Water jet is a cutting method of cutting materials by using jet of water. This can be done by utilizing water only for soft/less dense material such as foam. The water is forced through a precision orifice, to create a well-defined stream of water. This stream of water is typically produced under pressure of 40,000 to 60,000 psi (pound per square inch). It is simple to explain, operate and maintain. The process, however, incorporates extremely complex materials technology and design. To generate and control water at pressure 87,000 psi requires science and technology. At this pressures a slight leak can cause permenant damage to component if not properly design.Water jet generated when water flows from a high pressure pump, through plumbing and out from a jewel nozzle with tiny opening. At 300 MPa (approximately 40,000 psi), the water jet exits out of the jewel orifice at 680 m/s while it is over 1021 m/s then pressure goes upto 400 MPa (approximately 60,000 psi ). This remarkable water jet bears considerable amount of energy which turns into forces for cutting , trimming ,slicing and cleaning as well.[1]
Fig 1.1 Water Jet cutting apparatus[1]
Water jet cutting system are the world’s most versatile machine tool. Water jet process is also recognized as the most versatile and fastest growing process in almost all. It is proven to be more benificial and cost effective then traditional technologies such as machining by laser, plasma, EDM wire cut. The machines are extremly easy to use. Operator can handle the machines after few hours training and produce high quality parts in hours. Water jet system are suitable for production of high volumes, short runs or prototype parts.
In water jet cutting, pressure and velocity of water streaming through the nozzle are two distinct forms of energy. Material is removed due to stream of water that tears away microscopic pieces or grains of material. In this cold cutting process, the water jet performs an erosion process which ‘grinds" away small grains of material to be cut. Abrasive can be added to the stream to increase the efficiency of the process many times. It is a complex technology because system has to generate and control water at 60,000 psi which is very demanding task and since at these pressure, a slight leak can cause permanent erosion damage to components (if not properly designed). Water jet compliments other technologies such as Non-conventional (laser, EDM and plasma) or conventional (milling) processes. There are no noxious gases or liquids used in water jet cutting. Water jets do not create environmental hazardous materials or vapours. There is no heat affected zones or mechanical stresses on a water jet cut-surface. Water jet is a versatile, productive and cold cutting process. Water jets remove material without heat.
1.2 BASIC WATER JET PRINCIPLE
Waterjets 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 creates high 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 soft wood, but are not effective for cutting harder materials.
Fig 1.2 cutting process[2]
The inlet water for a pure waterjet is pressurized between 90 to 135 bar. This is forced through a tiny hole in the jewel which is typically 0.8 to 1.3 mm. This creates a very high velocity, very thin beam of water (that is why some people refer to waterjets as ‘water lasers’) .
Fig 1.3 cut work piece[2]
1.3 Direct Drive Pump For Pressurization Of Water
A Direct drive pump works like a car’s engine. A motor turns a crank shaft attached to 3 or more offset pistons. As crankshaft turns, the pistons reciprocate in their respective cylinders creating pressure in the water. Pressure and flow rate are determined by how fast the motor turns the crankshaft. Direct drive pumps cycle much faster than intensifier, on the order of 1500 rpm. Direct drive pumps generally are found in lower pressure application. Direct drive pumps can only run more than one cutting head only if all cutting heads are cutting the same part at the same time.[3]
Fig 1.4 Multi Cylinder Pressure Pump[3]
1.4 Water jet high pressure pump
Fig 1.5 High pressure pump.
Water is pressurized to very high pressure, in excess of 90 to 135 bar. This pressurization is accomplished with the use of multi cylinder pump. The high pressure water is transported through a series of stainless steel tubes to a cutting head. the cutting head is ‘pure water cutting head.’
In the cutting head, the high pressure water is forced through a small diameter orifice.The diameter of this orifice is anywhere from 0.8 to 1.3 mm. This step converts the pressure of the water jet stream into high speed converting potential energy to kinetic energy. Higher pressure result in higher speed and smaller diameter orifice yield a faster water jet stream.
1.5 Advantages of waterjet
‘ Can work with more materials
Waterjets can machine reflective materials that lasers cannot, such as copper annd alluminium. Water jets cut a wide range of materials with no changes in setup required. Also, materials which are heat-sensitive can be cut using waterjets.
‘ No heat- afected zone (HAZ) with waterjets
Water jet cutting does not heat the part. There is no heat ‘affected zone (HAZ) or thermal distortion which can occure with laser.
