Effects of Process Parameters on Depth of Cut in Abrasive Waterjet Cutting of Phosphate Glass Chithirai Pon Selvan M
Sahith Reddy Madara
Associate Professor Department of Mechanical Engineering Amity University Dubai, UAE
[email protected]
UG Research Scholar Department of Aerospace Engineering Amity University Dubai, UAE
[email protected]
Sampath S S Assistant Professor Department of Mechanical Engineering Manipal University Dubai, UAE
[email protected]
Abstract— Abrasive Waterjet Cutting (AWJC) process is superior to many other cutting techniques in processing variety of materials and has found wide applications in manufacturing industries. There are several associated parameters in this method, among which water pressure, abrasive flow rate, jet traverse rate and standoff distance are of great importance but accurately controllable. This project is conducted to investigate the effects of these variable parameters on depth of cut of phosphate glass. It is experimentally demonstrated that if the cutting parameters are selected properly, AWJC can increase the depth of cut. Keywords—phosphate glass; mass flow rate; traverse speed; standoff distance I. INTRODUCTION Manufacturing industry is becoming ever more time cognizant with respect to the worldwide economy. The requirement for quick prototyping and small generation clusters is expanding in present day enterprises. These patterns have set a premium on the utilization of new and propelled innovations for rapidly handling crude materials into usable merchandise; with no time being required for tooling. Material cutting by rough abrasive waterjets was first marketed in the late 1980’s as a spearheading leap forward in the region of unpredictable preparing advancements. Abrasive Waterjet Cutting has different unmistakable preferences over the other nontraditional cutting advancements, for example, high machining adaptability, no thermal contortion, least weights on the work piece, high adaptability and less cutting power and has been turned out to be a viable innovation for handling different designing materials [1]. Abrasive Waterjet cutting innovation can be portrayed as a controlled quickened disintegration process. This framework
Sarath Raj N S Lecturer Department of Aerospace Engineering Amity University Dubai, UAE
[email protected]
comprises of high-pressure water, blended with abrasives, that goes through a gage opening at three times the speed of sound. Such load delivers pure working force ready to cut any state of glass or different materials. In correlation with the customary precious stone cutting framework such as diamond, it has the accompanying preferences such as adaptability, high precision, work can be performed on any material, ease to use, absence of heat generation [2]. Material expulsion in the Abrasive Waterjet Machining procedure is refined using a ceaseless rough abrasive slurry, which is created by the expansion of grating particles to a high speed jet of water. In abrasive waterjet, water serves principally as an accelerating medium while the rough particles assume control over the part of material evacuation. High speed water exchanges force to the grating abrasive particles, quickening them to their impingement on the work piece [3]. The abrasive particles serve essentially as the erosive medium, giving a various gathering of small scale machining components aiding material expulsion. Very confined machining powers and low magnitude of generating are two points of interest offered by water driven grating abrasive slurry. The rough abrasive water jet (Fig.1) was connected to small scale machining and phosphate glass utilizing stagnation produced under the jet spout. With a specific end goal to complete a crack free surface, the procedure ought to be controlled so the rough particles stream evenly and impact onto the surface at little impingement edges. A surge of tiny rough particles is presented in the waterjet in such a way, to the point that waterjet force is somewhat exchanged to the grating abrasive particles. Water quickens extensive amounts of rough particles to a high speed and to deliver a high reasonable jet. This stream is then guided towards working territory to perform cutting [4].
