Advanced Materials Research Vol. 747 (2013) pp 282-286 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.747.282
Surface Roughness Model when Machining Aluminum Nitride Ceramic with Two Flute Square end Micro Grain Solid Carbide end Mill Mohan Reddy.M 1, a, Alexander Gorin 2 , Abou-El-Hossein.K.A.3 and Sujan.D1 1
Mechanical Engineering Department, Curtin University of Technology (Malaysia Campus), CDT 250, Miri, Sarawak, 98009, Malaysia 2 Chemical Engineering Department, Swinburne University of Technology,Kuching, 93350, Malaysia 3
Mechanical & Aeronautical Department of Mechatronics Engineering, Nelson Mandela Metropolitan University, Port Elezebeth, 6031, South Africa a
[email protected]
Keywords: Aluminum nitride ceramic, Surface roughness, and Carbide end mill
Abstract: This research presents the performance of Aluminum Nitride ceramic in end milling using two flute square end micro grain solid carbide end mill under dry cutting. Surface finish is one of the important requirements in the machining process. This paper describes mathematically the effect of cutting parameters on surface roughness in end milling process. The quadratic model for the surface roughness has been developed in terms of cutting speed, feed rate, and axial depth of cut using the response surface methodology (RSM). Design of experiments approach was employed in developing the surface roughness model in relation to cutting parameters. The predicted results are in good agreement with the experimental results within the specified range of cutting conditions. Experimental results showed surface roughness increases with increase in the cutting speed, feed rate, and the axial depth of cut. Introduction Aluminum nitride ceramic (AlN) is relatively more used and attractive engineering ceramic because plastic deformation nature have been identified in this ceramic[1]. AlN are commonly used in a variety of applications such as semiconductor industries and heat removal component, Substrates and wafers for electronic packages, electronically insulating components for the high power electronic industry, and crucibles for molten metal[2]. Machining AlN ceramics economically and efficiently is the main barrier hindering further applications due to its brittleness and high hardness. Grinding process is generally used for machining advanced ceramics under the conventional Methods. The grinding characteristics of advanced ceramics are different from metals [3]. Daniels [4] studied the effect of surface grinding parameters such as diamond abrasive, wheel speed, and down feed on the rupture strength of silicon carbide. It was found that there was a insignificant reduction of the mean rupture strength of the material. Huang and Liu [5], Klocke et al. [6], Hwang et al. [7] and Kovach et al. [8] conducted experiments on high speed grinding of ceramics for achieving high removal rate. Huang and Liu [5] focused on the material removal mechanism of advanced ceramics in high speed deep grinding. They observed that fractured and smeared areas were generated on the Al2O3-TiO3 surface after the grinding process. Klocke et al. [6] studied various process strategies for the high speed grinding of aluminum oxide and siliconinfiltrated silicon carbide at high removal rates. The results indicated that the high speed grinding at high removal rates did not reduce the fracture strength of the machined ceramic components. However, the above research work was concerned with grinding process, which is slow process. End milling is extensively used on metallic materials like aluminium, copper, brass and steel alloys to examine surface quality[9-12]. The surface roughness of the work piece is considered as one of the most important factor for machinability evaluation as it significantly affect the work performance, durability and reliability. Extensive research in this area may lead to the selection of the proper cutting parameters to obtain desired surface finish in endmilling for AlN ceramic. Mohan All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 1.9.195.66, Curtin University of Technology (Malaysia Campus), Miri, Malaysia-06/06/13,03:37:32)
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Reddy et al. [13] used end milling process on Machinable Glass ceramic to study performance of end milling process. The study shows Proper selection of cutting parameters improves the surface roughness of end milling process. Machining of advanced ceramics by conventional end milling is very limited in literature. This paper reports the performance of end milling process on aluminum nitride ceramic by using two flute square end micro grain solid carbide end mill. Response surface method (RSM) is used to develop predictive model to measure surface roughness for AlN through discovering the effect of cutting speed, feed rate and axial depth of cut. Experimental Procedure In the present study the experiments were planned Design of Experiments (DOE) approach using Central Composite design (CCD). Three significant machining parameters like cutting speed, feed rate, and axial depth of cut were taken as the input parameters. The machining parameters and their selected levels are shown in Table 1. The machining operation was carried out on V-30 vertical CNC machine using a two flute square end micro grain solid carbide end mill under dry cutting.
