Abrasive Water Jet Cutting Report Engineering Essay

Up until about the mid twentieth Century the bulk of production relied on two traditional functions of forming and machining ( Tlusty, 2000 ) . Forming is the subprogram of altering the form of the unscathed work piece, whereas machining removes merely genuine, and desired countries. Whilst these cardinal procedures still form the re tot eitheryy anchor of contemporary production, in that location has in addition been the demand for mod procedures to be developed.The traditional procedures, as t all in alllighted preceding(prenominal), fill a common fig tree of constitutional restrictions which limit their application to industry. In the instance of conventional machining procedures, a crisp submit alter shot is utilise to organize a bit from the work by shear distortion. This resultants in the formation of soaring forces in concert with the corresponding mechanical energies. unitedly with this ar a enroll of extra jobs that can originate. referable to sum of e nergy required to transport out the operation, a physique up of unwanted wake can happen, which frequently leads to deformation of the work piece and protrude snap. In certain instances, the forces introduced by the procedure tingeic number 18 naughtyly high and in decree to procure the work piece considerable clamping forces are required this excessively can take to deformation.Together with these restrictions, the development of stuffs with belongingss of high strength, high awkwardness and high stamina has set the debut of untraditional machining rules. Nontraditional machining ( NTM ) methods have been developed since World War II in an effort to turn to machining demands which can non be carried out by conventional methods entirely ( DeGarmo, egressting & A Kohser, 2003 ) . NTM methods provide the ability to machineComplex geometries Components with an first-class surface coating Delicate constituents, which otherwise would non defy the clamping forces andBrittl e stuffs or stuffs with really high hardness.There are four types of untraditional procedures sort harmonizing to the principle signifier of energy use to consequence stuff remotion. These include mechanical, electrical, thermic and chemical. One procedure which falls into the mechanical class is pesky H2O chiliad ( AWJ ) film change, and will be the central degree of this study. First, and prior to discoursing AWJ, the procedure of H2O jet ( WJ ) film editing will be introduced.Water kibibyte black ( WJC )Water jet film editing, which is besides known as waterjet machining and hydrodynamic machining, was fore nigh developed in 1968, followed by the first commercial brass in 1971 ( Zhong & A Han, 2003 ) . Through the usage of a all rightfield, hard-hitting, high-speed watercourse of H2O cultivateed at the work piece ( surface ) , a supply is created, as illust ordinated in figure 1 below. In order to bring forth the all right watercourse of H2O, a jab with an gap ( c rack ) typically in the order of 0.1 0.4mm is used ( Gro all over, 1996 ) . Together with this, runing force per unit areas of around 400MPa and in a higher place are used to supply sufficient energy for eluding to be carried out. Furthermore, the limpid of the jet can frequently make 900m/s and the cardinal procedure parametric quantities include H2O force per unit area, spread diam, H2O flow position and the working or standoff distance between the nose and the work piece. material body 1 Schematic of WJC Process ( Groover, 1996 )As the typical film editing force per unit areas as mentioned are required, a hydraulic handle is used to supercharge the fluid. The fluid is so passed through a valve, which regulates the flow rate in order to accomplish the optimal neck. The concluding phase of the fluid is to go through through the olfactory organ opening move and impact the work piece surface from a controlled tallness.Procedure ParametersThe stuff from which the nose is made is doubtless the closely of import parametric quantity in footings of procedure control ( as this greatly determines the opening diameter ) . The nozzle unit comprises of a unstained steel holder, together with a gem normally sky-blue, ruby or diamond. Of these stuffs, diamond lasts the longest but is the most expensive. Recent progresss in the production of man-made sapphire offer this stuff as non merely the most cost effectual solution, but besides imputable to other benefits excessively.Man-made sapphire can be machined moderately accurately and besides has a high opposition to have on. The most common causes of nozzle ill fortune are due to sedimentations come ining the fluid watercourse, in that respectfore underscoring the demand for high degrees of filtration of the fluid prior to pressurisation, to bed down nozzle wear. With proper nozzle object a tight, coherent waterjet can be produced and maintained really accurately.When transporting out the cutting proced ure, twain(prenominal) the