Investigation of the effect of cutting parameters and cutting strategy in micro-milling of thin-walled structures

In recent years, there has been an increased use of thin-walled microstructures with low weight and high structural efficiency in sectors such as aerospace, biomedical and electronics. These structures, which are generally produced by micro-milling, are favoured in applications requiring high geometric precision. However, deformations caused by low stiffness and cutting forces have adverse effects on surface integrity and dimensional accuracy. It is therefore imperative to ascertain the most suitable machining strategies and optimum cutting parameters at the micro scale. This study investigates the effects of cutting parameters, cutting strategies, cutting tool geometry and coating types on surface quality, wall deformation and burr formation during the micro milling process of micro thin-walled structures made of Al 6061-T6 aluminium alloy. The variable feed strategy proposed in this thesis is a pioneering contribution to the existing literature on the subject, with the plastic deformation occurring at the beginning and end of the cutting process being reduced by up to 47%. With regard to the deformation of the cutting edge, the up-down milling yielded values that were 10 to 15 times lower than those observed with the up-up and down-down milling. Furthermore, the impact of tool geometry and surface properties on process performance has been demonstrated through the utilisation of cutting tools with varying coatings (AlTiN, TiSiN, ZrN, DLC) with 0°, 5°, and 15° rake angles. While it was found that optimum results were obtained with cutting tools that had DLC coating, cutting forces were reduced up to 22% and wall deformation up to 64% with cutters that had a 15° rake angle. Taguchi and ANOVA methods were employed to analyse the effect size of the cutting parameters, and it was found that the effect of feed rate on deformation was 87.3%, with a confidence level of 92.2%. These findings enabled the optimisation of parameters for the purpose of reducing deformation and improving surface quality in micro-milling of thin-walled structures.