Engineers and manufacturers are constantly exploring ways to reduce costs, and waterjets are now very effective at reducing costs and generating greater profits.
Therefore, it is necessary to learn more about the application of waterjet technology in order to use the lowest cutting costs to create more profits.
The waterjet cutting industry is considered to be the most versatile and fast-growing industry in terms of cutting costs.
In addition to the above, the waterjet cutter is one of the most productive machines in the world.
At the same time, waterjet cutting does not produce harmful gases or liquids and generate heat on the surface of the workpiece, it is a truly versatile, efficient and cold cutting process.
Waterjet cutting can do some processing that cannot be done by other simple processes.
It can punch holes in titanium and cut various patterns in stone or glass, all of which show the uniqueness of the waterjet itself.
It produces no heat when cutting materials.
During this cold processing, it produces supersonic water arrows that can achieve ideal results when shot at the surface of the cutting material, and the mixture of water and sand enhances its cutting ability even more.
Waterjet, which is water as the knife, is the original name of high-pressure water jet cutting technology.
The technology first originated in the United States and was used in the aerospace and military industries.
Its cold cutting will not change the physical and chemical properties of the material and is very popular.
Later, after continuous technical improvements, mixing the high-pressure water with garnet sand, diamond sand and other abrasives to assist cutting greatly improving the waterjet cutting speed and cutting thickness.
Waterjet has been widely used in ceramics, stone, glass, metal, composite materials and many other industries. In China, the maximum pressure of the waterjet has been achieved to 420MPa.
Some technologically advanced companies have perfected 3-axis and 4-axis waterjets, and 5-axis waterjets are also becoming mature.
Waterjet, also known as waterjet cutting, is a machine that uses high-pressure water to cut.
It can carve the workpiece arbitrarily under the control of the computer, and it is little affected by the texture of the material.
Because of its low cost, ease of operation, and high yield, waterjet cutting is becoming the mainstream cutting method in industrial cutting technology.
It can cut any material in any curve in a single process (all other cutting methods except water cutting are limited by the variety of materials).
The heat generated during cutting will be immediately taken away by the high-speed flow of water jets, and does not produce harmful substances, no thermal effect on the material (cold cutting), no need or easy secondary processing after cutting, safe, environmentally friendly, faster, more efficient, can achieve any curve cutting process, convenient and flexible, versatile.
Water cutting is a mature cutting process method with good applicability.
UHP water cutting, also known as waterjet and water jets, is a high energy (380MPa) water flow generated by ordinary water after multi-stage pressurization, and then jet cutting at a speed of nearly 1,000 meters per second through an extremely fine ruby nozzle (Φ0.1-0.35mm), and this cutting method is called UHP water cutting.
Classification of waterjet
Waterjet can be divided into pure waterjet and abrasive waterjet.
The pure water waterjet was the first method of water cutting. The first commercial application began in the mid-1970s for cutting corrugated cardboard.
The largest applications for pure water waterjets are cutting disposable diapers, cotton paper and automotive upholstery.
For cotton paper and disposable diapers, waterjet technology leaves the least amount of water on the material compared to other technologies.
Features of pure water waterjet
Very fine water flow (common diameter range: 0.004 to 0.010 inches) Very detailed geometry.
Very little material cut loss, no heat generated while cutting, can cut very large or very thin thicknesses, fast cutting speeds, ability to cut soft, lightweight materials (e.g., fiber glass insulation up to 24″ thick), very low cutting forces, simple fixturing, continuous operation 24 hours a day.
Abrasive waterjets differ from pure waterjets in only a few ways. In a pure waterjet, the material is eroded by supersonic water flow. In an abrasive waterjet, particles of abrasive material are accelerated by water jets, and then these particles (not water) erode the material.
Abrasive waterjets are hundreds or thousands of times more powerful than pure waterjets. Both pure waterjets and abrasive waterjets have their place.
Pure waterjets cut soft materials, while abrasive waterjets cut hard materials such as steel, stone, composites and ceramics.
Abrasive waterjets using standard parameters can cut materials with a hardness equal to (or even slightly exceeding) that of alumina ceramics (often called alumina, AD 99.9).
Features of abrasive waterjet
- Fine water flow (0.020 to 0.050 inch diameter).
- Very complex geometries can be cut.
- Thin material cutting 10 inch thickness cuts, stacked cuts, very little material cut loss.
- Simple fixturing, low cutting forces (less than 1 lb. when cutting), and only one setup for almost all abrasive waterjet jobs.
- Easily switch from single to multiple cutting heads.
- Quickly switch from pure waterjet to abrasive waterjet, reducing auxiliary operations.
- Few or no burrs.
Classification of water cutting
Divided by the sand situation: water cutting is divided into two ways: sand-free cutting and sand cutting.
Divided by equipment: water cutting is divided into large water cutting and small water cutting.
Divided by pressure: water cutting is divided into the high-pressure type and low-pressure type, generally with 100MPa as the boundary. 100MPa or more for high-pressure type, 100MPa or less for low-pressure type. And more than 200MPa for ultra-high pressure type.
