Experimental Analysis of Spiral Finishing Process on EDM Drilled Hole in Titanium

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Introduction
Electrical Discharge Machining is a nonconventional machining procedure that involves multiple recurrent electrical discharges of short duration and high current density between the workpiece and the tool [1][2][3].Today, EDM is a common machining technique in a variety of industrial facilities across the globe.Te majority of standard machining procedures such as drilling, grinding, and milling fail to manufacture geometrically complicated or challenging forms and sizes [4,5].For that advancement, EDM has been chosen for drilling on titanium material, and for a better surface fnish, abrasive fow fnishing process was added further.Te main purpose of Abrasive Flow Finishing (AFF) is to deburr, polish, and fnish hard-to-reach surfaces and edges by allowing an abrasive-flled polymer to fow from two vertically opposed cylinders [6][7][8][9].Te medium (a mixture of viscoelastic material, say, polyborosiloxane, additives, and abrasive particles) enters the workpiece through the tooling [10,11].Te abrasive particles (SiC, Al 2 O 3 , CBN, and diamond) penetrate the workpiece surface depending upon the extent of the radial force acting on them.Due to the tangential/axial force, the material is removed in the form of microchips [12][13][14][15].
Yan et al. [16] presented research that investigates the spiral polishing technique and micro-fnishing device for alloy steel.Tey did this by employing a slurry of SiC abrasive grains together with polymer, wax, and silicone carrier oil as their machining medium.In addition to the polymer, wax, and silicone oil, abrasive granules of 12, 30, and 150 mm were added to the mixture.Te fndings indicate that increasing the rotation speed and the amount of machining time during the micro-fnishing process resulted in a reduction in the medium viscosity and an improvement in the hole surface roughness.Jain [17] investigated the efect that the parameters of the Abrasive Filming (AFM) process had on the amount of material removed and the surface fnish.Modeling and simulation were employed to investigate the mechanics of AFM, which includes abrasive grains making indentations on the surface of the workpiece in order to remove material.In addition to that, the research investigated tangential force, specifc energy, and heat transport.Using surface roughness measurement, atomic force, and scanning electron microscopy, Yamaguchi and Shinmura [18] investigated how processing afects the surface texture of a material.Tey suggested using an internal magnetic abrasive fnishing method for manufacturing tubes with highly fnished interior surfaces for use in critical applications such as clean gas or liquid piping systems.According to the fndings, magnetic abrasive fnishing is more efective at removing material than magnetic jig fnishing, making it a good choice for surfaces that need a lot of material to be removed.Jha and Jain [19] designed a smart magnetorheological polishing fuid for use in their precision fnishing technique for intricate interior geometries.Te procedure was validated by conducting tests on workpieces made of stainless steel at varying intensities of the magnetic feld.After ending with a zero magnetic feld strength, the results indicated no signifcant change in the surface roughness; nevertheless, the roughness steadily decreased as the magnetic feld intensity increased.Kuriyagawa et al. [20] conducted research on an electrorheological fuidassisted micro-spherical generator system, which is a machine that can both micro-grind and micro-polish.Tey discovered that grinding frst led to better polishing performance for smaller regions.Te research also investigated the behavior of abrasive particles and electrorheological particles near the tool tips, and it found that the electrorheological efect makes it easier to gather particles.Jain [21] employed neural networks to model and optimize AFM process parameters.However, they discovered that previous approaches were difcult to process complex surfaces and were sluggish.Te abrasive concentration, the mesh size, the number of cycles, and the medium fow speed were the most important process parameters.Te greater the number of cycles and the magnifcation, the more clearly the tool markings may be seen.An investigation into the use of magnetic force for inner wall spiral polishing was carried out by Chen and Yan [22].Tey came up with an idea for a container that was hollow and had a spindle attached to a CNC or machining tool.A combination of steel grits, polystyrene balls, silicon oil, and SiC particles was employed as the abrasive in this process.According to the fndings of the research, increasing the amount of time spent machining results in improved fuidity of the abrasives, which produces polishing surfaces of a better quality.Patel and Pandey [23] examined a variety of standard and unconventional methods, including laser shock peening, heat treatment, and machining, with an emphasis on material removal and thermal procedures to improve the mechanical characteristics, dimensional accuracy, and quality of metal-based additive manufacturing components.Gong et al. [24] provided a useful solution for micro-hole manufacturing without the need for additional clamping or tool changes by demonstrating via the fabrication of micro-bearing bushings that high machining efciency, little wear, and no recasting layer are achievable.Abeni et al. [25] analyzed process performances, surface roughness, and burr extension, providing insights into the optimal processing conditions and parameters for postprocessing 3D-printed metal samples, facilitating comparisons and evaluations of machining conditions for enhanced surface quality and dimensional accuracy.
Tis paper describes the experimentation on the spiral fnishing process of EDM-drilled holes on Titanium material using the parametric design of Taguchi's methodology.Tungsten was picked as the material for this study because it is being used in more and more ways to make tools.No spiral fnishing operation has been done before with these parameters and titanium holes.Te efect of various surface fnishing parameters such as speed of rotation of the motor shaft, time of rotation, i.e., fnishing time, abrasive concentration, and liquid media on surface roughness has been studied through surface fnishing of Titanium holes.Te selection of optimum values is essential for the process of surface fnishing.Te use of spiral fnishing to titanium holes is not common, but it highlights the potential for additional developments and surface quality improvements in the area of advanced fnishing.Start by using the Wire-Cut EDM machine to smooth down any sharp edges, and then divide the sheet in half so you can easily hold the tasks in the vice while you drill them.For this experiment, a tungsten rod measuring 35 mm in length and 5 mm. in width and 5 mm in diameter was employed.Figure 2 shows an image of a tungsten cutting tool and a titanium workpiece taken just before EDM machining.Te material characteristics of the workpiece are listed in Table 1.When drilling with a high current and short on/of period, the resulting holes have a terrible fnish.After many iterations, we fnally nailed down the optimal cutting parameter for our material and cutter.We drilled a total of twenty-one holes in the two titanium pieces of the workpiece.Most of the holes were drilled at intervals of around 120 to 180 minutes.Some of the holes required more machining time and had subpar top and bottom surface fnishing.Figure 3 is an image showing the titanium substance with holes cut into it.4.

