Microsoft Word - Advantage of Use Water Jet

8/14/2019 Microsoft Word - Advantage of Use Water Jet

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Master of Engineering in ManufacturingAdvanced

MAINTENANCE AND RELIABILITY MANAGEMENT

Trimester 2 2009/2010

Assignment Title:Waterjet Cutting

Lecturer name:

Students Name:

FARID KEYHANI (1091900093)


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Introduction

Beyond cost cutting, the waterjet process is recognized as the most versatile andfastest growing process in the world. Waterjets are used in high productionapplications across the globe. They compliment other technologies such as milling,laser, EDM, plasma and routers. No noxious gases or liquids are used in waterjetcutting, and waterjets do not create hazardous materials or vapors. No heat effectedzones or mechanical stresses are left on a waterjet cut surface. It is truly a versatile,productive, cold cutting process.The waterjet has shown that it can do things that other technologies simply cannot.From cutting whisper thin details in stone, glass and metals; to rapid hole drilling oftitanium; to cutting of food, to the killing of pathogens in beverages and dips, thewaterjet has proven itself unique.

1. The Pump of Waterjet

One of the important part of water jet system is pump. Two types of pump can beused for waterjet machines applications first is an intensifier based pump and secendone is direct drive based pump. [1]

1.2 Intensifier Based Pumps

The water circuit consists of the inlet water filters, booster pump, intensifier, andshock attenuator. Ordinary tap water is filtered by the inlet water filtration system usually comprising of a 1 and a 0.45 micron cartridge filter. The filtered water thentravels to the booster pump, where the inlet water pressure is maintained atapproximately 90 psi ensuring the intensifier is never starved for water. Thefiltered water is then sent to the intensifier pump and pressurized to up to 60,000 psi.Before the water leaves the pump unit to travel through the plumbing to the cuttinghead, it first passes through the shock attenuator. This large vessel dampens thepressure fluctuations to ensure the water exiting the cutting head is steady andconsistent. Without the attenuator, the water stream would visibly and audibly pulse,leaving marks on the material being cut. [1]

The hydraulic circuit consists of an electric motor (25 to 200 HP), hydraulic pump, oilreservoir, manifold, and piston biscuit/plunger. The electric motor powers thehydraulic pump. The hydraulic pump pulls oil from the reservoir and pressurizes it to3,000 psi. This pressurized oil is sent to the manifold where manifolds valves createthe stroking action of the intensifier by sending hydraulic oil to one side of thebiscuit/plunger assembly, or the other. The intensifier is a reciprocating pump, in thatthe biscuit/plunger assembly reciprocates back and forth, delivering high-pressurewater out one side of the intensifier while low-pressure water fills the other side. Thehydraulic oil is then cooled during the return back to the reservoir.The advancedtechnology in the pump is found in the intensifier. As mentioned briefly in thedescription of the water circuit, the intensifier pressurizes the filtered tap water to up

to 60,000 psi. [3]


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Intensifier pumps utilize the intensification principle.

Hydraulic oil is pressurized to a pressure of, say, 3,000 psi. Theoil pushes against a piston biscuit. A plunger with a face area of20 times less than the biscuit pushes against the water.

Therefore, the 3,000-psi oil pressure is intensified twentytimes, yielding 60,000-psi water pressure. The intensificationprinciple varies the area component of the pressure equation tointensify, or increase, the pressure.

Pressure = Force /Area

If Force = 20, Area = 20, then Pressure = 1. If we hold the Force constant and greatlyreduce the Area, the Pressure will go UP. For example, reduce the Area from 20 downto 1, the Pressure now goes up from 1 to 20. In the sketch below, the small arrowsdenote the 3,000 psi of oil pressure pushing against a biscuit face that has 20 times

more area than the face of the plunger. The intensification ratio, therefore, is 20:1. [1]

In the illustration below, the biscuit and plungers are in the green section and outlinedin red. The biscuit contains the small arrow suggesting movement to the left. The twowater plungers extend from either side of the biscuit. High-pressure water is deliveredout the left side while low-pressure water refills the right. At the end of travel, thebiscuit/plunger assembly sequence is reversed [1]

