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

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.

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.

Study noStudyYearNumber of Data 1Balamugundan et al Yang et al Maiyar et al Sreeivasulu et al Pang et al Mansour et al Sukumar et al Hassanpour et al Lakshmanan et al Lebaal et al

The results of partial correlation test Study nor feed p r depth of Cut p r cutting speed p

Heterogeneity test for feed rate Q- valuedf(Q)p-valueI2I E Study norLower limitUpper limitz valuep value Random Effects

Heterogeneity test for depth of cut Q- valuedf (Q) p- valueI2I Study norLower limitUpper limitz valuep value Fixed Effects

Heterogeneity test for cutting speed Q- valuedf (Q) p- valueI2I E Study norLower limitUpper limitz valuep value Random Effects

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 tau z p (1-tailed) P (2-tailed)

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.

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.