th International & 26th All India Manufacturing Technology, Design and - PDF document

th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT Guwahati, Assam, India
Experimental Evaluation and Optimization of Dry Drilling Parameters of AISI304 Austenitic Stainless Steel using Different Twist Drills Nayan G Kaneriya1*,Gaurav Kumar Sharma2 Mechanical Engineering Department1*, R.K University, Rajkot-360020, India, E-Mail: nayukaneriya@gmail.com Mechanical Engineering Department, R.K University, Rajkot-360020, India, E-Mail: gaurav.sharma@rku.ac.in Abstract AISI 304 austenitic stainless steel is widely used in areas such as buildings, automobile, aircrafts and medical surgical equipment, but machining of AISI 304 austenitic stainless steel is difficult due to high tensile strength, high ductility, low heat conductivity and high fracture toughness. The cutting temperature at drill tool-chip interface affects drill hole quality, lowers tool life, reduces hole finishing and blunt edges of drill tool that decreases productivity. The main objective of this work is to reduce temperature caused in drill tool while dry drilling of AISI 304 austenitic stainless steel by optimizing drilling parameters and selecting suitable drill tool material . The performances of HSS, Cobalt coated HSS and K20 Solid Carbide drill tool were evaluated in terms of temperature, material removal rate and drill tool life. The performance parameters viz. feed rate and spindle speed are experimentally investigated to minimize the temperature at drill tool bit. The experiments were carried out on vertical machining center (VMC 1050) machine equipped with maximum spindle speed of 8000 rpm and 15.8 kW drive motor. VMC part programs were created with ProENGINEER CAD/CAM software on an Intel IV (1.0 GHz) personal computer. The values of drill tool bit temperatures were measured using infrared thermometer. The experiments were performed by varying spindle speeds from 1200 rpm to 1500 rpm at constant feed rate 0.05 mm/rev and varying feed rate from 0.05 mm/rev to 0.09 mm/rev for each drill tool material. Experimental results were simulated with DEFORM 3D software. Drilling parameters like feed rate and spindle speed were optimized to minimize temperature and to maximize material removal rate (MRR) using responsesurface methodology (RSM), a multi objective optimization technique. Keywords: Drilling, AISI 304, Temperature, RSM.1 Introduction Drilling is a significant metal cutting operation compared to other traditional machining processes (Chenet al. 1999). The drill point geometry, drill and workpiece materials, drilling parameters like feed rate and spindle speed directly affect drill performance. Accuracy of drilled hole, surface roughness of machined surface, drill flank wear and burr height depend on tool material (Ulas Caydas et al. 2011). High hot hardness and low coefficient of friction are basic requirements of drill tool since drill tool have to sustain high frictional forces, high temperature and large mechanical loads (Kalidaset al. 2001). Coatings on drill tools are rottenly used to provide hard and chemically stable surface with thermal protection which improves tool life and hole quality (Chenet al. 1995). AISI 304 austenitic stainless steel is widely used in areas where high corrosion occurs (Ulas Caydas et al.2011). It is frequently used in air craft fittings, cryogenic vessels and aerospace components such as bushings, shafts, valves and special screws (Mahdavinejadet al. 2011). Machining of AISI 304 austenitic stainless steel is difficult due to its superior properties like high tensile strength, high toughness, low thermal conductivity and high wear resistance (Groover 2010). Due to above properties, high temperature emerges between drill bit and chip which directly affect surface roughness of drilled hole, tool wear, hole perpendicularity and hole cylindricity (Eyup Bagci et al.2005). In order to increase the tool life, coating on a tool is broadly used in modern days (Ulas Caydas et al. 2011). Linet al. (2000) have found that TiN-coated or TiCN-coated drills have better performance compared to CrN-coated or TiAlN-coated drills in drilling of SUS 304 stainless