Abrasive Finishing Process Setup Development.
Te primary part of this research is the operation of spiral polishing using abrasive.Te angle plate of dimensions of 4″ in length, 7″ in width, and 10 mm in thickness is collected where both the plates are made of iron, to make the fxture for holding the workpiece and tool in a proper manner to carry out the fnishing experiment.In this operation, rotate the tool both clockwise and anti-clockwise during the fnishing of the through holes' internal surface.Tat is why we purchased a stepper motor with a digital speed controller and power supply.We used the motor to rotate the tool using various speeds of motor shaft rotation.Te features and control of the motor are shown in Figure 4.Ten the angel plate is machined in the Shaper Machine to make the surface of the angel plate smooth and also to check that the two sides of the angel plate are exactly perpendicular to each other.Te research motto is to get the desired surface fnish in operation.For this reason, every step during setup was done very carefully to get the desired precession outcome.
After machining the angel plate, we cut a small part of the plate to attach with the angel plate by welding to make the system for holding the motor.For that purpose, a small plate is attached in the middle of the angel plate's one side in such a way that the motor should ft on the plate vertically as shown in Figure 5.After this, using a lathe machine, a hole is made on the attached small plate in the proper position so that the motor shaft can be passed through the hole as shown in Figure 6.Now four holes are made in the small plate for the screws of the motor to fx it on the plate.Ten the motor is screwed with the attached plate so that the motor shaft remains vertically fxed with the motor shaft facing toward the bottom side of the angel plate.Ten a drill chuck is attached to the motor shaft to hold the drill bit during rotation while operating surface fnishing.Te whole system made till this point is shown in Figure 7. Next, during spiral fnishing, the fxture for the workpiece material is created.For that, a circular hole on the bottom side of the angel plate, about 5 cm in diameter just below the drill chuck which is connected to the hanging plate, is created.Make this hole because the space gap between the angel plate bottom side and the drill chuck is very small to hold the drill during operation.After making the big hole, easily hold the drill bit in the drill chuck and also pass through the holes of titanium material.Te fxture of workpiece material is made so that every hole can be used for fnishing.Another plate of the same dimension is taken as the bottom side of the angel plate to ft it on the angel plate for holding the workpiece.A few holes of diameter 5 mm are cut on that plate so that every hole can be used for fnishing operation.Four small bushes are made to attach the plate on the bottom side of the angel plate.
Some wooden arrangements are made to mount the arrangements on the wooden structure.Make holes in the wooden structure to fx it with the angel plate in such a manner that the big hole on the bottom side plate remains in between the two wooden pillars.Tis is made so that the abrasive mixture pot is just beneath the bottom surface of the workpiece material as shown in the fgure.Assembling all the parts completes the required setup for this experiment.Te complete setup for spiral polishing is shown in Figure 8.
So, the present experiment, according to the concept of spiral polishing with abrasive, designed a set of apparatus onto a steel plate attached to the angel plate.With the help of abrasive and rotating tools, precision spiral polishing can be carried out.Te fxed rotating tool is used by the equipment for the micro-abrasive medium with the spiral polishing technique to pick up the abrasive medium along with the rotation.During the operation, the abrasive media make direct contact with the workpiece.Tus, the workpiece surface is cleared of minute pieces and dirt by the abrasive medium.Te revolving tool polishes the workpiece surface while spinning at a high speed.

