ORIGINAL ARTICLE Optimization study of dry peripheral milling process for improving aeronautical part integrity using Grey relational analysis Walid Jomaa 1 & Julie Lévesque 1 & Philippe Bocher 2 & Arnaud Divialle 3 & Augustin Gakwaya 1 Received: 11 October 2016 /Accepted: 15 November 2016 # Springer-Verlag London 2016 Abstract Dry machining is one of the reliable eco-friendly techniques since it enables avoiding the use of harmful/ expensive cutting fluids, reducing part costs, and increasing productivity. This study attempts to optimize the dry periph- eral milling conditions with regard to the surface finish and residual stress (RS) of machined aeronautical Al–Zn–Mg–Cu alloy. The proposed approach involves a multi-objective opti- mization of five machining parameters, including cutting tool geometry, milling mode, feed per tooth, cutting speed, and radial depth of cut. The multi-objective optimization approach is developed based on the Taguchi method combined with the Grey relational analysis (GRA). An improvement of the mul- tiple performance characteristics by 104%, as compared to the initial cutting conditions, has been obtained using the pro- posed approach. The analysis of variance (ANOVA) has shown that the feed per tooth, the cutting speed, and the inter- action between cutting tool and milling mode significantly influence the surface quality of dry peripheral milled parts. This study demonstrated that the dry peripheral milling of aluminum parts can be an efficient sustainable process in terms of part quality if the machining conditions are adequate- ly selected and optimized. Keywords Multi-objective optimization . GRA . Dry peripheral milling . Aluminum alloy . Surface roughness . Residual stress 1 Introduction The manufacturing of landing gear parts made of high-strength aluminum alloys requires the machining of complex shapes and a large volume of removed material, which may significantly increase machining cost and lead time. To be more efficient and competitive, manufacturers have adopted different machining techniques and strategies such as implementing high-speed machining (HSM) and using advanced cutting tools and/or lubrication/cooling me- dia. The use of these techniques, either separately or com- bined, affects differently the productivity, the environment, and the surface integrity. This is particularly important since the fatigue life of high-strength aluminum parts is known to be strongly sensitive to the surface integrity after machining and the surface roughness and residual stresses are the key parameters controlling the process [1, 2]. Several research works have been performed to study ex- perimentally the effect of machining parameters on the surface finish of aluminum parts [3–7]. It was found that the surface quality is strongly related to the buildup edge formation [3–6] and the cutting feed has the most significant effects on surface roughness variation [8]. The effect of cutting speed on surface roughness was found to be controversial [7, 8]. Rahmati et al. [9] and Sayuti et al. [10] have shown that molybdenum disul- fide (MoS2) nanolubrication enhances surface finish of end- milled 6061-T6 alloy thanks to the positive impact of the suspended MoS2 nanoparticles. However, the use of lubri- cants has been widely criticized because of their threat to ecology and health of workers [11]. Moreover, lubricants * Walid Jomaa walid.jomaa.1@ulaval.ca; http://orcid.org/0000-0002-1286-3263 1 Mechanical Engineering Department, Laval University, 1065 Avenue de la Médecine, Québec, QC G1V 0A6, Canada 2 Mechanical Engineering Department, École de technologie supérieure, 1100 Rue Notre-Dame O, Montreal H3C 1K3, Canada 3 Héroux-Devtek Inc, 4925 Chemin de la Savane St-Hubert, Québec J3Y 9G1, Canada Int J Adv Manuf Technol DOI 10.1007/s00170-016-9777-8