How Waterjet Works

8/8/2019 How Waterjet Works

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How Waterjet WorksWaterjet Cutting articulates the use of a ultra high pressure waterjet, focused into a

small beam, slicing through virtually all materials.

The process can be applied with or without an abrasive, dependant on application. Abrasiveparticles are introduced to the beam at the cutting head to cut hard materials. Softer materialsdo not require the abrasive component. Whatever the option, there is never any heat generatedand therefore your first choice for accuracy, stability and cleanliness of cutting.

Comparison - Waterjet vs cutting with heat

WaterjetCutting

Cold-cut edges, as createdduring cutting with awaterjet are free of burrs,structural and dimensionalcomprose.

Cutting with HeatThe heat generated during cutting

using laser, plasma and oxy-acetalene changes the structure of the material. Defects, distortion andburrs occur with these processes.
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Overview of waterjets

Waterjet is a generic term used to describe equipment that uses a high pressure stream of water for cutting orcleaning purposes. Abrasivejet is a subcategory of waterjet in which abrasive is introduced to accelerate theprocess. Pure waterjet and water-only cutting are phrases for specifically distinguishing waterjets that do notuse abrasive.In other words: abrasivejet and pure waterjet are kinds of waterjet , and waterjet is a kind of machinery.It is normal, and common, to use the term waterjet to refer to abrasivejets , though in some cases it can beconfusing. On this web site, we'll use waterjet when referring to topics that cover both pure waterjets andabrasivejets , and use the terms pure waterjet and abrasivejet when discussing topics that are specific to one orthe other.

Article Contents How do waterjets work? Basic waterjet principles Advantages of waterjet machining Where waterjets are used What it costs to make waterjet parts

How do waterjets work?Take ordinary tap water and pressurize it to 60,000 psi (4,000 bar) and force it through a very small hole. Mix thewater with garnet abrasive and you have a very thin stream of water traveling very fast that will rapidly erodemost materials.Some waterjets are "pure waterjets" and don't add the garnet abrasive. These are used to cut softer materials, suchas food, rubber, and foam.What can waterjets cut? What can't they cut?Waterjets can cut just about any material that can be made into a sheet and placed in front of them.The most popular materials are metals (especially aluminum, because it's relatively soft and cuts quickly),because waterjets can cut intricate shapes to a high precision quickly and economically. Since metals are the mostcommon material cut by machining shops, waterjets tend to cut a lot of metal.Waterjets also commonly cut stone and glass, because the waterjet can get intricate shapes not possible usingtraditional machining methods. These materials are popular with artists who like to work with these materials andwaterjets because it lets them create almost anything they can envision.Among the very few materials that waterjets cannot cut are diamonds and tempered glass. Diamonds are too hardto cut (and there may be a few other very hard materials that can't be cut). Tempered glass will shatter when it iscut with a waterjet (tempered glass is designed to shatter when it's disturbed and is frequently used in windshieldsfor this very reason).A few advanced ceramics are so hard that it's not economical to cut them. Some composite materials (layers of different materials sandwiched together) can't be cut because the water can seep between the layers and"delaminate" the material. Many composite materials cut just fine, though, and there are some techniques tocutting laminated materials .What do they cost?Waterjets typically come as complete systems, including the high-pressure water pump, a system to preciselyposition the waterjet nozzle, a tank to catch the waste water, and an abrasive feed system. Prices run from $50,000to 300,000, with $150,000 being about average for a mid-range waterjet system.Prices can run considerably higher than this for custom systems or very large waterjet cutting systems.Waterjet systems are not currently something for the home workshop. You'll find them in use in machining shopsand industrial workshops. Among other factors, you need industrial levels of electricity to power the pumps(which can pull as much as 50 amps; some pumps require 250 amps to get started).For the hobbyist interest in waterjets, the more economical approach is to work with a job shop to make the parts.Most job shops can accept computer drawings you create to make exactly the part you want.List of waterjet job shops by state and country
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Basic waterjet principlesWaterjets are fast, flexible, reasonably precise, and in the last few years have become friendly and easy to use.They use the technology of high-pressure water being forced through a small hole ( typically called the "orifice"

or "jewel" ) to concentrate an extreme amount of energy in a small area. The restriction of the tiny orifice createshigh pressure and a high-velocity beam, much like putting your finger over the end of a garden hose.Pure waterjets use the beam of water exiting the orifice to cut soft material like diapers, candy bars, and thin softwood, but are not effective for cutting harder materials.

Typical design of a pure waterjet nozzleThe inlet water for a pure waterjet is pressurized between 20,000 and 60,000 Pounds Per Square Inch (PSI) (1300to 6200 bar). This is forced through a tiny hole in the jewel, which is typically 0.007" to 0.020" in diameter (0.18to 0.4 mm). This creates a very 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 or 960 km/hr).An abrasivejet starts out the same as a pure waterjet. As the thin stream of water leaves the jewel, however,abrasive is added to the the stream and mixed. The high-velocity water exiting the jewel creates a vacuum whichpulls abrasive from the abrasive 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 harder materials.

(Left): A diagram of an abrasivejet nozzle. (Right): Photograph of the same nozzle, with the guard removed,cutting out some parts.

The cutting action of an abrasivejet is two-fold. The force of the water and abrasive erodes the material, even if the jet is stationary (which is how the material is initially pierced). The cutting action is greatly enhanced if the


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abrasivejet stream is moved across 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 of abrasive. Controlling the speed of the abrasivejet nozzle is crucial to efficient and economical machining.

(Left) A typical waterjet nozzle to the left of an abrasivejet nozzle.(Right) An abrasive nozzle installed on a machine. The white tube protruding from the side of the abrasive nozzle

brings the abrasive to the nozzle.

This video shows a waterjet cutting a small design from what looks like 1/4"aluminum. The cutting takes place above water which makes it noisier, buteasier to see what's happening. This is only the last part of the cutting, butnote the intricate shape that the waterjet achieved.

Waterjet nozzle fired into the airIn this video below, a waterjet nozzle is raised a few inches above the work surface, and fired for a few seconds

into the air. Keep in mind that there is about 30 horsepower going through that little stream of water.

Cutting 1/2" aluminum at Westec trade showThis video was taken at the Westec trade show some years ago (1997 or so). The video shows cutting fromvarious angles, with narration.

