Demand for Chemically Strengthened (CS) glass has steadily increased for the past decade predominantly by the electronic devices industry. One of the major reasons are due to its superior strength and crack resistance properties. However, due to its superior properties which resistant to compressive loads causing drawback to the subsequent secondary manufacturing process i.e. hole drilling. Conventional drilling process towards this glass tends to generate high tensile thrust that consequently affect the hole performances and accuracy. Considering these facts, in this paper a new drilling technique which assisted by the ultrasonic vibration frequency known as Rotary Ultrasonic Assisted Drilling (RUAD) is

propose aim to increase the hole quality. A set of experimental work was conducted in order to assess the effects of the RUAD parameter namely cutting speed, feed rate, ultrasonic frequency and vibration amplitude towards hole quality. The analytical results demonstrated that the presence of the intermittent ultrasonic vibration amplitude was able to minimize the chipping area and enhance the hole quality with acceptable tolerance value

Abdul Aziz, Mohd Sanusi

Kasim, Mohd Shahir

Kasman, Muhammad Zaki

Lamat, Arshad

Liew, Pay Jun

Raja Abdullah, Raja Izamshah

Raja Abdullah, Raja Syamsul Azmir

Rosman, Muhammad Rafiq

Universiti Teknikal Malaysia Melaka (UTeM) Repository

International Journal of Nanoelectronics and MaterialsVolume 14 (Special Issue) August 2021 [353-362]___________________________________*Corresponding author: izamshah@utem.edu.myQuality Evaluation on Rotary Ultrasonic Assisted Drilling forChemically Strengthened GlassR. Izamshah1*, A. Lamat2, M. Rafiq2, M.Z. Kasman2, M.S. Kasim1, P.J. Liew2 , M.S.A. Aziz2 and R.S.A. Abdullah31Advanced Manufacturing Centre (AMC), Universiti Teknikal Malaysia Melaka,Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia2Fakulti Kejuruteraan Pembuatan, Universiti Teknikal Malaysia Melaka,Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia3School of Information Technology and Electrical Engineering, The University of Queensland,Brisbane, Queensland 4072, AustraliaABSTRACTDemand for Chemically Strengthened (CS) glass has steadily increased for the past decadepredominantly by the electronic devices industry. One of the major reasons are due to itssuperior strength and crack resistance properties. However, due to its superior propertieswhich resistant to compressive loads causing drawback to the subsequent secondarymanufacturing process i.e. hole drilling. Conventional drilling process towards this glasstends to generate high tensile thrust that consequently affect the hole performances andaccuracy. Considering these facts, in this paper a new drilling technique which assisted bythe ultrasonic vibration frequency known as Rotary Ultrasonic Assisted Drilling (RUAD) ispropose aim to increase the hole quality. A set of experimental work was conducted inorder to assess the effects of the RUAD parameter namely cutting speed, feed rate,ultrasonic frequency and vibration amplitude towards hole quality. The analytical resultsdemonstrated that the presence of the intermittent ultrasonic vibration amplitude wasable to minimize the chipping area and enhance the hole quality with acceptable tolerancevalue.Keywords: Precision drilling, rotary ultrasonic assisted drilling, chemicallystrengthened glass.1. INTRODUCTIONDue to its superior properties i.e. high durability and high strength, the application of ChemicallyStrengthened (CS) glass has steadily increased. Compared to the thermal tempering glassproperties, CS glass outperform the performances up to six times in terms of toughness andresistance to crack. For this reason, most of the CS glass application