steel. Chenet al. (2000) have evaluated performances of TiN-coated and TiCN-coated twist drills in drilling of JIS SUS 304 stainless steel. They Experimental Evaluation and Optimization of Dry found that TiN- coated drill have better cutting performance. The main objective of this article is to identify effects of drill tool materials and drilling parameters such as feed rate, spindle speed and load on drill bit temperature and tool life for dry drilling of AISI 304 austenitic stainless steel. The optimal parameter values obtained from the study will minimize undesir drilling defects and hence reduce manuf 2 Experimental work The drilling experiments involved dry drilling of AISI 304 austenitic stainless steel with vertical machining centre (VMC 1050) machine equipped with maximum spindle speed of 8000 rpm and 15.8 kW drive motor. VMC part programs were created with ProENGINEER CAD/CAM software on an Intel IV (1.0 GHz) personal computer. After completely drilled the hole, drill tool was immediately removed from workpiece and drill bit temperature was measured using infrared thermometer. 2.1 Drilling tools and workpiece materials For the purpose of experiment HSS, Cobalt coated HSS and K20 solid carbide drill tools were used for the dry drilling of AISI 304 austenitic stainless steel. dimensional properties of HSS, Cobalt coated HSS and K20 Solid Carbide drill tools are given Table 1 Dimensional properties of coated HSS and K20 Solid C arbide drill tools Parameters Specifications Tool diameter 10 mm Drill type 2 flute Point angle 140 Helix angle 30
Flute length 90 mm for HSS 110 mm for Cobalt coated HSS 110 mm for K20 Solid carbide Shank length 45 mm for HSS 40 mm for Cobalt coated HSS 40 mm for K20 Solid carbide Shank type Cylindrical In the experiments , workpiece consisted of AISI 304 austenitic stainless steel. The dimen workpiece material are: 300 mm of length, 200 mm of width and 20 mm of thickness. Table 2 information on mechanical and physical the workpiece material (Ulas Caydas et al. 2.2 Exp erimental setup and drilling conditions The experimental setup for drilling of AISI 304 austenitic stainless steel with vertical machining centre Experimental Evaluation and Optimization of Dry Drilling Parameters of AISI304 Austenitic Stainless Steel using Different Twist Drills coated drill have better cutting The main objective of this article is to identify effects of drill tool materials and drilling parameters such as feed rate, spindle speed and load on drill bit dry drilling of AISI 304 The optimal parameter values study will minimize undesir able drilling defects and hence reduce manuf acturing cost. The drilling experiments involved dry drilling of AISI 304 austenitic stainless steel with vertical machining centre (VMC 1050) machine equipped with maximum spindle speed of 8000 rpm and 15.8 kW drive programs were created with ProENGINEER CAD/CAM software on an Intel IV (1.0 GHz) personal computer. After completely drilled the hole, drill tool was immediately removed from workpiece and drill bit temperature was measured using Drilling tools and workpiece materials HSS, Cobalt coated HSS and K20 solid carbide drill tools were used for the dry drilling of AISI 304 austenitic stainless steel. The HSS, Cobalt coated HSS and in Table 1. properties of HSS, Cobalt arbide drill tools Specifications 10 mm 2 flute 140

90 mm for HSS 110 mm for Cobalt coated HSS 110 mm for K20 Solid carbide 45 mm for HSS 40 mm for Cobalt coated HSS 40 mm for K20 Solid carbide Cylindrical , workpiece consisted of AISI stainless steel. The dimen sions of the are: 300 mm of length, 200 mm of width and 20 mm of thickness. Table 2 exhibits detailed and physical properties of et al. 2011). erimental setup and drilling The experimental setup for drilling of AISI 304 austenitic stainless steel with vertical machining centre (VMC 1050) machine is shown in Figure 1. The AISI 304 austenitic stainless steel plate was fix shown in Figure 1 and drill tool was fixed in tool holder with help of sleeve. An i nfrared thermometer was used to measure temperatures of drill tool bits. Figure 1 Close up photo of experimental setup To drill AISI 304 austenitic stainless steel workpiece material, three