Two Types of Waterjets : Pure Waterjet vs Abrasive Waterjets

 

The two types of waterjets are the pure waterjet and the abrasive waterjet. Both have unique capabilities proven a benefit to industry.

iwm 5x10 Two Types of Waterjets :  Pure Waterjet vs Abrasive Waterjets

 Pure Waterjet

Pure waterjet is the original water cutting method. The first commercial applications were in the early to mid 1970s, and involved the cutting of corrugated cardboard. The largest uses for pure waterjet cutting are disposable diapers, tissue paper, and automotive interiors. In the cases of tissue paper and disposable diapers the waterjet process creates less moisture on the material than touching or breathing on it. Unplanned down time, common to other cutting processes, cost over $20,000 per hour (US dollar) in some diaper or tissue plants. The waterjet provides the 24 hour per day, 7 day per week, 360 day per year operation required by such applications – maintenance can be scheduled into production.

Pure waterjet attributes:

VERY THIN STREAM (0.004 TO 0.010 INCH IN DIAMETER IS THE COMMON RANGE)

EXTREMELY DETAILED GEOMOETRY

VERY LITLE MATERIAL LOSS DUE TO CUTTING

NON-HEAT CUTTING

CUT VERY THICK

CUT VERY THIN

USUALLY CUTS VERY QUICKLY

ABLE TO CUT SOFT, LIGHT MATERIALS (E.G., FIBERGLASS INSULATION UP TO 24”

THICK)

EXTREMELY LOW CUTTING FORCES

SIMPLE FIXTURING

24 HOUR PER DAY OPERATION

 

Pure Waterjet Cutting Heads

As you may recall from an earlier section of this document, the basic waterjet process involves water flowing from a pump, through plumbing, and out a cutting head.

 In waterjet cutting, the material removal process can be described as a supersonic erosion process. It is not pressure, but stream velocity that tears away microscopic pieces or grains of material. Pressure and velocity are two distinct forms of energy. But how is the pump’s water pressure converted to this other form of energy, water velocity? The answer lies in a tiny jewel. A jewel is affixed to the end of the plumbing tubing. The jewel has a tiny hole in it. The pressurized water passes through this tiny opening changing the pressure to velocity. At approximately

40,000 psi the resulting stream that passes out of the orifice is traveling at Mach 2. And at 60,000 psi the speed is over Mach 3.

 

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Question: How hot is the water in a Mach 3 waterjet stream?

Answer: The water is warmed as it is accelerated to high speed. Frictional forces and other

factors warm the stream as it exits the orifice. In let water temperature provides the starting point.

Water temperature is then raised 2 to 3 degrees for each 1,000 psi. The quick answer is the

Mach 3 jet is approximately 170 to 180 degrees F.

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Pure waterjet orifice diameter ranges from 0.004 to 0.010 inch for typical cutting. When waterblasting concrete with a nozzle traversing back and forth on a tractor, a single large orifice of up to 1/10th of an inch is often used.

The three common types of orifice materials (sapphire, ruby, diamond) each have their own unique attributes. Sapphire is the most common orifice material used today. It is a man-made, single crystal jewel. It has a fairly good quality stream, and has a life, with good water quality, of approximately 50 to 100 cutting hours. In abrasive waterjet applications the sapphire’s life is ½ that of pure waterjet applications.

Ruby can also be used in abrasive waterjet applications. The stream characteristics are well suited for abrasivejet, but are not well suited for pure waterjet cutting. The cost is approximately the same as the sapphire.

Diamond has considerably longer run life (800 to 2,000 hours) but is 10 to 20 times more costly.

Diamond is especially useful where 24 hour per day operation is required. Diamonds, unlike the other orifice types, can sometimes be ultrasonically cleaned and reused.

776px Evolution of the Abrasive Waterjet Nozzle Two Types of Waterjets :  Pure Waterjet vs Abrasive Waterjets

Abrasive Waterjets

The abrasive waterjet differs from the pure waterjet in just a few ways. In pure waterjet, the supersonic stream erodes the material. In the abrasive waterjet, the waterjet stream accelerates abrasive particles and those particles, not the water, erode the material. The abrasive waterjet is hundreds, if not thousands of times more powerful than a pure Waterjet. Both the waterjet and the abrasive waterjet have their place. Where the pure waterjet cuts soft materials, the abrasive waterjet cuts hard materials, such as metals, stone, composites and ceramics. Abrasive waterjets using standard parameters can cut materials with hardness up to and slightly beyond aluminum oxide ceramic (often called Alumina, AD 99.9). In the next section we will explore abrasive waterjet attributes and how the abrasive waterjet cutting head works.