opening diameter and the standoff distance moldiness be closely monitored to keep a constant deepness of cut. As the nozzle wears, compensatory alterations in the collect tallness must be made. Although existent get by distances vary from beginning to beginning, distances in the order of millimeters are normal normally around 0.25 3.5mm.WJC Advantages and DisadvantagesWJC offers many advantages over conventional machining methods. This machining procedure provides the ability to cut stuffs without firing or oppressing the work piece. Furthermore, no important high temperature is generated, therefore, deformation is minimised and in some instances, eliminated. Unlike machining or grinding, no dust is produced ensuing in smaller environsal pollution. Other advantages include minimum material loss and easiness of mechanization when used with quantitative control and industrial automatons. Whilst such advantages exist, one of the chief disadvantage s to H2O jet film editing is that there are merely a limited figure of stuffs that can be cut economically ( MTU, 2009 ) . Although it is likely to cut tool steels utilizing this procedure, the provender rates have to be greatly reduced and therefore the advance clip increased. This, in kernel, consequences in a high cost procedure. Such stuffs that can be cut utilizing the H2O jet procedure include plastics, fabrics, complexs, floor tiles, rug, leather and composition board.Abrasive Water fountain Cutting ( AWJC )To allow the film editing of difficult stuffs such as ceramics, metals and glass, together with those softer stuffs, for illustration froth and apply elastic, the WJC procedure requires the add-on of scratchy atoms, therefore organizing the scratchy H2O jet ( AWJ ) cutting technique. In a equal mode to WJC, the procedure is carried out utilizing a high-pressure, high-speed watercourse of H2O nevertheless, the discrepancy beingness that an scratchy stuff is shake o ffn in by a vacuity, which is created by jet watercourse. participate 2 Schematic of AWJC Process ( Meier, Louis & A Pilot, 1995 ) plan 2 illustrates a typical apparatus for transporting out scratchy H2O jet film editing. It can be seen that this follows closely the agreement of WJC equipment, nevertheless, with the add-on of a couple of cardinal characteristics viz. the scratchy eating system and a catcher , which is required to protect the environment from the high energy jet.Procedure ParametersAs antecedently highlighted, the WJC procedure depends on a figure of parametric quantities. Whilst many of these are movable to the AWJC procedure, there are besides add-ons to deliberate the alteration in cutting method. Momber & A Kovacevic ( 1998 ) express a list of such parametric quantities, which can be seen in figure 3 below.Figure 3 AWJC procedure parametric quantities ( Momber & A Kovacevic, 1998 )Although it is by and large accepted by many writers including JankoviA ( 2008 ) that the nose or opening diameter is the cardinal film editing parametric quantity, in the instance of AWJC, the abrasive material besides has considerable influences on the reference of the cut achieved. A choice of the parametric quantities as listed above has been explored in the subsequent surgical incision, followed by an overview of the entire system control in the subdivision thenceforth.Procedure Parameters Overview of Observed InfluencesThe most of import parametric quantity, by far, is the orifice diameter. The deepness of cut is straight relative to the opening diameter nevertheless, making an optimal point at big diameters. Although related to pump force per unit area, figure 4 below clearly illustrates this point, demoing how the deepness of cut varies with opening diameter.Figure 4 Influence of opening diameter on the deepness of cut ( HeI?ling, 1988 )Another parametric quantity that is closely linked to the opening diameter is the focal point diameter. Th is component of the cutting equipment determines the strength of the watercourse, therefore holding a direct consequence on the material remotion rate as shown by figure 5 below.Figure 5 Influence of focal point diameter on the volume remotion rate( Blickwedel, 1990 )The focal point diameter is of import non merely in footings of the volume remotion rate but besides the deepness of cut. Figure 6 below shows how the deepness of cut is besides determined by this parametric quantity diminishing as the focal point diameter additions. The lessening in deepness of cut following an optimal point is realised by Himmelreich ( 1992 ) and has been attributed to high grades of turbulency. On the other manus, a inquisitively little focal point diameter gives rise to particle hit and clash, giving an inefficient procedure.Figure 6 Influence of focal point diameter on the deepness of cut ( HeI?ling, 1988 )Of the cutting parametric quantities listed, the crosspiece rate can be said to hold the greatest influence on the film editing procedure, followed closely by