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Waterjet Cut: The Process and How It Works

Machines used for waterjet cut have been so popular for 2D cutting of flat plate. This is applicable even in heavy applications like fabricators, equipment manufacturers, and steel service centers. One of the best things about water jet cutter are the lack of a heat-affected zone and the straightness of the cut. In order to better understand the advantages, it provides, below is how it works.

Waterjet Cut Process

Waterjet: A Non-Thermal Process

Unlike plasma, laser, or oxyfuel which are a thermal cutting process, waterjet is a mechanical sawing process. This can be considered like a band-saw- a thin strip of metal with sharp set of teeth and are pulled through the material that is being cut. Similarly, the process makes use of a thin stream of water that has sharp pieces of rock pushed through the material.

These pieces of rock or called as abrasive are often made from crushed garnet. Other materials are used in some applications but garnet is considered to be the most common when it comes to metal plate cutting. It is also often used in sandpaper.

 

Speed is what Makes it Work

Simply pouring the sandy water onto the plate won’t cut it. Speed is what really makes it work in which the abrasive hits the plate. The object’s momentum is equal to the mass and then multiplied by its velocity. This abrasive has very little mass so it does not have an effect on a steel plate- it needs a lot of velocity. Acceleration will happen when the abrasive is fast enough to cut through a hard material, the water is being pressurized reaching ultra-high pressure, and released through a small orifice. When playing with a garden hose, you will notice that as you make the opening of the nozzle smaller, you will be getting lesser volume, but comes out at a much faster speed.

 

Adding Abrasive

Basically, everything happens inside a waterjet cutting head- from the forming of water stream to the mixing of the abrasive to the stream. In order for the stream to get into the water, the stream needs to pass through a chamber that is shaped like a funnel. This is where the abrasive will be picked up by the water stream and then accelerated. Then, the water stream will carry the abrasive particles and will go through a nozzle or focusing tube where it gets all the abrasive fully involved into the water stream and moves in the same direction.

Result

Since the particles of the abrasive only moves small amount of material by erosion, just a little heat is being generated. At the same time, any heat that is being produced is quickly quenched by the water stream before it heats up the surrounding material. These fast-moving particles do not only cut with no heat affected zone, but the momentum coming from the water stream keeps them in a straight line after they exit the tube, thus resulting in an accurate and straight cut edge on various materials.