How Does a Waterjet Work

The motion control system is an essential element in an abrasive waterjet cutting system because the cutting stream bends as it cuts.
Basic Components and Operation

High Pressure Pump

The pump generates a flow of pressurized water for the cutting process.

Abrasive Waterjet Nozzle

Inside the nozzle the pressurized water passes through a small-diameter orifice and forms a coherent jet of water. The jet then passes through a venturi section where a metered amount of granular abrasive is drawn into the water stream. The mixture of water and abrasive particles passes through a special ceramic mixing tube and the resulting abrasive/water slurry exits the nozzle as a coherent cutting stream of abrasive particles travelling at very high speed.

Catcher Tank

The water-filled catcher tank dissipates the energy of the abrasive jet after it has cut through the material being machined.

Abrasive Hopper

The abrasive hopper and associated abrasive flow control system provide a metered flow of granular abrasive to the nozzle. Articulated Cutting Head

Articulated Cutting Head

As an add-on option to OMAX waterjets, this computer-controlled multi-axis cutting head permits angled cuts and can be used to automatically minimize taper for precise vertical cuts.

X-Y Traverse System

A precision X-Y motion system is used to accurately move the nozzle to create the desired cutting path.

PC-based Controller

Advanced motion controllers for abrasive waterjet systems are PC-based and permit production of accurate parts with minimal operator experience.

Accurate First Cut

The motion control system is an essential element in an abrasive waterjet cutting system because the cutting stream bends as it cuts. This means that a waterjet tends to undercut corners and swing wide on curves when moved as one would move a traditional rigid cutting tool. OMAX eliminates this issue by using an advanced computer model to accurately predict the motion and shape of the cutting stream and then by using a PC-based motion control system to compensate for undesired jet motion. The result is a fast, accurate part the first time. No trial and error and no need for an experienced programmer because the experience and the knowledge is in the control software.


Waterjet cutting systems utilize either the older, more complex hydraulic intensifier pump or the newer, simpler crankshaft-driven triplex plunger pump. Crankshaft pumps are inherently more efficient than intensifier pumps because they do not require a power-robbing hydraulic system. The crankshaft drive is a purely mechanical direct-drive system with minimal friction losses and so efficiencies between 85% and 90% are typical. This means that 85% or more of the electric power supplied to the drive motor can actually be delivered to the cutting nozzle, compared to the typical 65% or less of an intensifier. Historically intensifier pumps had an advantage of longer seal and check-valve life, but ongoing improvements in seal designs and materials and the wide availability and reduced cost of ceramic valve components now make it possible to operate a crankshaft pump in the 60,000 PSI (4,137 bar) range with long maintenance intervals and excellent reliability. OMAX uses high-efficiency crankshaft-driven direct-drive pumps exclusively for all of its systems. A direct-drive pump is more efficient than a traditional hydraulic intensifier pump and so it can deliver more net power to the cutting nozzle, resulting in faster cutting. It is quiet and clean, with no risk of messy hydraulic leaks. In addition, a direct-drive pump is simple to understand, to troubleshoot and to maintain. The OMAX Enduromax pump features a preventative maintenance interval of 1000 hours, offering the ultimate in reliable low-cost operation.


All abrasive waterjet nozzles use the basic operating principle of the aspiration nozzle, first patented in 1937 (Patent 2,131,660) and shown in its modern configuration in the diagram on the right. Note that for water-only nozzle designed for cutting of soft material, the venturi section and mixing tube are eliminated and the coherent jet of water alone cuts the material. In order for the aspiration nozzle to cut efficiently and with long component life, it is critical that the orifice be carefully aligned with the centerline of the mixing tube. All OMAX nozzles are factory-aligned and individually tested to assure efficient cutting and long life.

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