Some Facts to Consider When Choosing a Waterjet Cutter

Waterjet CutterWhen requiring waterjet cutting services, or a waterjet cutting device, it is very helpful to understand the differences between the many variations available.
Today, several options of waterjet cutting systems exist. There is one capable of performing almost any need or task. The most basic waterjet cutting systems are known as pure waterjet systems. The function and design of all alternative waterjet systems are based around pure waterjets.
In a pure waterjet system, an extremely pressurized and rapidly moving stream of water is used to cut materials. Typically, the jet of water moves at about 2,000 feet per second, under pressure of approximately 20,000 to 90,000 pounds per square inch (psi).
One of the great advantages of waterjet cutters over other cutters like plasma and laser devices, is the ability to cut plenty different sorts of materials. Waterjet systems can cut anything from foam, rubber, and plastic, to wood, stone, and marble, to titanium, stainless steel, and aluminum.
For stronger materials, abrasive waterjet cutters are most ideal.
In abrasive waterjet systems, the water is mixed with abrasives like garnet and aluminum oxide. Abrasive waterjet cutters come in two forms known as slurry and entrainment.
The difference between slurry waterjets and entrained is when, and how the abrasives are added to the water.
In abrasive slurry waterjet cutters, the abrasives are added to the water before it is pressurized. This allows for lower pressures and high material removal rates. However, while the equipment for this system is less expensive than others, it suffers from frequent wear as the abrasives travel throughout the entire machine. In entrained waterjet cutters, the abrasive solution is limited to a mixing chamber, or tube, preserving the rest of the equipment.
Two major flaws of concern with all waterjet systems are stream lag and taper.
Stream lag occurs when the point at which the waterjet enters (or cuts) the material is faster than when it exists (when cut is complete).
The stream of water is "lagging” as it reaches the exit point. This is a result of the waterjet losing momentum as it flows though the material. This is harmful as it results in:
  • Decreased accuracy
  • More cutting errors like Taper
  • Secondary procedures due to lack of accuracy, wasting time and money
Taper refers to an error in cutting that results in an unwanted "V” shape. This happens naturally when the strength of the water stream is gradually lost as the jet makes its way through the material (stream lag).
A more recent waterjet system known as Dynamic is becoming more, and more available to precision cutting companies.
The Dynamic waterjet systems were designed to resolve the issue of stream lag and taper. To reduce the probability of taper occurrences, the Dynamic waterjet head tilts automatically to the side when necessary. Furthermore, to avoid stream lag, the waterjet head automatically shifts forward, controlling the stream flow.
All waterjet systems are computer numerical control devices, or CNC. This includes Dynamic waterjets. In this newer system, the software performs all the necessary mathematic calculations to understand when and how to tilt the waterjet head.
Waterjet cutting systems come in many different options. Each perform slightly different functions to better suit various cutting results. For instance, pure waterjets are better suited to work with softer materials like rubber, while abrasives perform best with stronger materials like titanium. Additionally, there are a number systems to suit any budget. Knowing how each system works, helps to explain how they work and why some are more costly than others. This type of information makes it easier to decide which system is most appropriate for a particular task.
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