ESAB Knowledge center.
Waterjet Cutting Process Basics
May 6, 2014
The most versatile process for shape cutting
- Highest precision cutting on virtually any material
- Can be combined with plasma or oxy-fuel on the same part
- Most versatile cutting process
Water Jet cutting uses an ultra-high pressure stream of water to carry an abrasive grit. The abrasive does the cutting through a mechanical sawing action, leaving a smooth, precision cut surface.
Waterjet is the most versatile process, because it is able to cut almost any type of material. Limitations include materials that are highly brittle, such as tempered glass and some ceramics.
Water jet is a very precise cutting process. It has a narrow kerf width, allowing fine contours to be cut, and producing high tolerance parts. However, it is a very slow, expensive process when compared to plasma on most metals.
That is why ESAB offers the patented combination of waterjet and plasma on the same machine. This option allows you to take advantage of the accuracy of water jet where you need precision, and also benefit from the speed and low cost of plasma where high precision isn’t necessary. The effect is to produce the parts you need for substantially lower cost, in substantially less time.
How a Waterjet Intensifier Pump Works
The water jet cutting process starts with an intensifier pump, which creates the ultra-high pressure (up to 90,000 psi) water pressure required for cutting hard materials.
The Intensifier pump uses a hydraulic pressure over water system. A large horsepower motor drives a hydraulic pump, creating hydraulic pressure which powers a piston in a cylinder.
- Low pressure water inlet
- Boost pump
- Water filter
- Inlet check valves
- Hydraulic pump
- Intensifier piston
- Water Off Valve
- Cutting head
- Abrasive metering system
Clean water is pulled in through the low pressure water input (1) and forced through the inlet filter (3) then into the intensifier through the inlet check valves (4). The Hydraulic pump (5) pressurizes the hydraulic fluid and switches pressure back and forth between the two sides of the hydraulic piston (6) which in turn pressurizes the water in the intensifier. The pressurized water flows out of the intensifier and into the accumulator (7) which helps smooth out the pressure ripples. It then flows through high pressure tubing to the cutting head (9). Flow of the water to the cutting head is controlled by the off valve (8), allowing the CNC to start and stop the cutting process at the appropriate time. In the cutting head (9) garnet abrasive is mixed with the high pressure water in the mixing chamber. Flow of the garnet is controlled by the abrasive metering system (10).
How an Intensifier Creates Ultra High Pressure
The hydraulic pressure is amplified by the ratio of the larger hydraulic cylinder pushing a smaller piston into a cylinder filled with water, thus creating the ultra-high water pressure. So if the hydraulic cylinder size is 20 times the size of the water cylinder, then a 3,000 PSI hydraulic pressure is intensified to 60,000 PSI water pressure, or with a 30:1 ratio 90,000 PSI water pressure.
How a Waterjet Cutting Head Works
The pressurized water is delivered to a cutting head by either high pressure tubing or hose. At the cutting head, the high pressure water is applied to an orifice with a typical diameter ranging from 0.005” to 0.020”. This orifice is made in a diamond or sapphire, to resist abrasion of the high pressure water. The orifice defines and creates the water stream which cuts through the material.
After the water stream exits the orifice, an abrasive can be added to the water stream, to allow it to cut hard materials. When cutting hard materials, including steel, stainless steel, aluminum, stone, wood, plastic, glass, etc., it is the abrasive that does the actual cutting using a mechanical sawing type action.
The abrasive is usually crushed garnet, the same type of material often used as the abrasive on sand paper. Some special applications utilize other abrasive types.
When cutting soft materials, such as rubber, leather, cloth, paper, cardboard, insulation, foam, etc., the high pressure water stream does the cutting, and no abrasive is used.
ESAB manufactures the Hydrocut CNC water jet cutting machines for large and small cutting applications, and can customize a machine to fit your exact needs.