Abrasive Finishing Process.
Te experimental setup is prepared to be used for the spiral polishing method.It is made in such a way that the setup is suitable for this type of abrasive fnishing process.In this process, a spiral lapping mechanism is applied so that the polishing media fow over the surface to be fnished back and forth.Figure 9 shows the mechanism of spiral polishing using the screw.
During the rotation of the screw in its axis, the abrasive medium is taken by a spiral groove provided on the screw surface.In this way, the polishing medium abrades the rough surface, and the fnishing process is carried out.Te rotation of the screw can be either one direction or CW-CCW type.Due to the spiral movement of working media, the fnishing proves to be uniform.Properties of tool material used in spiral polishing are shown in Table 5.

EDM Machining Results
. After a careful literature survey, several process parameters were taken to carry out the hole-cutting procedure.To eliminate the potential for measurement error caused by oil contamination, samples were dried with hot air after each hole-cutting experiment.Te performance of the EDM technique to make these holes was assessed through process performances such as overcut, taper, and tool wear.As mentioned in the preceding section, the material removal rate was determined by comparing the weight of the sample before and after the cutting of holes using high-precision weighing equipment.Similarly, the tool wear rate was determined by comparing the tool's pre-and postmachining weights on a high-precision weighing 4 Journal of Engineering     Journal of Engineering machine.Ten, using an optical microscope, we determined the amount of overcut by comparing the diameter of the drilled holes in the workpiece to the estimated diameter of the cutting tool.All the trials determined the hole taper using an equation.Information on the results of 16 diferent experiments is shown in Table 6.