Sophisticated check valves ensure the low pressure and high-pressure water is onlyallowed to travel one direction. The high-pressure cylinders and end caps that encasethe plunger and biscuit assembly are specially designed to withstand the enormousforce and the constant fatigue.The entire unit is designed for long life, while alsodesigned to fail in a safe way. Waterjet systems fail in a gradual, rather thaninstantaneous way. The seals and connections begin to leak slowly through speciallydesigned weep holes. The operator or maintenance person can see a drip escapingfrom a weep hole. The location of the drip and the amount of water indicate whenmaintenance should be performed. Usually, the maintenance person can schedule theperiodic maintenance of seals and check valves out 1 to 2 weeks into the future bysimply monitoring the gradual weeping. Warning and shutdown sensors also cover thepumping unit to further safeguard against pump damage. [1]

Troubleshooting of an intensifier is quite

simple. Dripping of hot water from aweep hole indicates a high-pressure leak,


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cold water indicates low-pressure. In theactual image, those drops labeled hot orwarm are in red, cold is in blue. [2]

2. Types of Waterjets

2.1 Pure Waterjet

Pure waterjet is the original water cutting method. The first commercial applicationswere in the early to mid 1970s, and involved the cutting of corrugated cardboard. Thelargest uses for pure waterjet cutting are disposable diapers, tissue paper, andautomotive interiors. In the cases of tissue paper and disposable diapers the waterjetprocess creates less moisture on the material than touching or breathing on it. [2]

2.1.1 Pure Waterjet Attributes

Very thin stream (0.004 to 0.010 inch in diameter is the common range)

Extremely detailed geometry

Very little 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 hours per day operation [2]

2.1.2 Pure waterjet cutting head

As you may recall from an earlier section of this document, the basic waterjetprocess involves water flowing from a pump, through plumbing, and out a cuttinghead.In waterjet cutting, the material removal process can be described as asupersonic erosion process. It is not pressure, but stream velocity that tears away

microscopic pieces or grains of material. Pressure and velocity are two distinctforms of energy. But how is the pumps water pressure converted to this other formof energy, water velocity? The answer lies in a tiny jewel. A jewel is affixed to theend of the plumbing tubing. The jewel has a tiny hole in it. The pressurized waterpasses through this tiny opening changing the pressure to velocity. At approximately40,000 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. Pure waterjet orifice diameter rangesfrom 0.004 to 0.010 inch for typical cutting. When waterblasting concrete with anozzle traversing back and forth on a tractor, a single large orifice of up to 1/10 th ofan inch is often used.

The three common types of orificematerials (sapphire, ruby, diamond) each


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have their own unique attributes.Sapphire is the most common orificematerial used today. It is a man-made,single crystal jewel. It has a fairly goodquality stream, and has a life, with good

water quality, of approximately 50 to 100cutting hours. In abrasive waterjetapplications the Sapphires life is thatof pure waterjet applications. Sapphirestypically cost between $15 and $30 each.

2.2 Abrasive Waterjets

The abrasive waterjet differs from the pure waterjet in just a few ways. In purewaterjet, the supersonic stream erodes the material. In the abrasive waterjet, thewaterjet stream accelerates abrasive particles and those particles, not the water, erode

the material. The abrasive waterjet is hundreds, if not thousands of times morepowerful than a pure waterjet. Both the waterjet and the abrasive waterjet have theirplace. Where the pure waterjet cuts soft materials, the abrasive waterjet cuts hardmaterials, such as metals, stone, composites and ceramics. Abrasive waterjets usingstandard parameters can cut materials with hardness up to and slightly beyondaluminum oxide ceramic (often called alumina, AD 99.9).

2.2.1 Abrasive Waterjet Cutting Heads

Within every abrasive waterjet is a pure waterjet. Abrasive is added after the purewaterjet 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 screenedand sized. The most common abrasive is garnet. Garnet is hard, tough andinexpensive. Like the pink colored sandpaper found at the hardware store, differentmesh 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 areapproximately 3 inches long, inch in diameter, and have internal diameters rangingfrom 0.020 to 0.060 inch, with the most common being 0.040 inch. Although theabrasive waterjet machine typically is considered simple to operate and bullet proof,the mixing tube does require operator attention. A major technological advancementin waterjet was the invention of truly long-life mixing tubes. Unfortunately, the longerlife tubes are far more brittle than their predecessors, tungsten carbide tubes. If thecutting head comes in contact with clamps, weights, or the target material the tubemay be broken. Broken tubes cannot be repaired. Todays most advanced systemsincorporate collision detection to spare the mixing tube.