the draw distance. Both of these parametric quantities are controlled by machine design and therefore are bound by the makers specification.Figures 7 and 8 overleaf illustrate the influence of both the crossbeam rate and draw distance. It can be clearly seen that the deepness of cut lessenings as the crossbeam rate additions, following closely that of a squared map. However, on the other manus, the relationship between the draw distance and the deepness of cut is moderately additive with the deepness of cut decreasing as the draw distance additions.A big figure of scratchy stuffs are available for usage in AWJC. typically these are loosely categorised as either oxides or silicates and there are, in a similar manner to the whole procedure, many parametric quantities that determine the features of an abradant.Figure 7 Influence of crossbeam rate ( left ) and standoff distance ( right ) on the deepness of cut ( Blickwedel, 1990 )Whilst it is hard to state simply which parametric quantity has the greatest influence on the procedure, it is clear that both the hardness of the stuff together with the atom form and size of it, need friendliness. Typical hardness values vary from 30 HV for Cd up to 200 HV for B carbide ( Kriegel & A Palmour, 1961 ) .Figure 8 shows the influence of both the atom form and size, whereas figure 9 overleaf high spots the significance of the deal flow rate of abradant on the deepness of cut achieved.Figure 8 Influence of abradant ( atom ) diameter and size on the deepness of cut( Ohlsen, 1997 Oweinah, 1989 )Figure 9 Influence of scratchy mass flow on the deepness of cut( Oweinah, 1989 )Abrasive Water jet plane Cutting Associated ProblemsIt is clear from the old subdivision that there are many parametric quantities that have an consequence on the AWJC procedure. If such parametric quantities are non carefully controlled, so the efficiency of the procedure decr eases along with the quality of the machined portion. Some of the associated jobs are presented in table 1.Problem and definitionParameter ( s ) affected byConsequence on constituentTaper. This characteristic arises due to a difference in the breadth of the cut at the top surface and the bottom surface and is minded(p) as a ratio ( besides flank angle ) .Abrasive mass flow rateFocus diameterStandoff distanceTrave rateThis characteristic determines the dimensional truth of the portion. sign Damage Zone. Abrasive atoms impact the surface at normal angles doing craters and abrasive-wear paths.Standoff distanceFocus diameter( Abrasive atom size composite stuffs )Some fictile distortion can happen.Change ( adulteration ) in surface roughness/waviness.Trave rateFocus diameter/lengthAbrasive mass flow rateAbrasive atom size/typeSurface belongingss of stuff are non as desired.Decrease in fatigue life of cut stuff due to check formation.Abrasive atom sizeFatigue life reduced. Onset of str ess-corrosion snap.Surface indurating due to procedure.Abrasive stuffVariation of hardness at distance from cut.Micro-structural alterationsSurface checkingPhase alterationsAbrasive-particle fragment implantingDelamination in composite stuffsBurr formation consortAssortedTable 1 Problems that can originate when transporting out AWJCAbrasive Water Jet Cutting guarantee MethodsTo guarantee such issues as those mentioned in table 1 do non happen, accurate control mechanisms must be in topographic point. There are many supervising mechanisms in topographic point today, some of which have been briefly described below. These methods lead to the control of the cutting procedure nevertheless, this is non automated in these instances.Jet-Structure Monitoring used to command focal point diameter. Diameter of entry to concentrate point monitored to reflect alterations of focal point diameter. Wear rate can be monitored utilizing this method.Acoustic Sensing used to carry off overall foca l point conditions. System based on the fact that a alteration in the focal point conditions ( orifice diameter and concentrate diameter ) affects the sound generated by the system. Figure 10 ( overleaf ) illustrates the difference between the acoustic form of a new and worn nose.Inductive standard used to supervise scratchy H2O jet speed. Method requires magnetic scratchy atoms. Abrasive jet is encircled by two little spirals, which is connected to a detection system. When the atom passes through the spiral, a little electric signal is created and the velocity determined. Figure 11 shows the typical apparatus of equipment, in this instance. Besides, laser systems similar to the above, nevertheless utilizing light pulsations alternatively.Material-Removal Visualisation used to supervise material remotion rate. In a similar mode to Acoustic Sensing, noise of cut is monitored. Frequency of signal indicates type of cut ( inter-granular/trans-granular failure ) and therefore determin es the efficiency of the cut.Workpiece Reaction Force used to supervise deepness of incursion and