Spiral Finishing Process.
Te machined holes that are generated in the EDM process are fnished by the spiral fnishing process.Before conducting the spiral fnishing process, the circularity of each hole was examined by measuring the area and perimeter of the hole.Tese values of the area and perimeter of the hole were taken from the microscopic images of holes.After the experimentation of spiral fnishing, again, the circularity of each hole was measured by the same procedure.For measuring the circularity, the image processing software ImageJ Version 1.44 was used.Te value of the circularity of the hole indicates the quality of the hole.Holes having circularity value 1 indicate the hole to be ideally circular.Te measured circularity value for the holes before and after spiral fnishing is given in Tables 7 and 8 for the top and bottom surfaces.Te result of the percentage of improvement of circularity is shown in Table 9.
After the experimentation of spiral fnishing, again, the internal wall surface roughness of each hole was measured by a surface texture measuring instrument.Surface roughness, often shortened to roughness, is a component of surface texture.It is quantifed by the deviations in the direction of the normal vector of a real surface from its ideal form.If these deviations are large, the surface is rough; if they are small, the surface is smooth.In surface metrology, roughness is typically considered to be the high-frequency, short-wavelength component of a measured surface.

Journal of Engineering
However, in practice, it is often necessary to know both the amplitude and frequency to ensure that a surface is ft for a purpose.Ra is measured for the hole surface which is the arithmetical average value of all absolute distances of the roughness profle from the center line within the measuring length.Te measured values of surface roughness are shown in Table 10.

Analysis of Results of Spiral Finishing Process.
After conducting the spiral fnishing process of all 16 experiments designed using the Taguchi methodology, the results of circularity and surface roughness were analyzed by using graphical plots obtained in Minitab software (version 18).Tese plots are discussed here under.

Results and Discussion on Top Hole Circularity.
Figure 10 shows the graphical representation of the main efect plot for S/N ratios of top-hole circularity.Te graph is created with the help of Minitab software using diferent values of the four parameters, i.e., Powder concentration, Time of rotation, Speed of rotation, and Liquid media, with respect to the percentage improvement of top hole circularity.From the plot, it is seen that the circularity of holes improves when the powder concentration values are 5 and 9.
On the other hand, the circularity improvement is low while the powder concentration value is 3; also, taking the value 7, it gives the least improvement of hole circularity.Coming to the next parameter, i.e., time of rotation, the graph clearly shows that the circularity is achieved while the fnishing time of rotation is 2 minutes.Taking 1 minute time of rotation, the circularity improves but when the time of rotation during spiral fnishing is 3 or 4 minutes, it gives less improvement in circularity.Tat means a better fnishing result can be achieved with less time for fnishing operation.In the case of speed of rotation during spiral fnishing, it is observed from the graph that the speed of rotation plays an As the values of speed of rotation are taken at 30, 50, or 90 rpm, the circularity of holes get improved after spiral fnishing.Te result has been achieved while taking the value of 30 rpm for rotation speed.But taking a speed of rotation value of 70 gives the least improvement in fnishing result among all the experiments.For liquid media, the plot shows that improvement of hole circularity is achieved when the liquid medium for the abrasive mixture is made with handwash and liquid soap.In the case of liquid soap, the result is achieved.Taking glycerine and shampoo as liquid media has less efect on circularity improvements of holes.
Te top hole circularity result may be obtained by merging these four plots, which suggests that the four fnishing operation factors have varying impacts on the improvement of hole surface quality.Te circularity can be achieved by taking these values of parameters as powder concentration of 5 gm, time of rotation of Journal of Engineering 2 minutes, speed of rotation of 30 rpm, and liquid media as liquid soap.Tis is the result of the improvement of the top surface of the holes.