Divided by the technical principle: water cutting is divided into front-mixed and post-mixed.
Divided by mechanical structure: water cutting is divided into cantilever type and gantry type.
Divided by safety cutting: water cutting is divided into safety cutting class and non-safety cutting class, the difference is mainly in the water pressure above, 100MPa below the low-pressure type water cutting can be used in special industries such as: hazardous chemical, petroleum, coal mining, hazardous materials treatment, etc..
After a lot of experiments people found that when the water pressure exceeds a certain threshold, even pure water will detonate certain sensitive chemicals, and sand-containing water cutting because the water contains abrasive sand, sand potential energy and impact and object collision, the energy generated will also cause instability of special chemicals, after a lot of experiments and argumentation, and finally came to its threshold in about 237.6MPa.
Therefore, in the water cutting industry, more than 200MPa water cutting is mainly used in the machining industry
Water jet cutting speed chart
Table1 Water jet cutting speed for common materials
|Material||Cutting thickness||Water pressure|
|Carbon Steel||12 , 50||350||0.25/0.76||0.4, 0.1|
|Stainless Steel||13, 25||350||0.25/0.76||0.4, 0.2|
|Titanium||3.2, 6.4||350||0.25/0.76||0.8, 0.6|
|Aluminum||12 , 100||350||0.25/0.76||0.6, 0.12|
Origin of water cutting
Dr. Norman Franz has long been recognized as the father of the waterjet.
He was the first person to research ultra-high pressure (UHP) waterjet cutting tools.
UHP is defined as higher than 30,000 psi.
Dr. Franz was a forestry engineer who wanted to find a new way to cut large tree trunks into lumber.
In 1950, Franz first put very heavy weights on a column of water and forced the water through a very small nozzle.
He obtained a brief high-pressure jet (many times exceeding the pressure used today) and was able to cut wood and other materials.
His later research involved a more continuous stream of water, but he found it very difficult to obtain continuous high pressures.
Also, the life of parts was measured in minutes, not weeks or months as it is today.
Dr. Franz never built a mass-produced wood cutter.
Today, wood cutting is one of the least important applications for UHP technology.
But Dr. Franz proved that high-speed convergent water flow has tremendous cutting power – a power that has applications far beyond Dr. Franz’s wildest dreams.
In 1979, Dr. Mohamed Hashish, working at Flow Research, began investigating ways to increase the cutting power of waterjets for cutting metals and other hard materials.
In 1979, Dr. Mohamed Hashish, working at Flow Research, began investigating ways to increase the cutting power of waterjets for cutting metals and other hard materials.
Dr. Hashish is recognized as the father of the abrasive waterjet and invented the method of adding abrasives to a regular waterjet.
He used garnet (a material commonly used on sandpaper) as the abrasive.
With this method, the waterjet (with abrasive) can cut almost any material.
In 1980, abrasive waterjets were first used to cut metal, glass and concrete.
In 1983, the world’s first commercially available abrasive waterjet cutting system was introduced and was used to cut automotive glass.
The first users of this technology were the aerospace industry, which found the waterjet to be an ideal tool for cutting stainless steel, titanium and high-strength lightweight composites used in military aircraft, as well as carbon fiber composites (now used in civilian aircraft).
Since then, abrasive waterjets have been adopted by many other industries such as fabricators, stone, tile, glass, jet engines, construction, nuclear, shipyards, and more.
The development process of water cutting can be roughly divided into the following stages.
The early 1960s exploration experimental stage, mainly used in low-pressure water jet mining and oil pipeline cleaning.
The late 1960s to the early 1970s of the basic equipment development and research stage, the main development of high-pressure pumps, booster and high-pressure pipe fittings and the promotion of high-pressure water jet cleaning technology.
The early 70’s to the early 80’s industrial experiments and industrial application stage, a large number of high-pressure water jet coal mining machine, cutting machine and cleaning machine came out one after another and industrial experiments.
Since the 80s is the rapid development of high-pressure water jet stage, the main feature is the high-pressure water jet research further deepened, abrasive water jet, abrasive jet, cavitation jet and self-excited shock jet and other new jet technology is developing rapidly.
Development of water cutting
At present, there are more than 40 countries engaged in the research and application of water jet processing technology: mainly the United States, Russia, Japan, Germany, Switzerland, the United Kingdom, France, Canada, Australia, India, South Korea, Singapore and other countries.
The scope and field of application of water jet technology is very wide. It generally includes industrial cutting, excavation, mining and drilling, rock cutting and excavation, surface cleaning, material crushing, etc.
How high-pressure water is generated
The basic principle of this is both simple and complex. The water jet starts with a pressurized pump, passes through a high-pressure tube, and then shoots out of the cutting nozzle.
A very simple explanation. However, it is designed very intricately to produce 60,000 PSI of pressure.
A small leak somewhere in the design process can cause lasting damage to the parts by erosion.
So manufacturers and engineers will carefully handle the processing of high-pressure materials, using special technology to combine this machine.