usage are predominantly bythe electronic devices industry such as camera lens, optical component, mobile phone, tablet PCsscreen, etc. [1-2]. In such aforementioned applications, micro holes drilling is required as toserve for the particular purposes such as camera lenses, speakers and proximity sensors asshown in Figure 1.R. Izamshah, et al. / Quality Evaluation on Rotary Ultrasonic Assisted Drilling…354Figure 1.Micro holes’ positions at mobile phone screen.However, due to its superior properties which resistant to impact loads has cause problem tothe subsequent secondary manufacturing process i.e. hole drilling. Conventional drilling processtowards this glass tends to generate high tensile thrust that consequently affect the holeperformances and accuracy. Therefore, significant development on techniques for processing CSglass has steadily increase for the past year. Recently, an ultrasonic application to improve themachining process has gained great attention with promising result especially for hard andbrittle material known as Ultrasonic machining (USM). In USM process, the material are removesvia micro chipping and hammering of abrasive slurry to the part surface with 20-40 kHzvibration [3-4]. By employing this technique, the thrust force that create crack initiation forbrittle material such as glass and ceramic can be minimized. Although USM provide withpromising result, its low in material removal rate limits its application. Based on this, with theaim to improve the hole quality for drilling CS glass this paper propose a new drilling techniquewhich assisted by the ultrasonic vibration frequency known as Rotary Ultrasonic AssistedDrilling (RUAD).Unlike USM process, for RUAD the material are removes through the combination betweenultrasonic vibration frequency and rotating carbide drill bit. Theoretically, by incorporatingbetween both actions causes the cutter to shear whilst periodically vibrate perpendicular to thework surface creating an intermittent cuts at a constant feed that substantially decrease thethrust force magnitudes and improve the material removal rate [5-6]. Rotary ultrasonicmachining of borosilicate crown glass has been reported by Zeng et al. [7]. They claimed that byemploying ultrasonic vibration capable to minimize the magnitudes of compressive loads andreduce the hole chipping size. In other feasibility attempt on ultrasonic machining of K9 glass,Zhang et al. showed that lateral cracks can be minimized through compressed air as coolant [8].Figure 2 depicts the mechanics of RUADmaterial removal process.International Journal of Nanoelectronics and MaterialsVolume 14 (Special Issue) August 2021 [353-362]355Figure 2.Mechanic of cutting for RUAD.Although several researchers have claimed on the success of RUAD for glass material, one thingto be highlighted is the type of glass used in those experiment were made from heatstrengthening method glass which are six times less tough than the chemically strengtheningmethod. Hence, in this paper, a feasibility study of RUAD on chemically strengthening glass wasperformed to evaluate the occurrence of surface chipping at the hole entry and exit. Theevaluation will include on the influences of RUAD parameter namely cutting speed, feed rate,ultrasonic frequency and vibration amplitude towards hole quality.2. EXPERIMENTAL SETUPA one mm thickness CS glass manufactured by Corning Inc. was employed as a specimen for theexperimental work. The glass has a density of 2.39 g/cm3, Young Modulus of 69.3 GPa, Poisson’sRatio of 0.22 and Shear Modulus of 28.5 GPa. Table 1 depicted detailed properties of chemicallystrengthening (CS) glass used in the experiment.Table 1 End mill specificationR. Izamshah, et al. / Quality Evaluation on Rotary