Results and Discussion on Bottom Hole Circularity.
Figure 11 shows the graphical representation of the main efect plot for S/N ratios of bottom-hole circularity.Te graph is also created with the help of Minitab software using different values of the four parameters, i.e., powder concentration, time of rotation, speed of rotation, and liquid media, with respect to the percentage improvement of bottom hole circularity.From the plot, it is seen that the circularity of holes improves when the powder concentration values are 3 and 7.
On the other hand, the circularity improvement is low while the powder concentration value is 9; also, taking the value 5, it gives the least improvement of hole circularity.Coming to the next parameter, i.e., time of rotation, the graph clearly shows that the circularity is achieved while the fnishing time of rotation is 3 minutes.Taking 1 minute time of rotation, the circularity improves but when the time of rotation during spiral fnishing is 2 or 4 minutes, it gives less improvement in circularity.Especially when the time of rotation is taken as 2 minutes, the graph shows very little improvement of bottom hole circularity.In the case of speed of rotation during spiral fnishing, it is observed from the graph that the speed of rotation plays an important role in spiral fnishing operation.When the values of speed of rotation are 30 or 90 rpm, the circularity of holes improved after spiral fnishing.Te result among all the experiments has been achieved while taking the value of 90 rpm for rotation speed.But taking a speed of rotation value of 50 or 70 rpm gives less improvement in the fnishing result.For liquid media, the plot shows that improvement of hole circularity is achieved when the liquid medium for the abrasive mixture is made with handwash, glycerine, and shampoo.In the case of liquid soap, the lowest quality of surface fnishing is achieved.Taking liquid soap as liquid media, it has very little efect on circularity improvements of bottom holes.Te combination of these four plots yields a bottom-hole circularity result, indicating that the four fnishing operation factors infuence hole surface quality improvement to varying degrees.Te circularity can be achieved by taking these values of parameters as powder concentration of 3 gm, time of rotation of 3 minutes, speed of rotation of 90 rpm, and liquid media as handwash.Tis is the result of the improvement of the bottom surface of holes.

Results and Discussion on Surface Roughness.
Figure 12 shows the graphical representation of the main efect plot for S/N ratios of surface roughness.Te graph is also created with the help of Minitab software using different values of the four parameters, i.e., Powder concentration, Time of rotation, Speed of rotation, and Liquid media, with respect to the surface roughness of the internal wall of Titanium holes.From the plot, it is seen that the surface roughness of holes improves when the powder concentration values are 5 and 7. On the other hand, the surface roughness improvement is low while the powder concentration value is 3; also, taking the value 9, it gives the least improvement of roughness (Ra).Coming to the next parameter, i.e., time of rotation, the graph clearly shows that the surface roughness is achieved while the fnishing time of rotation is 3 minutes.Taking 1 minute and 4 minutes of rotation, the roughness is not so improved but when the time of rotation during spiral fnishing is 2 minutes, it gives the lowest improvement in surface For liquid media, the plot shows that improvement of surface roughness is achieved when the liquid medium for the abrasive mixture is made with handwash.In the case of liquid soap, the lowest quality of surface fnishing is achieved.Glycerine and shampoo as liquid media have average efects on surface roughness.
By combining these four plots, it can be concluded that for roughness values (Ra), the four parameters of the fnishing operation have more or less efects on hole surface quality improvement.Te surface roughness of this spiral fnishing can be achieved by taking these values of parameters as powder concentration of 5 gm, time of rotation of 3 minutes, speed of rotation of 90 rpm, and liquid media as handwash.Tis is the result of the improvement of surface roughness.

Analysis of Microscopic Images of Finished Holes.
Using an optical measuring microscope as shown in Figure 13, images of the hole at the top surface and bottom surface were taken for all experiments and the quality of the holes was compared using diferent images.In Figure 13, the quality of holes machined by EDM is compared while machining at diferent parameter settings.By observing these images, it is clear that by proper controlling of process parameters, high-quality holes can be achieved during EDM drilling of titanium material.In addition, the images of the identical holes taken before and after spiral polishing are compared.Te results indicate that improved surface fnishing of the inside walls of holes may be obtained by using spiral polishing at diferent rotational speeds and with lower powder concentrations.In Figure 13, from the microscopic photograph of holes before and after spiral fnishing at diferent fnishing parameters, it can be observed that the internal surface of holes has been improved in terms of surface quality after spiral polishing.

