Water jet Cutting

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Waterjet Cutting استاد : دکتر خوش کیش تهيه کننده: مرتضی عسگری 

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۱ Introduction to Water jet Q Waterjet cutting works by forcing a large volume of water through a small orifice in the nozzle. 4 The constant volume of water traveling through a reduced cross sectional area causes the particles to rapidly accelerate. This accelerated stream leaving the nozzle impacts the material to be cut. Q The extreme pressure of the accelerated water particles contacts a small area of the work piece and develop small cracks. 4 The crack caused by the waterjet impact propagate until the material is cut through. 

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9 to Water jet Fastest growing machining process One of the most versatile machining processes Compliments other technologies such as milling, laser, EDM, plasma and routers True cold cutting process - no HAZ, mechanical stresses or operator and environmental hazards Not limited to machining - food industry applications Water jet cutting has proven to save time and money on countless applications 

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Thickness and Kerf ~ Guting Thick Natori QO WJ can cut materials ranging from 10" stainless steel to 0.010" acrylics. O Stacking of very thin materials to increase productivity is possible. OKerf ranges from 0.020" to 0.050". 

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Taper and Edge Finish O Taper and edge finish are directly related to cut speed. O The greater the speed, the more taper and the coarser the edge finish. Q For a finer edge finish, use a finer abrasive. Taper 

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History QDr. Franz in 1950’s first studied UHP water cutting for forestry and wood cutting (pure wy) 41979 Dr. Mohamed Hashish added abrasive particles to increase cutting force and ability to cut hard materials including steel, glass and concrete (abrasive WJ) OFirst commercial use was in automotive industry to cut glass in 1983 QSoon after, adopted by aerospace industry for cutting high-strength materials like Inconel, stainless steel and titanium as well as composites like carbon fiber 

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cutting 1. Pure Waterjet cutting: Waterjet cutting uses only a pressurized stream of water to cut through material. 2. Abrasive Waterjets cutting: An abrasive waterjet entrainment system mixes the abrasive with the waterjet in a mixing chamber just after the nozzle. In most systems being built today, a venturi effect is utilized to pull the abrasive into the waterjet. The abrasive pa rticles are accelerated into the stream and then with the stream out the orifice. 

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Pure W/ Cutting “pure cuts soft materials - corrugated cardboard, disposable diapers, tissue papers, automotive interiors Very thin stream (0.004-0.010 dia) Extremely detailed geometry Very little material loss due to cutting “Can cut thick, soft, light materials like fiberglass insulation up to 24” thick or thin, fragile materials Very low cutting forces and simple fixturing Water jet erodes work at kerf line into small particles 

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Pure WJ Cutting cont. ‘Water inlet pressure between 20k-60k psi Forced through hole in jewel 0.007- 0.020” dia Sapphires, Rubies with 50-100 hour life ‏هم‎ J Diamond with 800- 2,000 hour life, but | they are pricey Inlet Water 

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Abrasive ۱۷۷ Cutting QUsed to cut much harder materials Water is not used directly to cut material as in Pure, instead water is used to accelerate abrasive particles which do the cutting 480-mesh garnet (sandpaper) is typically used though 50 and 120-mesh is also used OStandoff distance between mixing tube and workpart 15 typically 0.010-0.200 - important to keep to a minimum to keep a good surface finish 

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Abrasive WJ Cutting cont. Evolution of mixing tube technology Standard Tungsten Carbide lasts 4-6 hours 00 (not used much anymore) ۲ Premium Composite gy Abrasive Carbide lasts 100-150 5 hours Consumables include gyarg— Mixing Tube Inlet Water water, abrasive, orifice and mixing tube 

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6۳۵۵3۲۵۳ 0۴06 20۳23 7۳۷/۵۲۳7 stream Water Inlet Mixing Mixing Tube Approx. 2200 mph (3657 kph) 

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۷ 1 - Water pressurized at 50,000 psi or greater enters the cutting head at relatively slow speed. ’ 2 - The water is forced through an orifice that has a small diameter orifice, anywhere from 0.004" to 0.045" depending upon the application. These orifices are made of extremely hard material, such as diamond, sapphire or ruby. This step converts the water stream from a high pressure stream to a high velocity stream. At this point the water is moving in excess of 2200 miles per hour (3657 kilometers per hour). 

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’3 - The high velocity of the jet creates a Venturi effect, or vacuum, in the mixing chamber located immediately beneath the orifice. Abrasive, typically garnet is metered from a mini-hopper through a plastic tube down to the cutting head and is sucked into the water jet stream in the mixing chamber. ’ 4 - The abrasive is fully mixed in the water jet stream and is accelerated to approximately the speed of the water jet stream. This step does steal some energy from the water jet stream, slowing it down slightly. 