Ultrasonic Assisted Drilling…356The drilling experiment was conducted using a cnc milling machine. A dedicated ultrasonictooling system was designed and developed to suit with the machine spindle to perform theRUAD process. The ultrasonic tooling system capable to transmit ultrasonic frequency from thegenerator oscillating from 20 kHz to 27 kHz with maximum of 3 µm amplitude. An aluminaoxide abrasive grit with the concentration ranging 5-15 % was used throughout the experiment.The developed RUAD system and CS glass arrangement are illustrate in Figure 3 below. Inaddition, special design jig and fixturing were fabricated to minimize the present of chatter.Since the CS glass has superior strength and crack resistance properties a dedicated jig designwas fabricated to hold the sample. The design of the work holding device need to be rigid tocater the compressive stress occur during the RUAD process in both entry and exit surfaces.Figure 3. Rotary ultrasonic drilling setup and tool holder.A special designed electroplated diamond tool dedicated for drilling CS glass consist of two chipdischarge area was employed. Table 2 and Figure 4 depicted detailed specification for theelectroplated diamond tool.Table 2 Electroplated diamond tool specificationsParameter ValueTool diameter 1.0 mmTool shank 3 mmDiamond grit size 25-35 µmMaterial SK5International Journal of Nanoelectronics and MaterialsVolume 14 (Special Issue) August 2021 [353-362]357Figure 4. SEM images of the tool tip.Historical Design matrix of Response Surface Methodology (RSM) technique was used as theDesign of Experiment (DoE) to evaluate the RUAD parameters input to the output responses.The independent variables and levels namely; spindle speed (A), feed rate (B), ultrasonicfrequency (C) and vibration amplitude(D) as explained in Table 3. The upper and lower limitvalue for the input variables were based from cutting tool’s manufacturer recommendationsand from the literature [2]. Optical microscope was used to captured the drilled holes images forthe analysis. Subsequently, the image to be process by the ImageJ® software for measuring thechipping area at both entry and exit surface. To ensure the accuracy of the reading, themeasurements were done five times.Table 3 Factors and levelsFactor Range UnitCutting speed, N 6000-7000 (rpm)Feed rate, f 0.25-0.75 (mm/min)Frequency, f 20-27 (kHz)Amplitude, a 1-3 (μm)3. RESULTS AND DISCUSSIONTable 4 and Figure 5 tabulated the calculated chipping area for the entry and exit surfacerespectively. The observed chipping area value varied between 0.4976 mm2 to 1.1706 mm2 forentry surface and 0.2666 mm2 to 0.9196 mm2 for exit surface. The variations on the observedchipping area values indicate that the RUAD drilling parameters has significant effects on thehole’s quality.Table 4 Chipping area results for entry and exit surfaceRun Frequency Amplitude Speed Feed rate Entry chipping area Exit chipping area(kHz) (µm) (rpm) (mm/min) (mm²) (mm²)1 23.5 3 6500 0.75 0.957 0.4792 27 1 6500 0.5 1.17 0.4823 20 1 6500 0.5 1.11 0.9194 27 3 6500 0.5 1.026 0.8465 20 2 6500 0.25 1.017 0.5456 23.5 2 6500 0.5 0.738 0.667 23.5 3 7000 0.5 1.013 0.8878 23.5 2 7000 0.25 0.91 0.3539 20 3 6500 0.5 1.014 0.88110 23.5 2 6500 0.5 0.808 0.51111 23.5 2 6000 0.25 0.775 0.4412 20 2 7000 0.5 0.824 0.736R. Izamshah, et al. / Quality Evaluation on Rotary Ultrasonic Assisted Drilling…35813 23.5 1 7000 0.5 0.998 0.89814 27 2 6000 0.5 0.767 0.56715 23.5 1 6500 0.75 0.83 0.71216 23.5 2 7000 0.75 0.678 0.38917 20 2 6000 0.5 0.684 0.54118 23.5 2 6500 0.5 0.645 0.40719 23.5 1 6000 0.5 0.921 0.86820 23.5 3 6000 0.5 1.01 0.49621 20 2 6500 0.75 0.583 0.3622 23.5 1 6500 0.25 0.931 0.89523 27 2 6500 0.25 1.013 0.37724 23.5 3 6500 0.25 0.543 0.3925 23.5 2 6500 