Cutting a foam mouse padA large mouse-pad, that is designed to wrap around a keyboard, is cut from foam."The reason I chose to film foam being cut is because it is fast enough that the video can be worth watching, andyou can see a complete part from start to finish," said Carl Olsen . "I also used an abrasive nozzle, which wasreally unnecessary. I could have used a water-only nozzle which would have made a nicer edge finish, but I did
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not have one handy. Also, because this was foam, I could have cut it much faster, but I chose a slower speed sothat I could have time to react, should it want to float away on me."

Advantages of waterjet machining"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 the mid-1990's. Actually there area number of reasons, listed below, but they mostly come down to "versatility." A waterjet is a versatile andflexible machining tool. You can cut a wide variety of material efficiently and cost-effectively and can create awide variety of parts.

Machine any two-dimensional shape with one tool

Cut virtually any materialBecause waterjets cut using water and abrasive, they can work with a wide variety of materials. These materialsinclude:

Copper, brass, aluminum: Pre-hardened steel Mild steel Exotic materialss such as titanium, Inconel and Hastalloy 304 stainless steel

Brittle materials such as glass, ceramic, quartz, stone. Laminated material Flammable materials

One of the few materials that cannot be cut with a waterjet is tempered glass. Because tempered glass is understress, as soon as you begin to cut it, it will shatter into small fragmentsas it is designed to do.

Pictured here is a dragon machined from 1" (2.5 cm) thick bulletproof glass, and inlay of marble and granite

Fast setup and programmingWith waterjet machining, a flat piece of material is placed on a table and a cutting head moves across the material(although in some custom systems, the material moves past a fixed head). This simplicity means that it's fast andeasy to change materials and that no tool changes are required. All materials use the same cutting head, so there isno need to program tool changes or physically qualify multiple tools.The movement of the machining head is controlled by a computer, which greatly simplifies control of thewaterjet. In most cases, "programming" a part means using a CAD program to draw the part. When you "pushprint," the part is made by the waterjet machine. This approach also means that customers can create their owndrawings and bring them to a waterjet machine for creation.Little fixturing for most parts
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There are very low sideway forces with waterjet machining--cutting the material doesn't push it. The downwardforces are also small, in the range of a few pounds. Typically, the largest force is from the water in the tank pushing back up against the material.Fixturing is generally a matter of weighing down the material by placing weights on it. Small parts might requiretabs to prevent them from falling into the tank.The low side forces, means you can machine a part with walls as thin as 0.01" (0.25 mm). This is one of thefactors that make fixturing is so easy. Also, low side forces allow for close nesting of parts, and maximummaterial usage.Almost no heat generated on your partWhat little heat is generated by the waterjet is absorbed by the water and carried into the catch tank. The materialitself experiences almost no change in temperature during machining. During piercing 2" (5 cm) thick steel,temperatures may get as high as 120 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 of a HAZ means you canmachine without hardening the material, generating poisonous fumes, recasting, or warping. You can alsomachine parts that have already been heat treated.No mechanical stressesWaterjet machining does not introduce any stresses into the material.

Machine thick materialWhile most money will probably be made in thicknesses under 1" (2.5 cm) for steel, it is common to machine upto 4" (10 cm). The thicker the material, the longer it will take to cut. A part made from material twice as thick willtake more than twice as long. Some companies make low tolerance parts out of metal that is up to 5" to 10" thick (12.5 cm-25 cm), but it takes a long time and tends to be an occasional operation. Typically, most waterjet partsare made from metal that is 2" (5 cm) or thinner.

Pictured here is a part made from 2" (5 cm) thick 304 stainless steel

Are very safeObviously, you don't put any body parts in front of a waterjet machining head while it is on. Anything that can cutthrough 2" steel will make short work of flesh and bone. Aside from this, however, waterjets are very safe. A leak in a high-pressure water system tends to result in a rapid drop in pressure to safe levels. Water itself is safe and

non-explosive and the garnet abrasive is also inert and non-toxic. One of the largest hazards is cuts from the sharpedges of material created by the waterjet.Modern systems are now very easy to learnControl of the waterjet head is complicated and requires careful calculation to get the proper speed that will givethe best result. This means that the system needs to be controlled by a computer, which means that the user-interface for the system can be simplified and made friendlier. Modern systems are designed the same way asmany other computerized CAD systems and are quickly learned.Environmentally friendlyAs long as you are not machining a material that is hazardous, the spent abrasive and waste material becomesuitable for land fill. The garnet abrasive is inert and can be disposed of with your other trash.If you are machining lots of lead or other hazardous materials, you will still need to dispose of your wasteappropriately, and recycle your water. Keep in mind, however, that very little metal is actually removed in the

cutting process. This keeps the environmental impact relatively low, even if you do machine the occasionalhazardous material.
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In most areas, excess water is simply drained to the sewer. In some areas, water treatment may be necessary priorto draining to sewer. In a few areas, a "closed loop" system that recycles the water may be required.The pumps do use a considerable amount of electricity, though, so there is some additional environmental (andcost) impact due to this.No start hole requiredStart holes are only required for materials that are difficult or impossible to pierce. A few poorly bondedlaminates can fall into this category, in which case pre-drilling or other special methods may be used.Narrow kerf removes only a small amount of materialThe amount of material removed by the waterjet stream is typically about 0.02" (0.5 mm) wide, meaning that verylittle material is removed. When you are working with expensive material (such as titanium) or hazardousmaterial (such as lead), this can be a significant benefit. It also means that you can get more parts from a givensheet of material.When machining or roughing out expensive materials such as titanium, your scrap still has value. This is becauseyou get chunks, not chips.

Advantages of waterjets compared with lasersLaser cutting involves using a laser focused on material to melt, burn, or vaporize the material. The laser can be agas laser (such as CO 2) or a solid-state laser. The laser beam can be static, and the material moves in front of the

laser, or the laser can itself be moved across the material. When the laser moves across the material, additionaloptics are required as the distance from the emitting end of the laser changes. Lasers have the advantage overtraditional machining methods that the laser never touches the material (avoiding contamination) and the HAZ isrelatively small.

Advantages of waterjetsWaterjets have a number of advantages over lasers. In many respects, however, the two tools are complementaryand many machine shops own both of them.