Fig.1 Abrasive Waterjet Machining Process Parameters [4]
The purpose of this paper is to recognize the impact of each cutting parameter on the depth of cut and is considered as the execution measure as in numerous modern application it is the primary requirement on the procedure relevance. More work is required to completely comprehend the impact of the critical procedure parameters on depth of cut of Phosphate glass. The demonstrating approach depends on relapse investigation of test/experimental information including depth of cut estimations. Accordingly exploratory and hypothetical examinations have been embraced in this venture to research the impacts of water weight, standoff distance, nozzle cross speed, abrasive mass stream rates on depth of cut of Phosphate glass. II. EXPERIMENTAL WORK A. Material Glass merchandises have applications in design of engineering, and they can take care of numerous uncommon issues. These materials can work in circumstances in which plastics and metals would fizzle and should be a piece of creator's assortment. In a few circumstances, by utilizing these materials, some troublesome issues would be comprehended. The glass family is immense and is in ceaseless improvement. After a seemingly endless amount of time, new sorts of glass with new properties expand their use area. The usage area of glass in structural configuration have a great deal of features from worn-out gaps or jugs to antinuclear radiation compartments; from engineering and auxiliary glasses to phosphate glasses utilized as a part of machine controls. The present world glasses can be for all intents and purposes specially crafted to fit into any ecological conditions and offer particular appearances and execution. [5] The expectations of the Abrasive Waterjet cutting model are patterned against a huge record of cutting outcomes for an extensive variety of parameters and glass sorts. Materials are described by two properties such as the threshold edge particle speed, and the dynamic stream stress. The dynamic stream stress utilized as a part of the disintegration show was found to
associate with a common modulus of flexibility for glasses. The threshold molecule speed was controlled by best fitting the model to the exploratory outcomes. P 2O5 solidifies in no less than four structures. The most commonplace polymorph involves particles of P4O10. Alternate polymorphs are polymeric, however for each situation the phosphorus atoms are bound by a tetrahedron of oxygen molecules, one of which frames a terminal P=O bond. The O-frame receives a layered structure comprising of interconnected P6O6 rings, same as the structure embraced by certain polysilicates [6]. The recent improvements of phosphate glasses for an assortment of mechanical applications, from uncommon earth particle has for strong state lasers to low temperature fixing glasses, have prompted restored interest for understanding the structures of these bizarre materials. Phosphate glasses with low scattering and moderately high refractive indices which was contrasted and silicate-based optical glasses were created for colorless optical components around 100 year's prior by Schott and colleagues. Ensuing interest for antacid earth phosphate glasses originated from their high straightforwardness for bright light, again when contrasted with silicate glasses [7]. Nonetheless, the poor chemical strength of these early photosensitive glasses restricted their applications and disheartened their further advancement. Salt aluminophosphate arrangements have glass progress/transition temperatures under 400°C and thermal development coefficients more noteworthy than 150 x 10-7 /°C as are utilized for forte hermetic seals [8]. Phosphate Silicate glass of 50 mm thickness was used for the experimentation. B. Abrasive waterjet cutting setup The equipment (Fig. 2) utilized for machining the sample of phosphate glass was Water Jet Sweden cutter which was furnished with KMT ultrahigh weight pump with the planned weight of 4000 bar. The machine is outfitted with a gravity nourish kind of rough container, a grating feeder framework, a pneumatically controlled valve and a work piece table with measurement of 3000 mm x 1500 mm. Sapphire opening was utilized to change the high-weight water into a collimated stream, with a carbide spout/nozzle to frame a abrasive waterjet.
Fig. 2 Abrasive waterjet cutting equipment
All through the examinations, the spout was often checked and supplanted with another one at whatever point the spout was exhausted essentially. The abrasives were conveyed utilizing compacted air from a container to the blending chamber and were directed utilizing a metering circle. The flotsam and jetsam of material and the slurry were gathered into a catcher tank. The constant parameters of abrasive waterjet cutting equipment utilized for the investigations are appeared in table 1. TABLE I. Specifications of abrasive waterjet cutter
Machine Model Jet Impact Angle Energy consumption Orifice diameter Nozzle Length Nozzle diameter Density of abrasive particle Average diameter of abrasive particles Abrasive consumption Water consumption
CLASSICA-50 HP (KMT) 90° 37 kWh 0.35 mm 76.5 mm 1.05 mm 4100 kg/m3 0.18 mm 100-900 g/min 3.6 lt/min
Fig. 3 Abrasive waterjet cutting head
C. Experimental Design Design of investigation is an effective apparatus that can be utilized as a part of an assortment of test circumstances. Design of investigations systems empower inventors to decide at the same time the individual and intuitive impacts of many variables that could influence the yield about any outline. To accomplish an exhaustive cut it was required that the combinations of the procedure factors give the jet stream enough vitality to enter through the samples. In the present examination few process parameters and levels were chosen in view based on the literature survey conducted for a few
