Water jet Cutting

Water jet Cutting

اسلاید 1: Waterjet Cuttingپروژه درس روش های تولیداستاد : دکتر خوش کیشتهیه کننده: مرتضی عسگری

اسلاید 2: Introduction to Water jet Waterjet cutting works by forcing a large volume of water through a small orifice in the nozzle. 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. The extreme pressure of the accelerated water particles contacts a small area of the work piece and develop small cracks. The crack caused by the waterjet impact propagate until the material is cut through.

اسلاید 3: Introduction to Water jetFastest growing machining processOne of the most versatile machining processesCompliments other technologies such as milling, laser, EDM, plasma and routersTrue cold cutting process – no HAZ, mechanical stresses or operator and environmental hazardsNot limited to machining – food industry applicationsWater jet cutting has proven to save time and money on countless applications

اسلاید 4: Thickness and Kerf WJ can cut materials ranging from 10 stainless steel to 0.010 acrylics. Stacking of very thin materials to increase productivity is possible. Kerf ranges from 0.020 to 0.050.

اسلاید 5: Taper and Edge Finish Taper and edge finish are directly related to cut speed. The greater the speed, the more taper and the coarser the edge finish. For a finer edge finish, use a finer abrasive.

اسلاید 6: HistoryDr. Franz in 1950’s first studied UHP water cutting for forestry and wood cutting (pure WJ)1979 Dr. Mohamed Hashish added abrasive particles to increase cutting force and ability to cut hard materials including steel, glass and concrete (abrasive WJ)First commercial use was in automotive industry to cut glass in 1983Soon after, adopted by aerospace industry for cutting high-strength materials like Inconel, stainless steel and titanium as well as composites like carbon fiber

اسلاید 7: Types of Water jet cutting1. 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.

اسلاید 8: Pure WJ CuttingPure cuts soft materials – corrugated cardboard, disposable diapers, tissue papers, automotive interiorsVery thin stream (0.004-0.010 dia)Extremely detailed geometryVery little material loss due to cuttingCan cut thick, soft, light materials like fiberglass insulation up to 24” thick or thin, fragile materialsVery low cutting forces and simple fixturingWater jet erodes work at kerf line into small particles

اسلاید 9: Pure WJ Cutting cont.Water inlet pressure between 20k-60k psiForced through hole in jewel 0.007-0.020” diaSapphires, Rubies with 50-100 hour lifeDiamond with 800-2,000 hour life, but they are pricey

اسلاید 10: Abrasive WJ CuttingUsed to cut much harder materialsWater is not used directly to cut material as in Pure, instead water is used to accelerate abrasive particles which do the cutting80-mesh garnet (sandpaper) is typically used though 50 and 120-mesh is also usedStandoff distance between mixing tube and workpart is typically 0.010-0.200 – important to keep to a minimum to keep a good surface finish

اسلاید 11: Abrasive WJ Cutting cont.Evolution of mixing tube technologyStandard Tungsten Carbide lasts 4-6 hours (not used much anymore)Premium Composite Carbide lasts 100-150 hoursConsumables include water, abrasive, orifice and mixing tube

اسلاید 12: Creation of the abrasive water jet stream

اسلاید 13: 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).

اسلاید 14: 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.

اسلاید 15: 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 waters 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.

اسلاید 16: Types of pumps 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).

اسلاید 17:

اسلاید 18: The pressurization process in intensifier pumps1. 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

اسلاید 19: 3. The plunger moves to the left4. 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.

اسلاید 20: 8. 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.

اسلاید 21: Direct Drive: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, creating pressure in the water.

اسلاید 22: Parts of the intensifier pump1. Electric motor and hydraulic pumpThe electric motor and hydraulic pump create the oil pressure needed for the oil side of the intensifier.

اسلاید 23: 2. Directional control valvesThe directional control valve controls the direction of flow of the hydraulic oil to and from the intensifier.

اسلاید 24: 3. IntensifierThe intensifier proper consists of the hydraulic cylinder (4), high pressure cylinders (7), and check valves (8) and end caps (9).

اسلاید 25: 4. Hydraulic cylinderThe 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 cylinder to the high pressure cylinder.

اسلاید 26: 5. PistonThe 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.

اسلاید 27: 6. PlungerThe 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.

اسلاید 28: 7. High pressure cylinderThe 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.

اسلاید 29: 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 pressure water to exit the intensifier.

اسلاید 30: 9. CapsThe 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.

اسلاید 31: 10. High pressure tubingHigh 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.

اسلاید 32: 11. Pressure attenuatorThe 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

اسلاید 33: 12. Inlet water filtersThe 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 respect to Total Dissolved Solids (TDS), pH, organic matter, temperature, etc. For these one or more filters just prior to entering the intensifier

اسلاید 34: 13. Controls and PLCThe 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.

اسلاید 35: Other parts On-Off ValveThe pneumatic On-Off valve controls the flow of water to the cutting head. This valve must be in good working order to protect against accidental high pressure water discharge at the cutting head.

اسلاید 36: 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.

اسلاید 37: Pressurized Bulk hopper Abrasive is transported via tubing and pressure from a large bulk hopper located near the waterjet cutting system to a mini-hopper near the cutting head. Mini-hopperA mini-hopper is typically mounted near and above the cutting head. Many mini-hoppers 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.

اسلاید 38:

اسلاید 39: Setup

اسلاید 40: 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.This part is shaped with waterjet using one tool. Slots, radii, holes, and profile in one 2 minute setup.

اسلاید 41: 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. This reduces the problems of accelerating and decelerating the robot head, as well as taking less energy.Get nice edge quality from different materials.

اسلاید 42: Disadvantages 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. 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 wider cut at the bottom of the part than the top. It can also cause a rough wave pattern on the cut surface.Waterjet lag

اسلاید 43: 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 problem.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.

اسلاید 44: 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.After laser cuttingAfter waterjet cutting

اسلاید 45: 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-fast EDM machines with less precision.Waterjets are much faster than EDM.

اسلاید 46: Waterjets vs. Plasma Waterjets provide a nicer edge finish. Waterjets dont heat the part. Waterjets can cut virtually any material. 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 plasma cuttingAfter waterjet cutting

اسلاید 47: Waterjets vs. Other ProcessesFlame 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 similar parts.

اسلاید 48: Waterjet in Any IndustryThe 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/AcrylicsRubberGasketsFiberglass

اسلاید 49: GlassWood Food PreparationPrinted Circuit BoardsWire StrippingStones

اسلاید 50: Referenceswww.waterjet.comwww.waterjets.orgwww.wardjet.com