Can work with more materialsWaterjets can machine reflective materials that lasers cannot, suchas copper and aluminum. Waterjets cut a wide range of material withno changes in setup required. Also, materials which are heat-

sensitive can be cut using waterjets. No heat-affected zone (HAZ) with waterjets

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

Waterjets are more environmentally friendlyAbrasivejets typically use garnet as the abrasive material. Garnet is anon-reactive mineral that is biologically inert. The only issue withwaterjets is when you are cutting a material that is potentiallyhazardous (such as lead), since small pieces of the material will beabraded and mix in with the spent garnet.

Waterjets are safer There are no noxious fumes, such as vaporized metal, and no risk of fires. The distance between the end of the waterjet nozzle and thematerial is typically very small, although caution is needed when thewaterjet nozzle is raised.

Uniformity of material not importantWith lasers, the material needs to be relatively uniform. In particular,when cutting over uneven surfaces, the laser can lose its focus andcutting power. A waterjet will retain much of its cutting power overuneven material. Although the material may deflect the cutting

stream, it typically has a negligible effect. Lower capital equipment costs


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

Better tolerances on thicker partsWaterjets offer better tolerances on parts thicker than 0.5" (12 mm).For thinner parts, both waterjets and lasers offer comparabletolerances.

Waterjets can machine thicker materialsHow thick you can cut is a function of how long you are willing towait. Waterjets easily handle 2" (5 cm) steel and 3" (7.6 cm).Although some people have used waterjets at thicknesses of up to10" (25 cm) in steel, it is difficult to maintain precision in materialsthicker than 2" (5 cm). Lasers seem to have a maximum practicalcutting thickness of 0.5" (12 mm) to 0.75" (19 mm).

Simpler maintenanceMaintenance on a waterjet is simpler than that of a laser.

Simpler operationWaterjets are computer controlled, so that the operator does nothave to be highly skilled and trained.

Better edge finishMaterial cut by waterjets have a fine, sand-blasted surface becauseof the way the material was abraded, which makes it easier to makea high-quality weld. Material cut by laser tends to have a rougher,scaly edge, which may require additional machining operations toclean up.

Advantages of waterjets compared with EDMEDM stands for Electrical Discharge Machining and is used to machine electrically conductive materials, such assteel and titanium. An electrical arc rapidly discharges between an electrode and the workpiece material. Theseries of arcs removes metal by melting it and vaporizing it, essentially eroding the metal using electricity. Theparticles are flushed away by a continuously circulating non-conducting fluid, such as deionized water orkerosene. EDM can create intricate shapes in hard materials that are difficult to machine using traditionalmethods.

Advantages of waterjets

Although the above part could be made using EDM, it's much faster to make it using a waterjet Many EDM shops are also buying waterjets. Waterjets can be considered to be like super-fast EDM machineswith less precision. This means that many parts of the same catagory that an EDM would do can be done fasterand cheaper on an abrasivejet, if the tolerances are not extreme.New technology allows Abrasive jets to obtain tolerances of up to +/-.003" (0.075mm) or betterAbrasive Jet machining is useful for creating start holes for wire insertion later on. (a mill could do the job, butonly after spotting the hole, changing tools to drill a pilot, then changing tools again to drill out the hole).

FasterAbrasive jets are much faster than EDM, which slowly removes the


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metal. Can work with more materials

Waterjets can machine non-conductive materials that EDM cannot,such as glass, wood, plastic, and ceramic. There is almost no limit tothe type of materials that can be machined with waterjets.

Uniformity of material not importantA waterjet will retain much of its cutting power over uneven material.Although the material may deflect the cutting stream, it typically hasa negligible effect. Such material aberrations would cause wire EDMto lose flushing.

Waterjets make their own pierce holesSome types of EDM, such as wire-cut EDM, a hole needs to be firstmade in the material, which has to be done in a separate process.Waterjets can pierce the material, requiring no additional fixturing ormachining.

No heat-affected zone (HAZ) with waterjetsWaterjet cutting does not heat your part. There is no heat-affectedzone (HAZ) or thermal distortion, which can occur with EDM.Waterjets do not change the properties of the material.

Waterjets require less setupMost of the fixturing with waterjets is weighing down the material sothat it does not shift in the water tank. The fixturing needs towithstand forces of pounds and does not need to be elaborate orprecise.

Make bigger parts The size of the part created with a waterjet is limited by the size of

the material. In setups where the material passes underneath thewaterjet, the finished part size can be huge. Even with an X-Y tablesetup, part sizes can be quite large.

Wire-cut EDM fixturing in a waterjet machining center. This makes precision fixturing possible. It also allows for pre-machining on the waterjet to release stresses in the material, and then use the exact same fixturing on the

EDM to do secondary operations and final cutting to extreme tolerance.


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The cheese slicer was made on a waterjetnote the very thin blade

Advantages of waterjets compared with plasmaIn plasma cutting, a stream of gas is blown at high speed while an electrical arc is passed through it. This causessome of the gas to become very hot plasma. The gas, at about 27,000 F (15,000 C), then melts the metal or othersubstance it comes into contact with. The gas is moving fast enough that the molten metal is blown away from thecutting area.

Advantages of waterjetsThe clearest advantage that waterjets have compared with plasma cutting is that waterjets operate at much lowertemperatures. During piercing, the temperature of the material may rise as high as 120 F (50 C), but cuttingtypically happens at room temperature. The presence of the catch tank (a large tank full of waste water) helps tomoderate the temperature as well. This lower temperature means there is no Heat Affected Zone when material iscut with a waterjet.Waterjets also can cut materials that don't easily melt (such as granite) or that are destroyed by melting (manylaminates). Waterjets are also more precise than plasma cutting.Plasma cutting is typically faster than waterjet, particularly with very thick metal. Plasma torches can pierce andcut steel up to 12" (30 cm) thick.

Modern waterjets machines are relatively clean and quiet

Advantages of waterjets compared with flame cuttingFlame cutting, or oxy-fuel cutting, is used to cut metals by heating them to a high temperature and thenintroducing oxygen to melt the metal and perform the cut. Flame cutting only be used with iron and steel.In flame cutting, the cutting torch combines oxygen with a fuel, such as acetylene, that heats up the metal. Oncethe metal is cherry red, a trigger on the torch is pressed that blasts oxygen at the metal. The hot metal reacts with

the oxygen to form iron oxide (rust), which has a lower metal point than iron or steel. The iron oxide then flowsaway from the cutting zone. Some iron oxide may remain on the cut as slag, but it is easily removed by tapping orwith a grinder.

