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|
|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|
|Soft, or thin wood||Exotic materials||Kevlar|
|Hard, or thick Wood||Granite|
|Glass (even bullet proof!)||Mixed materials|
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.