examinations that had been archived on Abrasive Waterjet Cutting on graphite overlays [9], metallic covered sheet steels [10] and fiber-fortified plastics [11], water weight/pressure [12], mass stream/flow rate [13], nozzle cross/transverse speed [14] and spout/nozzle standoff distance [15] on the profundity of cut are in an indistinguishable manner from revealed in past investigations for different materials. This impacts each of these parameters is examined while keeping alternate parameters considered in this investigation as constant. To accomplish a careful cut it was required that the combinations of the procedure factors give the jet stream enough vitality to infiltrate through the samples. The four factors (Table II) in AWJC which was shifted are: nozzle transverse speed from 1.7 mm/s to 4.3 mm/s, water pressure 225 MPa to 325 MPa, standoff distance 2 mm to 5 mm and mass flow stream rate of abrasive particles from 3 g/s to 6 g/s. Readings were brought with different mixes of process parameters to accumulate the required information. Three distinct readings were taken at each example and the normal readings were ascertained as to limit the mistake TABLE II. Various levels of parameters used in research
Parameter
Unit MPa mm/s
Level 1 225 1.7
Level 2 275 3
Level 3 325 4.3
Water pressure (p) Traverse speed (u) Mass flow rate (ma)
g/s
3
4.5
6
Standoff distance (s)
mm
2
3.5
5
D. Data Collection For each sample examination, the machining parameters were set to the pre-characterized levels as per the orthogonal exhibit array. All machining strategies were finished utilizing a solitary pass cutting. The abrasives were conveyed utilizing packed air from a container to the blending chamber and were controlled utilizing a metering circle. The rough stream rates were adjusted by measuring the time spent for a specific weight of abrasives to be totally expended in the container. The supply weight was physically controlled utilizing a weight gage. The standoff distance is controlled through the controller in the administrator control stand. The cross speed supply of abrasives were consequently controlled by the abrasive waterjet framework customized by NC code. The profundity depth of cut for each test was measured by utilizing a "Sigma Scope 500" profile projector at an amplification of 10 times. With this amplification together with a vast shadow screen on the projector and exactness computerized readouts, the estimation precision was relied upon to be more than satisfactory with the end goal of this investigation. For each cut, no less than three measures were made and the normal was taken as the final reading.
III. EXPERIMENTAL RESULTS AND DISCUSSIONS By investigating the sample information of all the chose materials, it has been discovered that the ideal determination of the four essential parameters, i.e., water weight/pressure, rough abrasive mass stream rate, nozzle traverse speed and spout standoff distance are imperative on controlling procedure yield, for example, profundity of cut. The numerous specifications of abrasive waterjet cutter includes: Machine Model Classica is of 50 HP (KMT), Energy consumption (kWh) is of 37, Abrasive consumption (g/min) is of 100-900, Nozzle diameter (mm) is of 1.05, Nozzle length (mm) is of 76.5, and Water consumption (lt/min) is of 3.6. A 0.35 mm breadth sapphire hole was utilized to trans-frame the high weight water into a collimated jet. The abrasives were conveyed utilizing compacted air from a container to the blending chamber and were controlled utilizing a metering plate. The rough abrasive waterjet weight is physically controlled utilizing the weight gage. The standoff distance is controlled through the controller in the administrator control stand. The transverse speed was controlled naturally by the abrasive waterjet framework modified by NC code. The following are the constant process parameters [16]. Results demonstrate that the water weight/pressure and rough abrasive mass stream rate emphatically influence the profundity of cut in that an expansion in these factors brings about an increment inside and out of cut, while standoff distance separation and nozzle traverse speed unfavorably impact the profundity of cut, i.e. the expansion in these two parameters is related with a reduction in the profundity of cut. In this manner it is suggested that a blend of high water weight/pressure, more grating abrasive mass stream rate, low cross/traverse speed and short standoff distance be utilized to create more profundity of cut. By and large, the impact of water weight/pressure and mass stream rate is articulated higher contrasted with navigate speed with the standoff distance having negligible impact. A. Effect of water pressure on depth of cut This examination applies rough abrasive water jet to machining of phosphate glass. The rough water jet forms are initially performed to cut materials with water containing grating grains at a high weight. Fig.4, the results of water pressure on depth of cut show that, inside the working extent selected, increase of water pressure brings about increment in profundity of cut when mass stream/flow rate, transverse speed and standoff distance were kept steady. At the point when water pres-beyond any doubt is expanded, the jet active vitality builds that prompts more depth/profundity of cut.