The standoff distance between the mixing tube and the target material is typically0.010 to 0.200 inch. Larger standoff (greater than 0.080 inch) can cause a frosting to


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appear atop the cut edge of the part. Many waterjet systems reduce or eliminate thisfrosting by cutting under water or using other techniques.

The consumable items in an abrasive waterjet are the water, abrasive, orifice (usuallyRuby) and mixing tube. The abrasive and mixing tube are exclusive to the abrasive

waterjet. The other consumables are also found in the pure waterjet.

2.2.3 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 abrasive jet jobs

Easily switched from single to multi-head useQuickly switch from pure waterjet to abrasive waterjet [2]

3. Basic waterjet principles

Waterjets are fast, flexible, reasonably precise, and in the last few years have becomefriendly and easy to use. They use the technology of high-pressure water being forcedthrough a small hole (typically called the "orifice" or "jewel") to concentrate anextreme amount of energy in a small area. The restriction of the tiny orifice creates

high pressure and a high-velocity beam, much like putting your finger over the end ofa garden hose.Pure waterjets use the beam of water exiting the orifice to cut softmaterial like diapers, candy bars, and thin soft wood, but are not effective for cuttingharder materials.


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Typical design of a pure waterjet nozzle A diagram of an abrasivejet nozzle

The inlet water for a pure waterjet is pressurized between 20,000 and 60,000 PoundsPer Square Inch (PSI) (1300 to 6200 bar). This is forced through a tiny hole in the

jewel, which is typically 0.007" to 0.020" in diameter (0.18 to 0.4 mm). This creates avery high-velocity, very thin beam of water (which is why some people refer towaterjets as "water lasers") traveling as close to the speed of sound (about 600 mph or960 km/hr).

An abrasivejet starts out the same as a pure waterjet. As the thin stream of waterleaves the jewel, however, abrasive is added to the the stream and mixed. The high-velocity water exiting the jewel creates a vacuum which pulls abrasive from theabrasive line, which then mixes with the water in the mixing tube. The beam of wateraccelerates abrasive particles to speeds fast enough to cut through much hardermaterials.

The cutting action of an abrasivejet is two-fold. The force of the water and abrasiveerodes the material, even if the jet is stationary (which is how the material is initiallypierced). The cutting action is greatly enhanced if the abrasivejet stream is movedacross the material and the ideal speed of movement depends on a variety of factors,including the material, the shape of the part, the water pressure and the type ofabrasive. Controlling the speed of the abrasivejet nozzle is crucial to efficient andeconomical machining. [4]

4. Advantages of waterjet

"If you need a machine and don't buy it, then you will ultimately find you have paid for it but don't have it" -Henry Ford.

There is a reason that waterjet machining has rapidly grown in popularity since themid-1990's. Actually there are a number of reasons, listed below, but they mostlycome down to "versatility." A waterjet is a versatile and flexible machining tool. Youcan cut a wide variety of material efficiently and cost-effectively and can create awide variety of parts. [4]

4.1 Cut virtually any material

Because waterjets cut using water and abrasive, they can work with a wide variety ofmaterials. These materials include:Aluminium, brass, copper, Pre-hardened steel,Mild steel, Exotic materials such as titanium, inconel and hastalloy, 304 stainless steel,

brittle materials such as ceramic, quartz, stone, laminated materials, flammable

materials [4]

One of the few materials that cannot be cut with a waterjet is tempered glass.


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4.2 Fast setup and programming

With waterjet machining, a flat piece of material is placed on a table and a cuttinghead moves across the material (although in some custom systems, the material movespast a fixed head). This simplicity means that it's fast and easy to change materials

and that no tool changes are required. All materials use the same cutting head, so thereis no need to program tool changes or physically qualify multiple tools.