Advantages of waterjetsWhile flame cutting can work only with iron or steel, waterjets can machine many different types of materials,both metal and non-metallic. Waterjets also do not appreciably heat up the material they cut--during piercing,temperatures may rise to 120 F (50 C), but during cutting the material is heated only a degree or two.The edge finish created with a waterjet is smooth, similar to a sandblasted finish, rather than the rough edges leftby flame cutting. Waterjets are more precise than flame cutting and have a much smaller kerf as less material isremoved (particularly important when cutting expensive material).Flame cutting can be faster than waterjets, especially when done using a multi-torch cutting machine, and as aresult is cheaper than waterjet cutting.
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The part on the top was roughed out with a waterjet, with secondary machining creating the part shown on thebottom

Advantages of waterjets compared with millingMilling is typically done with a milling machine that can perform a series of operations on material, typicallycutting, drilling, lathing, and planing. Most modern milling machines are six-axis machines that can performcomplex sequences of milling operations rapidly and precisely.

A typical modern milling machine

Advantages of waterjetsAlthough mills cut faster, in most cases, than waterjets, the setup and fixturing with waterjets is much simpler.Setup with waterjets is typically a matter of just loading the part drawing into the controller software, setting thematerial and thickness and beginning machining. Similarly, fixturing is mostly a matter of weighing down the

material so that it doesn't move on the table during machining. Clean-up on a waterjet is also faster and simpler.As a result, overall, a waterjet can have a greater throughput than a mill on similar parts.Waterjets can also machine almost any material, including brittle materials, pre-hardened materials, and otherwisedifficult materials such as Titanium, Hastalloy, Inconel, SS 304, and hardened tool steel.

With a waterjet, there is also no tool changing. The waterjet nozzle is theonly tool used, and it is used for all the different types of materials that awaterjet cuts. There is also less wear on tools, especiall in harder andgummier materials, because the cutting action of the waterjet is the streamof water and abrasive. While there is wear on the mixing tube and high-pressure water componenets, this wear tends to be constant with time, anddoesn't change with different materials.Waterjets are frequently used for complimenting or replacing milling operations. They are used for roughing outparts prior to milling, for replacing milling entirely, or for providing secondary machining on parts that just cameoff the mill. For this reason, many traditional machine shops are adding waterjet capability to provide acompetitive edge.
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This is a part you might otherwise do on a mill. It took less than 20 minutes to make with an abrasive jet,including setup and cleanup time! Actual machining time is about 6 minutes. Material is 0.5" (13mm) thick

hastalloy with a tolerance about 0.002" (0.05 mm).

Advantages of waterjets compared with punch pressesA punch press uses a set of punches and dies to form parts out of metal. The metal is formed and cut by the punchpress into a part, which may have secondary machining done to it or not. Coins are a common part that are formedusing punch presses. The typical commercial punch press exerts about 20 tons of pressure.

Advantages of waterjetsWaterjets have a lower cost-per-piece for short runs than a die press, because of the expense (and time) involvedin creating the dies and punches. Creating the drawing for a part on a waterjet machine is all that's needed to beginmachining the part, where with a punch press, the drawing is usually only the first step to creating the die.Lateral forces wtih a waterjet are negligible, which means that holes can be placed very close to the material edge,which is not the case with a punch press. Waterjets can also work with very thick materials, while punch pressesare limited in thickness to the amount of pressure they can apply. And, of course, waterjets can work with manydifferent types of materials, including brittle materials and laminates .Some stamping houses are using waterjets for fast turn-around and rapidprototyping work. Waterjets make a complimentary tool for punch pressesbecause they offer a wider range of capability for similar parts. For highproduction of thin sheet-metal, the stamp will be more profitable in manycases, but for short runs, difficult material, and thick material, waterjets

have their place.

Five minutes is all it took to make this custom fileWaterjets also play a big part as just one part in a larger manufacturing process. For example, waterjets are oftenused to machine features into an existing part, or to do pre-machining to remove material before precisionfinishing on other machinery.

Where waterjets are usedWaterjet machines are not specialty machines for niche applications. They are general purpose tools that areuseful in any machine shop. Following is is a small sampling of specialized applications.General purpose machine shopsWaterjets are good all-around machine tools, as it is fast and easy to gofrom idea to finished part. Waterjets can also work with many differenttypes of materials with minimal fixturing and setup.ArtistsArtists use waterjets because they can create intricate designs in materials that have traditionally been difficult to
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work with, such as stained glass, marble and stone.ArchitecturalSimilar to the art market, there are many machines out there makingcustom flooring from stone, as well as making architectural details frommetalAerospaceCompanies that makes parts for the aerospace industry maching lots of aluminum, which is easily machined on awaterjet. Exotic metals such as Inconel , titanium, and Hastalloy can also be machined by waterjets.ManufacturingWaterjets are used for making parts of products that are sold, as well asmany of the parts used to make the machines on the assembly lines.Automotive & transportationPrototyping and production parts for automobiles, and the tooling for making automobiles. Also there are a lot of custom race car parts made on waterjets.Laser shopsLasers and waterjets are highly complementary tools. They both pick up

where the other leaves off.EDM shopsSome of the small size and higher precision waterjet machining centers are great complementary tools to EDMbecause they allow for higher speed machining of similar shapes, and can provide other services for the EDMsuch as pre-drilling start holes or stress relieving the part prior to skim cutting on the EDM.Model shops / rapid prototypingFast turn-around of single piece production in nearly any material makeswaterjets great for these kinds of applications.SchoolsMany of the larger size universities that offer engineering classes also have waterjets. They are great tools for theclassroom environment because they are easy to learn, program, and operate, and because they can make one-off kind of parts quickly. They also provide a great service to other departments within the university that may need

job-shop services.Looking for somebody to make your part? Check our listings of waterjet job shops .

