Shop Talk Magazine, February 2008

Excerpt from “Grow your Shop into Waterjet Cutting”

By: Victor M. Cassidy

This “fastest growing major machine tool process in the world” has narrow kerf, delivers heat-free cuts and smooth, clean edges

Waterjet cutting uses a narrow stream of water at pressures of up to 87,000 pounds per square inch to cut through metals, wood, glass, foam, stone, and other materials. Forced through a small orifice in the nozzle of a cutting system, the water accelerates to about 1,000 miles per hour. As the water jet strikes the material, it erodes away small particles that are washed aside until the material is cut through.

Waterjet cutting is typically done on a flat worktable. Beneath is a three-foot-deep catch tank filled with water, which absorbs the kinetic energy of the waterjet after it makes the cut. To improve cutting speed and effectiveness, shops add abrasive particles such as garnet to the waterjet.

The contents of the catch tank consist of water, particles of the cut material, and particles of abrasive if it was used. None of this is hazardous. The water and abrasive can be recycled. If toxic material is cut, the effluent must be treated to remove the waste particles.  

Advantages of waterjet

Waterjet cutting offers multiple advantages:

• Because it creates no heat as it cuts metal, waterjet can produce net-shaped parts with no heat-affected zone, heat distortion, or mechanical stresses. Heat-free cutting is essential for tool steels whose properties can be changed by heat and valuable with materials whose cut edges might be distorted by heat.    
• The kerf can be as narrow as a human hair, which minimizes material lost during cutting. The cut edges are smooth, which eliminates sanding or grinding. There's no wasteful dross.
• Because side forces hardly exist when cutting with waterjet, time required for setup and fixturing is minimal. A shop can move quickly from job to job.
• Waste particles produced during waterjet cutting end up in the catch tank. There's no need for hoods over work areas.
• Waterjet technology is completely modern. Cutting is done by software-controlled robotic motion systems-not hard tooling-so there are no costly, time-consuming tool changes to accommodate different shapes.
• Operators can import a CAD drawing into the PC control system or program the system to cut out the part.
• Parts can be tightly nested to save raw material and cutting is easily automated. Systems can be provided with multiple cutting heads for further productivity improvement.

•  Waterjet cutters are much lighter than an equivalent laser cutter when mounted on an automated robot. This simplifies robot acceleration and deceleration-and reduces energy needs.

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Bells and whistles

WARDJet, Inc., Tallmadge, Ohio, offers its X-Series Waterjet system and controllers which is said to have a motion control system "that can take your waterjet cutting business to the next level."

Among key X-Series features are advanced Internet connection to the shop's waterjet controller, a direct communication link to technical support, dual touch screen controller, simultaneous multiple head five-axis capability, and taper compensation. The controls allow direct connection to WARDJet for technical support and interface with customers.

WARDJet manufactures several lines with options that include a drill and reamer head, bevel cutting, and abrasive recycling. With the drill and reamer head, a shop can drill and then cut with waterjet. The pneumatic drill allows a hole to be drilled automatically through the material at a specific offset from the waterjet cutting head. Once the hole is drilled, the waterjet automatically starts the cut inside the pre-drilled hole. The pneumatic reamer waterjet cuts and then reams a hole to tight tolerances, says the manufacturer.

Bevel cutting up to 45° is accomplished with the bevel head option. The operator sets the angle of the cut and can make changes throughout the part program.

According to WARDJet, its abrasive removal and recycling system returns clean, dry abrasive from a waterjet tank in just three minutes. Called "WARD" for Waterjet Abrasive Recycling Dispenser, this option is said to pay back fast. WARD removes sludge from an abrasive waterjet cutting tank, separates reusable abrasive from waste particles, washes and dries the reusable abrasive, and deposits it back in the bulk feed hopper.

For more information, visit http://www.wardjet.com.