The movement of the machining head is controlled by a computer, which greatlysimplifies control of the waterjet. In most cases, "programming" a part means usinga CAD program to draw the part. When you "push print," the part is made by thewaterjet machine. This approach also means that customers can create their owndrawings and bring them to a waterjet machine for creation. [5]

4.3 No mechanical stresses

Waterjet machining does not introduce any stresses into the material.

4.5 Almost no heat generated on your part

What little heat is generated by the waterjet is absorbed by the water and carried intothe catch tank. The material itself experiences almost no change in temperature duringmachining. During piercing 2" (5 cm) thick steel, temperatures may get as high as120 F (50 C), but otherwise machining is done at room temperature.

The result is that there is no heat affected zone (HAZ) on the material. The absence ofa HAZ means you can machine without hardening the material, generating poisonous

fumes, recasting, or warping. You can also machine parts that have already been heattreated. [4]

4.6 Are very safe

Obviously, you don't put any body parts in front of a waterjet machining head while itis on. Anything that can cut through 2" steel will make short work of flesh and bone.Aside from this, however, waterjets are very safe. A leak in a high-pressure watersystem tends to result in a rapid drop in pressure to safe levels. Water itself is safe andnon-explosive and the garnet abrasive is also inert and non-toxic. One of the largesthazards is cuts from the sharp edges of material created by the waterjet. [4]

4.7 Modern systems are now very easy to learn

Control of the waterjet head is complicated and requires careful calculation to get theproper speed that will give the best result. This means that the system needs to becontrolled by a computer, which means that the user-interface for the system can besimplified and made friendlier. Modern systems are designed the same way as manyother computerized CAD systems and are quickly learned. [4]


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4.8 Environmentally friendly

As long as you are not machining a material that is hazardous, the spent abrasive andwaste material become suitable for land fill. The garnet abrasive is inert and can bedisposed of with your other trash.If you are machining lots of lead or other hazardous

materials, you will still need to dispose of your waste appropriately, and recycle yourwater. Keep in mind, however, that very little metal is actually removed in the cuttingprocess. This keeps the environmental impact relatively low, even if you do machinethe occasional hazardous material.In most areas, excess water is simply drained to thesewer. In some areas, water treatment may be necessary prior to draining to sewer. Ina few areas, a "closed loop" system that recycles the water may be required.Thepumps do use a considerable amount of electricity, though, so there is some additionalenvironmental (and cost) impact due to this. [4]

4.9 No start hole required

Start holes are only required for materials that are difficult or impossible to pierce. Afew poorly bonded laminates can fall into this category, in which case pre-drilling orother special methods may be used.

4.10 Narrow kerf removes only a small amount of material

The amount of material removed by the waterjet stream is typically about 0.02" (0.5mm) wide, meaning that very little material is removed. When you are working withexpensive material (such as titanium) or hazardous material (such as lead), this can bea significant benefit. It also means that you can get more parts from a given sheet ofmaterial.When machining or roughing out expensive materials such as titanium, your

scrap still has value. This is because you get chunks, not chips. [4]

5. Advantages of waterjets compared with lasers

Laser cutting involvesusing a laser focused onmaterial to melt, burn, orvaporize the material. Thelaser can be a gas laser(such as CO2) or a solid-state laser. The laser beam

can be static, and thematerial moves in front ofthe laser, or the laser canitself be moved across thematerial. When the lasermoves across the material,additional optics arerequired as the distancefrom the emitting end ofthe laser changes. Lasershave the advantage over

traditional machiningmethods that the laser


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never touches the material(avoiding contamination)and the HAZ is relativelysmall. [7]

Waterjets have a number of advantages over lasers. In many respects, however, thetwo tools are complementary and many machine shops own both of them.

1. Waterjets can machine reflective materials that lasers cannot, such as copperand aluminum. Waterjets cut a wide range of material with no changes insetup required. Also, materials which are heat-sensitive can be cut usingwaterjets.

2. Waterjet cutting does not heat your part. There is no heat-affected zone (HAZ)or thermal distortion, which can occur with lasers. Waterjets do not change theproperties of the material.