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’ 5 - The abrasive water jet stream exits the mixing tube with extreme speed and power. The abrasive erodes the material to be cut. The process is referred to as “abrasive water jet cutting" because it is the abrasive that is actually doing the cutting. The water's role is simply to give speed and power to the abrasive. In pure water jet cutting, used for soft materials like foam and food, the force of the water jet stream alone is enough to cut the material and abrasive is not required. 

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Types of pumps U Intensifier: Intensifier pumps use the concept of pressure intensification to generate the desired water pressure. If you apply pressure to one side of a cylinder and __ the other side of the cylinder is half area, the pressure on the other side will be doubled. Generally with intensifier pumps there is a 20 times difference between the large surface area (where the oil pressure is applied) and the small surface area (where the water pressure is generated). 

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Surface ۸۱8۵ 2 in? 

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e-pressurization-proce: intensifier pumps Intensifier Concept 1. Oil is forced into the right half of the hydraulic cylinder. 2. The piston-plunger assembly moves to the left. Oil is displaced out of the left half of the hydraulic cylinder and the water in the left high pressure cylinder is pressurized 

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3. The plunger moves to the left 4. Once pressure has begun to build, the high pressure water is forced out of the intensifier through the center of the check valve. 5. While the piston-plunger assembly is moving to the left, it is also allowing fresh water to flow into the right high pressure cylinder. 6. When the plunger-piston assembly has reached the end of its stroke to the left, the right high pressure cylinder is now full of water. 7. The directional control valve receives a signal via a proximity sensor near the piston to reverse the flow of hydraulic oil. 

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. Oil is displaced out of the right half of the hydraulic cylinder while the water in the right high pressure cylinder is pressurized by the right plunger. Intensifier Concept 8, Water pressurized 

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Direct Dri A direct drive pump works like a car’s engine. A motor turns a_ crankshaft attached to 3 or more offset pistons. As the crankshaft turns, the _ pistons reciprocate in their respective cylinders, nrantina nraccura in tha untar DirectDrive Pump Concept 2 or mote plstons ۱ Water Water motortuns 7 03 مه ‎cutting head‏ 

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Parts of the intensifier— pump 1. Electric motor and hydraulic pump The electric motor an hydraulic pump creat: ۲ the oil pressure ced for the oil side of thengy intensifier. 

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2. Directional control valves The directional control valve controls the direction of flow of the hydraulic oil to and from the intensifier. 

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3. Intensifier The intensifier proper consists of the hydraulic cylinder (4), high pressure cylinders (7), and check valves (8) and end caps (9). 

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4. Hydraulic cylinder The hydraulic cylinder houses the piston and is the area where the hydraulic oil does its work. At each end of the hydraulic cylinder is an end plate that is used to connect the hydraulic high pressure cylinder. 

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5. Piston The piston is the larger diameter cylindrical part located within the hydraulic cylinder. The piston effectively splits the hydraulic cylinder into a left side and a right side. 

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6. Plunger The plungers are the two smaller diameter shafts that are connected to each side of the piston. The attachment point is inside of the hydraulic cylinder. The plungers are made out of either stainless steel, or, more recently, ceramic. Ceramic is used because of its ability to handle heat and high pressure with little thermal expansion. 

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7. High pressure cylinder The two high pressure cylinders are where the water is pressurized. The high pressure cylinders are machined out of very thick stainless steel and treated in order to withstand the extreme pressures they are put under on a continual, cyclical basis. 

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سكا سس« 8. Check valve There is one check valve at the end of each high pressure cylinder at the end opposite from the hydraulic cylinder. The check valve allows fresh water to enter the high pressure cylinder — and high press" 

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9. Caps The end cap is either a cylindrical or square item. The end cap has a hole in the center for the check valve and outlet body. It will also have a connection point for the incoming fresh water. 

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10. High pressure tubing High pressure 304 or 316 stainless steel tubing is attached to the outlet of each check valve. The high pressure tubing carries. the pressurized water to the pressure attenuator. Additional high pressure tubing will channel the high pressure water to the cutting head. 

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11. Pressure attenuator The pressure attenuator smoothes out variations in pressure after the high pressure water has exited the intensifier. With each reversal of cycle of the intensifier, there is a slight delay in the increase of water pressure in the opposite high pressure cylinder 

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12. Inlet water filters The inlet water must be able to maintain a specified flow rate and pressure to ensure that the intensifier receives enough water. Incoming water must also meet certain requirements with nrecnort to Total Dissolved Solids (TDS pH, organic matter, temperature, etc. For these c or more filters just prior to | entering the intensifier 

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13. Controls and PLC The controls and PLC (not pictured) control the valves in the hydraulic circuit to determine the pressure and flow of the hydraulic oil to and from the intensifier. 

