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Waterjet vs. abrasivejet nozzles
Written by Staff   

There is a difference between a pure waterjet nozzle and an abrasivejet nozzle. With the abrasivejet nozzle, an opening in the side of the nozzle allows for the introduction of the abrasive to the high-pressure water stream. The two are mixed in a mixing tube and then exit the nozzle. With a pure waterjet nozzle, there is no opening and no mixing tube and the high-pressure water is directed to the material after it exits the jewel.

If you will always be cutting the same type of material, you can choose the nozzle that works best for that material. In most cases, however, you will be cutting a variety of different materials (one of the strengths of a waterjet) and you may want to change nozzles as needed.

Many machines let you swap nozzles in a matter of minutes. Alternately, you can simply turn off the abrasive, and get a somewhat inefficient water jet from your abrasive jet nozzle. You can improve the performance somewhat by plugging the abrasive hole.

Which nozzle is best for my material?

 

Water Jet Nozzle AbrasiveJet Nozzle
Soft rubber Hardened tool steel Plastic
Foam Titanium Nylon
Extremely thin stuff like Foil Aluminum Graphite
Carpet Hard Rubber Many ceramics
Paper and cardboard Stone Carbon Fiber
Soft Gasket material Inconel® Composites
Candy bars Hastalloy mild steel
Diapers Copper Stainless Steel
Soft, or thin wood Exotic materials Kevlar
  Hard, or thick Wood Granite

Glass (even bullet proof!) Mixed materials
  Marble Brass

Cost comparison

Complete water jet nozzle assemblies cost around $500.00 to $1000.00 (US), while abrasive jet nozzles cost from $800 to $2000. The abrasive nozzle also requires support hardware for abrasive feed which can cost anywhere from $500 to $2,000. (These numbers are not precise—for exact pricing, contact a waterjet supplier or waterjet equipment manufacturer.) Cost of operation is much higher for the abrasivejet because of mixing tube wear, and abrasive consumption.

Limitations to pure waterjet nozzles

Typically, the only problems that arise with a pure waterjet nozzle will be with the jewel (the orifice with the tiny hole that the water squirts through).

Jewels can crack, plug, or form deposits on them. Cracking and plugging happens as a result of dirty inlet water, and is typically avoided with proper filtration. Deposits accumulate gradually as a result of minerals in the water. Depending on your water supply, slightly fancier filtering may be necessary. Jewels are easily replaced in about two to ten minutes, and are typically cheap ($5 to $50). There are also diamond orifices for sale for $200 and up, which can last longer in many applications.

Limitations of abrasivejet nozzles

Despite their simple design, abrasivejet nozzles can be troublesome at times. There are many designs, but they share the same problems:

  • Short life of the mixing tube
    The abrasive jet can cut through just about anything—including itself. This mixing tube is expensive and wears out in only a few hundred hours of use. Replacing mixing tubes will be a large part of your operating cost.
  • Occasional plugging of mixing tube
    Plugging is usually caused by dirt or large particles in abrasive. This used to be a big problem with abrasivejet nozzles, but has been getting better as manufacturers fine-tune mixing tube designs.
  • Wear, misalignment, and damage to the jewel
    The jewel needs to be precisely positioned in the nozzle while water and thousands of pounds of pressure impacts it.
 
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