3. Abrasivejets typically use garnet as the abrasive material. Garnet is a non-reactive mineral that is biologically inert. The only issue with waterjets iswhen you are cutting a material that is potentially hazardous (such as lead),since small pieces of the material will be abraded and mix in with the spentgarnet.

4. There are no noxious fumes, such as vaporized metal, and no risk of fires. Thedistance between the end of the waterjet nozzle and the material is typicallyvery small, although caution is needed when the waterjet nozzle is raised.

5. The cost of a waterjet machine is generally much lower than that of a laser.For the price of a laser, you can purchase several waterjet machining centers.

6. With lasers, the material needs to be relatively uniform. In particular, whencutting over uneven surfaces, the laser can lose its focus and cutting power. Awaterjet will retain much of its cutting power over uneven material. Althoughthe material may deflect the cutting stream, it typically has a negligibleeffect.

7. How thick you can cut is a function of how long you are willing to wait.Waterjets easily handle 2" (5cm) steel and 3" (7.6 cm). Although somepeople have used waterjets at thicknesses of up to 10" (25 cm) in steel, it isdifficult to maintain precision in materials thicker than 2" (5 cm). Lasersseem to have a maximum practical cutting thickness of 0.5" (12 mm) to 0.75"

(19 mm).8. Maintenance on a waterjet is simpler than that of a laser9. Waterjets are computer controlled, so that the operator does not have to be

highly skilled and trained.10.Material cut by waterjets have a fine, sand-blasted surface because of the way

the material was abraded, which makes it easier to make a high-quality weld.Material cut by laser tends to have a rougher, scaly edge, which may requireadditional machining operations to clean up. [4]

6. A Research and design the nozzle of water jetCrusher [4,5,6,7,8,9,10,11,15]

The nozzle is the core engine of the water jet crusher and can launch a fan-shapedwater jet and control the density of water jet (that is, the distance between watermolecules). If the needs of smaller particles, the distance between water molecules


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should be smaller. If the biological needs of larger particles, the distance betweenwater molecules should be bigger, with direct proportion of its function: y = f (x). Thefan-shape water jet is fired through nozzles.

In this picture, we can see fromd4, d3, d2, d1 the water density is

different. We summarised thedistance between water moleculesexpansion multiplierformulation[6,7,8] in accordancewith the relevant principles ofmathematics.the expansion of

e dn,

The expansion formula of the distance between water molecules [6,7,8] rn= r0nrn denotes the distance between water molecules after expansion, r0 denotes theoriginal distancebetween water molecules beforemultiples. According to last picture and calculation we can know r1


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installed in factories it was anticipated that theequipment would be able to operate for aconsiderable period of time without needing agreat deal of maintenance and upkeep. However,as equipment began to be installed in factories in

different regions, a particular and unexpectedproblem arose form the water. The problem isthat local water is not all of the same quality. Thestandards which the water must meet, may makethe water acceptable for drinking and normal use,but can sometimes give problems in equipmentwhere the water is subject to pressures above 350MPa and where it is moving in excess of 700m/sec.

The presence of small amounts of solid material in the jet fluid can cause anaccelerated wear of either the nozzle body or other points within the circuit where jet

velocities are high. Also, slight changes in water chemistry can significantly affect theerosion resistance of some of the components within the pump mechanism. Theproblem of water quality has been recognized and addressed by the vendors of theequipment. As a result it has been found necessary to set water quality standards inorder to operate high-pressure water jet cutting systems effectively. Many localitiesdo not have water sources that satisfy these requirements. It has been found that if thewater supply is inadequate then the result is equipment malfunction. A solution wasfound through water preparation system.There are several ways to treat the water prior to use. The simplest is a watersoftening treatment similar to that used in the household. The second method isreverse osmosis, which consists of passing the water through a very fine membranewhich filters out the impurities on the molecular level. And the third is de-ionizingcircuit.Ordinary tap water is used to feed the water jet systems. 90% of all water jet andabrasive water jet users require only water softening prior to sending that waterthrough the pumps inlet water filters and then to the intensifier. Reverse Osmosis(RO) and De-Ionizers (De-I) tend to make the water so pure that it becomes "ionstarved." This aggressive water seeks to satisfy its ion starvation by taking ions fromsurrounding materials, such as the metals in the pump and high-pressure plumbinglines. RO and De-I can greatly extend orifice life,while simultaneously performingvery expensive damage to the intensifier and plumbing. Orifices are rather

inexpensive. High-pressure cylinders, check valves, and end caps damage will faroutweigh orifice life improvements. A high concentration of total dissolved solids(TDS) in your shops water supply causes accelerated wear of pump components. Ifmaximum values for TDS silica content and pH are exceeded, then water treatment -ranging from water softening to deionization or reverse osmosis - is required. [8]