Users only need to know the basics of operation.
Abrasive cutters have been used in industry since 1982, the first ones appeared in 1970, in the industry mainly in the automotive, aerospace and glass industries, from which the precision of cutting has been continuously improved.
The pressure of the abrasive cutter can reach 55,000 PSI, and this high-pressure water is shot through a tiny nozzle at a speed of 762m/s, which is 2.5 times faster than the speed of sound.
Mixing the garnet sand into this high-velocity water jet by mixing it in a mixing tube and then shooting it directly from the sand tube to the material being processed at 305M/s, this cutting process is actually a grinding and cutting process, the force and action is generated by the water.
Basic principle of water jet
In short, the basic principle of the water jet is: using the principle of liquid pressurization, the mechanical energy of power source (motor) is converted into pressure energy through a specific device (booster port or high-pressure pump), and the water with huge pressure energy passes through a small hole nozzle (another energy converter), and then the pressure energy is converted into kinetic energy to form a high-speed jet (WJ).
Therefore, it is often called high-speed water jet.
Forms of water cutting
In terms of water quality
UHP water cutting has two forms
Pure water cutting, whose cutting slit is about 0.1-1.1mm.
Adding abrasive cutting, whose cutting slit is about 0.8-1.8mm.
In terms of structure form
There can be various forms, such as: gantry structure and cantilever structure with two to three CNC axes, which are mostly used for cutting plates.
Five to six CNC axes of robot structure, this structure is mostly used for cutting automotive interior parts and car’s inner lining, etc.
Features of water cutting
1. Wide cutting range
Can cut most of the materials, such as: metal, marble, glass, etc.
2. Good cutting quality
Smooth kerf, no rough and burr edge.
3. No heat processing
Because it is cut with water and abrasive, no heat (or very little heat) is generated during processing, and this effect is very ideal for materials affected by heat. For example: titanium.
4. Environmental friendliness
This machine uses water and sand cutting, this sand does not produce toxic gas in the process, can be directly discharged, more environmentally friendly.
5. No need to replace the cutter
You do not need to replace the cutting machine unit, a nozzle can process different types of materials and shapes, saving costs and time.
6. Reduce burr
Waterjet cutting with abrasive grit, only less burr in the cut
7. Programming quickly
The program is mainly generated by CAD drawing software, you can design line drawings at will in the software, or input DXF files generated from other software, in addition, the machine supports third-party software, such as nesting layout software (used to add graphics in the workpiece, can minimize the loss of workpiece).
8. Fast programming
You can transfer the program generated by other software into the machine, it can build up the tool path from the CAD, and the precise positioning of the cutter head and cutting speed in excess of 2,000 points/inch (800 points/cm) calculated, all you need to do is specify the material and thickness you want to cut, the rest of the work to the machine to complete.
9. Combined with other equipment, can be operated separately
Water cutting machine can be combined with other processing equipment (such as drilling head) to make full use of its performance and optimize the use of materials.
10. Reduce the number of adjustments
Only a small side pressure is needed to fix the workpiece, reducing the trouble caused by complex clamping.
Advantages and disadvantages of water jet processing
- High processing efficiency.
- absence of heat reaction zones.
- High machining accuracy.
- No change in the mechanical properties of the material to be machined.
- Almost all materials can be processed, etc.
- High power of equipment;
- The nozzle wears fast;
- The surface quality is poor;
- It is not suitable for large parts and large burr removal;
- The processing of soft materials and elastic materials is not ideal.
- High hardness materials, such as steel, cermet, high strength composite materials and hard rock, can not be cut by pure water jet, while abrasive water jet has the problems of nozzle wear and high cutting cost.
- The equipment cost of high-pressure water jet is higher than other cutting methods.
- In some applications, compared with laser cutting, plasma arc cutting, wire electrode EDM and other methods, there are shortcomings such as low feed rate and poor machining accuracy.
- In the cutting process, there are many parameters that affect the cutting quality, and the conditions are complex, sometimes the cutting results in the stratification and stripes of the section.
Concept of water jet processing technology
High-pressure Water Jet Machining
High-pressure water jet machining is to use water or liquid with additive in water to pressurize the supercharger through the water pump, then make the high-pressure liquid flow stable through the liquid storage accumulator, finally form a high-speed liquid flow of 300-900 M / s through the nozzle, and spray it to the workpiece surface for material removal and modification.
Abrasive jet machining
Abrasive jet machining (AWM) is a kind of high-speed jet flow which is composed of micro-abrasive and high-pressure air or other gases. Through a specially designed nozzle, the material on the surface of the workpiece can be removed and modified by the high-speed impact and erosion of the abrasive.
Abrasive Water Jet Machining
Abrasive water jet machining (AWJ) is a kind of method which takes water as medium, obtains huge energy through high-pressure generating device, and then adds abrasive into high-pressure water beam through feeding and mixing device to form liquid-solid two-phase mixed jet. It can remove surface material and finish machining by high-speed impact and scouring of abrasive and high-pressure water beam. It is a combination of the advantages of abrasive jet and water jet, so that the processing range is expanded.