‘ Water jets 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 the material is typically very small, although caution is needed when the waterjet nozzle is raised.
‘ Lower capital equipment costs
The cost of water jet machine is generally much lower than that of a laser.
‘ Better tolerances on thicker parts
Water jets offer better tolrences on parts thicker than 0.5′ (12mm). for thinner parts, both waterjets and lasers offer comparable tolerances.
‘ Simpler maintenance
Maintencance on a water jet is simpler than that of a lase.
‘ Simple operation
Water jets are manually operated, so that the operator does not have to be highly skilled and trained.
1.6 Application of water jet machine
Virtually anything can be cut with jet-edge water jet. Here are a just a few examples of what can be cut with jet edge waterjet cutting system.
‘ Soft rubber
‘ Hard rubber
‘ Soft gasket material
‘ Foam
‘ Nylon
‘ Thermocol
Chapter: 2 LITERATURE REVIEW
Though many researchers have worked on abrasive jet / water jet machining, below are the few listed researchers works related to jet machining are presented.
Elmer N. Leslie [4]
Apparatus and method are disclosed utilizing a high strength fluid jet in an operative cutting system. A computer driven carriage and nozzle movable on the carriage effectuate cutting in the X-Y direction and a Sensor arrangement is used Position the nozzle in the Z-direction. The work piece rests on a flexible wire bed which supports the work piece and at the same time allows a fluid catcher to pass under the work piece in registration with the nozzle. A support channeled for allow for movement of the fluid catcher provides support for the work piece in the area of the cut.
David J. Burns; Gene G. Yie; Udo H. Mohaupt[5]
A high pressure pulsed water jet apparatus and process operable in a vertical position especially suitable for automated pavement and rock fracture. The apparatus and process of this invention is used in combination with a thrust generator providing a substantially flat power stroke output thereby providing a pulsed water jet operating on the principle of pressure extrusion to generate repetitive water jet pulses of high velocity and at high repetitive frequency. The apparatus and process of this invention is especially suitable for providing an apparatus and process for fracturing pavement on a single self-contained vehicle which may be operated by a pre-programmed program means.
Gerald JI Julien[6]
A liquid Jet nozzle for forming a high velocity liquid Jet from a Pressurized liquid, includes a monolithic Nitinol body having an input side and an output side. A tapering lead-in channel opening in the input side and tapers to a central web, through which extends a small diameter orifice, communicating through the Web from the lead-in channel to an egress opening in the output side of the body. The orifice interacts with the high pressure liquid to shape the pressurized liquid into a narrow, high velocity liquid jet which exits the body through the egress opening. A surface layer of nickel titanium oxide on the Nitinol in the orifice provides enhanced resistance to erosion by the high pressure liquid.
Hem J- Gerber; David R. Pearl[7]
A machine utilizing a high velocity fluid jet for cutting is provided with a receiver to absorb the jet after it passes through sheet material in a cutting operation. The receiver comprises a jet-deflection chamber having an inlet positioned to receive the fluid jet and an inside wall which turns or deflects the jet in a whirling or circular path to dissipate the energy or momentum of the jet. A drain from the chamber may be provided to continually evacuate the spent fluid of the Jet.
Bobby L. Higgins[8]
A fluid jet cutter utilizing a multitude of heads and flexible pressurized feed system is disclosed. The cutter utilizes a carriage which has mounted on it a plurality of fluid jet cutting heads which are maintained in registration with jet catchers operably disposed beneath the carriage. The cutters and jet catchers are movable either as a unit in synchronization with each other or moved separately to be spaced apart from a center head. Cutting in the Y-direction is effectuated by means of head movement along the carriage. Cutting action in the X-direction can be effectuated either by movement of the carriage or, alternatively, by movement of the cutting table bed. A tower disposed outside the cutting area is used to provide high pressure fluid to the cutting heads. The tower, with its flexible coupling, reduces the dynamic loads on the positioning system for the cutter heads, thereby allowing increased performance. Coverage of the full cutting area is effectuated by use of an overhead boom configuration coupled with a helical coil capable of extending and bending during motion of the carriage.
Christopher L. Higgins; Stanley R. Burgess[9]
Apparatus for cutting erosive materials such as stone and the like includes a high-velocity, high-pressure water lance which can be raised and lowered as necessary. The lower end of the water lance carries a cutting head in the form of a nozzle assembly able to be rotated about the longitudinal axis of the water lance. The water lance is mounted upon a carriage which can be propelled in directions at right angles to each other and the water lance may be supported by a vertically dis posed truss, which itself may be re- locatable about the longitudinal axis of the lance.