drilling tools HSS, Cobalt coated HSS and K20 Solid Carbide tool different spindle speeds and different feed rates. The experiments were divided in three drilling tests depending o n drill tool materials. consisted of HSS drill tool, d rilling test 2 consist Cobalt coated HSS drill tool and d rilling test 3 consist of K20 Solid C arbide drill tool. Location on workpiece are shown in Figure 2. tests, holes numbers of 1 to 4 ( as 2)were drilled at constant feed rate 0.05 Figure 2 Location of 24×Ø10 holes in AISI 304 austenitic stainless steel plate mm/rev and varying spindle s peed from 1200 rpm to 1500 rpm, i.e. for hole number 1, Drilling Parameters of AISI304 Austenitic Stainless Steel using Different Twist Drills 
(VMC 1050) machine is shown in Figure 1. The AISI 304 austenitic stainless steel plate was fix ed in vise as drill tool was fixed in tool holder nfrared thermometer was used to measure temperatures of drill tool bits. Figure 1 Close up photo of experimental setup AISI 304 austenitic stainless steel workpiece material, three drilling tools HSS, Cobalt Carbide tool s were used at different spindle speeds and different feed rates. The divided in three drilling tests n drill tool materials. Drilling test 1 rilling test 2 consist edof rilling test 3 consist ed arbide drill tool. Location s of the holes are shown in Figure 2. For all drilling as shown in Figure drilled at constant feed rate 0.05 holes in AISI 304 austenitic stainless steel plate peed from 1200 rpm to 1500 rpm, i.e. for hole number 1, 2, 3 and 4 spindle th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT Guwahati, Assam, India
speeds were 1200, 1300, 1400 and 1500 rpm respectively. For all drilling tests, holes numbers of 5 to 8 (as shown in Figure 2) were drilled at constant spindle speed of 1500 rpm and feed rate varying from 0.06 mm/rev to 0.09 mm/rev, i.e. for hole number 5, 6, 7 and 8 feed rates were 0.06, 0.07, 0.08 and 0.09 mm/rev respectively. The drill bit temperature and maximum load on the machine were recorded for each successfully drilled hole. The depth of holes were kept constant (20 mm) throughout the experiments. Table 2 Mechanical and thermal properties of AISI 304 austenitic stainless steel Property Amount Density 8000 Poisson’s ratio 0.28 Elastic modulus (GPa) 194 Tensile strength (MPa) 515 Yield strength (MPa) 206 Elongation (%) 41 Hardness (HRB) 87 Thermal expansion (10 - 6 /
C) 17.4 Thermal conductivity(W/m-k) 15.8 2.3 Experimental results and discussions In dry drilling of AISI 304 austenitic stainless steel using HSS drill tool (Drilling test 1), hole number of 1 to 5 were successfully drilled but as feed rate was increased from 0.06 to 0.07 mm/rev for hole number 6, drill tool weared and was not able to drill the hole. Therefore holenumber 6 is a blind hole.It was concluded that drilling at 1500 rpm spindle speed and feed rate above 0.06 mm/rev using HSS drill for workpiece material AISI 304 austenitic stainless steel is uneconomical. For Cobalt coated HSS drill tool (Drilling test 2), hole number of 1 to 6 were successfully drilled but during drilling of 7 number of hole, tip portion of drill blunted and weared and it was blind hole. It can be concluded that at 1500 rpm and feed rate above 0.07 mm/rev drilling is uneconomical. The holes drilled by K20 Solid Carbide drill tool (Drilling test 3) were successfully drilled. The drill tool bit temperatures and maximum loads on machine were recorded for all successfully drilled holes. The photograph of drilled workpiece made with AISI 304 austenitic stainless steel after drilling experiments is shown in Figure 3. Figure 3 Photograph of AISI 304 austenitic stainless steel plate after performing experiments Measured values of temperature and maximum load for each successfully drilled hole are listed in Table 3. In Table 3, 1 to 5 Exp. Runs, 6 to 11 Exp. Runs and 12 to 19 Exp. Runs exhibit 1 to 5 holes of drilling test 1, 1 to 6 holes drilling test 2 and 1 to 8 holes of drilling test 3 respectively. Table 3 Experimental measured values of temperature and maximum load Exp. Runs Measured temperature (°C) Maximum load (N) 1 220 1176 2 250 1098 3 265 940 4 295 860 5 335 940 6 200 1098 7 235 1020 8 260 1000 9 290 810 10 310 860 11 340 1176 12 190 1040 13 230 860 14 253 700 15 260 630 16 272 850 17 290 1020 18 304 1255 19 330 1333 The effects of spindle speed on temperature and maximum load are shown in Figure 4 and Figure 5 respectively. Experimental Evaluation and Optimization of Dry Drilling Parameters of AISI304 Austenitic Stainless Steel using Different Twist Drills 