What it costs to make waterjet partsThere are a variety of ways to calculate the cost of making parts with a waterjet. This is true of most businesses,and the calculation of "Cost of Goods" is the subject of many books and business classes. This page looks at someapproaches to calculating the cost of goods for parts made with a waterjet, which will then help you determinehow much to charge for a part.A lot of people price the work on their machines on dollars per hour basis. This may make sense for some kindsof machines, but not for a waterjet. A job shop with a multi-head machine running two pumps or a high powerpump might have a much higher cost of operation than a shop with a small machine with a low power pump. If these two shops compete against each other purely on dollars per hour, then the shop with the smaller cheapermachine will make a lot more money. This is because the parts will take longer to make, and they will be cheaperto make, so the customer pays more yet the part costs less to make. The shop with the faster machine musttherefore charge more per hour to take advantage of their faster machine.
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A waterjet machine with four heads (Photo courtesy Pegasus Northwest, Inc.) Another strategy is to price the work based on a dollars per square inch basis. This has the drawback that a partwith a lot of geometry to it (curves and corners and pierces) will take a much longer time than a straight line cut,because the waterjet must slow down to avoid blow-out at the corners and turns. Likewise, material thickness andmany other factors come into play, and cutting speed is not a linear function relating to thickness. So, while$/square inch may make sense for some machines, it does not for waterjets.The best approach is to figure out how much it will cost you to make the part. Then estimate how much it wouldcost to make the part by competitive methods (either other kinds of machines, or your competitor with anwaterjet). See if there are other savings such as being able to squeeze more parts from expensive material. Then,price from there. Your customer does not need to know if you are charging them $100per hour. They are notpaying you for your time, they are paying your for the part.Another option that can work, if you prefer a simpler, more objective formula, is to simply cost your work basedon your true cost to make the part. Many machines have software built in to make this easy. Simply take the costto make the part, and multiply by a factor, and there you have it.The cost to make your part should include the following factors:

How much time will it take to program the path into a tool path? (Andif the customer provides the toolpath in a compatible file format, anyprice break you might choose to give them.)

How much risk is there that you might break something (such as

when cutting glass) and need to scrap it and start over? Does the customer provide the material, or do you need to purchase

the material? How many times must you pierce the material? Each pierce is extra

wear and tear on machine, and the associated risk of a nozzle plug ormaterial cracking during piercing.

How much do your consumables cost you?o Electricityo Watero Abrasiveo Spares and wear parts

Is there any special setup or risk to consider? How much time will it take to actually do the cutting? How much time will it take you to load and unload the parts and

material, and clean up the machine afterwards? Is the customer ordering a large quantity? Is this taking your machine away from doing another possibly more

profitable job?Typical price rangesPrices range up to $2000.00 per hour for some parts, but $100 to $135 per hour is more typical, and it can be aslow as $80/hour. You should look at the part to machine, and think of what it would cost on a mill, or other

competing equipment. Then price the part slightly under that, and make a good profit. However, pricing andpricing strategies are highly dependant on local market conditions.
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Bidding If you are looking to have a part made, you should contact several job shops in your area . Each job shop has theirown strengths and weaknesses. Some are better at long production runs of the same part over and over, whileothers are better at short runs, cheap prototyping, or high precision.They may charge you quite a bit more money per hour for waterjet machine time, than they would for time onother machines. However, you will probably also get more parts per hour for an overall savings. If you don't likethe dollars per hour that they charge, then consider getting your own machine so that you can start your ownbusiness.Note that often you get what you pay for. The lowest bid is not necessarily the best part, on time, and with goodservice.

Pump sizeIf you are going to be machining thick metal and machining time is very important, then get a pumpcapable of putting a lot of power to the nozzle. How much power you use does not really affect howthick you can cut, but it does affect how long you will have to wait for your part to finish. If you aremachining thin metal, soft materials, or if price and operating cost are important, then you may want toget a cheaper, lower power pump. Keep in mind that the bottom line is making money, and that maynot always mean making parts as fast as possible at all costs.Pump horsepowerHow fast you can cut is determined by how much horsepower goes through the nozzle (and howconcentrated it is) not the horsepower of the motor driving the pump. For example, you may have a 50hp (37 kW) intensifier pump, but it is probably generating about 30 hp (23 kW) at the nozzle. The restgoes to heat in the hydraulic system. There is nothing wrong with this in terms of cutting ability, butthe operating cost will be higher if the power generated is not doing useful work.Before buying the pump, check the availability of power to your shop. Many shops do not have theelectrical wiring for higher horsepower electric motors. It can be very expensive to bring in new highpower wires to your shop. This may or may not be a limiting factor in your pump purchasing decision.Ask for the actual horsepower at the nozzle, or actual separation cut cutting speed data. Use theWaterjet Web Reference Calculator provided in the software download are of this web site to guideyou. Don't rely on the horsepower of the electric motor as a determiner of cutting speed.Pressure vs. MaintenanceYou may be looking at a 55,000 to 60,000 psi (3800 to 4100 bar) pump, but is it economical to run atthat pressure? You may find that it is most economical to run at 40,000j to 50,000 psi (2700 to 3800bar) for maintenance reasons. High pressure seals, check valves, swivels, on/off valves, hose and otherplumbing items all wear out faster the higher pressure you go.At pressures higher than 55,000 (3800 bar) you have to consider additional problems due to metalfatigue. Drive your machine like a Honda, and it will last like a Hondadrive it like a race car, and itwill last like a race car. Running at 60,000 PSI (4100 bar) is typically the top of the ceiling before themaintenance issues become too severe to be practical in nearly all applications because of metalfatigue.Ask your salesperson to give you component life information at the pressure that you will be operatingat. Remember that this pressure may be different than the rated pressure of the pump.

Maintenance issues How easy is the pump to maintain? How long does it take to rebuild the pump? What spare parts are involved? What do spares cost? How often do you need to change seals, and what do they
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cost?Dual pressureIf you plan to do any cutting of brittle material, then be sure to get a dual-pressure pump, or other dual-pressure technology (dual-pressure is sometimes implemented by shuttling part of the water directly tothe drain, reducing the effective pressure at the nozzle). It is also nice to be able to reduce the pressure

for marking, milling, or other artistic reasons.For most machine shops, this option is not necessary, but for those machining glass, stone, composites,or other brittle materials, this is important. Low pressure modes are also useful for part marking,etching, and scribing for various purposes.For maximum flexibility, make sure the controller will automatically change pressures for you. Forexample, you may want the controller to pierce at low pressure, then cut at high pressure, then etch atlow pressure, and so on. If the controller does not do this automatically, you will be forced to do alllow pressure work first, then turn up the pressure and finish the piece at high pressure. This can betime-consuming and tedious, especially if you are doing any kind of production runs.NoiseIf your waterjet system lets you quietly cut under water, then you will want a quiet pump to go alongwith it. Intensifier pumps are noisier than crankshaft pumps, but they can be placed in a nearby room if desired. Some also offer extra sound protection built into the cabinets. If your system will not let youcut underwater, then a loud pump may be fine because the nozzle will be much louder than your pump,and you will be wearing hearing protection anyway.Deciding on a pumpOne way to choose a pump is to determine what will cut your parts the fastest at the lowest cost, andstill provide the features you need. In other words, what is the ratio between cost and benefit?To answer this, you need to determine three things:

Cost per hour to run (the "cost") Cutting speed (the "benefit") Other features that are important ("side benefits")

Determining cost per hourHere are some pump related costs to consider:What does it cost to maintain? ($/hour)

Consider cost of "consumable" spare parts: filters seals check valves other items that need regular replacing or repair Cost of downtime of machine during maintenance: Labor Loss of use of machine

What does it cost to operate? ($/hour)

Utilities: Water for cutting Water for cooling Electricity Sewage

What does it cost to purchase? (monthly payment)Add up all of the above to determine your overall cost to run the pump.

