Ordinary water is pressurized to 4000 bar (60,000psi) by an ultra-high pressure pressurizer, and then passes through a tiny nozzle (with a diameter of 0.004 inch to 0.0 16 inch), which can produce water arrows with a speed of 9 15 meters per second (about three times the speed of sound). This kind of water arrow can be used for various surface treatment and cutting.
For cutting all kinds of metals and hard materials such as stones, glass, ceramics and tiles, Fulu has developed a patent and a more perfect design, which is to mix sand with water arrows to enhance the cutting ability. This high-speed sand-adding water knife can cut almost any material.
Therefore, there is a high demand for water, pipes and nozzles. For example, in the pipeline, the water jet is injected after water is pressurized by a high-pressure tool, which requires extremely high pressure to cut hard cutting materials. Therefore, the pipeline must be able to withstand extremely high pressure, far greater than 700 MPa, because the thin steel plate (cutting material) itself can withstand the pressure of 700 MPa.
Secondly, it is wrong that the water used for water knives has no impurities at all. Because the water pressure is much greater than 700 MPa, pure water will always make them wear and leak for sealing equipment such as pipelines, no matter how good the sealing performance is. In order to solve this problem, 5% soluble emulsified oil should be added to the water jet to improve the sealing effect. For the high-pressure pump, some oil should be added to improve its sealing performance.
As mentioned above, the nozzle of water jet is made of cemented carbide, sapphire and other materials. The diameter of the nozzle is only 0.05 mm, and the inner wall of the hole is smooth and flat, which can bear the pressure of 1700 MPa, so the sprayed high-pressure water can cut the material like a knife. Some water is also added with some long-chain polymers, such as polyethylene oxide, to increase the "viscosity" of water and make the sprayed water look like "thin lines".
Its machining accuracy is high, and the cutting width is only 0. 1-0.8mm, so it can be used to machine parts with complex surfaces. The cut of the processed parts is smooth and tidy, and no trimming is needed. Especially for the processing of materials that are easily deformed by heat, "water knife" has unique advantages.
It doesn't have the problem of tool wear, and the abrasive and wastewater mixed into the water jet can be recycled, with simple equipment and low processing cost. The vibration and noise generated by machining are very small, and the chip amount is only 15%-20% of that of machining. The chip will go with the water flow and will not fly up to hurt the operator.
"Water knife", because it is not a knife, has opened up a wide range of uses. The cutting of composite materials is a difficult problem in processing. If traditional processing methods are used, delamination and tearing will occur, and "water knife" is an ideal tool to solve this problem. It is better to remove the ceramic coating of parts with "water knife" than mechanical method and chemical method. "Water knife" can be used to punch holes and crush materials. It is also convenient to clean the attachments on the hull and propeller surface and the scale in the chemical pipeline with the "water knife".
Water knives can also be used in surgery. The medical college of Tokyo University used a water knife with a pressure of 0.7 MPa to do experiments on rabbits. The results showed that it can be used for the operation of liver, kidney and other organs, without damaging the surrounding tissues and easily causing infection. 〕