Table 1: Selected range of cutting parameters Factors
Minimum
Central
Maximum
-1
0
1
Spindle Speed (RPM)
3000
4000
5000
Feed Rate (mm/min)
10
20
30
Depth of Cut (mm)
0.1
0.2
0.3
Coded factor
Table 2: Experimental design and corresponding surface roughness results Standard Order
Spindle Speed (rpm)
Feed Rate (mm/min)
Depth of Cut (mm)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
5000 4000 5000 4000 3000 5000 4000 4000 4000 4000 3000 5000 4000 3000 3000 2318 4000 5681 4000 4000
10 20 30 20 10 30 36.8 20 20 20 10 10 20 30 30 20 3.18 20 20 20
0.3 0.2 0.3 0.368 0.3 0.1 0.2 0.2 0.0318 0.2 0.1 0.1 0.2 0.1 0.3 0.2 0.2 0.2 0.2 0.2
Surface Roughness (µm) 0.713 0.552 0.835 0.881 0.573 0.693 0.82 0.543 0.462 0.513 0.581 0.543 0.511 0.621 0.752 0.411 0.523 0.783 0.553 0.531
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Results and Discussion Mitutoyo surface tester was used for obtaining the average surface roughness data. Cutting conditions and the surface roughness values obtained based on CCD are presented in Table 2. Using experimental results the surface roughness model was developed by Response surface methodology. The fit and summary tests suggested that the following quadratic model (Eqn 1) is significant.
Eqn (1) To verify the adequacy of the model, ANOVA was used and the results are shown in Table 3. Table 3: ANOVA table for surface roughness quadratic model Source Model A-Cutting Speed B-Feed Rate C-Depth of Cut AB AC BC 2
A
Sum of Squares
DOF
Mean Square
F-value
P-value
0.30
9
0.034
7.50
0.0021
0.057
1
0.057
12.76
0.0051
0.072
1
0.072
16.07
0.0025
1
0.095
0.095 3.511×10
-4
4.465×10
-3
1.540×10
-3
8.664×10
-3
21.27
0.0010
3.511×10
-4
0.079
0.7850
4.465×10
-3
1.00
0.3412
1.540×10
-3
0.34
0.5703
1
8.664×10
-3
1.94
0.1941
8.34
0.0162
8.34
0.0162
24.62
0.016
1 1 1
2
0.037
1
0.037
2
0.037
1
0.037
B C
-3
Residual
0.045
10
4.471×10
Lack of Fit
0.0043
5
8.593×10-3
5
-4
Pure Error
1.745×10
Cor Total
0.35
-3
3.490×10
significant
significant
19
The parametric analysis was carried out to study the influence of the process parameters on surface roughness based on the RSM quadratic model. Figure 1 shows the trends of each cutting parameter on the surface roughness, Ra, which increases with increasing the cutting speed, feed rate and the axial depth of cut.
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A = cutting speed = 4000 rpm
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B = 10; B=30 C = axial depth of cut = 0.2
B = feed rate = 20 mm/min C=axial depth of cut=0.2 mm
Fig 1: Perturbation plot Ra Vs. A, B, and C Fig 2: Interaction plot for A and B C= 0.1; C=0.3 B = feed rate = 20
C = 0.1;
C=0.3
A= cutting speed =4000
Fig 3: Interaction plot for C and A
Fig 4: Interaction plot for B and C
Figure 2 represents the effects of cutting speed on the surface roughness at two different feed rate values. Surface roughness increases with the cutting speed increase. At low feed rate value the surface roughness value is low compared to high feed rate value. Figure 3 shows the effects of the cutting speed with a different axial depth of cut on the surface roughness. Here, it can be observed that surface roughness increases as the cutting speed increases. The trend shows that an increased axial depth of cut leads to an increase in the surface roughness at a given cutting speed. The surface roughness increases rapidly at a high axial depth of cut, and this reveals that improved surface roughness is achieved at a low axial depth of cut 0.1mm.The surface roughness is plotted against feed rate for two different axial depths of cut values as shown in Figure 4. It is clear that the surface roughness increases as the feed rate increases. The surface roughness value is higher at larger axial depth of cut even in this case. Improved surface roughness is, thus, possible at low axial depth of cut. Developed quadratic model Eqn (1) has been utilized to optimize the cutting parameters. After identifying the most effective parameters, experimental tests were conducted for optimal combination(3006 rpm, 14.2 m/min feedrate and 0.15 mm depth). The results of the tests show that the surface roughness value 0.4820 is close to the predicted value of 0.4591. A better surface finish was obtained at a combination of 3006 rpm (cutting speed), 14.2 mm/min (feed rate), and 0.15 mm (axial depth of cut).