Conclusions and Future Work
Tis investigation uses an abrasive medium applied to a microlapping surface to examine the machining properties of the spiral fnishing technique.Te following fndings are supported by the developing experimental evidence: (a) When the current, Ton, and Tof are all higher, the hole-cutting on the material has a very rough fnish.Even so, it can make a hole with a melted surface on the object.(b) A smooth surface (Ra) was achieved by determining the optimal parameter values.One possible option to establish the parameters for the process conditions utilized in the research is to use handwash as the liquid medium, with a powder content of 5 gm, a rotation period of 3 minutes, and a rotation speed of 90 rpm.(c) Experiments were done to fnd out the speed of the motor shaft's movement, the time it takes for the shaft to turn, the amount of grit in the medium, and the type of medium (liquid or solid) that afected circularity.Te circularity for bottom surface holes can be achieved by setting the parameters to 3 g powder content, 3 minutes of spin, 90 rpm rotation speed, and handwash as the liquid medium.You can make the holes on the top surface round by setting the powder content to 5 g, the time of rotation to 2 minutes, the speed of rotation to 30 rpm, and the liquid medium to liquid soap.(d) Utilizing the signal-to-noise ratio (SNR) analysis, determine the ideal parameter combination that maximizes circularity and minimizes Ra.

Future Work
(a) Exploit innovative optimization techniques to improve spiral fnishing on titanium EDM-drilled holes for better surface quality and faster machining.(b) Analyze titanium's specifc features to optimize spiral fnishing process settings for material hardness and thermal conductivity.

2. 1 .
Material Preparation.A sheet of commercially pure titanium (Ti) measuring 150 mm in length, 85 mm in width, and 3.5 mm in thickness served as the workpiece.Te fowchart of the experimental setup is shown in Figure 1.

Figure 1 :
Figure 1: Flowchart of the experimental setup.

Figure 2 :
Figure 2: Photographic view of (a) tungsten tool and (b) titanium material before machining in EDM.

Figure 3 :
Figure 3: Photographic view of titanium material after making through holes on EDM.

Figure 4 :
Figure 4: Machining on lathe for making the system for motor holding.

Figure 5 :
Figure 5: Photographic view of angel plate with attachment for holding motor.

Figure 6 :
Figure 6: Photographic view of angel plate with motor and drill chuck attachments.

Figure 7 :
Figure 7: Photographic view of four bushes made for additional plate attachments and drill chuck attachment.

Figure 8 :
Figure 8: Diferent angle photographic view of complete setup for spiral.

Figure 9 :
Figure 9: Photographic view of complete setup with abrasive mixture holding system.

Figure 12 :
Figure 12: S/N ratio plot of surface roughness.

Powder Concentration 3 Figure 13 :
Figure 13: Optical photograph of holes before and after spiral fnishing at diferent parameter settings.

Table 2
displays the characteristics of common hole-cutting tool materials.

Table 1 :
Properties of workpiece material.

Table 2 :
Properties of tool material used in hole cutting.Plan of Experiment.Te EDM process parameter in this work is mentioned in Table3.Four diferent process parameters, namely, Powder Concentration (3, 5, 7, and 9 gm), Time of rotation (1, 2, 3, and 4 min.),Speed of rotation (30, 50, 70, and 90 rpm), Liquid media (Handwash, Glycerine, Shampoo, and Liquid Soap), are selected with their four diferent levels in this work.A total of 16 experiments done as per Taguchi's L 16 orthogonal array will be considered in this EDM approach as shown in Table

Table 4 :
Experimental combination of process parameters for spiral fnishing.

Table 3 :
Details of process parameters and their ranges.

Table 5 :
Properties of tool material used in spiral polishing.

Table 6 :
Experimental results of EDM process performances.

Table 7 :
Results of circularity measurement of top surface.

Table 8 :
Results of circularity measurement of the bottom surface.

Table 9 :
Results of improvement of hole circularity.

Table 10 :
Results of surface roughness.