Characteristics of abrasive water jet machining
Strong adaptability, wide cutting range, can cut metal, non-metal materials and all kinds of brittle, plastic and difficult to process materials;
Abundant water and abrasive sources, low price;
No harmful gas, dust, smoke, etc., no pollution, environmental protection;
It can realize the simultaneous operation of multiple cutting heads with fast cutting speed and high efficiency;
High flexibility, strong versatility, can process all kinds of complex parts;
Good working environment, safety, no fixture, easy operation;
Good processability, narrow cutting seam, smooth cutting surface, no burr;
Cold processing will not damage the physical and mechanical properties and intergranular structure of the material.
Classification of water jet
Water jet can be divided into the following three types:
- Continuous jet
- Pulse jet
- Cavitation jet
(1) According to the characteristics of the jet, it can be divided into:
① Liquid jet (including water jet and other liquid jet);
② Liquid solid jet (abrasive jet);
③ Liquid-gas-solid jet (pneumatic conveying abrasive).
(2) According to the jet pressure, it can be divided into:
① Low-pressure jet
For the water jet whose working pressure is less than 10MPa, the main engine of the system is the centrifugal pump or low-pressure reciprocating pump;
② High-pressure jet
When the working pressure is 100MPa, the main engine of the system is high-pressure reciprocating pump;
③ Ultra high-pressure jet
For the water jet with working pressure not less than 100MPa, the main engine of the system is mostly ultra-high pressure reciprocating pump and supercharger.
(3) According to the media around the jet, it can be divided into:
① Submerged jet
Water jet in water or other liquid;
② Non-submerged jet
Water jets are ejected in the air.
(4) According to the use of the jet, it can be divided into:
① Atomization jet (dust suppression, sprinkler irrigation, etc.);
② Modeling jet (fountain, artificial waterfall, water curtain, etc.);
③ Vacuum jet (water jet suction);
④ Cylindrical jet (fire fighting, cleaning, etc.);
⑤ Fine jet (cleaning, cutting, etc.).
The pulse jet is a discontinuous jet, and the image of this discontinuous jet is very similar to that of a bullet,
It is produced in the following ways:
(1) Sudden release of shaped energy, or water cannon;
(2) Pressure extrusion;
(3) Flow regulation, also known as “water hammer”.
The performance of these jets depends on the frequency of water hammer formation, the ratio of water hammer length to jet diameter and the energy of the water hammer.
Cavitating jet is a kind of continuous jet which naturally produces cavitating bubbles in the jet.
In this way, the growth of cavitation nuclei (bubbles in the fluid) is stimulated
These bubbles are drawn into the jet and grow further until they are close to the surface being cleaned or cut and break due to blockage.
During the fracture process, very high pressure and micro jet are produced, and the target stress is higher than the tensile strength of most materials.
Advantages of water jet cutting
- No limitation of cutting direction → various cutting shapes can be completed.
- The transverse and longitudinal force generated is very small, which can reduce the setting time and the cost of using the fixture.
- The same machine can complete the drilling and cutting function, which can reduce the processing time and cutting cost.
- There will be no thermal effect or deformation or tiny cracks → no secondary processing is required, which can save time and manufacturing cost
- It will not produce toxic gas → it can provide a better working environment for operators.
- It can reduce the time and cost of workpiece manufacturing.
- It can reduce the production of a large number of waste materials and save the direct manufacturing cost.
- It can complete the cutting of the workpiece in one time and has good cutting quality → it can reduce the processing time and cost.
What kind of material can ultrahigh-pressure water jet cut
Ultra high-pressure water jet can cut all kinds of thick and hard materials, such as stainless steel, aluminum, copper, steel, marble, alloy metal, glass, plastic, ceramics, tiles and all kinds of visible materials.
Application of water jet
High-pressure water jet cutting is carried out by using high-speed jet with high kinetic energy (sometimes called high-speed water jet processing). It belongs to the category of high-energy beam processing like laser, ion beam and electron beam.
As a high and new technology, high-pressure water jet cutting is a revolution in the cutting field in a sense, and has a very broad application prospect. With the maturity of technology and the overcoming of some limitations, it is a perfect supplement to other cutting processes.
Because water jet processing technology has many advantages, it is widely used in the aerospace industry, automobile industry, machinery manufacturing industry, construction industry, medical equipment industry, electronic power industry, chemical industry, sporting goods industry, military industry, new material-related fields.
The applications of the main industries are summarized as follows:
It can be used to cut various alloy materials and new materials, such as carbon fiber composite, plastic glass, etc. It belongs to cold cutting, no thermal effect, no damage to material properties, no post-treatment.
It can be used to cut all kinds of non-metal and composite materials, such as body outer panel, door frame, gas box, etc., to meet the characteristics of modern automobile production mold with strong versatility and high flexibility.
It can be used for the destruction of weapons and the cutting of inflammable and explosive facilities, armored plate of combat vehicle, bulletproof glass, turret, etc.
