the development and utilization of the ocean, the underwater cutting technology of ultra-high-pressure abrasive water jet is bound to develop rapidly.
• 11. Harmful and poisonous on-site cutting, in earthquake rescue and post-disaster reconstruction work, ultra-high pressure water jet spray dust reduction and cutting concrete structures, etc. Water jet cutting technology is especially suitable for cutting workpieces in flammable and explosive environments.

Waterjet vs Other Cutting Methods

Compared with other cutting methods, water cutting has its own unique advantages.

1. vs laser cutting

Laser cutting is a very advanced cutting technology with fast cutting speed and high precision, but its limitation is that it is mostly used for cutting thin steel plates and some non-metallic materials, and it will cause thermal effects at the slit during cutting, which is harmful to aluminum and copper. The cutting effect of non-ferrous metals and alloys is not ideal. For thick metal plates, the cutting speed is slow, or even impossible to cut. Waterjet cutting is suitable for almost all kinds of materials, the cutting thickness is large, there is no thermal effect, and there is basically no limitation of laser cutting. But the cutting speed of water jetting is not as fast as laser cutting.

2. vs plasma cutting

Plasma cutting uses a high-temperature plasma arc to cut. The thermal effect is obvious, the precision is not high, and a large amount of toxic fumes are generated during the cutting process, which is poor in environmental protection. Waterjet cutting belongs to cold state cutting, no thermal deformation, good cutting precision, safety and environmental protection.

3. vs wire cutting

Wire cutting belongs to the category of electrical processing and has high precision for metal processing. The disadvantage is that it can only cut conductive metal materials, and the speed is slow and the efficiency is low. Sometimes it is necessary to punch a process hole in the workpiece in advance to thread the wire. The electrode wire used for cutting is easy to break, and the cutting size is greatly limited. Waterjet cutting is not limited by materials, with fast cutting speed and high efficiency, and a wide range of optional processing sizes.

4. vs other traditional cutting methods

Flame cutting is often used for cutting metal sheets. Compared with water cutting, its thermal effect is obvious, the cutting surface quality and accuracy are poor, and secondary processing is generally required; punching and shearing processing has high efficiency and fast speed, and is generally suitable for large quantities of small pieces. The disadvantage of processing is that it requires specific molds and tools, and it is difficult or impossible to process materials with large thickness and high hardness. Water cutting is not affected by material shape, thickness, hardness, etc., and has better versatility.

Prospects of waterjet cutting technology

The further development of water flow processing technology is mainly in the following aspects.

1. Develop intelligent control. Using high-pressure water jet to process parts with high precision requirements or complex shapes, the production and application of water jet CNC machining machines with more than 5 axes is a necessary prerequisite. This requires a large number of processing experiments to determine the process parameters in different situations, so that the process parameters can be adaptively adjusted during the process, so as to improve the machining accuracy of the machine tool. It is extremely necessary for the design and development of this kind of high-precision water jet processing machine tool, which is directly related to whether the high-pressure water jet technology can meet the practicality of the entire process from rough machining to finishing.

2. Improve processing efficiency. Optimize the process parameters of abrasive water jet processing, further improve efficiency, reduce abrasive consumption and energy consumption, and make the cost of abrasive water jet processing more competitive. Using abrasive water jets to process various difficult-to-machine materials of different materials and cutting of various composite materials, the processing efficiency is still relatively low. Further development of water jet processing technology to improve the processing efficiency and quality of these materials is the focus of future technological development. difficulty.

3. Open up research on new types of jets. Different processing requirements will inevitably require different types of processing capabilities. Different types of high-pressure water jets such as cavitation jets, pulse jets, coolant beam jets, high-viscosity additive jets, magnetorheological fluid jets, and room temperature freezing point jets must have a wider range of applications. Application prospect.

4. Continuously expand the application range of water jet processing. With the research and application of various new materials, the corresponding processing technology must develop rapidly, and the water jet technology will be more and more widely used because of its unique advantages. Water jet technology still has a very broad application prospect in the field of finishing and ultra-precision machining, but the problems that need to be overcome are also extremely difficult.

5. Comprehensive application of other processing technologies. The organic combination of other processing technologies such as laser, ultrasonic, electrolytic processing and high-pressure water jet technology will significantly improve the application range and processing efficiency of water jet technology.