Determining cutting speedA good way to determine the relative cutting speed that a given pump can produce is to look at theamount of power it can put to the nozzle. This is calculated as a function of the pressure the pump willrun at (continuously), and the largest size jewel (orifice) that the pump can sustain at that pressure. To

make that calculation, use the Waterjet Web Reference Calculator , which you can download from thisweb site. For even more accuracy, use the Waterjet Web Reference Calculator as follows:
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Pick a standard material and thickness, such as " (1.3 cm)aluminum that you will use as a baseline for comparing all thepumps in question.

Find out what the maximum continuous duty pressurerecommended by the manufacturers of the pumps you areevaluating, to get their advertised seal life.

Find out the maximum size jewel they recommend for thatpressure and maintenance interval.

Download the Waterjet Web Reference Calculator from thisweb site.

Enter in the value for pressure and jewel diameter. Enter in your "baseline material" (such as 0.5" (13mm)

aluminum). Leave the abrasive feed rate and mixing tube diameter alone.

These are factors that affect cutting speed, but areindependent of the pump.

Write down the linear cutting speed for that pump. Repeat the above for each pump in question.

When finished, you should have information that will determine which pump cuts the fastest.

Other features that are importantOnce you have the cost and cutting speed information, all you need to do is make sure the pumpsupports any other features you might need, such as:

Support for dual pressure Comfortable sound levels Meets your space requirements Meets your electrical requirements (what your shop can

supply) Consistent, even pressure delivery Quick starting

Do you leave the pump on all day, or start it up each time youmake a part? Some pumps take a long time to warm up,making it impractical to turn it off between runs, causing morehours to accumulate on the pump without actually makingparts.

Capability of running multiple nozzles Capability of running multiple machines Compatibility with the rest of your machine Skill level required to maintain

Crankshaft vs intensifier pumpThis topic of crankshaft vs. intensifier pumps is a somewhat controversial subject with a lot of differentopinions.NoteCrankshaft pumps are also referred to as "direct drive" pumps.The basic difference between the two pumps is that crankshaft pumps use a crankshaft to move theplungers that pressurize the water, and intensifiers use hydraulics. Because there is no hydraulicsystem, crankshaft style pumps tend to be much more efficient, and thus put a higher percentage of horsepower to the nozzle. This lets a lower power crankshaft pump compete in cutting power (speed)

with a higher power intensifier pump, and dominate in terms of operating cost. Note that cutting speedis also greatly a function of the control software, and how well it predicts, compensates, and optimizesfor the jet behaviours around corners.
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For example, generally speaking a 30 horsepower (23 Kw) crankshaft pump is about the same cuttingspeed as a 50 horsepower (37 Kw) intensifier, but the the intensifier is creating about 20 horsepower(15 Kw) of heat that is doing nothing but wasting gobs of electricity.Intensifiers, however, have advantages in terms of high pressure seal life, and their ability to runmultiple machines from a single pump. The extended seal life is an effect of running the plungers at aslow speed, while crankshaft pumps typically operate at faster speeds, and therefore wear faster.Intensifiers are good for running multiple machines from a single pump because they can maintain arelatively constant pressure output at one machine when a nozzle on another machine being turned onand off.

The main advantage of the crank-shaft style pump isthat is provides more cutting power per dollar, and istherefore cheaper to purchase and run.

The main advantage of an Intensifier style pump is thatthe high pressure seals last a little bit longer.

With both systems, component life is an inverse function of operating pressurethe lower thepressure, the longer the life.There is also a slight difference in the way both pumps are used. With direct drive pumps, the pump is

typically turned on when a part path is started, then turned off when the path is complete. An intensifierpump is often turned on at the beginning of a shift, and then left on, regardless of whether or not themachine is cutting parts. When no flow is being drawn, the plunger is motionless. During this time, nosignificant wear is created. However, it does inflate the "pump hours" that one can expect betweenmaintenance intervals, making the intensifier seem like it is significantly longer lasting than a directdrive pump, when in fact, they are closer than it seems in this regard.Which should you buy? This is a tough question, and the answer depends a lot on your preferences,and a big factor is the answer to the question: What is more important, operating cost, or frequency of maintenance? If the answer is that you want the least frequent maintenance, then an intensifier mightbe right for you. If the answer is that you want the lowest operating cost, then a crankshaft pump isprobably a better choice.

Pump horsepowerPump horsepower, in waterjet marketing literature, almost always refers to the horsepower of theelectric motor that drives the pump, and not the actual horsepower that makes it to the nozzle. Forexample, due to inefficiencies, a 50 hp (37 kW) intensifier pump typically puts out 30 hp (22 kW) atthe nozzle, while a 20 hp (15 kW) crankshaft type pump typically puts 19 hp (14 kW) to the pump. Forthis reason, talking about pump horsepower is misleading. Instead, you should consider nozzle, orcutting horsepower.Nozzle HorsepowerNozzle horsepower is how much cutting power is at the nozzle. The more you have the faster you cut.A great way to compute nozzle horsepower, is to use the Waterjet Web Reference Calculator .


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Nozzlehorsepoweris computedfrom:

Pressure Jewel

DiameterSo, if you have a0.014" (0.36 mm)

jewel, and you have apressure of 40,000 PSI(2800 bar) trying topush water through it,you are cutting with19 (14 kW)horsepower.Or, if you have a0.015" (0.38 mm)

jewel, and 50,000 PSI(3500 bar), then youare cutting with 30.5(22.7 kW)horsepower.