Machinery manufacturing and construction
It can be used to cut all kinds of metal, non-metal, brittle plastic materials and difficult to process materials, such as marble, ceramics, concrete, floor tiles, etc., with high quality, high efficiency, high utilization rate and other significant advantages.
Application of water jet technology in cutting
The water jet is used in the paper industry, rubber industry, while abrasive waterjet can be used in the stone industry, ceramics industry, aerospace industry, automotive manufacturing, metal processing industry.
Especially worth mentioning the automobile manufacturing industry, with the rapid development of the automotive industry in recent years, the expansion of the output value of the major automobile manufacturers, the continuous updating of the model, the shortening of the production cycle, the supporting automobile interior parts (such as carpets, instrument panels, headliners, etc.) manufacturers, the early manual processing of automotive interior trim cutting and punching methods, due to low efficiency, poor product accuracy, labor intensity, obviously can not meet the needs of the current development of the automotive industry.
At this time, the water jet equipment combined with robots stands out. The high-pressure water pipe is spirally wound on the robot arm, and the robot arm and wrist can make the nozzle of the water jet head run rapidly along a straight line or arc to achieve the purpose of 3-dimensional processing of interior parts.
Application of water jet technology in industrial cleaning
The water jet technology can be applied to the cleaning of spray booth in the automobile industry, the cleaning of inner and outer tubes of heat exchanger in the petrochemical industry, the rubber cleaning of aircraft runway, the surface treatment of industrial rust removal and anti-corrosion engineering, the cleaning of engine parts in the aerospace industry, the cleaning of radiation pollution in nuclear power plant, etc.
In recent years, some companies have applied ultra-high pressure technology in food anti-virus to achieve the purpose of food preservation, and successfully entered the food preservation industry (for example, the famous American Hemell company has used ultra-high pressure equipment for food preservation), and achieved good reputation.
Water jet can be used to clean cars, high-rise buildings, airport runways, heat exchangers in chemical plants, etc.
A variety of cleaning machines and cleaning facilities have come out one after another, and a large number of them have been put on the market. Various cleaning companies and service companies have also been established to provide services for users.
According to the latest research of Missouri Rolla University, high pressure water jet has great potential in use. It can crush coal into fine particles for cleaning and producing clean fuel. It can also separate wood fiber by hydraulic pulping.
In 2002, the flow company of the United States brought the ultra-high pressure technology into a revolutionary stage, and released the ultra-high pressure water jet equipment with the highest pressure up to 87000mpa, which greatly improved the production efficiency and reduced the use cost by 40% compared with before.
With the continuous development, promotion and application of water jet technology, its development and application prospects will be unlimited.
Factors affecting water jet machining
- System parameters: water jet system pressure;
- Nozzle structure parameters: nozzle diameter, chamfer radius, mixing pipe length, mixing pipe diameter;
- Abrasive parameters: abrasive material, particle diameter, abrasive flow, particle shape;
- Mixing mode: pressure drive or negative pressure suction;
- Mixing state of abrasive: dry powder or slurry;
- Cutting parameters: feed speed, target distance, times of cutting, jet angle;
- Material parameters: strength, hardness, density, etc.
Accuracy of water jet cutting
The cutting accuracy of water cutting is between 0.1 mm and 0.25 mm. The cutting accuracy depends on the accuracy of the machine, the size range of the cutting workpiece and the thickness and material of the cutting workpiece. Generally, the positioning accuracy of the machine system is 0.01 mm to 0.03 mm.
How wide is the cutting slit of the waterjet
It depends on the size and thickness of the material to be cut and the nozzle used.
Generally speaking, the kerf of abrasive cutting is about 1.0mm to 1.2mm, and as the diameter of the abrasive tube expands, the kerf becomes larger.
What kind of bevel will be produced by water jet cutting
The quality of the beveled edge depends on the cutting speed. Most of the good cutting quality is about 0.1 mm.
Abrasive used in water cutting
The abrasives used in water cutting are quartz sand, garnet, river sand, diamond sand, etc..
The grain size of abrasives is generally 40-70 mesh, the higher the hardness of the abrasive the larger the grain size, and the stronger the cutting ability.
What kind of material should be cut with waterjet
Generally speaking, the materials with complex patterns, thick, difficult to cut, fragile and afraid of heat are most suitable for water jet cutting.
Comparison of several cutting methods
Waterjet vs milling
For cutting and drilling the periphery of a workpiece, instead of using blind holes, drilling and threading, it is much faster, easier to arrange and cheaper to use an abrasive cutter.
The main reason for this is that we can cut the workpiece in a single pass with a waterjet, without having to grind all the metal to pieces.
When high precision workpieces need to be cut, the abrasive cutter is a tooling machine that can be used to produce close to the finished product, in one pass and without thermal effects.
In addition, the scrap produced by an abrasive cutter is often valuable because it is in the form of whole pieces rather than chips, and can be reused.
Water jet vs flame cutting
Obviously, flame-cutting is a hot process, which causes a thermal effect on the finished product. With an abrasive cutter, the surface finish is usually better, and there is no slag on the back of the workpiece, which reduces secondary processing.
