Waterjet Cutting

Waterjet (water jet cutting) - type of cutting, in which the material is processed by a thin super-fast stream of water. With waterjet cutting to increase the destructive force of water jets in the high hard particles are added to her material - abrasive.

Standard notation
GAR - waterjet WJC - Water Jet Cutting - Cutting the water (or water and abrasive) jet AWJC - Abrasive Water Jet Cutting - Abrasive water jet cutting

The essence of the process
If the normal water pressure to compress about 4,000 atmospheres, and then passed through a hole with a diameter less than 1 mm, it will flow faster than the speed of sound by 3-4 times. Being directed at the workpiece, a jet of water becomes a cutting tool. With the addition of abrasive particles increases its cutting capacity hundreds of times, and it can cut almost any material.

Waterjet Cutting

Waterjet cutting technology is based on the principle of erosion (abrading) the impact of abrasive and water jet. Their high-speed solid-phase particles act as carriers of energy and particles striking the product, tear off and remove the last of the cut cavity. The rate of erosion depends on the kinetic energy of impacting particles, their mass, hardness, shape and angle of attack, as well as on the mechanical properties of the material.

Cutting Technique
Water is pumped to ultrahigh-pressure atmosphere of the order of 1000-6000, served in the cutting head. Breaking through a narrow nozzle (nozzle) is usually 0,08-0,5 mm diameter okolozukovoy or supersonic speeds (up to 900-1200 m / c and above), the jet of water enters the mixing chamber, where he began to mix with the particles of abrasive - garnet sand , fused grains, silicon carbide or other high hard material. The mixed stream emerges from the mixing (mixing) of the tube with an inner diameter of 0.5-1.5 mm and cut material. In some models, the abrasive cutting heads is fed into the mixing tube. To quench the residual energy of the jet used by the water layer thickness is generally 70-100 centimeters.

Waterjet cutting process

mixing abrasive particles

With waterjet (without abrasives) scheme is simplified: the water escapes under pressure through a nozzle and is directed to the cutting unit.

TABLE. A typical field of application technology of cutting water

Waterjet	Waterjet Cutting
Leather, textiles, felts (footwear, leather, textiles)	Sheets of steel and metals
Plastics and rubber products (automotive industry)	Various metal parts (castings, gears, etc.)
Electronic boards	Aluminum alloys, titanium, etc., composite materials, thick-walled plastic (aerospace)
Laminated materials (aerospace)	Concrete, concrete, gypsum blocks, solid pavers and other construction materials
Thermal insulation, sealing materials and shumoponizhayuschie	Stone, granite, marble, etc.
Food - Frozen Food, dense foods, chocolate, cookies, etc.	Glass, armored glass, ceramics
Paper and cardboard	Composite materials, coated materials
Tree	Tree
Thermo-and duroplast	Reinforced Plastics

With waterjet cutting, destructive power of the jet creates a much greater extent due to the abrasive, and water serves mainly transport function. The size of the abrasive particles is chosen equal to 10-30% of the diameter of the cutting jet to ensure its effective and sustainable impact of expiration. Typically, the grain size is 0.15-0.25 mm (150-250 mm), and in some cases - about 0.075-0.1 mm (75-100 mm) if necessary to obtain the cut surface with low roughness. It is believed that the optimal size of the abrasive must be less than the value (d ST - d wc ) / 2, where d ST - inner diameter of the mixing tube, d wc - the inner diameter of the water nozzle.

As there are different abrasive materials with Mohs hardness of 6.5. Their choice depends on the type and hardness of the workpiece, as well as it should be noted that the harder the abrasive wears out faster than the cutting head components.

TABLE. Typical applications of some abrasive cutting

Name	A typical field of application
Garnet sand (consisting of corundum Al2 O 3 , quartz sand, SiO 2 , iron oxide Fe 2 O 3 and other components)	Widespread cutting of various materials, particularly high-alloy steels and titanium alloys
Grains of fused (consists mainly of corundum Al 2 O 3 and impurities) or its variants	Artificial materials with very high Mohs hardness.Used for cutting steel, aluminum, titanium, reinforced concrete, granite and other materials
The grains of silicon carbide (SiC) - green or black
Silica sand (SiO 2 )	Glass cutting
The particles of silicate slag	Cutting plastic, fiber reinforced glass or carbon fibers

The nozzles are usually made of sapphire, ruby ​​or diamond. The service life of sapphire and ruby ​​nozzles up to 100-200 hours of diamond nozzles - up to 1000-2000 hours. If you do not apply waterjet nozzle ruby ​​and sapphire are typically 2 times longer.

