Waterjet cutting has many applications, and there are many reasons why waterjet cutting is preferable over other cutting methods. Listed below are several advantages, along with a brief explanation.
- In waterjet cutting, there is no heat generated. This is especially useful for cutting tool steel and other metals where excessive heat may change the properties of the material.
- Unlike machining or grinding, waterjet cutting does not produce any dust or particles that are harmful if inhaled.
- The kerf width in waterjet cutting is very small, and very little material is wasted.
- Waterjet cutting can be easily used to produce prototype parts very efficiently. An operator can program the dimensions of the part into the control station, and the waterjet will cut the part out exactly as programmed. This is much faster and cheaper than drawing detailed prints of a part and then having a machinist cut the part out.
- Waterjet cutting can be easily automated for production use.
History
Waterjet cutting can be traced back to hydraulic mining of coal in the Soviet Union and New Zealand. Water was collected from streams and aimed to wash over a blasted rock face carrying away the loose coal and rock. This method of mining was redeveloped in South African gold mines to remove blasted rock from the work area into a collection drift or tunnel. In the California Gold Country between 1853-1886, pressurized water was first used to excavate soft gold rock from the mining surfaces. The pressurized water allowed the miner to stand further back from the face being washed. This was safer because there was less danger of being covered by a collapsing wall of blasted rock. By early 1900s this method of mining had re ached Prussia and Russia. In these two countries the pressurized water was used to wash blasted coal away.
In the 1930s it was Russia that made the first attempt at actually cutting the rock with the pressurized water. A water cannon was used to generate a pressure of 7000 Bars.
Dr. Norman Franz is regarded as the father of the waterjet. He was the first person who studied the use of ultrahigh-pressure (UHP) water as a cutting tool. The term UHP is defined as more than 30,000 pounds per square inch (psi). Dr. Franz, a forestry engineer, wanted to find new ways to slice thick trees into timber. In the 1950's, Franz first dropped heavy weights onto columns of water, forcing that water through a tiny orifice. He obtained short bursts of very high pressures (often many times higher than are currently in use), and was able to cut wood and other materials. His later studies involved more continuous streams of water, but he found it difficult to obtain high pressures continually. Also, component life was measured in minutes, not weeks or months as it is today.
Dr. Franz never made a production timber cutter. Ironically, today wood cutting is a very minor application for UHP technology. But Franz proved that a focused beam of water at very high velocity had enormous cutting power - a power that could be utilized in applications beyond Dr. Franz's wildest dreams.
What is Water Jet?
Waterjet cutting technology is a unique, advanced level of automation able to cut almost all materials efficiently and maintaining a cost effective advantage. Waterjet, simply put, takes normal tap water pressurizes it up to 60,000 psi then pushes it through a diamond orifice and focusing tube. The orifice and focusing tube allow for a precise stream of either pure water or abrasive waterjet giving you a well finished edge ready for application to finished goods.
Waterjet allows tremendous flexibility and versatility in manufacturing and provides for more cutting possibilities.
How Water Jet Works
The energy required for cutting materials is obtained by pressurizing water to ultra-high pressures, and forming an intense cutting stream by focusing this high-speed water through a small, precious-diamond orifice There are two main steps involved in the waterjet cutting process. First, the ultra-high pressure pump or intensifier pressurizes normal tap water at pressure levels up to 60,000 psi (4,137 bar); to produce the energy required for cutting. Second, water is then focused through a small precious diamond orifice to form an intense cutting stream. The stream moves at a velocity of Mach 3, three times the speed of sound, depending on how the water pressure is exerted. The process is applicable to both water only and abrasive jets.
For abrasive cutting applications, abrasive garnet is fed into the abrasive mixing chamber, which is part of the cutting head body, to produce a coherent and an extremely energetic abrasive jet stream. Cutting harder materials requires adding a fine mesh abrasive to the cutting stream. Various abrasive materials which can be used include olivine, garnet, and corundum with a particle size of between 50 to 120 mesh (0.2 to 0.5 mm). When abrasive is required, KMT Waterjet provides an abrasive unit consisting primarily of an abrasive hopper, an abrasive feeder system, a pneumatically controlled on/off valve, and the abrasive cutting nozzle which contains the specialized mixing chamber.
The abrasive is first stored in the pressurized hopper and travels to a metering assembly, which controls the amount of particles fed to the nozzle. The abrasive is then introduced into the cutting stream in a special mixing chamber within the abrasive cutting head. Abrasive cutting allows harder materials to be cut at a faster rate by accelerating the erosion process. After the cut, residual energy from the cutting stream is dissipated in a catcher tank, which stores the kerf material and spent abrasive.
To achieve these pressures, water is introduced into the unit by way of a booster pump and filter. This filtering process is very important as water must be clean before reaching ultra-high pressures in order to protect the high pressure parts and provide a consistent cutting stream. A water treatment system is sometimes needed to remove harmful minerals from the water. After being filtered, the water enters the high pressure cylinder where it is pressurized to the desired level. The water is then carried to either an abrasive or straight-water cutting nozzle, depending on the application. The cutting nozzle can be stationary or integrated into motion equipment, which allows for intricate shapes and designs to be cut. Motion equipment can range from a simple cross-cutter to 2D systems and 3D machines as well as multiple axis robots. CAD/CAM software combined with CNC controllers translate drawings or commands into a digitally programmed path for the cutting head to follow.