Nozzle sizesIn basic terms, there are three critical dimensions in a nozzle: jewel diameter, mixing tube diameter,and mixing tube length.

Jewel (orifice) DiameterAs you can see in the picture below, the jewel is where the high pressure exits the plumbing and entersthe air in the nozzle. This jewel is sized so that it maintains pressure behind it, while allowing water toflow at extremely high velocity into the Venturi mixing chamber of the nozzle. The larger the diameterof the hole in the jewel, the more water it flows, and the bigger the pump you need to maintain thesame pressure.
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Mixing tube diameterThe inside diameter of the mixing tube determines how fast the mixing tube will wear out, how preciseof a cut you can make, and how quickly you can cut.Properties of a small diameter mixing tube:

Slightly improved cutting rate Slightly decreased nozzle life Improved precision Smaller kerf width

Properties of a large diameter mixing tube: Slightly reduced cutting rate Slightly increased nozzle life Slight decrease in precision Larger kerf width

Mixing tube diameter directly relates to kerf width diameter.

Mixing tube LengthMixing tube length effects the ability of the nozzle to focus. Typically, longer mixing tubes focusbetter than shorter ones, because of their longer length. This will give you slightly more precision dueto reduced taper.Importance of pressureGenerally speaking, the higher the pressure of the water, the faster the speed of cutting. However,pressure is only one of many factors to consider. Among the other factors are:

Operating cost Your operating costs are often much lower for lower powermachines. This is simply because lower pressures and lowerwater flow rates translate directly into longer life of everycomponent that touches the water. It also translates into

fewer consumables, because machines that run at lowerpressure wear mixing tubes and jewels slower, and typically
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consume less garnet.

MaintenanceHigher pressure means higher wear on components, and thatmeans more frequent maintenance, such as replacing sealsand rebuilding pumps. The costs of maintenance extendbeyond the price for replacement parts, as you also havedowntime when you aren't cutting.

Fatigue limits of all high pressure componentsAt pressures of 60,000 PSI (4,100 bar) and higher, metalfatigue becomes a serious issue with many components.Although pumps that can reach 100,000 PSI have been aroundfor many years, nobody runs them at such pressures becauseof the extreme maintenance issues involved. For this reason,most manufacturers purposely limit their pumps to below60,000 PSI (4,100 bar).

Cutting speedHow quickly you cut material comes down to how much cutting power is exiting the nozzle. This isdetermined not only by pressure, but also by the size of the hole you are sending the water through(jewel size).To illustrate this concept, have a look at a few nozzle combinations, at various pressures:

30,000 PSI 40,000 PSI 50,000 PSI 100,000 PSI0.010" Jewel 5.84 HP 8.99 HP 12.56 HP 35.52 HP0.012" Jewel 8.40 HP 12.94 HP 18.08 HP 51.15 HP

0.014" Jewel 11.44 HP 17.61 HP 24.61 HP 69.62 HP

0.016" Jewel 14.94 HP 23.0 HP 32.15 HP 90.93 HP

2,000 bar 2,800 bar 3,400 bar 6,900 bar 0.25 mm Jewel 4.36 kW 6.70 kW 9.37 kW 26.5 kW0.30 mm Jewel 6.26 kW 9.65 kW 13.5 kW 38.1 kW

0.36 mm Jewel 8.5 kW 13.1 kW 18.4 kW 51.9 kW

0.41 mm Jewel 11.1 kW 17.1 kW 24.0 kW 67.8 kW As the above chart shows, even at 100,000 PSI (6,900 bar), you are still cutting at 35.52 horsepower(26.5 kW), if you run a 0.010" (0.25 mm) jewel. Compare that to a system pumping 50,000 PSI (3,400bar) through a 0.016" (0.41 mm) jewel, which even at half the pressure, is still cutting at nearly thesame rate.Of course, few people really run at 100,000 PSI, because that puts an extreme amount of wear on allthe high pressure components! Nevertheless, it is an important illustration that pressure by itself is notvery meaningful.To make the example even more extreme, consider the case of 1,000,000 PSI (69,000 bar) behind a

jewel that does not have a hole in the middle. In this case, you have a lot of pressure, but no watercoming out at all, which means it doesn't cut at all.As a general rule of thumb, it is horsepower at the nozzle (cutting horsepower), not the power of themotor turning the pump (pump horsepower), or pressure that determines how quickly a given systemcan cut.This is a generalization, though. The best way to answer questions about how the various factors effectcutting speed, is to use the Waterjet Web Reference Calculator . This calculator answers many

questions regarding cutting speed in a variety of materials, pressures, nozzle, and pump configurations.


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Water quality

Written by Staff

The main reason you care about water quality when you use a waterjet is that it has a large effect onhow long various components in your machine last. Components in high-pressure water pumps andnozzles will wear out much faster if you have poor water quality, especially if there are a lot of mineralsin it.

Paradoxically, you don't want your water to be too clean, as water is an excellent solvent and if youremove all the trace materials from it, it will begin to dissolve your pump and nozzle parts.Have your water quality tested while you are evaluating equipment to purchase. Some manufacturerswill do this for you, and give you suggestions on any action you may need to take if your water requiresit. In the worst case scenario, you will have to purchase some sort of water cleaning system such as a

reverse osmosis filter, or water softener, or water chiller. Follow the manufacturer's recommendation. If they say you need extra equipment, then believe them. They don't want unnecessary technical supportcalls, and neither do you.Also remember that just because you have your water quality tested once, does not mean your waterquality will stay consistently good. When there is unusual weather, or for other reasons, your waterdepartment may switch reservoirs. If you suddenly find that you are wearing out nozzles faster thannormal, suspect water quality to be the culprit.Make sure your water quality is tested for "total dissolved solids" (or TDS), and not just bacteria. Youwon't be drinking the wateryou will be using it to make parts. It is the dissolved minerals in the waterthat will cause the most trouble. Other problem areas are solids in the water that may clog filters.

Water temperatureWater temperature has a big effect on seal life in high-pressure water pumps. Keep the water cold

(below 70 F / 20 C). Otherwise, the seals may tend to soften, extrude much faster than normal, andresult in dramatically more frequent maintenance of the pump. If you are recycling your water this isespecially important, since heat will accumulate in the water as it cycles through the system. In somecases, a water chiller may be recommended. Talk to your manufacturer for recommendations.

