Buzz
Standard waterjet.
Image courtesy of OMAX CorporationA waterjet is a machine tool that uses a powerful jet of water to cut through metal parts. It's surprising, but with the right speed, water can actually slice through metal.
Imagine a waterjet operating at around 30 times the pressure of a typical car wash power washer. A car wash's power washer is a familiar example of water cutting through grime on a vehicle's body, wheels, and tires.
The secret to cutting metal with water lies in maintaining the spray’s consistency. Waterjets are effective because they force the water through a tiny, high-pressure nozzle that keeps the spray intact. Unlike metal-cutting tools, waterjets don't dull or overheat.
Low-pressure waterjets were initially used for gold mining in California in 1852. In the early 1900s, steam and hot water jets were employed for cleaning purposes. High-pressure waterjets began being used for mining in the 1960s, and roughly a decade ago, industries adopted waterjets for cutting. Abrasive waterjets (abrasivejets) were first introduced in industry around 1980.
In earlier times, only one metal piece could be cut at a time using a saw or other mechanical cutting methods. These processes were both time-consuming and costly. Today, computer-controlled waterjet and abrasivejet cutting techniques allow industries to cut a wide range of soft and hard materials. The mixture of plain water and abrasive exits the nozzle at speeds exceeding 900 mph. The most advanced machines can cut with precision to within two thousandths of an inch, and their jet speeds approach Mach 3.
Waterjets are capable of cutting the following materials:
- Marble
- Granite
- Stone
- Metal
- Plastic
- Wood
- Stainless steel
A waterjet can cut through a “sandwich” of various materials up to four inches thick. This process is odorless, dust-free, and produces relatively low heat. It is also capable of cutting materials as thin as five thousandths of an inch. The precision of the fine jet stream ensures that the first cut is also the final finished surface. This single-step cutting process reduces both material and machining costs. For instance, an engineer can simply send a gear design to the cutting shop via diskette or email and receive the finished gear in return.
An abrasivejet machine with a cutting area of 26 inches square. Notice the reddish garnet sand abrasive reservoir.
Courtesy of OMAX CorporationWaterjets are used for cutting softer materials, while abrasive jets are reserved for harder substances. The actual cutting process is often conducted underwater to minimize splash and reduce noise. Faster feed rates are employed to ensure the jet doesn’t cut entirely through the material.
Water pressure typically ranges from 20,000 to 55,000 pounds per square inch (PSI). The water is pushed through a tiny orifice, ranging from 0.010" to 0.015" in diameter, made from a jewel.
A waterjet has the ability to strip bark from a tree from a distance of up to 40 feet if the composition of plain water is altered by adding SUPER-WATER®, which can be obtained from Berkeley Chemical Research. SUPER-WATER® is a soluble polymeric chemical that forms a series of molecular “spinal columns” or reinforcement bars, binding the water molecules together in a more organized structure to create a coherent jet. This could be used for cutting down roadside weeds.
How fast does a waterjet cut?
Parts cut by abrasivejets.
Courtesy of OMAX CorporationAn abrasive jet can slice through half-inch thick titanium at a rate of 7 inches per minute when powered by a 30 HP pump. The motion of the abrasive jet is comparable to a slow-moving pen plotter.
Abrasive jets have been utilized to:
- Eliminate materials from inside train tunnels
- Assist in rescuing "Baby Jessica" from the well in Midland, Texas
- Carve nearly any shape in bullet-proof glass
- Cut parts for the F-22 and Stealth bomber, along with various aircraft and spacecraft
- Slice into the hull of the submarine Kursk, using diamond powder abrasive, to recover the bodies of the Russian crew
- Remove highway marking strips
- Carve wooden signage
- Create sculptures
- Cut logs at sawmills
Industries that can apply abrasive waterjet and abrasivejet technologies include:
- Building: Stone materials for flooring can be shaped into patterns. Stone and metal pieces for lettered signage can be precisely matched and cut. Additionally, custom shapes for metal and tile roofing are achievable.
- Manufacturing: Fine-tuned gears and other intricate items, such as foam and rubber components, can be cut with accuracy, without generating heat, unlike laser cutting methods.
- Designers: Delicate shapes for jewelry, sculptures, and mirrors can be precisely cut.
- Other: Waterjets are also used for cutting candy bars and diapers. A specialized drilling bit for oil exploration is equipped with waterjets at the bottom to enhance the drilling speed. Additionally, when used with directional jets, a waterjet can tunnel under roads to lay fiber optic cable.
Click on the pressure reading to watch and listen to a 5-second video clip demonstrating a Flow Corporation abrasivejet. The 50 HP pump generates 52,400 PSI, allowing a jet of water and garnet abrasive mixture to slice through 1/16-inch steel. The abrasivejet features an internal .013" ruby orifice, producing a .040" diameter water jet. Be on the lookout for a few sparks!
Special thanks to ADR Hydro-Cut of Morrisville, N.C., Carl Olsen at WaterJets.org, and W. Glenn Howells at Berkeley Chemical Research, Inc. for their technical assistance in the preparation of this article.