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Other parts Q On-Off Valve The pneumatic On-Off valve controls the flow of water to the cutting head. This valve must be in good wo ** x» protect against accident. high pressure water ۳ discharge at the cutting | Pneumatic mort vave 

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Q Nozzles(mixing tube) This is a tube, made from extremely hard material, that focuses the abrasive and water into a coherent beam for cutting. This is also where the abrasive mixes with the water. 

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4 Pressurized Bulk hopper Abrasive is transported via tubing and pressure from a large bulk hopper near the waterjet cutting system toa 8 mini-hopper near the cutting head. 4 Mini-hopper A mini-hopper is typically mounted near and above the cutting head. Many mini-hopp| control the amount of abrasive that can go down to the cutting head with the use of a slide with different size holes in it. 

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Accumulator Sapphire nozzle 

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ار و ماع Motion system (“&@ateh tank 

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This part is shaped with waterjet using one tool. Slots, radii, holes, and profile in one 2 minute setup. Advantages + Cheaper than other processes. + Cut virtually any material. (pre hardened steel, mild steel, copper, brass, aluminum; brittle materials like glass, ceramic, quartz, stone) * Cut thin stuff, or thick stuff. + Make all sorts of shapes with only one tool. + No heat generated. * Leaves a satin smooth finish, thus reducing secondary operations. + Clean cutting process without gasses or oils. * Modern systems are now very easy to learn. * Are very safe. + Machine stacks of thin parts all at once. 

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a ~ Advantages (continued + Unlike machining or grinding, waterjet cutting does not produce any dust or particles that are harmful if inhaled. + The kerf width in waterjet cutting is very small, and very little material is wasted. + Waterjet cutting 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. This is much faster and cheaper than drawing detailed prints of a part and then having a machinist cut the part out. + Waterjets are much lighter than equivalent laser cutters, and when mounted on an automated robot. Get nice edge quality from different materials. 

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۶20 vantages + One of the main disadvantages of waterjet cutting is that 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, and the time to cut a part can be very long. Because of this, waterjet cutting can be very costly and outweigh the advantages. Waterjet leg + 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, or to have a eee ‏مر‎ 

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Disadvantages (continued) + 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. Decreasing the speed of the head may reduce this, although it can still be a Stream lag caused inside corner damage to this 1-in.-thick stainless steel part. The exit point of the stream lags behind the entrance point, causing irregularities on the inside corners of the part. The thicker the material is or the faster an operator tries to cut it, the greater the stream lag and the more pronounced the damage. 

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After laser cutting After waterjet cutting “Waterjets vs. Lasers + Abrasive waterjets 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 waterjet. + Waterjets do not heat your part. Thus there is no thermal distortion or hardening of the material. + Precision abrasive jet machines can obtain about the same or higher tolerances than lasers (especially as thickness increases). + Waterjets are safer. + Maintenance on the abrasive jet nozzle is simpler than that of a laser, though probably just as frequent. 

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= — " Waterjets vs. EDM + Waterjets are much faster than EDM. + Waterjets machine a wider variety of materials (virtually any material). + Uniformity of material is not very important to a waterjet. + Waterjets make their own pierce holes. + Waterjets are capable of ignoring material aberrations that would cause wire EDM to lose flushing. + Waterjets do not heat the surface of what they machine. + Waterjets require less setup. + Many EDM shops are also buying waterjets. Waterjets can be considered to be like super- Waterjets are much faster than 

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Waterjets vs. Pla + Waterjets provide a nicer edge finish. + Waterjets don't heat the part. + Waterjets can cut virtually any material. ۰ Waterjets are more precise. + Plasma is typically faster. + Waterjets would make a great compliment to a plasma shop where | more precision or higher quality is required, or for parts where heating is not good, or where there is a need to cut a wider range of materials. After waterjet cutting 

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Flame Cutting: Waterjets would make a great compliment to a flame cutting where more precision or higher quality is required, or for parts where heating is not good, or where there is a need to cut a wider range of materials. Milling: Waterjets are used a lot for complimenting or replacing milling operations. They are used for roughing out parts prior to milling, for replacing milling entirely, or for providing secondary machining on parts that just came off the mill. For this reason, many traditional machine shops are adding waterjet capability to provide a competitive edge. Punch Press: Some stamping houses are using waterjets for fast turn- around, or for low quantity or prototyping work. Waterjets make a great complimentary tool for punch presses and the like because they offer a wider range of capability for ا 

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Waterjet in Any Industry The versatility of the waterjet allows it to be used in nearly every industry. There are many different materials that the waterjet can cut such as: Alloys Laminates Composites Plastics/Acrylics Rubber Gaskets Fiberglass 

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Glass Wood Food Preparation Printed Circuit Boa. o2 Wire Stripping Stones 

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