8. REQUIRED WATER QUALITY

Firs step in the process of making decision of hether water preparation system isneeded or not is to analyze a sample of local water on certified laboratory and makea treatment recommendation.Water should be lean top water. Although the water passes though a filtering systembefore it reaches the pump, the cleaner the water the less frequently you will need to

service the filter. If you are using a separate water filtering system, you should makesure you service the filters at the recommended intervals. The water should not be


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hard or contain large quantities of dissolved iron and silica. These materials causeproblems in both the pump and the nozzle. The water circuit consists of the inlet waterfilters, booster pump, intensifier, and shock attenuator. Ordinary tap water is filteredby the inlet water filtration system usually comprising of a 1 and a 0.45 micrometercartridge filter. For these reasons the original 5 micrometer fiber cartridge filter fitted

to the first machine has not always been adequate to protect the pump and jet deliverysystem, even though, in that installation, no erosion of the seals and shafts hadoccurred after the first six months of operation. In these circumstances, slight changesin water chemistry can significantly affect the erosion resistance of some of thecomponents within the pump mechanism.

Water quality required for an Ingersoll-Rand Water jet Cutting System

9. Water jet can cutting alloy steels w ith out change the properties .Look at the diagram, minimum heat for transforms ferrite to austenite is around 730digree. And maximum heat that waterjet creat is around 120 digree. It means waterjetcan cutting alloy steels with out change the properties. [10]

9.1 Low alloy steels can cutting with w aterjet

Low alloy steels contain alloying elements as Ni, Mn, Cr, Si, Mo, Nb, Cu. Thepercentage of all alloying elements does not exceed 5%. [9]


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9.2 High alloy steels can cutting w ith waterjet

High alloy steels contain alloying elements as Ni, Mn, Cr, Mo, Nb, W, V, Cu. Thetotal percentage of all alloying elements is higher than 5%. [9]

9.3 Stainless steels can cutting w ith waterjet

Stainless steels are high alloy steels. Their chromium content is at least 12%. forexample if cut stainless steels with laser cutting machines then chromium will beburn.

Refrences

[1]http://www.flowcorp.com/uploadedFiles/WJ%20Overview%20White%20Paper.pdf

[2] http://www.flowcorp.com/waterjet-resources.cfm?id=336

[3] http://www.edmtodaymagazine.com/TechTipsMyJun09.pdf

[4]http://waterjets.org/index.php?option=com_content&task=category&sectionid=4&id=46&Itemid=53

[5] http://www.hydrocut.org/abrasive_waterjet_cutting.htm

[6] http://www.iop.org/EJ/article/1742-6596/188/1/012036/jpconf9_188_012036.pdf?request-id=2425819c-20f5-4c5f-9ab1-ed92e942cb21


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[7]http://docs.google.com/viewer?a=v&q=cache:3ur7FaoWpNUJ:https://app.mfg.com/servlet/mfg.files.DownloadFilePublic%3FfileId%3D89617%26fileTypeId%3D2%26noRefresh%3D1+Laser+cutting+involves+using+a+laser+focused+on+material+to+melt,+burn,+or+vaporize+the+material.+The+laser+can+be+a+gas+la

ser+(such+as+CO2)&hl=en&gl=my&sig=AHIEtbTxNTCk121RmSEl3c50g2lV8OVKGg

[8] http://lyle.smu.edu/rcam/research/waterjet/par2.html

[9] http://www.wear-management.ch/?path=root+steel =en

[10] https://online.tu-graz.ac.at/tug_online/voe_main2.getVollText?pDocumentNr=63649

Microsoft Word - Advantage of Use Water Jet

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