1. META ANALYSIS OF FACTORS AFFECTING SURFACE ROUGHNESS IN MILLING Gökçe Mehmet Ay, M.Alper Sofuoğlu Eskişehir Osmangazi University, Department of Mechanical Engineering Eskişehir, Turkey

2. Introduction Factors such as cutting speed, feed rate, depth of cut etc. affect surface roughness. Surface roughness in milling is an important research area. In this field, each study investigates the effects of factors on a combination of different material and cutting parameters. Although there is knowledge on the effects of these parameters, no combinatory study existed. In order to solve this problem, a meta-analysis was conducted.

3. Meta-analysis study For this meta-analysis study, articles collected from SCIENCEDIRECT database were used. Search was conducted with search term given below: Optimization and milling and “surface roughness” The first 200 papers sorted by “relevance” filter of database were inspected. 37 papers which have clear experimental data and relevant to the study were chosen from this set. Frequency graph of factors affecting surface roughness obtained from those 37 papers was plotted. It was observed that mostly feed rate, cutting speed and depth of cut (axial) factors were studied. From chosen 37 papers, 10 papers were chosen in meta-analysis because in those studies only feed rate, cutting speed and depth of cut were investigated. In order to investigate the effect of cutting speed, feed rate and depth of cut variation separately, partial correlation test was conducted. COMPREHENSIVE META ANALYSIS software was used.

4. Study noStudyYearNumber of Data 1Balamugundan et al.20129 2Yang et al.20098 3Maiyar et al.20139 4Sreeivasulu et al.20139 5Pang et al.201427 6Mansour et al.200224 7Sukumar et al.201416 8Hassanpour et al.201530 9Lakshmanan et al.20149 10Lebaal et al.201112

5. The results of partial correlation test Study nor feed p r depth of Cut p r cutting speed p 10.6350.1250.7860.036-0.7760.04 20.9780.0010.3680.473-0.2370.652 30.9480.0010.6950.083-0.2120.648 40.170.715-0.2350.6120.30.513 50.0290.890.4630.02-0.2940.154 60.4350.0430.1810.421-0.140.534 7-0.4340.1210.2750.342-0.6810.007 80.82800.2550.19-0.7020 90.8870.0080.1820.696-0.5410.21 100.5230.1210.0380.9160.5380.108

6. Heterogeneity test for feed rate Q- valuedf(Q)p-valueI2I2 59.5219 1.66E- 0984.879 Study norLower limitUpper limitz valuep value 10.635-0.050.9141.8370.066 20.9780.8790.9965.030 30.9480.7660.9894.4380 40.17-0.5570.750.420.674 50.029-0.3550.4050.1420.887 60.4350.0380.7132.1360.033 7-0.434-0.7650.079-1.6760.094 80.8280.6670.9156.1410 90.8870.5420.9763.4480.001 100.523-0.0730.8441.7410.082 Random Effects0.650.2890.8493.1850.001

7. Heterogeneity test for depth of cut Q- valuedf (Q) p- valueI2I2 9.04590.4330.494 Study norLower limitUpper limitz valuep value 10.7860.2550.9532.5990.009 20.368-0.4550.8520.8630.388 30.6950.0570.932.1010.036 4-0.235-0.7780.508-0.5870.557 50.4630.1010.7172.4550.014 60.181-0.240.5450.8390.402 70.275-0.2560.6781.0180.309 80.255-0.1160.5641.3550.175 90.182-0.5480.7550.4510.652 100.038-0.5480.5990.1140.909 Fixed Effects0.3140.1480.4643.6090

8. Heterogeneity test for cutting speed Q- valuedf (Q) p- valueI2I2 25.0949 2.87E- 0364.135 Study norLower limitUpper limitz valuep value 1-0.776-0.95-0.231-2.5360.011 2-0.237-0.8070.561-0.540.589 3-0.212-0.7680.526-0.5270.598 40.3-0.4550.8040.7580.448 5-0.294-0.6060.097-1.4840.138 6-0.14-0.5140.279-0.6460.518 7-0.681-0.88-0.28-2.9960.003 8-0.702-0.848-0.457-4.5270 9-0.541-0.8870.192-1.4830.138 100.538-0.0520.851.8040.071 Random Effects-0.339-0.583-0.038-2.20.028

9. Kendal Tau test Feed rate (without continuity correction) Feed rate (with continuity correction) Depth of cut (without continuity correction) Depth of cut (with continuity correction) Cutting speed (without continuity correction) Cutting speed (with continuity correction) Kendal tau0.330.310.110.090.110.09 z1.341.250.450.360.450.36 p (1-tailed) 0.090.10.330.360.330.36 P (2-tailed) 0.170.210.650.720.650.72

10. Conclusion In this study, effect of feed rate, depth of cut and cutting speed on surface roughness was investigated in milling. It was concluded that all the variables have significant effect on the surface roughness (p<0.05). It was found that there is a positive correlation of feed rate and depth of cut with surface roughness and a negative correlation of cutting speed and surface roughness. The results obtained from this study show that feed rate has greater effect and depth of cut has the lowest effect on the surface roughness These results are consistent with literature.

11. Conclusion In order to have better surface roughness, feed rate should be taken into account first. The change in surface roughness would be more observable when feed rate is changed. The effect of depth of cut and cutting speed are less effective. Further study on this topic should consider the other factors and combine more study and data.