0.5 0.566 0.46926 23.5 2 6500 0.5 0.564 0.42127 27 2 6500 0.75 0.497 0.26628 23.5 2 6000 0.75 0.939 0.87829 27 2 7000 0.5 0.892 0.623Figure 5. Comparison between chipping area at entry and exit surface.Referring to the obtained results, it was found that for all the runs entry chipping area werelarger than at the exit. One of the possible reason for this cause can be related to the knockingimpact at the beginning stage of the drill process i.e. tool tip approaching the glass surface. Atthis stage, due to the compressive stress resulting from the diamond grits and alumina oxideparticles chipping the glass surface. The magnitudes of the compressive stress will affect thecracks propagation rate. Figures 6 and 7 show the holes and chipping areas for the minimumand maximum at the entry and exit surface respectively.International Journal of Nanoelectronics and MaterialsVolume 14 (Special Issue) August 2021 [353-362]359(a) Minimum chipping area (b) Maximum chipping areaFigure 6. Entry holes’ image.(a) Minimum chipping area (b) Maximum chipping areaFigure 7. Exit holes’ image.Statistical ANOVA (Table 5) was performed to further investigated the relationship of RUADparameters towards the chipping area for both entry and exit surfaces. Based on the ANOVA, aquadratic model was selected to exemplify the cutting parameters effects towards the chippingarea for both entry and exit surfaces.In addition, from the analysis if the obtained P-values of the cutting parameters smaller than0.05 specify that it is statistically significant towards the outputs, in this case entry and exitchipping areas [9-10]. For both models (entry and exit), the lowest calculated P-value werefound to be twice of vibration amplitude factor i.e. B2. The results revealed that, the hammeringimpact resulting from the vibration amplitude intensely has a direct effect towards the holequality.Although others parameters were not statistically significant, one thing to be highlighted arethese parameters need to be considered i.e. spindle speed and feed rate as this experimentalwork employed a RUAD technique. Excluding these parameters will make the experimentalbecome a normal USM process. Therefore, further analysis on the effect of RUAD on materialremoval rate need to be perform to access the feasibility on implementing RUAD technique fordrilling CS glass material which are not covered in this paper.R. Izamshah, et al. / Quality Evaluation on Rotary Ultrasonic Assisted Drilling…360Table 4 ANOVA results for entry and exit surfaceFigure 8 and 9 illustrate a 3D response surface plot of the RUAD parameter and chipping areasfor the entry and exit surface respectively. From the figures it shows that, the effects of RUADcan significantly affect the quality of the holes. Unsuitable combination of parameter will resultin large edge chipping area due to the high knocking impact on the glass surface.Figure 8. Surface plot of RUAD parameter and chipping areas for hole entry.Entry ExitSource SS DoF MS F-value Prob>F Source SS DoF MS F-value Prob>FModel 0.5789 14 0.0414 1.4545 0.2462 Model 0.7753 14 0.0554 1.7541 0.1524A 0.0019 1 0.0019 0.0668 0.7985 A 0.0566 1 0.0566 1.7928 0.202B 0.0129 1 0.0129 0.4538 0.512 B 0.0529 1 0.0529 1.6756 0.2163C 0.0039 1 0.0039 0.1372 0.7183 C 0.0008 1 0.0008 0.0253 0.977D 0.434 1 0.4340 15.2661 0.2368 D 0.0006 1 0.0006 0.0190 0.8909A² 0.0856 1 0.0856 3.0110 0.1047 A² 0.0054 1 0.0054 0.1710 0.6853B² 0.3379 1 0.3379 11.8858 0.0039 B² 0.3424 1 0.3424 10.8457 0.0053C² 0.0522 1 0.0522 1.8362 0.1968 C² 0.0588 1 0.0588 1.8625 0.1937D² 0.0001 1 0.0001 0.0035 0.9865 D² 0.0693 1 0.0693 2.1951 0.1605AB 0.0006 1 0.0006 0.0211 0.8888 AB 0.0402 1 0.0402 1.2734 0.2781AC 0.0001 1 0.0001 0.0035 0.9605 AC 0.0048 1 0.0048 0.1520 0.7016AD 0.0025 