The mixing tube is made of superalloys. The service life - typically up to 150-200 hours.

Technological parameters
The main technological parameters of the process of waterjet cutting are:

• cutting speed;
• appearance, properties and thickness of the cut products;
• inner diameter of the water nozzle and mixing tube;
• type, size, flow rate and concentration in the mixture of abrasive cutting particles;
• pressure.

Cutting speed (the speed of movement of the cutting head along the surface of the workpiece) significantly affects the quality of the cut. At high speeds is the deviation (mole) of water-abrasive jet straightness, as well as significantly weakening the jet appears as cutting material. As a consequence, increased taper of the cut and its surface roughness.

The separation can be performed on the cutting speed is 80-100% of maximum. Usually corresponds to high-quality cutting speed range of 33-65%, thin cut - in the 25-33% precision cutting - in 10-12.5% ​​of the maximum speed.

Type of cut surface, depending on the speed of the water-abrasive cutting

In some models, cutting heads used technology to automatically compensate for taper, for example, Dynamic Waterjet Company Flow. Compensation taper is achieved by software-managed dynamic tilt the cutting head to a certain degree. It allows to increase the cutting speed while maintaining the quality of cut and, consequently, reduce production costs.

With decreasing the inner diameter of the mixing tube (ceteris paribus) increase productivity and accuracy of cutting, cutting width is reduced (it is approximately 10% greater than the inner diameter of the tube). At the same time is reduced and the life of the tube. In the operation of the mixing tube of internal diameter increases by about 0.01-0.02 mm per every eight hours.

TABLE. Sample sizes for different modes of abrasive cutting

Application	The particle size of garnet sand (Garnet)		Int. diameter water nozzle		Int. diameter of the mixing tube
	mesh (U.S.)	micron	inches	mm	inches	mm
Industry standard configuration	80	178 (300–150)	0.013–0.014	0.330–0.356	0.04	1.02
High-speed cutting	60	249 (400–200)	0.014–0.018	0.356–0.457	0.05	1.27
	50	297 (600–200)
Precise cutting	120	125 (200–100)	0.012–0.013	0.305–0.330	0.036	0.91
	80	178 (300–150)
Precision Cutting	120	125 (200–100)	0.010–0.011	0.254–0.279	0.03	0.76

Abrasive consumption depends on the diameter of the mixing tube and a water nozzle, cutting conditions, etc. Estimated optimal values ​​are given in the table below.

TABLE. The optimal flow of abrasive material in some mixing tube diameter ratio and nozzle

The inner diameter of the water nozzle (mm)	The inner diameter of the mixing tube (mm)	Abrasive consumption (g / min)
0.25	0.76	270–360
0.36	1.02	500–640
0.46	1.27	800–1100

Maximum operating pressure is typically 3000-3200, 3800, 4150 or 6000 bar. The higher the pressure, the higher the speed and efficiency of cutting. At the same time require more frequent replacement of gaskets in the pump.

TABLE. The dependence of the linear velocity of separation (draft), cutting the material thickness at a pressure of pump P = 4100 bar (about 4046 atm)

Type of material	Cutting speed (m / hr) * thickness
	5 mm	10 mm	20 mm	50 mm	100 mm
Stainless steel	52.62	28.56	13.02	3.84	1.44
Titan	68.46	37.20	16.98	4.98	1.86
Aluminum	142.20	77.40	35.40	10.20	3.72
Granite	251.40	137.10	62.76	18.00	6.60
Marble	295.20	160.80	73.50	21.24	7.80
CFRP	247.20	134.70	61.74	17.70	6.60
Glass	272.76	148.62	67.92	19.62	7.26
* : pressure - 4,100 bar mark abrasive - Kerfjet # 80; abrasive consumption - 250-450 g / min, the inner diameter of the nozzle - 0.25 mm, 0.35 mm internal diameter of the mixing tube - 0.76 mm, 1, 01 mm / Data Company "TehnoAlyansGrupp", Moscow, install GAR BarsJet