Figure 4 Spindle speed v/s temperature When spindle speed varies from 1200 rpm to 1500 rpm, temperature increases and maximum load decreases for all three drill tool materials. When feed rate varies from 0.05 mm/rev to 0.09 mm/rev, both temperature and maximum load are increase for all three drill tool materials. The effect of feed rate on temperature is more than that of spindle speed. Figure 5 Spindle speed v/s maximum load 3 Numerical simulation and validation In this study, the temperature of drill bit was analyzed using DEFORM 3D software for validation purpose. Drilling simulations in DEFORM 3D are time consuming, hence it is necessary to select workpiece as small as possible. Generally, selection of workpiece geometry isa round with a diameter roughly 20% larger than drill to reduce simulation time. In this drilling simulations, the workpiece diameter was 12 mmand drill diameter was 10 mm. Figure 6, Figure 7 and Figure 8 show the temperature distribution on drills for 0.05 mm/rev feed rate and 1200 rpm spindle speed with HSS, Cobalt coated HSS and K20 solid carbide drill tool materials respectively. Maximum temperature values were 237 °C, 264 °C and 215 °C for HSS, Cobalt coated HSS and K20 Solid Carbide drill material respectively at end step of simulations when drill tools achieved 20 mm drill depth. Figure 6 Temperature distribution on HSS drill tool Through drilling simulation, drill bit temperature values were obtained for all successfully drilled holes. Experimental and simulation results in term of temperature values are shown in Table 4. Figure 7 Temperature distribution on Cobalt coated HSS drill tool Figure 8 Temperature distribution on K20 Solid Carbide drill tool Table 4 Validation of results th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT Guwahati, Assam, India
Exp. Runs Temperature (°C) Experimental Simulation 1 220 237 2 250 289 3 265 303 4 295 312 5 335 354 6 200 264 7 235 275 8 260 284 9 290 324 10 310 345 11 340 361 12 190 215 13 230 249 14 253 261 15 260 287 16 272 302 17 290 340 18 304 354 19 330 383 Figure 9 shows validation of temperature values. The experimental and simulation results were similar and not a large difference in temperature values. All measured temperature values through experiments were less than that of simulation result and it may be due to measurement error during the experiment. Figure 9 Validation of results 4 Response surface methodology (RSM) Response surface modelling is used to establish the mathematical relationship between the responses, y and the various machining parameters, with the eventual objective of determining the optimum operating conditions for the system. A general Second-order polynomial response surface mathematical model is used to analyze the parametric influences on the various response criteria as follows (Lijo Paul et al. 2013).


==ijjuiuijiuiiiu11,(1) Where, y is the corresponding response for temperature and material removal rate (MRR), xiu is the coded value of the ith machining parameter of the uth experiment, k is the number of machining parameters, , ii, ij are the second-order regression coefficients. In this study, k=3 due to three process parameters: feed rate, spindle speed and load. For feed rate, spindle speed and load respective coded values are x, x and x. Coded variables are calculated using following equation,  \n\r \n  \n \r \n  \n  , (2) In the above equation, xij is the ith natural variable for jth experimental run. MINITAB 14 software has been used to establish mathematical models and for parametric optimization to achieve maximum material removal rate and minimum temperature.Using MINITAB 14 software the values of regression coefficients are found and shown in Table 6. Table 5 Coded values for process parameters Exp. Runs 1 2 3 1 -1.0000 -1.0000 0.4657 2 -1.0000 -0.3333 