Abrasive Waterjet attributes:

EXTREMELY VERSATILE PROCESS

NO HEAT AFFECTED ZONES

NO MECHANICAL STRESSES

EASY TO PROGRAM

THIN STREAM (0.020TO 0.050 INCH IN DIAMETER)

EXTREMELY DETAILED GEOMETRY

THIN MATERIAL CUTTING

10 INCH THICK CUTTING

STACK CUTTING

LITTLE MATERIAL LOSS DUE TO CUTTING

SIMPLE TO FIXTURE

LOW CUTTING FORCES (UNDER 1 LB. WHILE CUTTING)

ONE JET SETUP FOR NEARLY ALL ABRASIVEJET JOBS

EASILY SWITCHED FROM SINGLE TO MULTI-HEAD USE

QUICKLY SWITCH FROM PURE WATERJET TO ABRASVIE WATERJET

REDUCED SECONDARY OPERATIONS

LITTLE OR NO BURR

Abrasive Waterjet Cutting Heads

Within every abrasive waterjet is a pure waterjet. abrasive is added after the pure Waterjet stream is created. Then the abrasive particles are accelerated, like a bullet in a rifle, down the mixing tube.

 The abrasive used in abrasive waterjet cutting is hard sand that is specially screened and sized.

The most common abrasive is garnet. Garnet is hard, tough and inexpensive. Like the pink colored sandpaper found at the hardware store, different mesh sizes are used for different jobs.

120 Mesh – produces smooth surface

80 Mesh – most common, general purpose

50 Mesh – cuts a little faster than 80, with slightly rougher surface.

The mixing tube acts like a rifle barrel to accelerate the abrasive particles. They, like the orifice, come in many different sizes and replacement life. Mixing tubes are approximately 3 inches long,

¼ inch in diameter, and have internal diameters ranging from 0.020 to 0.060 inch, with the most common being 0.040 inch.

Although the abrasive waterjet machine typically is considered simple to operate and ‘bullet proof,’ the mixing tube does require operator attention. A major technological advancement in Waterjet was the invention of truly long-life mixing tubes. Unfortunately, the longer life tubes are far more brittle than their predecessors, tungsten carbide tubes. If the cutting head comes in contact with clamps, weights, or the target material the tube may be broken. Broken tubes cannot be repaired. Today’s most advanced systems incorporate collision detection to spare the mixing tube.

The standoff distance between the mixing tube and the target material is typically 0.010 to 0.150 inch. Larger standoff (greater than 0.080 inch) can cause a frosting to appear atop the cut edge of the part. Many Waterjet systems reduce or eliminate this frosting by cutting under water or using other techniques.

The consumable items in an abrasive Waterjet are the water, abrasive, orifice (usually Ruby) and mixing tube. The abrasive and mixing tube are exclusive to the abrasive waterjet. The other consumables are also found in the pure waterjet.

Water Jet: Over Flow to Drain System

 Overflow to Drain System      

150 Micron Nylon Bag Pre Filter
50 Gallon Stainless Steel Settling Weir with Removal Baffles
Stainless Steel 07A Size 1 Bag Vessel
5 Micron, Size 1, Polyester Felt “ Posi-Seal ” Final Filter
.5” Cast Iron Heavy Duty Sandpiper AOD Pump
Adjustable Air Regulator with Gauge
Pre Plumbed and Mounted on an 18” x 42” Steel Base with Casters

over flow ro drain system  Water Jet:   Over Flow to Drain System

 

How Does Water Jet Cutting Machine Work

A water jet machine has essentially two components: a high intensity pump that pressurizes water to 40,000 — 90,000 PSI , and a cutting head assembly mounted on a frame that can move along the  x-y-z direction over the material being cut. Pressurized water is forced through a tiny nozzle hole to create high energy density stream that can erode and tear the surface of materials to achieve a cutting affect.  Pure water ca alone can cut plastics, foam, wood, resilient floor coverings, rubber and similar soft substances.  In some cases, water is mixed with a garnet abrasive to cut harder materials such as metals, stone, ceramics, glass and dense composites.