There is no limit to the thickness of the cutter, and the layout spacing of the cut pattern can be reduced to save material costs.
The investment in laser cutting equipment is large. At present, it is mostly used for cutting thin steel plate and some non-metallic materials. The cutting speed is fast and the precision is high. But when laser cutting, it will cause arc mark and thermal effect at the cutting seam;
In addition, for some materials, laser cutting is not ideal, such as aluminum, copper and other non-ferrous metals, alloys, especially for the cutting of thicker metal plate, the cutting surface is not ideal, or even unable to cut.
At present, the research of high-power laser generator is trying to solve the cutting of thick steel plate, but the cost of equipment investment, maintenance and operation consumption is also considerable.
Water cutting has the advantages of small investment, low operation cost, wide range of cutting materials, high efficiency and convenient operation and maintenance.
Water jet is better than laser in some aspects
- There is no cut thickness limit
- Reflective materials such as brass and aluminum can also be cut
- There is no need to put in heat energy, so it will not burn or produce thermal effect
- When you change the cutting speed, the only thing you need to change is the cutting speed; there is no need to change the gas, focus, or other objects
- More cutting heads can be easily installed to increase production capacity
- Laser equipment maintenance is more professional and difficult
- You only need to buy laser equipment 1 / 2 to 1 / 3 of the price to have a complete set of water jet equipment.
Water jet vs plasma cutting
Plasma cutting has obvious thermal effect, low precision, and the cut surface is not easy to be re-processed.
Water cutting is cold cutting, no thermal deformation, good quality cutting surface, no secondary processing, if needed, it is also easy to secondary processing.
Water jet vs wire cutting
For metal processing, WEDM has higher accuracy, but the speed is very slow. Sometimes it needs other methods to cut, such as piercing and threading. Moreover, the cutting size is greatly limited. Water cutting can punch and cut any material, with fast cutting speed and flexible processing size.
Comparison of water cutting and other cutting methods
Compared with this cutting method, water cutting is more flexible and can be used to cut any shape workpiece at any time. Especially in the case of thick material and high hardness, punching and shearing technology will be difficult or impossible to achieve, while the water cutting method is more ideal;
Flame cutting is also a common cutting process in the metal field. The thickness range of cutting is very large, but compared with water cutting, it has an obvious thermal effect, poor cutting surface quality and accuracy. In addition, water cutting can solve the cutting of some special materials such as high melting point, alloy, composite materials and so on.
In glass, stone, ceramics and other cutting processing industries, the traditional method is to use diamond tools for cutting, sawing, milling, etc., the cutting thickness range is very large, and the speed is fast
But for the plate with normal thickness, water cutting can be used to cut any curve with high precision, with high yield, low production cost, and greatly improve the added value of processed products.
Generally speaking, when laser, plasma, flame, wire cutting, sawing, milling and other processing methods can basically meet the requirements of processing technology, water cutting is not suitable. After all, the operation cost of water cutting is high. Nozzle, guide sleeve and high-pressure seal are imported consumables, and the price is expensive.
What should a complete set of water jet cutting equipment include?
A complete set of water jet cutting equipment should at least include ultra-high pressure pump, water jet cutting head device, CNC cutting table, computer control cabinet, etc. The details are as follows:
- Working table
- High-pressure pump
- Cutting head
- Sand conveying system
- Cooling device
- Filter system
Five-axis water cutting technology
Due to the effect of energy gradient, the deeper the cutting plane is (the farther away from the nozzle), the worse the cutting ability of laser, oxy, plasma, jet and other cutting means. Therefore, the formed cutting surface is often not perpendicular to the workpiece surface, which is called cutting slope, which is an inherent defect of all cutting means.
Although the cutting slope can be partially reduced by increasing the cutting energy or reducing the cutting speed, there is still a problem that the cutting can not be completely vertical.
Therefore, the idea of tiltable cutting head was put forward in 1997. At present, there are commercial products in the world. This is the most direct and effective method to solve the problem of cutting inclination and improve accuracy.
The principle is that the cutter head can swing in any direction by adding two rotation axes on the basis of the original three-axis platform, and by using the slope model set in the system in advance, through real-time calculation of the cutting trajectory, and then according to the material and thickness of the workpiece to be cut, the cutter head can continuously swing in the process of cutting, so that the workpiece to be cut can achieve perfect non-interference slope state.
Waterjet cutting machine troubleshooting
For waterjet cutting machine with water hydraulic press
1) Pulsation: the pressure is unstable, for example, from 150MPa to 230MPa
Check whether the pulsation of the water inlet transparent pipe is normal. After determining which high-pressure cylinder has problems, disassemble and check the water inlet valve core, water outlet valve seat and spring. Generally, repair them first, and replace them when the problem cannot be solved. There are many problems with the spring.
2) The pressure is stable at a pressure, but not in a normal state.
For example: normal 230MPa, now 170Mpa or 140MPa.