Fig.4 Water pressure versus depth of cut
B. Effect of mass flow rate on depth of cut Increment in grating abrasive mass stream rate additionally builds the profundity of cut. The effect between the grating abrasive molecule and the material decides the capacity of the rough abrasive waterjet to cut the material. Since cutting is an aggregate technique, the speed of the rough abrasive particle and the repeat of particle impacts are both precarious. The speed of the molecule decides the imprudent stacking on the material and the potential vitality exchange from the molecule to the material. Fig.5, the recurrence of the effect decides the rate of vitality exchange and thus, the rate of cut profundity development. The mass flow rate of the rough abrasive particles incompletely deflect the recurrence of the affecting particles and in part decides the speed at which they hit. Likewise, with the more noteworthy mass flow rates, the dynamic vitality of the water must be spread over more particles.
Fig.5 Abrasive mass flow rate versus depth of cut
C. Effect of traverse speed on depth of cut Cross/Transverse speed is the propel rate of nozzle on even horizontal plane per unit time amid cutting operation. Fig.6, results demonstrate that expansion of cross speed diminishes the profundity of cut inside the working reach chose, by keeping alternate parameters considered in this examination as constant. The more drawn out the grating abrasive waterjet remains at a specific area, the more profound the cut will be on account of the surge of rough abrasive particles has more opportunity to dissolve the material. This impact is because of two reasons. In the first place the more drawn out the stay time the more noteworthy the quantity of affecting grating particles hit the material and the more noteworthy the smaller scale harm, which begins the disintegration procedure. Furthermore,
the water from the stream/flow has an inclination to get into the smaller scale splits and on account of the subsequent hydrodynamic weight, the break development comes about. At the point when the smaller scale splits develop and associate, the included material will loosen up from the parent material and the profundity of cut increments. Therefore, it appears reason-ready to expect a reverse connection between the traverse speed and the profundity of cut.
Fig.6 Nozzle traverse speed versus depth of cut
D. Effect of standoff distance on depth of cut Standoff distance is the separation between the spout nozzle and the work piece amid cutting operation. For the most part, higher standoff distance enables the jet to extend before impingement which may build/increase weakness to outside external drag from the encompassing condition. Fig.7, along these lines, increment in the standoff distance comes about an expanded stream width as cutting is started and thusly, diminishes the dynamic vitality of the jet at impingement. So depth of cut increment with increment in standoff distance.
Fig.7 Standoff distance versus depth of cut It is alluring to have a lower standoff distance which may deliver a smoother surface because of expanded motor vitality. The machined surface is smoother close to the highest point of the surface and winds up plainly rougher at more prominent profundities from the best surface. On the off chance that we keep other operational parameters steady, when standoff expel distance extends, significance of cut reduces. Conversely,
standoff distance on profundity of cut isn't much persuasive when contrasted with alternate parameters considered in this examination [17]. CONCLUSIONS AND FUTURE SCOPE OF WORK Experimental investigations have been carried for the depth of cut in abrasive waterjet cutting of phosphate glass. The effects of different operational parameters such as: pressure, abrasive mass flow rate, traverse speed and nozzle standoff distance on depth of cut have been investigated. As a result of this study, it is observed that these operational parameters have direct effect on depth of cut. It has been found that water pressure has the most effect on the depth of cut. An increase in water pressure is associated with an increase in depth of cut. These findings indicate that the use of high water pressure is preferred to obtain overall good cutting performance. Depth of cut constantly increases as mass flow rate increases. It is recommended to use more mass flow rate to increase depth of cut. Among the process parameters considered in this study water pressure and abrasive mass flow rate have the similar effect on depth of cut. As nozzle traverse speed increases, depth of cut decreases. This means that low traverse speed should be used to have more depth of but is at the cost of sacrificing productivity. This experimental study has resulted that when standoff distance increases, depth of cut decreases. Therefore to achieve an overall cutting performance, low standoff distance should be selected. Based on the results, findings and the achievement performed from this project, further studies needed to be carried out for the effects of process parameters on surface roughness and kerf taper which are other cutting performance measure in AWJC. To further continue the current study, an experimental study needs to be conducted to investigate the macro material removal process of AWJC. This study will provide a significant insight into the mechanisms of the effect of process parameters on the cutting performance measures. It will also enable to develop a basis for fully modeling the cutting process and a strategy for further increase of the cutting performance.
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