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Advantages of waterjet cutting over other cutting methods

All cutting processes require a certain amount of energy. Waterjet cutting is a chip-cutting method to separate materials. Potential energy, which is transferred in the form of pressure (up to 6200 bar) through the water, is converted into kinetic energy that is bundled by the precious stone orifice measuring only a few tenths of a millimetre. The water jet thereby reaches speeds of up to 3 times the speed of sound. This high-energy jet consists of pure water or a mixture of water and abrasive. It is the actual tool of the micro-cutting process. One of the main advantages of waterjet cutting technology is the fact that it is a cold cutting process. This is particularly important for the cutting of metals, as the process does not affect the structure of the material along the cutting edge and does not result in any loss of material.

The main advantages of waterjet cutting at a glance:

• As no heat is generated that might affect the structure of the metal, there is generally no need for costly reworking
• Extremely low loss of material thanks to minute cutting gaps
• Material can be cut in all directions
• The cutting edge is of a consistently high quality, as the tool cannot become blunt or dirty 
• Allows for easy integration into flexible production systems
• Existing cutting tools in online processes can normally be replaced with waterjet cutting units without any difficulties 

The table below shows a comparison of laser, plasma and waterjet cutting and the respective material and processing characteristics. Each method has certain advantages and disadvantages, depending on the material to be cut.

Waterjet cutting - frequently asked questions

• Which materials can be cut?
  In principle, water jets can be used to cut all types of materials. The method is most commonly used to cut metals, stones and plastics. Water jets can however also cut glass, foodstuff or leather.
• How fast can the material be cut?
  The cutting speed is determined by the following factors: pump pressure, efficiency of high pressure generation and cutting head configuration, material thickness and properties, desired cutting edge quality, orifice diameter, abrasive quantity and abrasive quality. See also cutting speed table below.
• What is the maximum material thickness that can be cut with water jets?
  For metals, the maximum thickness is normally 150 mm. Waterjet cutting is however also used in special applications for materials of up to 400 mm thickness.

Cutting speeds:

The cutting speed is determined by the following factors:

1. Pressure:
   The higher the pressure, the greater the power density of the cutting jet and the greater the cutting performance. Cutting with 6200 bar is for example up to 35% faster than with lower pressures.

2. Material thickness:
   The following rule of thumb applies: halving the thickness of the material allows for double the cutting speed.

3. Orifice diameter:
   A larger orifice bundles more energy onto the material so that the cutting speed is increased. If the orifice size is doubled, the volume of cutting water fed through is quadrupled. This means that the cutting speed is increased by up to 80%, depending on the application. It is therefore often useful to use small orifices to cut several parts together.

4. Quantity of abrasive:
   The higher the abrasive concentration in the cutting jet, the higher the cutting speed. By doubling the abrasive flow rate, the cutting speed can be increased by 20 to 40%, depending on the material.

5. Cutting quality:
   The processing time varies considerably depending on whether the material is just to be separated or whether a high quality cutting edge is to be achieved.  

Special advantages of waterjet cutting:

• Multilayer cutting
  Waterjet cutting can be used to cut several workpieces or multiple layers of different materials in one process. Cavities between the layers might however impair the cutting effect, especially if a hard layer is followed by a soft layer. The hard top layer of the material slows down the jet at its edges, while the centre jet cuts with the initial high energy. As a result, the jet is affected by a kinetic component that works sideward, which leads to a spreading of the jet. When entering the second layer of material, the water jet is thus considerably wider than when it exited the orifice.

• Cutting hollow bodies:
  To cut pipes with the water jet method, you need a specially adapted machine. This is necessary as the jet spreads outwards after it has penetrated the upper pipe section, so that the water jet impacting on the opposite pipe wall is not as bundled as would be required for proper cutting. A solution to this problem is a lathe system that ensures that the water jet impacts at a constant angle of 90° on the pipe.

• Angle faults
  Depending on the requirements as regards cutting edge quality, excellent angle accuracy can be achieved by adjusting the pump pressure, the abrasive flow rate and the cutting speed accordingly. There are also software-based guiding systems on the market that help optimise angular accuracy by adjusting the angle of the cutting head.  

KMT products for waterjet cutting

• High pressure pumps
  KMT Waterjet Systems offers a range of high pressure pumps that cater for all applications. They cover everything from maximum cutting waterjet pressures of up to 6200 bar to maximum volumetric flows of more than 15 l/min and simultaneous operation of a large number of cutting heads.
  - STREAMLINE 60/125 PRO – waterjet cutting with 6200 bar
  - STREAMLINE SL-V 15-100
  - STREAMLINE SL-V 30/50 Classic
  - STREAMLINE SL-V 150/200

• Cutting heads for abrasive and pure water cutting:
  ACTIVE AUTOLINE PRO – abrasive cutting head for 6200 bar
  ACTIVE IDE PRO – compact abrasive waterjet cutting head for 6200 bar
  ACTIVE AUTOLINE II – modular abrasive waterjet cutting head for 4100 bar
  ACTIVE IDE II – compact abrasive waterjet cutting head for 4100 bar
  AQUALINE – reliable pure water cutting head

• Abrasive systems for abrasive waterjet cutting
  - AMS III – abrasive management system consisting of an ABRALINE III abrasive bulk transfer system, a FEEDLINE IV metering system and ACTIVE AUTOLINE II or ACTIVE IDE II cutting heads
  - ABRALINE III –  abrasive bulk transfer system
  - FEEDLINE IV – abrasive metering system 

About KMT Waterjet Systems

KMT Waterjet Systems is a leading multinational manufacturer of waterjet cutting systems. The company develops complete solutions for a wide range of industries and applications. Since 1971 the company has been dedicated to long-term customer relationships. Continuous investment in innovation has made KMT Waterjet Systems the market leader in the waterjet cutting industry. High pressure pumps, cutting heads, abrasive systems, high pressure tubes, original spare parts and a global service network are among the key products and services of the company.