David E. Chupka; Peter Seifert; Christopher M. Vitoria[10]
Broke handling and reducing apparatus and method for comminuting a moving continuous sheet or web material such as paper broke in the dryer or converter section of a papermaking machine, includes a high pressure water jet cutting nozzles mounted in spaced-apart relation transversely to the direction of movement of the material and are mounted so as to direct high pressure cutting jets into the path of movement. The nozzles are mounted so that at-least some of the nozzles are cyclically moved with respect to others nozzles to form plurality of mutually intersecting jet cutter paths to reduce the material into a multiplicity of smaller discrete or easily separable pieces.
Thus, it can be concluded from the work of various researchers on jet machining that water jet machining is a simple method to cut soft materials accurately over traditional hand cutting methods.
So, an attempt is being made to fabricate a water jet set up to cut soft materials like rubber, foam, etc.
‘
Chapter 3 OBJECTIVE
‘ By varying parameters like stand-off distance, the effect on cutting surface will be studied like roughness, burrs, etc.
‘ Moreover, number of passes for cutting will be studied for different materials for cutting parameters like stand-off distance.
‘ Analysis of different material with cutting roughness.
‘ To develop a machine with effective cost to cut soft materials.
‘ To compare depth of cut for different materials by varying parameters like stand -off distance by keeping pressure constant.
‘
Chapte 4 FABRICATION OF WATERJET MACHINE
4.1 Base table
‘ Main base frame is a main supporting part/structure of the project.
‘ The main base frame placed on a four legs.
‘ The main base frame is made of M.S.
‘ L shape angle plates are used.
‘ Size of base table:
Length-1200 mm
Width-750 mm
Thickness-5 mm
L-shape angle size-35*35*5 mm
Leg size-37*37*2 mm
Height of table-950 mm
Fig 4.1 Base table.
Fabrication steps
‘ Cut L angle plate and legs as per the dimension
‘ Weld the angle plate as per requirement
‘ Join the legs
‘ Place the guide ways for the movement of carriage
‘ Machinery requirement: Hand cutter, Welding machine
4.2 Sliding carriage (X-X direction)
‘ Sliding carriage is used for movement of nozzle in X-X direction
‘ It is made of L-shape angle
‘ It contains 4 wheels on the bottom side for the moving purpose
‘ Size of sliding carriage
Length-730mm
Width-500mm
Thickness-5mm
Fig 4.2 sliding carriage (x-x direction)
Fabrication steps
‘ Cut L angle plate as per required dimension
‘ Join the angle plates by welding
‘ For fixing the wheels holes is done by drilling
‘ Place guide ways for the movement of carriage
‘ Machinery used- Hand cutter, Welding machine, Drilling machine
4.3 Sliding carriage (Y-Y direction)
‘ Sliding carriage is used for movement of nozzle in Y-Y direction
‘ It also contains 4 wheels for sliding movement of carriage
‘ It contains nozzle rod
‘ Size of sliding carriage
Length-480mm
Width-220mm
Thickness-5mm
Fig 4.3 sliding carrage (Y-Y direction)
‘
4.4 Lead screw
‘ Lead screw is used for calculated movement of sliding carriage
‘ It contains handles on the end for movement of carriage
‘ It contains ‘V’ threads
‘ ‘V’ threads provide self-locking property
‘ Size of lead screw
‘ For X-X direction
Diameter-20mm
Pitch of threads-3mm
‘ For Y-Y direction
Diameter -17mm
Pitch of threads-2mm
Fabrication steps:-
Lead screw with nut arrangement
‘ Take a shaft as per requirement
‘ Manufacture V-thread on it.
Fig 4.4 lead screw
4.5 Bearing
‘ Bearing used for the supporting the lead screw and easy rotation of lead screw
‘ Automobile bearing is used in this set up
Bearing no. No. of bearing used
6202 2
6302 2
4.6 Other equipment
‘ In this set up small screw and nut is used for fixing the wheel on the sliding carriage
‘ Hexagonal nut is used to attached the lead screw to the sliding carriage
4.7 Final assembly
Fig.4.5 Project Setup
There is a one base table which is contain two cages and nut & lead screw mechanism used for facilitates nozzle movement in x and y direction.
