Waterjet Cutting Process Basics

How Does Waterjet Cutting Process Work

Waterjet technology is a cold cutting process where supersonic water or water and abrasive is used for cutting material.

Why is this process popular among fabricators? Here are a few reasons:

• It is the most versatile process for shape cutting
• The technology provides the highest precision cutting on virtually any material
• The process can be combined with plasma or oxy-fuel on the same part

Most Versatile Cutting Process

Waterjet cutting is a versatile process because the waterjet can cut virtually any material. The process uses an ultra-high-pressure stream of water to carry an abrasive grit. This abrasive waterjet does the cutting through a mechanical sawing action, resulting in a smooth, precision-cut surface. Limitations include highly brittle materials, such as tempered glass and some ceramics.

Waterjet is also very precise. 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.

ESAB offers the patented combination of waterjet and plasma on the same machine. This option allows you to take advantage of the accuracy of waterjet where you need precision. It also benefits from the speed and low cost of plasma where high precision is not 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 waterjet 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 hydraulic pressure over the water system. A large horsepower motor drives a hydraulic pump, creating hydraulic pressure which powers a piston in a cylinder.

The various components of the intensifier pump include:

1. Low-pressure water inlet
2. Boost pump
3. Water filter
4. Inlet check valves
5. Hydraulic pump
6. Intensifier piston
7. Accumulator
8. Water Off Valve
9. Cutting head
10. 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). This 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). The flow of the water to the cutting head is controlled by the off valve (8). This allows 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 abrasive 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. For example, let us assume that the hydraulic cylinder size is 20 times the size of the water cylinder. Then a 3,000 PSI (Per Square Inch) hydraulic pressure is intensified to 60,000 PSI water pressure, or with a 30:1 ratio of 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 a 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 the 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 sandpaper. Some special applications utilize other abrasive types.

When cutting soft materials, such as rubber, leather, cloth, paper, cardboard, insulation, foam, etc., the ultra-high-pressure jet stream does the cutting, and no abrasive is used.

ESAB manufactures the Hydrocut CNC waterjet cutting machines for large and small cutting applications and can customize a machine to fit your exact needs.