Introduction to Water jet-<br />It is a tool capable of slicing metal or other materials using a jet of water at high velocity and pressure<br />The process is same as water erosion found in nature but is greatly accelerated and concentrated.<br />True cold cutting process – no HAZ,nomechanical stresses and environmental hazards.<br />Not limited to machining – It has food industrial applications.<br />They are fast, flexible, reasonably precise.<br />
Why Water Jet?<br />It can cut almost everything, with greater efficiency and productivity.<br />It is one of the fastest growing major machine tool processes in the world due to its versatility and ease of operation.<br />Water jets cut accurately, reduced scrap — saving money through greater material utilization.<br />As it is software oriented, we get correct shape, dimensions and size.<br />
History-<br />Dr. Franz in 1950’s first studied UHP water cutting for forestry and wood cutting.<br />1979 Dr. Mohamed Hashish added abrasive particles to increase cutting force and ability to cut hard materials including steel, glass and concrete.<br />First commercial use was in automotive industry to cut glass in 1983.<br />Soon after, adopted by aerospace industry for cutting high-strength materials like stainless steel and titanium as well as composites like carbon fiber.<br />
How water jet works?<br />High pressure (60,000 psi), high velocity up to twice the speed of the sound jet of water, which when bombarded on the work piece erodes the material.<br />A high velocity water jet when directed at a target in such a way that, its velocity in virtually reduced to zero on striking the surface. Because of this water jet will make a hole in the material if the pressure is high enough.<br />Many variables such as nozzle orifice diameter, water pressure, cutting feed rate and the stand distance affect the performance.<br />
Types of Water Jet-<br />The two types of water jets are the pure water jet and the abrasive water jet.<br />A pure water jet is used to cut soft materials, and within just 2 minutes the very same water jet can be transformed into an abrasive water jet to cut hard materials by adding abrasives to it.<br />Pure water jet uses pure pressurized water whereas abrasives water jet uses abrasives like Aluminum oxide, silicon carbide and garnet.<br />
Pure Water Jet-<br />Pure Water jet is the original water cutting method.<br />The largest uses for pure water jet cutting are disposable diapers, tissue paper, and automotive interiors .<br /> Provides Very thin stream (0.004 to 0.010 inch in diameter is the common range) .<br />Very little material loss due to precise cutting. <br />Non-heat cutting ,Usually cuts very quickly .<br />Able to cut soft, light materials(e.g., fibreglass insulation up to 24" thick) .<br />Extremely low cutting forces .<br />
Abrasive Water jets- <br />In the abrasive waterjet, the waterjet stream accelerates abrasive particles and those particles, not the water, erode the material. <br />The abrasive Waterjet is hundreds of times more powerful than a pure Waterjet.<br />Extremely versatile process,No Heat Affected Zones,No mechanical stresses <br />Easy to program, Little or no burr<br />Thin stream (0.020to 0.050 inch in diameter) <br />10 inch thick cutting,Little material loss due to cutting <br />Quickly switch from pure waterjet to abrasive waterjet<br />
Unlike other machining tools, water jets never get dull.</li></ul>This part is shaped with waterjet using one tool. Slots, radii, holes, and profile in one 2 minute setup.<br />
Advantages (continued)-<br /><ul><li> Unlike machining or grinding, waterjet cutting does not produce any dust or particles that are harmful if inhaled.
Waterjetcutting can be easily used to produce prototype parts very efficiently. An operator can program the dimensions of the part into the control station, and the waterjet will cut the part out exactly as programmed.
water jets are much lighter than equivalent laser cutters, and when mounted on an automated robot. This reduces the problems of accelerating and decelerating the robot head, as well as taking less energy.</li></ul>Get nice edge quality from different materials.<br />
Disadvantages-<br />A limited number of materials can be cut economically. While it is possible to cut tool steels, and other hard materials, the cutting rate has to be greatly reduced.<br />Another disadvantage is that very thick parts can not be cut with waterjet cutting and still hold dimensional accuracy. If the part is too thick, the jet may dissipate some, and cause it to cut on a diagonal.<br />Taper is also a problem with waterjet cutting in very thick materials. Taper is when the jet exits the part at a different angle than it enters the part, and can cause dimensional inaccuracy.<br />Water jet lag <br />
Water jets vs. Lasers-<br /><ul><li>Abrasive water jets can machine many materials that lasers cannot. (Reflective materials in particular, such as Aluminum and Copper.
Uniformity of material is not very important to a water jet.
Water jets do not heat your part. Thus there is no thermal distortion or hardening of the material.
Maintenance on the abrasive jet nozzle is simpler than that of a laser, though probably just as frequent.</li></ul>After laser cutting<br />After waterjet cutting<br />
Water jets vs. EDM-<br /><ul><li> Water jets are much faster than EDM.
Water jets machine has a wider variety of materials (virtually any material).
Uniformity of material is not very important to a water jet.
Water jets do not heat the surface of what they machine.
water jets require less setup and can cut even non conducting materials.
water jets can be considered to be like super-fast EDM machines with less precision.</li></ul>Water jets are much faster than EDM.<br />
Conclusion-<br />Relatively new technology has caught on quickly and is replacing century-old methods for machining.<br />Used not only in typical machining applications, but food and soft-goods industries<br />As material and pump technology advances faster cutting rates, longer component life and tighter tolerances will be achievable<br />Gave us the way for new machining processes that embrace simplicity and have a small environmental impact<br />