The net is provided below the sliding cage to place a workpiece or rubber sheet.Net is also resist flow of water.
Fig 4.6 Nozzle Assembly Fig 4.7 Water jet nozzle
‘
4.8 circuit diagram
Fig 4.8 circuit diagram
Where , v-1 inet water valve
s-1 electric supply to (240 volt , 50 Hz)
E-2 Pressure pump
p-1 inlet water to pressure pump
p-2 pressurrise water outlet
E-4 Nozzle outlet
E-1 Base table
Chapter 5 ANALYSIS
After the fabrication of the setup, an attempt was made to conduct experiments on the machine by cutting materials of three types like foam, rubber, and thermocol.
The depth of cut for different materials was obtained by varying parameter like stand – off distance (distance between nozzle & work piece) and results are tabulated as shown below
5.1 Variation of depth of cut with stand-off distance for foam
Sr. no Stand-off distance ( in mm) Depth of cut
(in mm) Result
1 20 7 Smooth cut
2 20 14 Rough cut in last 7 mm
3 40 7 Smooth cut
4 40 14 Rough cut in last 5 mm
5 60 14 Rough cut
6 80 6 Smooth cut
7 80 12 Rough cut
Table 5.1 Depth of cut for foam
Fig 5.1 foam cutting
In this experimental work stand-off distance increase then the depth of cut decrease.
5.2 Variation of depth of cut with stand-off distance for Rubber
Sr. no Stand-off distance ( in mm) Depth of cut
( in mm) Result
1 20 3 Smooth cut
2 20 6 Rough cut
3 40 3 Smooth cut
4 40 6 Rough cut
5 60 6 Very Rough cut
Table 5.2 Depth of cut for rubber
Fig 5.2 Rubber cuting’
5.3 Variation of depth of cut with stand-off distance for thermocol
Sr. no Stand-off distance ( in mm) Depth of cut
( in mm) Result
1 80 30 Smooth cut
2 80 60 Rough cut in last 20 mm
Table 5.3 depth of cut for therocol
Fig 5.3 Thermocol cutting
5.4 Comparison of foam, rubber and thermocol
It can be concluded that the depth of cut for foam was found to be more as compare to rubber and thermocol. Hence the fabricated set up is suitable for cutting foam type of material accuretly as well as for cutting rubber and thermocol for fixced perssure.
‘
Chapter 6 CONCLUSION
This project was aim to develop a set-up for cutting soft materials, for which from experiments were carried out on different materials and the results are presented below.
(1) Maximum depth of cut of 7mm is achieved in foam material at stand’off distance of 20mm.
(2) Maximum depth of cut of 3mm is achieved in rubber material at stand-off distance of 20mm.
(3) Maximum depth of cut of 30mm is achieved in thermocol material at stand-off distance of 20mm.
After when, the stand’off distance increases as the depth of cut decreases.
‘
Chapter 7 REFERENCES
[1]http://www.waterjets.org/index.php?option=com_content&task=category§ionid=4&id=46&Itemid=53 [2]http://www.waterjets.org/index.php?option=com_content&task=category§ionid=4&id=46&Itemid=53t
[3] http://www.wardjet.com/02-waterjet-relationship-parameters.html
[4] Elmer N. Leslie ‘FLUID JET CUTTING SYSTEM’7/9/1976 Cansco , Inc., Richardson,Tex.US
[5] David J.Burns; Gene G. Yie; ‘HIGH PRESSURE PULSED WATER JET APPRATUS AND PROCESS’21/2/1978 Institutes of gas Tech., Chicago
[6] Gerald JI Julien ‘LIQUID LET NOZZLE’6/4/2004 Nitinol Tech., Inc., Edgewood, WA(US)
[7] Hem J Gerber ;David R.Pearl ‘FLUID CUTTING RECIVER’6/2/1979 Gerber German Tech. South Windsor
[8] Booby L. Higgins ‘FLUID JET CUTTER’20/2/1979 Cansco, Inc,.Tex.
[9] Christopher L. Higgins; Stanley R. Burgess ‘APPRATUS FOR CUTTING EROISIVE MATERIAL USING HIGH PRESSURE WATER DEVICE’26/7/1994 Australian Stone Tech. Pty., Ltd. Australia
[10] David E. Chupka ; Peter Seifert ‘HIGH PRESSURE WATER JET COMMINUTTING’10/8/1993 The Black Clawson Company Middletown Ohiosss