An Ebco brand closed-loop filtration systemA closed-loop filtration system will recycle your water and filter it, both reducing your water

consumption and keeping your water clean. If you are cutting a lot of toxic substances such as lead,something like this may be necessary. If you do use a closed-loop filtration system, you may need to add
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a chiller to keep your water temperature low to avoid excessive wear on your water pump.Waterjets use between and two gallons (2 to 8 liters) of water per minute when cutting. Some of thewater is used for cutting, and some for cooling. The water is typically treated as "gray water" which canbe recycled, or sent directly to the sewer. Again, if you are cutting something toxic, you may need tofilter water, and recycle or dispose of it in special circumstances.

SUPER-WATERSUPER-WATER is a chemical you can add to the water of an waterjet to focus the cutting stream,increase cutting speed, and reduce wear of high pressure components. Traditionally it has been used forhigh-pressure cleaning and water-only cutting applications. Although it is not widely used in thewaterjet cutting industry, it may offer some benefits. More information on SUPER-WATER.

Hiddencosts

Written by Staff

There are ways that you can end up paying more for a waterjet than you planned. This topic covers afew of them.Goofy "guarantees"A manufacturer will "guarantee" that the seals on their pump will last for X hours, or they will pay forthem for the first year . Sounds great doesn't it? Actually, seals are relatively cheap. A manufacturer willgladly replace a few dollars worth of pump seals so that they can sell you an expensive machine. That'snot to say the guarantee is worthless, but consider that it might not be worth as much as it seems.Price of extra software seats and upgradesWaterjets are controlled by software, and the part drawings are typically done in software specific toeach waterjet machine. That means you need special software to draw the part to be made on themachine. Each computer that the software is installed on requires another "seat," or copy of thesoftware. If you want to install the software on two computers (one at the machine, and one in youroffice, for example), you will need to purchase two seats.[And it is relatively easy to copy-protect the software to make sure that each seat will only run on onemachine.]So be sure to check for how much it costs for each additional copy of the software. Some companieswill offer additional seats for free, while others will charge up to $1,000 for each copy.You will almost certainly want at least two seats of software. One for the machine itself, and another foroff-line programming, job scheduling, and cost estimation. You may also want a third copy to put on alaptop computer, for when you are at your customers.Software upgrades are another area where costs can surprise you. Waterjet related software is changingrapidly with many new features and optimizations that allow older machines to be more and moreproductive. In many cases, it is very useful to upgrade twice per year. Check to see what the averagecost of upgrades is--and remember that you may need to purchase an upgrade for each of your software

seats.One other point on software upgrades: even if you don't use the new features, or care about bug fixes,AutoCAD releases new versions of their software frequently. Each time they typically make new"flavors" of DXF and DWG files. If nothing else, you will need to update your waterjet CAD/CAMsystem to be able to support loading of these files.Find out what parts are normal wear partsYour warranty may seem generous and offer full replacement, except for "normal wear parts." Check and find out what those parts are. Some wear parts might include high-pressure components, bellows,and so forth.Check prices of spare partsSpare parts include wear parts that need to be regularly replaced, and as a result, the prices of spare partsdetermine your operating costs . Ask if any spare parts are included with the machine. Also check on

prices for critical wear parts like pump seals, jewels, nozzle assemblies, and mixing tubes.Training costs
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Although you can learn to use your waterjet machine through trial-and-error or by reading thedocumentation, it's typically much more efficient to go to training classes and be shown the correct way.Some manufacturers charge extra for training, while others include training in the price of the machine.Remember, too, that as operators leave your company, you may need to invest in training for newoperators. Make sure this is available and find out the costs.Installation costsIn most cases, the manufacturer will send out a technician to install the machine. Depending on the sizeof the machine, it may only take a few hours, or it may take several days for a large machine. Find outwhat the manufacturer will charge.Also find out what needs to be available for the installation to occur (water, power, air). You don't wantto pay to have a technician sit and wait for the proper power to be installed before your waterjet isinstalled.Warranty work Check the details of the warranty provided by the manufacturer. If something breaks and is underwarrantee, who pays for the parts and labor? You might find that the parts are free, but you pay for thelabor.

Buying a used waterjetmachine

Written by Staff

Buying a used waterjet can be a good way to save some money.However, as in buying a used car, there are things to watch out for.

Old TechnologyWhen you buy a used waterjet, you will be buying older technology. This is a rapidly evolving industry,and the new machines are significantly better than the old ones. The cost of a new machine may be

worth the extra money when operating cost, efficiency, precision, and other factors are accounted for. Inparticular, the controller technology will have changed a lot. Contact the manufacturer of the equipmentand see what kind of upgrade options are available prior to buying used equipment. Even if you don'tbuy the upgrades at the same time you buy the used waterjet, you will be glad to know that you canupgrade later.SupportWhen you buy a new waterjet machine from the factory, you will often get free support, and a lot of training. When you buy a used waterjet, the factory doesn't make a dime. The only incentive they haveto support you is the sale of spare parts. Therefore, they will probably charge you for support, training,and so forth. It is important that you are properly trained on the machine when you get it, so you shouldadd $5000 or more to the price of your used machine for training and support.Getting proper training and support at the beginning will prove much cheaper than learning by trial-and-

error, which will result in many mistakes.MechanicsA used waterjet machine has been used, and some parts may be worn. Particular areas to look at include:

Watch out for garnet on the ball-screws. A lot of oldermachines do not have fully enclosed bellows, and it is likelythat grit leaked in and settled on the ball-screws.

Check the bellows themselves for small tears. Even a smalltear or hole in the bellows can let abrasive enter, and this willadversely affect the performance of the waterjet.

Get a ball-bar test to test the accuracy of the machine, anddiscover any potential problems with the precision components


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before you buy the machine.Where to buyCheck out the Waterjet Web Reference Discussion Group .Post a message on it indicating that you are interested in purchasing a used waterjet, and you willprobably get several responses. You can also contact the manufacturers of new machinery and see if

they have demo units or trade ins. If you buy from the factory, you can get high-quality factoryrefurbished machines with training and warranty. Also, check out the "Used Equipment" link at thefollowing web site: http://groups.yahoo.com/group/waterjets/links
http://groups.yahoo.com/group/waterjets/http://groups.yahoo.com/group/waterjets/linkshttp://groups.yahoo.com/group/waterjets/linkshttp://groups.yahoo.com/group/waterjets/http://groups.yahoo.com/group/waterjets/links

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