Comparison Metal Water Jet Cutting with Laser and Plasma Cutting

Nowadays, we used many different materials for the production which generally have to be respectively formed by a more or less complicated cutting operations. In this article, I will focus attention on three ways of shaping the workpiece materials, namely: water jet cutting, laser and plasma cutting. These methods will be compared only in terms of cutting metals, which significantly reduces the scope of discussion and at the same time doing their precision. In the literature I have not found a good comparison of these three techniques cutting simultaneously.

Water jet cutting

Water jet is the method consisting of cutting the material (or a water jet can relate to cleaning it) by the use of thin water jets under high pressure with added abrasive slurry used to cut the target material by means of erosion. The technique with using high pressure water for cutting materials was first time patented in 1968 by researcher in USA, but fast development of water jet cut method was starting in early ‘80s. Today is a rapidly developing technology, that is used in industry for processing variety of engineering materials. It is an emerging technology, which has many advantages over the other non-conventional cutting technics. Often, in order to improve the performance of the process additive is used in the form of abrasive grains of garnet, which allows cutting of very hard materials. The correct name of this technology is so cutting hydro-abrasive treatment (abrasive water jet).

Cutting process can be described briefly as follows. The water fed by a pump under pressure, after passing through the water causes the suction nozzle to the abrasive mixing chamber. Then a mixture of water and abrasive is directed to the mixing nozzle in order to form and stabilize. The result is a stream of hydro-abrasive, which has enough power to cut through even the toughest materials.

Water jet we can applied in many areas of modern industry, such as automotive industry, aerospace industry, construction engineering, environmental technology, chemical process engineering, and industrial maintenance. Typical water jet cutting machines have a working space from few square feet to hundreds of square feet. In this moment the high pressure water pumps are available from 276 MPa up to 689 MPa.

Laser cutting

Laser cutting is a technology, which enables a laser to cut of various materials using the high-point of the cutting jet by the introduction of energy and technical gas of high purity. Laser radiation is characteristic, and thus practically unattainable by other methods. Gets plenty of power here in the choice, but a very narrow area of the spectrum. Its characteristics include consistent in time and space radiation, and the most polarized beam with low divergence. Depending on the cutting device is carried out in three ways: by burning, melting or sublimation.

Creation of the laser beam generally involves stimulating a lasing material by electrical discharges or lamps within a closed container. The beam is reflected internally through a partial mirror, until it achieves sufficient energy to escape as monochromatic coherent light. Generally, the narrowest part of the focused is less than 0.32 mm in diameter. Of course, taking into account the thickness of the material, the width of the gap as small as 0.10 mm are possible.

Plasma cutting

Plasma cutting is basically a process that is used to cut generally steel and sometimes other metals of different thicknesses. This process consists of metal melting, and then disposing of the cut metal from the slot. This is done by means of a concentrated plasma arc, having a large kinetic energy. In fact, plasma cutting uses a high temperature that prevails in the core plasma arc and high speed plasma stream. The electric arc is formed between the tungsten electrode and the cut object. Principles of its formation is as follows: by passing the gas stream in the compressed form of the arc for the phenomenon is a result of ionization and high power density is possible to produce a stream of plasma. The most commonly used gas plasma cutting is air and also in high-power devices used argon, nitrogen, hydrogen, carbon dioxide. Plasma arcs are extremely hot and are in the range of 25 000 ° C. Due to the high temperature plasma cutting edge of a destructive influence on the confluence. This method we can usually cut from 50 mm to 150 mm thick. This is a large range of metal cutting.

Comparison of water jet, laser and plasma cutting

Water jet cutting as compared to laser and plasma technology is primarily a more versatility. We cut here virtually any type of material, are not so restricted as in the case of a laser to homogeneous materials which do not reflect light, or as in the case of the plasma to the conductive material. For example, a perfect choice for cutting stone of varying thickness, shape and properties. Due to the small cutting force ceramic does not break, when cutting of complicated shapes. Here, there are quite a lot (in terms of waterjet technology) limitations on cutting speed, but keep in mind that this technology does not release harmful gases, UV radiation and other hazardous substances harmful to the machine operator. Technology same water jet cutting is so safe that we can use it to cutting food. Strength cutting head is relatively large, and the price of water - the basic cutting agent low. Texture of cut material here does not affect the quality of the processing, as is the case with the laser, where it may lead to distortion of the beam. You may also cut highly reflective materials such as aluminium and copper, and the cutting of holes does not make too much trouble here as in the case of plasma cutting.

One of the greatest advantages of hydro-abrasive machining, compared to the technique of laser cutting of materials is the possibility of limited practical geometry of the machine. It is mainly about cutting materials over 30 mm, where the waterjet works very well, and lasers are starting to have the first problem. When we continue this thought and move on to more than 100 mm cut material, it turns out that the hydro-abrasive machines are already unbeatable compared to laser technology, and it is not yet the end of their ability. Please note that, as usual, the thickness of the cut material is associated with a relatively longer duration of cutting, which should also be taken into account because it is not the fastest cutting techniques. Compared to laser plasma seems to be more universal, because it can be used to cut materials in the range from 0.5 mm to about 160 mm. However, as the thickness of the material also increases the wear of the electrode.

Another important advantage of water jet machining is the lack of any thermal deformation of the material being cut, and thus no melted edges. The temperature in the vicinity of the treatment increases in small areas as compared to other methods, and the process further location in the water, will accelerate the removal of heat from the treatment zone. As a result, the amount of heat generated at the cutting does not affect in any way the shaped material. For these reasons we can declare that the structure was preserved, because no significant change in the existing structure.

The structure of the cut surface in waterjet machining has a very high quality. The edges are rounded here, and additionally are not formed burrs. This results in a lack of need for a finishing process, which can significantly shorten the duration of the production of parts, and allows you to reduce the number of machines. Water jet machining this is a way to cut without heat Interactions. The lack of high-temperature cut material is not distorted area at near cut, so you do not need to use excess material that must then delete. It is the preferred method when the materials being cut are sensitive to the high temperatures generated by other methods. Little downside hydroabrasive technique is less precise cuts and relatively large compared to the noise in the laser cutting. However, the worst falls here plasma technology, which is both highly inaccurate and loudest.

Both the water jet machining, laser and plasma cutting can be easily attached the starting material. In water jet cutting the cut object is laid directly on a special grid, which prevent to the object from falling into the tank with water. In the absence of forces which could move the workpiece is used specific weights or fixtures. All compared treatment techniques are easy to program, which practically consists of the appropriate cutting path planning. There is no a problem choice of tools. With the right software it is possible to determine the shape of the cutting time.