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What is Waterjet Cutting?

Posted by on 14-11-2018
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Process of waterjet cutting

Waterjet cutting is arguably the most versatile cutting process. The technology can be used in high performance cutting of virtually all materials, with the exception of highly brittle materials such as ceramics and tempered glass.

It uses an ultra-high pressure stream of water (for soft cutting) or contains an abrasive grit (for abrasive cutting) to cut both soft and hard materials, respectively, through a mechanical sawing motion that produces a smooth, precisely cut surface.

How Waterjet Cutting Works

Waterjet cutting utilizes the energy of a rapidly moving jet of water to erode a material and cut it. The stream of water also clears any debris for a high quality cut, and acts as a cooling agent to eliminate heat.

The process uses a stream of water at ultra-high water pressure of up to 90,000 psi to erode a narrow line in the material and essentially cut it. To achieve such high pressures, the waterjet machine uses a large horsepower motor to drive a hydraulic intensifier pump, which generates hydraulic pressure to power a small piston into a cylinder filled with water.

The size of the water cylinder is only a small fraction of that of the hydraulic cylinder. If the latter is 20 times bigger, then a 2,500 PSI hydraulic pressure can be intensified to 50,000 PSI water pressure. If the ratio is 30:1, you can achieve 75,000 PSI water pressure, and so on.

Here is the typical process for waterjet cutting:

  1. Clean water is sucked in via a low pressure water input and passed through the inlet filter.
  2. It is then forced through the inlet check valves into the intensifier.
  3. The hydraulic fluid is pressurized by the hydraulic pump, and alternates high/low pressure between the two sides of the hydraulic piston, which pressurizes water in the intensifier.
  4. Pressurized water flows from the intensifier into the accumulator to help smooth out pressure ripples.
  5. The pressurized water then flows to the cutting head via high pressure tubing.
  6. The operator uses the off valve to control water flow to the cutting head. This is necessary to start or stop the cutting process as needed.

The high pressure water is applied through a very small opening with a diameter of between 0.005 and 0.020 inches or 0.1–0.2 mm. Considering that the cut is about a hairline wide, it can cut very sharp contours with great precision. The orifice is made in sapphire or diamond to withstand the abrasive force of the water.

Pure-Water vs. Abrasive Cutting

The high pressure stream of water alone is enough to cut soft materials such as paper, leather, rubber, foam, textiles, insulation, and cardboard, among others. These materials can be cut at very high speeds, depending on how fast the cutting nozzle or material moves. Carpeting is usually cut at a rate of 15 to 30 m/min, while plastic and paper foils can be cut at 200 m/min, which makes waterjet cutting a great alternative for blade cutting.

The water used must be very pure—drinkable level—which makes waterjet cutting suitable for applications in the food industry, such as for cutting frozen fish or cakes.

But to cut hard materials such as steel, stone, aluminum oxide, glass composite, wood, plastic, or titanium, a granular abrasive (usually crushed garnet) is added to the water stream after it exits the orifice. It is the abrasive that does the actual cutting. Other types of abrasives may be used for special applications.

Since the abrasive is added at the orifice, the operator can easily switch between water-only and abrasive waterjet cutting. But keep in mind that abrasive cutting is considerably slower than pure-water cutting, usually less than 1 m/min. The speed depends on the type of material, its thickness, and the desired surface quality.

Advantages of Waterjet Cutting

  • It is a high-precision cutting technology. Waterjet cutting has a narrow kerf width that makes it possible to cut fine contours and produce high tolerance parts.
  • Abrasive cutting can be used to cut thick materials that cannot be efficiently cut using other methods, like copper, brass, stainless steel, and titanium.
  • These metals can be cut without heating the cutting edge, without any stress, and with a clean cut that eliminates the need for post-cut finishing work.
  • There is no upper thickness limit for waterjet cutting. It is typically used for applications measuring 3 to 30 mm, with a few applications going up to 100 mm, and rare applications of greater thickness, like 180 mm concrete plates or 400 mm steel parts. But the cost and processing time increases with thickness.
  • Waterjet cutting produces a 1 mm kerf width, which is considerably thinner than most milling tools. This allows for cutting of finer contours, as well as cuts that start inside the material without the need for pre-drilling entry holes.
  • The thin water jet also creates a minimal incision that results in negligible loss of material compared to traditional cutting processes.
  • Water jets cut in any direction. They can be used to produce a wide array of shapes and forms on different materials, with precise specifications and dimensions.
  • All materials are cut without the adverse effects of heat, like with thermal processes. This prevents warping, hardening, amalgamation, or dripping slag.
  • The technique helps to prevent any deformation in the material, while providing a highly precise cut without ridges or fraying. This is because the water jet does not create any direct surface pressure on the material.
  • The technique is environmentally friendly.

Waterjet cutting offers numerous benefits compared to other cutting techniques, though it may not be the most practical choice for some materials due to its slow and expensive process.

Is Waterjet Cutting Right for Your Application?

Pure-water cutting can be used to cut most thin materials, including sheets of metal, while abrasive waterjet cutting has almost no limitations in terms of type of material or thickness.

The technology plays a major role in many industries, including:

  • Food cutting
  • Glass cutting
  • Automotive
  • Aerospace
  • Stone and tiles
  • Wood cutting
  • Artistic and architectural

Any industry can take advantage of the unique capabilities of waterjet cutting to produce high accuracy cuts without heat, pollution, and other negative effects associated with alternative methods. You simply need to find the right equipment (in terms of nozzle diameter, abrasive feed, and cutting pressure) for your type of material, thickness, and desired quality.

For more information about waterjet cutting, call Dwight Crane at 416-639-2638 or contact us here.

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