① Check the pulse of water inlet pipe to see if there is impurity in one high-pressure cylinder to block the water inlet valve core
Check whether the pressure relief valve leaks and return water to the small water tank.
Check all parts of the main engine for water leakage
3) The pressure is only tens of Mpa, or no pressure
① Check whether water, electricity and gas are normal
② Is the belt slipping or loose
③ whether the diamond sand added
Whether the three high-pressure cylinders do not work, when the two high-pressure cylinders do not work at the same time, the pressure will be very small or no pressure.
4) The abnormal noise of high-pressure cylinder of the crankcase, the large jump range of ammeter and unstable pressure.
- There are two possible reasons for the noise
(1) the big nut of the crankshaft connecting rod is loose;
(2) the inlet valve core of the large valve body is blocked or the limit plate is not well matched.
(1.) tighten the connecting rod nut.
(2) disassemble the valve core, limit plate and small water inlet nut, and grind off the dirt or scar on the surface of the valve body and valve core with 1000# sandpaper, or replace the limit plate.
5) Cut glass will crack
- Is the glass level
- Is there sand feeding
- Is the pressure too high
- Whether the sand production is too large or too small
- Replace a piece of glass to determine whether the material is the same.
6）Gemstone and sand pipe
The normal use time of gems is 17 hours, 7-14 days. When gems are used for a long time, it will appear that when cutting, the fog around the cutter head is big, and the water arrows are scattered, which is worse than the normal cutting quality, such as edge skipping, sharp teeth, and the pressure display value is different from the normal frequency
Normal life 3-8 months, depending on their own quality and time to determine. In general use, the nozzle becomes larger, eccentric hole or ellipse appears after a long time, which makes the cutting workpiece appear high slope, bell mouth, angle collapse, etc. the workpiece will not only become larger or smaller, but also the cutting speed will not decline.
7）The pressure is normal, the water line is normal, but the cutting ability is poor
Cause of failure:
- The sand supply plastic pipe is damaged
- The sand flow is too small
- The sand inlet pipe is damaged
- Replace the sand supply plastic pipe with a new one
- Adjust the sand flow adjusting knob to increase the sand flow
- Replacement of sand inlet pipe
8) The system pressure is normal, but the cutting ability is poor
Cause of failure:
- The nozzle is damaged
- Wear of mixing chamber
- The sand pipe is damaged
- The sand supply is too small
- Replacement of gem nozzle
- Replacement of sand mixing chamber
- Replacement of sand pipe
- Increase sand flow
9) When the high pressure is turned on, there is no water ejecting from the sand pipe, while there is water ejecting from the sand inlet pipe
Cause of failure:
- The sand pipe is blocked
- Replace the sand pipe with a new one or remove the foreign matters in the sand pipe with high pressure
10) The water line without sand addition is normal, and the water is divergent after sand addition, and the cutting ability is decreased
Cause of failure:
- Replacement of sand pipe
- The sand pipe is damaged
For waterjet cutting machine with oil hydraulic press
1. Cutting flying sand
1) Check whether the cutting material is just cut to the grid bar.
2) Check whether the sand quantity is even or insufficient.
3) Check whether the pressure is normal.
4) Whether to change the gem.
2.Directional valve does not work
1) Check whether two signal lights of the directional valve are on.
2) Check that the pressure drops to 0.
3) Check whether the relay of reversing valve is on.
If there are the above factors, check whether the relay is loose and whether the striker on side 2 of the directional valve is stuck.
3. The main motor is working abnormally
1) Check if the emergency stop button is pressed.
2) Whether the power supply has enough current.
3) Whether the relay will be on, whether the incoming wire is loose or broken.
If the host repeatedly star starts for triangle start, you must see whether the upper limit pressure set by the temperature controller exceeds.
4. Pressure gauge alarm
1) When the pressure increases to 400-500, check whether the gem of the cutter head is blocked, or the sand pipe is blocked by impurities.
2) The transmission line of the pressure gauge is broken, or the pressure gauge is broken.
5. Cabinet failure
1) The computer can’t start, and the fan of the electric cabinet doesn’t work.
Check if the connector in the middle of the cabinet is loose. Check whether multiple leakages and air switches are turned down. Whether the voltage regulator lights normally and whether the switch trips.
2) The blade will not work.
Check whether the relay reacts and whether the two power supplies are on. The outside and the inside of the cutter head determine whether it is stuck.
3) Encoder alarm
Determine whether the XY axis reaches the limit position and whether the emergency stop button is released. Whether the incoming and outgoing lines are disconnected. Ruled out the above conditions, you can try to play the emergency stop, 15 seconds interval in the release, to see if the situation is solved. After that, the power can be cut off and the whole machine can be restarted. If not, contact the manufacturer.
6. Large valve body
1) The water leakage of the safety hole is very small.
Try to turn off the high pressure and tighten the nut.
2) The water leakage of the safety hole is very large
Open and check the outlet valve seat for wear or explosion. Just replace it. If there is no problem, check the contact surface between the large valve body and the outlet valve seat, and check whether there are cracks on the whole appearance of the large valve body. If there are cracks, it is estimated that the large valve body is exploded and must be replaced. It cannot be used any more.