0.2563 3 -1.0000 0.3333 -0.1670 4 -1.0000 1.0000 -0.3820 5 -0.5000 1.0000 -0.1670 6 -1.0000 -1.0000 0.2563 7 -1.0000 -0.3333 0.0469 8 -1.0000 0.3333 -0.0067 9 -1.0000 1.0000 -0.5160 10 -0.5000 1.0000 -0.3825 11 0.0000 1.0000 0.4657 12 -1.0000 -1.0000 0.1006 13 -1.0000 -0.3333 -0.3820 14 -1.0000 0.3333 -0.8120 15 -1.0000 1.0000 -1.0000 16 -0.5000 1.0000 -0.4093 17 0.0000 1.0000 0.0469 18 0.5000 1.0000 0.6778 19 1.0000 1.0000 1.0000 Table 6 Regression coefficients and p-values of parameters on responses Term Coefficient values p-values Temp. MRR Temp. MRR Cons. 258.633 8079.81 0.000 0.000 F -111.697 2704.50 0.486 0.000 Experimental Evaluation and Optimization of Dry Drilling Parameters of AISI304 Austenitic Stainless Steel using Different Twist Drills 
S 54.526 92.25 0.314 0.102 L 179.534 -130.86 0.350 0.486 F*F -111.548 -84.90 0.371 0.487 S*S -24.171 42.64 0.524 0.267 L*L -49.098 113.44 0.629 0.273 F*S 6.213 -512.12 0.929 0.000 F*L 164.572 -172.11 0.474 0.450 S*L -52.999 128.78 0.626 0.247 Two responses are modelled as below, Y Temperature= 258.633 - 111.697 × F + 54.526 × S +179.534 × L - 111.548 × F – 24.171 × S – 49.098 × 2 + 6.213 × F × S – 52.999 × S × L+ 164.572 × F × L, (3) Y MRR = 8079.81 + 2704.50 × F + 92.25 × S – 130.86 ×L – 84.90 × F + 42.64 × S + 113.44 × L2 – 512.12 × F × S + 128.78 × S × L - 172.11 × F × L, (4) Figure 11 and Figure 12 show effect of feed rate and spindle speed on temperature and material removal rate.At 0.07 mm/rev feed rate and 1500 rpm spindle speed drill bit temperature is maximum (340 °C) for cobalt coated drill tool. At 0.08 mm/rev feed rate and 1500 rpm spindle speed MRR is maximum for K20 solid carbide drill. Figure 11 Effect of feed rate and spindle speed on temperature Figure 12 Effect of feed rate and spindle speed on MRR 5 Conclusions 1. The feed rate has a greater influence on a twist drill bit temperature in dry drilling of AISI 304 austenitic stainless steel material. 2. The spindle speed has a smaller influence on a twist drill bit temperature in dry drilling of AISI 304 austenitic stainless steel material. 3. Dry drilling of AISI 304 austenitic stainless steel with 1500 rpm spindle speed and feed rate above 0.06 mm/rev using HSS drill is uneconomical. 4. Dry drilling of AISI 304 austenitic stainless steel with 1500 rpm spindle speed and feed rate above 0.07 mm/rev using cobalt coated HSS drill is uneconomical. 5. K20 Solid Carbide drill tool has a longer tool life compare to HSS and Cobalt coated HSS drill tools. 6. The minimum temperature value (190 °C) was found at 0.05 mm/rev feed rate and 1200 rpm spindle speed for K20 Solid Carbide drill tool. 6 ReferencesChen, W.C. and Liu, X.D. (2000), Study on the various coated twist drills for stainless steels drilling, Journal of Materials Processing Technology, Vol. 99, pp.226-230. Chen, W.C. and Tsao, C.C. (1999), Cutting performance of different coated twist drills, Journal of Materials Processing Technology, Vol. 88, pp.203-207. Chen, W.C. and Fuh, K.H. (1995), The cutting performance of different coated twist drills, Journal of Materials Processing Technology, Vol. 49, pp.183-198. Eyup Bagci and Babur Ozcelik (2005), Analysis of temperature changes on the twist drill under different drilling conditions based on taguchi method during dry drilling of Al 7075-T651, Int J Adv Manuf Technol.Groover, M.P. (2010), Fundamentals of Modern Manufacturing-Materials, Processes and Systems, John Willey & Sons Inc., USA. Kalidas, S., Devor, R.E. and Kapoor S.G. (2001), Experimental investigation of the effect of drilling coatings on hole quality under dry and wet drilling conditions, Surface and Coating Technology, Vol. 148, pp.117-128. Lijo Paul and Somashekhar S. Hiremath (2013), Response surface modeling of micro holes in electrochemical discharge machining process, Procedia Engineering, Vol. 64, pp.1395-1404. Lin, T.R. and Shyu, R.F. (2000), Improvement of tool life and exit burr using variable feeds when drilling stainless steel with coated drills, International Journal of Advanced Manufacturing Technology, Vol. 16, pp.308-313. th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT Guwahati, Assam, India
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