1 0.0025 0.0879 0.7734 AD 0.0013 1 0.0013 0.0412 0.8424BC 0.0014 1 0.0014 0.0492 0.825 BC 0.0328 1 0.0328 1.0390 0.3256BD 0.0663 1 0.0663 2.3321 0.149 BD 0.0185 1 0.0185 0.5860 0.4567CD 0.0392 1 0.0392 1.3789 0.2599 CD 0.0404 1 0.0404 1.2797 0.277Residual 0.398 14 0.0284 Residual 0.442 14 0.0316International Journal of Nanoelectronics and MaterialsVolume 14 (Special Issue) August 2021 [353-362]361Figure 9. Surface plot of RUAD parameter and chipping areas for hole exit.Figure 6 shows the SN ratios graph for cutting force. Lower cutting force values are required toproduce good machining quality. This is because the cutting force is often closely related to thefriction that leads to the cutting temperature. Therefore, 'smaller is better' is chosen to obtaingood machining quality. This graph shows that the cutting force is influenced by helix angle andspindle speed followed by rake angle and number of flutes. Based on this graph, the low cuttingforce value can be obtained if the helix angle value (60°) clearance angle value (18°), feed ratevalue (500 mm/min) and depth of cut value (1.5 mm) is high and the spindle speed value (1000rpm), rake angle value (5°) and number of flutes value (2) is low.4. CONCLUSIONIn this paper, experimental investigation of Rotary Ultrasonic Assisted Drilling (RUAD) ofchemically strengthen glass was performed. A set of experimental work was conducted toassess on the effects of RUAD parameter namely cutting speed, feed rate, ultrasonic frequencyand vibration amplitude towards chipping areas for the entry and exit surface. Theexperimental work proved that RUAD technique can be used to drill micro size hole atchemically strengthen glass surface with acceptable tolerance. However, further analysis on theeffect of RUAD on material removal rate need to be perform to consider on the feasibility ofimplementing RUAD technique for drilling chemically strengthen glass material.R. Izamshah, et al. / Quality Evaluation on Rotary Ultrasonic Assisted Drilling…362ACKNOWLEDGEMENTSThe authors are grateful to Malaysian Ministry of Higher Education and Universiti TeknikalMalaysia Melaka for their technical and financial support under Prototype Research GrantScheme No: PRGS/1/2019/TK03/UTEM/02/1 and GLuar/TOKUSHIMA/2017/FKP-AMC/A00010.REFERENCES[ 1] K. Noma, Y. Kakinuma, T. Aoyama, and S. Hamada, Journal of Advanced Mechanical Design,Systems and Manufacturing, vol 9, no. 2, (2015) pp.1-11.[ 2] K. Noma, Y. Takeda, T. Aoyama, Y. Kakinuma, and S. Hamada, Procedia CIRP, vol 14, (2014)pp.389-394.[ 3] R Azlan, R Izamshah, MS Kasim, S Ding, M Akmal, J. of Adv. Manuf. Technol. vol. 13, no.2(1), (2019) pp.1-13.[ 4] A. Sharma, A. Babbar, V. Jain, D. Gupta, Adv. Prod. Ind. Eng. (2021), pp.369-378.[ 5] H. Wang, Z.J. Pei and W. Cong, Int. J. Mach. Tools Manuf., vol 152, (2020) pp.103540.[ 6] Dongxi Lv, Mingda Chen, Youqiang Yao, Chun Yan, Gang Chen, Yingdan Zhu, Ultrasonics,vol 115 (2021) pp.106448.[ 7] Zeng, W., Li Z., Pei Z., Treadwell C., Int. J. Mach. Tools Manuf. vol 45, no. 12, (2005)pp.1468–1473,[ 8] Zhang, C.; Feng, P.; Zhang, J.; Wu, Z.; Yu, D., Int. J. Manuf. Technol. Manag., vol 25, no. 4,(2012) pp.248–266.[ 9] M Firdauz, R Izamshah, M Akmal, MS Kasim, S Ding, J. of Adv. Manuf. Technol. vol 14, no.2(2), (2020) inpress.[ 10] M. Amran, S. Laily, H.I.K. Nor, N.I.S. Hussein, M.R. Muhamad, B. Manshoor, M.A. Lajis, R.Izamshah, M. Hadzley, R.S. Taufik, Applied Mechanics Materials, vol 465, (2014) pp.1214-1218.

Quality Evaluation On Rotary Ultrasonic Assisted Drilling For Chemically Strengthened Glass

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Quality Evaluation On Rotary Ultrasonic Assisted Drilling For Chemically Strengthened Glass

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