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Tips for Water Jet Cutting Glass

Tips for Water Jet Cutting Glass

  • Reduce the risk of chipping by using a low-pressure pierce of approximately 10,000 psi.
  • Reduce low-pressure piercing time from two minutes to 10-15 seconds (depending on thickness) by cutting a tiny circle rather than leaving the jet fixed on one spot.
  • 120 grit garnet will produce the best edge quality. If speed is your priority and chipping not a concern, use 80 grit garnet
  • Cut at 75,000 PSI to increase cut speed by 50-75% and improve edge quality.
  • Support glass on a sheet of 3/16” corrugated PVC rather than directly on the metal slats. This reduces the risk of chipping and fogging.
  • If your projects require you to frequently raise and lower pressure, install a patented Jet Edge   dual pressure valve to save time and prolong  waterjet pump  component life.
  • Tempered glass cannot be cut with waterjet.

Water Jet Multi-Axis Cutting

5 Axis Water Jet Cutting Head  Water Jet Multi Axis Cutting
With recent advances in control and motion technology, 5-axis water jet cutting (abrasive and pure) has become a reality. Where the normal axes on a water jet are named X (back/forth), Y(left/right) and Z (up/down), a 5-axis system will typically add an A axis (angle from perpendicular) and C axes (rotation around the Z-axis). Depending on the cutting head, the maximum cutting angle for the A axis can be anywhere from 55, 60, or in some cases even 90 degrees from vertical. As such, 5-axis cutting opens up a wide range of applications that can be machined on a water jet cutting machine.

A 5-axis cutting head can be used to cut 4-axis parts, where the bottom surface geometries are shifted a certain amount to produce the appropriate angle and the Z-axis remains at one height. This can be useful for applications like weld preparation where a bevel angle needs to be cut on all sides of a part that will later be welded, or for taper compensation purposes where the kerf angle is transferred to the waste material – thus eliminating the taper commonly found on water jet-cut parts. A 5-axis head can cut parts where the Z-axis is also moving along with all the other axis. This full 5-axis cutting could be used for cutting contours on various surfaces of formed parts.

5 Axis Water Jet Part  Water Jet Multi Axis CuttingBecause of the angles that can be cut, part programs may need to have additional cuts to free the part from the sheet. Attempting to slide a complex part at a severe angle from a plate can be difficult without appropriate relief cuts.

 

Water Jet Cutting – Edge Quality Comparison

Edge quality for water jet cut parts is defined on a scale of 1 through 5. Lower numbers indicate rougher edge finish; higher numbers are smoother. For thin materials, the difference in cutting speed for Quality 1 could be as much as 3 times faster than the speed for Quality 5. For thicker materials, Quality 1 could be 6 times faster than Quality 5.

For example, 4” thick Aluminum Q5 would be 0.72 ipm (18 mm/min) and Q1 would be 4.2 ipm (107 mm/min), 5.8 times faster.

Water jet Edge qualities Water Jet Cutting   Edge Quality Comparison

The History Of Water Jet Cutting Machines

water jet cutter, also known as a waterjet, is a tool capable of slicing into metal or other materials using a jet of water at high velocity and pressure, or a mixture of water and abrasive substance. The process is essentially the same as water erosion found in nature but greatly accelerated and concentrated. It is often used during fabrication or manufacture of parts for machinery and other devices. It is the preferred method when the materials being cut are sensitive to the high temperatures generated by other methods. It has found applications in a diverse number of industries For example mining where it is used for operations such as cutting, shaping, carving, and remaining.

Cutting head The History Of Water Jet Cutting Machines A Diagram of a Water Jet Cutter:

 

  1. High-Pressure Water Inlet
  2. Jewel (ruby or diamond)
  3. abrasive (garnet)
  4. Mixing Tube
  5. Guard
  6. Cutting Water Jet
  7. Cut Material

>In the 1950s, forestry engineer Norman Franz experimented with an early form of water jet cutter to cut lumber. However, the technology did not advance notably until the 1970s when Mohamed Hashish created a technique to add abrasives to the water jet cutter. apple white background1 300x226 The History Of Water Jet Cutting Machines

Water jet manufacturing is such a versatile component in our industry. We are pleasantly surprised by the different applications we observe being considered.

Do you have a water jet application in shop?  Call us we would be happy to review any opportunities with you.

800-984-4540