surface topography. observational expression that takes into history all input parametric quantities excepting the crossbeam rate. Can go a force-feedback system leting parametric quantities to be modified to cut down the force.Figure 10 Acoustic form for new and worn nose ( Kovacevic & A Evizi, 1990 )Figure 11 Initiation monitoring system ( Swanson, Kilman & A Cerwin, 1987 )The above systems offer a chiefly generic attack to system patterning and supply small or no feedback. Modern control of AWJC makes usage of an intelligent monitoring and control system, which has full feedback capablenesss. Such an illustration by Srinivasu & A Babu ( 2008 ) utilises two systems machine-vision based monitoring and intelligent control. The vision based portion monitors the size of the concentrating nose and the control system, which uses unreal nervous webs, continually modifies each paramet ric quantity to accomplish the trump out cut. A full analysis of this system is nevertheless beyond the range of this study.Abrasive Water Jet Cutting Overview of ApplicationsThe applications of AWJC are huge, foiling industries such as aerospace, automotive and electronics. It is beyond the range of this study to cover any peculiar country in important item nevertheless a few illustrations have been given below. Traditional and perchance even simple procedures have been ignored, and alternatively this study concentrates on a few non-standard applications.Meat CutingOne application of AWJ cutting is in the meat processing industry. Harmonizing to Wang & A Shanmugam ( 2008 ) , meat film editing is an of import activity and factors such as the cost, the presentation and sliting all need consideration. In this instance, salt is used as an scratchy and really good quality cuts, when compared to conventional film editing and even trim H2O jet film editing, can be achieved.Crunching Wheel ProductionThis illustration is slightly different to all other applications of AWJC as in most instances a through cut is desired. Axinte et Al. ( 2009 ) present an turning application, whereby crunching wheels are shaped harmonizing to their specification. Whilst this is considered a niche market, the writers conclude that AWJC has non merely the economical but besides proficient advantage for fabrication of this constituent. Assorted determining operations can be carried out, ensuing in such merchandises as figure 12 below.Figure 12 Examples of crunching wheels manufactured utilizing AWJC ( Axinte et al. , 2009 )Polishing of SteelAnother application of AWJC is smoothing, and in peculiar steel. Yan et Al. ( 2008 ) describe this application, bring out that electrical-discharge machining ( EDM ) is normally used for mold production. The writers province that EDM typically leaves a brickle recast bed winning to the application of this smoothing method. When compared to tradi tional methods, AWJC has a lower scratchy ingestion and recycling is improved. In this illustration the abradant is SiC and to help the procedure is covered in wax. This consequences in a much finer surface coating.Complexs ProcessingThere are many applications of AWJC in relation to complexs treating as in some instances traditional single-point film editing procedures can non be used. For illustration, Komanduri ( 1997 ) describes that it is non possible to machine SiC whisker-reinforced aluminum oxide with a single-point film editing tool nevertheless, that it may be possible to determine by crunching. Whilst some complexs can be approached in this manner, rapid tool wear is experienced and therefore the debut of AWJC is a much better method.DecisionThe old subdivision provides a figure of non-standard illustrations where AWJC is being used. Although these give a general overview, AWJC can besides be used for alternate machining procedures, such as milling, turning, piercing, b oring ( although non level bottomed holes ) and thread film editing ( Momber & A Kovacevic, 1998 ) .Although such procedures as above can be achieved, in a similar instance to ahead there are many parametric quantities that need to be monitored. This is possibly a downside to this untraditional method unless modern control methods are introduced. Further disadvantages of the procedure include the fact that degradable stuffs can non be cut and the surface coating of machined constituents relies to a great extent on the procedure. Possibly the most important consideration of using this procedure is the apparatus cost which can be highly high in certain instances. One other disadvantage is the noise created by this fabrication procedure.Although, as highlighted above, there are many factors that control the procedure its application to modern industry has grown significantly since its debut in the 1970 s. This has been driven chiefly by technological promotions, therefore leting thi s procedure to be developed, but besides due to of all time germinating stuffs that serve technology applications of today.