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Conclusion Experimental studies shows that surface roughness Ra increases with increase in the cutting speed, feed rate, and the axial depth of cut. However, in order to reduce machining time and increase the material removal rate, the feed rate and axial depth of cut should be as high as possible. References [1] Guangli, H., Ramesh, K.T., Buyang, C., and McCaule, J.W., 2011. “The compressive failure of aluminum nitride considered as a model advanced ceramic”, Journal of the Mechanics and Physics of Solids, 59, 1076–1093 [2] Katahira, K., Ohmori, H., Uehara, Y., and Azuma, M., 2005. “ELID grinding characteristics and surface modifying effects of aluminum nitride (AlN) ceramics”, International Journal of Machine Tools & Manufacture 45, 891-896. [3] Tuersley, I.P., Jawaid, A., and Pashby, I.R., 1994. “Review: Various method of machining advanced ceramic materials”, Journal of Materials Processing Technology, 42, 377-390. [4] Mayer Jr.J.E., Fang.G.P., “Effect of grinding parameters on surface finish of ground Ceramics” Annals of the CIRP 44 (1), 1995, 279–282. [5] Daniels, W.H., 1989. “uper abrasives for ceramic grinding and finishing”, SME Technical Paper, EM 89-125. [6] Konig, W., and Sinhoff, V., 1992. “Lens and Optical Systems Design”, SPIE, 778-788. [7] Huang, H., and Liu.Y.C., 2003 “Experimental investigations of machining characteristics and removal mechanisms of advanced ceramics in high speed deep grinding” International Journal of Machine Tools and Manufacture 43 (8), 811-823. [8] Klocke.F., 1997. “Modern approaches for the production of ceramic components”, Journal of the European Ceramic Society, 17, pp. 457–465. [9] Hwang, T.W., Evans, C.J., Whitenon, E.P., and Malkin, S., 1999. “High speed grinding of silicon nitride with electroplated diamond wheels.1.wear and wheel life”, Manufacturing Science and Engineering, ASME, 10, 431-441. [10] Kovach, J.A, Laurich, M.A., Malkin, S., Srinivasan, S., Bandyopadyay, B., and Ziegler, K.R., 1993. “A feasibility of investigation of high speed, low damage grinding for advanced ceramics”, SME fifth international grinding process conference, Vol. 1, SME. [11] Rahaman.M, Senthil Kumar. A, Prakash J.R.S, 2001 “Micro milling of pure Copper”, Journal of materials Processing Technology 116, 39-43 [12] Takacs.M, Vero.B, Meszaros.I, 2003, “Micro milling of metallic materials”, Journal of Materials processing Technology 138, 152-155. [13] Wang, W., Kweon.S.H., and Yang.S.H, 2005. "A study on roughness of the micro-end-milled surface produced by a miniatured machine tool", Journal of Materials Processing Technology 162-163, 2005: 702-708. [14] Bernados.P.G, Vosniakos.G.C, 2003“Predicting surface roughness in machining: a review”, [15] International Journal of Machine Tools and Manufacture ,43(8), 833-944. [16] Mohan Reddy.M, Alexander Gorin and Abou-El-Hossein. K.A., 2011.“ Development of Cutting force Model for Aluminum nitride ceramic processed by End Milling” Applied Mechanics and Materials. 87, 223-229.