3) The pressure jump is very big, the drop range is between 400-200, some parts are cut through, some parts will fly out.
Then, feel the frequency of the blue hose with your hand. When the water enters, there is only one direction, that is, the water flows to the end cover joint of the high-pressure cylinder, and there is only one frequency of water entering. If there is a frequency of one in and one out, and the hose is hot, then disassemble the large valve body, check whether the water inlet valve core and limit plate are blocked by impurities, and whether the time is not clear, and whether there is rust? Remove the limit plate to see if the contact surface between the inlet valve core and the large valve body is worn. Grind the contact surface of valve body and valve core with 1000-1500 sandpaper. Blow it clean and try again.
7. Cutter head switch
1) It can’t seal the water. After cutting, when you move to the second position, the high pressure doesn’t stop. If you keep driving, it will cause the workpiece to grind.
First, check whether there is open air. Then check whether the air valve is sensitive and normal. If the problem can not be solved after troubleshooting, disassemble the relief valve of the cutter head, carefully observe whether the needle of the relief valve and the relief valve seat is worn or do not fit well, please replace the worn parts.
1) It won’t work
You can refer to section 5. If you can’t solve the problem after troubleshooting, check with a computer maintenance master. If the system is paralyzed, I have a backup in the hard disk. I can use “one click ghost; restore”. If it is other fault, you can give the computer shop repair. But make sure that after installing the new system, there should be Auto CAD software and Ncstudio cutting software. It can be used normally.
2) The computer department can connect the network cable to the Internet, otherwise poisoning may occur.
3) Clean the dust of the computer regularly.
9. Cutting software
1-1) when opening the cutting software, it will prompt: Hardware self check error, etc
You can first update the driver of the software, steps: right click my computer, device manager, CNC device card, double-click to open, find the Nike control card, right-click to update the driver, specify the location from the list, next step. Don’t search, go on to the next step until it’s done.
1-2) the above method is not enough, you can try to reinstall the cutting software. Try again later.
1-3) the above method is not enough. Take apart the computer, find the control board of Nikai, take it out, clean the dust with anhydrous alcohol or soft cloth, and then use an eraser to clean the metal finger, and then try again. If not, change a slot position and try again.
2) When you open the software, the prompt does not exist.
Can’t press anything, including can’t open, can install a cutting software. Still can’t, please give the computer antivirus. Do a new system installation. Maybe the software is infected by a virus.
3) Software can’t control the machine.
Check whether the three emergency stop buttons are released, check whether the software prompts for alarm, whether the encoder behind the electric cabinet alarms, and then check the software, diagnosis and hardware port.
The red solid is normal, and the green solid is problematic. You can modify the polarity according to F5 to see if it is OK. Or check whether XYZ reaches the limit. Check whether the pressure gauge and temperature controller give an alarm.
4) Turn off the power and try again.
5) The drawing can’t be opened
The current drawing may be opened together with CAD. Please close CAD and open the drawing to be loaded.
6) Origin position:
When checking whether it works, press the emergency stop, which will cause the origin to move. When checking whether XY is limited, it will also cause the origin to move. Check whether the workpiece is moving or not fixed.
7) XY axis inactive
Check if there is a limit, check if there is an emergency stop. Check whether the encoder alarms (behind the electric cabinet) and press the emergency stop for 15 seconds. Restart.
1) Refuel the machine regularly.
Including XYZ 3 axes. The oil tank of the lift table and the oil tank of the main engine. The oil we use is the hydraulic oil for the machine. High-temperature resistance can be used here. Check whether the oil in the oil tank is enough at intervals.
2) Clean the machine shell after work or shift every day.
Pay attention not to let the electric cabinet, the three motors of the machine tool and the host water. Otherwise, there will be electric leakage or burn parts.
3) Check every part and nut regularly for water leakage, sliding teeth and looseness.
4) Every time the parts are installed and removed, they must be cleaned up
When installing, the place with thread must be rubbed with blue glue (thread anti-sticking agent). Please be responsible for burning (sticking) parts with other butter and lubricating oil.
5) Regularly check whether the electrical components are loose, and the circuit section will fall off. (the power must be turned off)
Development prospect of water jet machining technology
Improve reliability and life
In particular, the service life of key components such as high-pressure pump, high-pressure hose, connector and nozzle can further improve efficiency, reduce abrasive consumption and energy consumption, so as to make the cost more competitive.
Developing intelligent control
The process parameters can be adjusted adaptively in the process of machining to improve the machining accuracy. It can be used to make parts with certain accuracy requirements, and its technical and economic effect can be comparable to that of plasma and laser machining.
Expand the scope of application
The application scope of water jet machining is constantly expanded, from two-dimensional cutting and deburring to hole machining and three-dimensional surface machining.
Strengthen theoretical research
Especially, the establishment of water jet machining model and the study of multiphase flow theory should be strengthened.