TABLE. The dependence of the linear velocity of separation (draft), cutting the material thickness at a pressure of pump P = 6,000 bar (about 5922 atm)

Type of material	Cutting speed (m / hr) * thickness
	5 mm	10 mm	20 mm	50 mm	100 mm
Stainless steel	86,64	47,16	21,48	6,12	2,40
Titan	112,38	61,50	28,08	8,22	3,06
Aluminum	233,76	127,44	58,44	16,92	6,24
Granite	413,46	225,42	103,08	29,70	10,92
Marble	485,28	264,60	121,02	34,80	12,84
CFRP	406,56	221,88	101,40	29,22	10,86
Glass	448,14	244,38	111,72	32,16	11,88
* : pressure - 6000 bar brand abrasives - Kerfjet # 80; abrasive consumption - 250-450 g / min, the inner diameter of the nozzle - 0.25 mm, inner diameter of the mixing tube - 0.76 mm, 1.01 mm / Data Ltd "TehnoAlyansGrupp", Moscow, install GAR BarsJet

Details obtained by water-jet cutting: a stainless steel 15 mm thick, aluminum alloy, 6 mm thick, made of aluminum 30 mm thick, made of plastic, fiber reinforced, thickness 20 mm, made of tool steel with a thickness of 60 mm

Advantages, disadvantages, and comparative analysis of Waterjet Cutting
With the help of water or an abrasive water jet can cut virtually any material. It does not appear any mechanical deformation blank (because the force of the impact of the jet is only 1-100 N), nor any of its thermal deformation, since the temperature in the cutting zone is about 60-90 ° C. Thus, in comparison with the technology of heat treatment (oxygen, plasma, laser, etc.) waterjet has the following distinguishing features:

• higher quality of cut because of the minimal thermal effect on the workpiece (without melting, melting or burning the edges);
• possibility of cutting the heat-sensitive materials (number of fire and explosion, laminated, composite, etc.);
• ecological purity of the process, the complete absence of harmful gas emissions;
• explosion and fire safety process.

The water-abrasive jet can cut the material thickness of up to 300 mm or more. Waterjet cutting can be performed on a complex contour with high precision (up to 0,025-0,1 mm), including for high-volume products. With it you can do bevels. It is effective with respect to aluminum alloys, copper and brass, due to the high thermal conductivity which are in thermal cutting methods require more powerful sources of heat. In addition, these metals are more difficult to cut the laser because of their low ability to absorb laser radiation.

The disadvantages of water and abrasive cutting include:

• significantly lower rate of cutting steel of small thickness compared to plasma and laser cutting;
• high cost of equipment and high operating costs (typical for laser cutting) due to consumption of abrasives, power, water and drain pipes mixing, water nozzles and seals that can withstand high pressure, as well as costs for waste disposal;
• increased noise due to the jet at supersonic speeds (typical for plasma cutting).

TABLE. Comparison of waterjet cutting with oxygen, plasma and laser cutting

Name	Characteristics of water and abrasive cutting in relation to the
	oxygen	Plasma	Laser
Range of cut material	greatly exceeds	greatly exceeds	even wider
The typical width of cut (mm)	much less	less	more  (for cutting water - comparable)
Quality	greatly exceeds	greatly exceeds	greater than
The zone of thermal influence	much less	much less	less
The restriction on the maximum thickness of the metal	inferior	greater than	much greater than
Cutting performance thin steel (up to 6 mm, batch cutting)	inferior	significantly inferior	significantly inferior
Cost of equipment	much higher	above	comparable
Cost of service	above	comparable	comparable

See also:
Waterjet cutting installation
Laser cutting equipment

Cutting technology:

Oxygen Cutting Oxygen Flux Cutting Oxygen Lance Cutting Air-arc cutting

Oxy-arc Cutting Plasma Cutting Laser Cutting Waterjet Cutting