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ABSTRACT
Micro-milling is recognized as one of the most important manufacturing technologies for producing micro-components/products. Amongst various materials, graphite has an important role in conventional micro-electrical discharge machining electrodes. This paper is focused on the investigation of the effect of micro-milling process parameters on the dimensional accuracy and surface quality of ultrafine grain graphite TTK-4. Depth of cut, spindle speed, stepover distance and feed rate have been considered as process variables of micro ballend milling in experimental design. Moreover, the influence of the workpiece's inclination angle was also investigated. Taguchi's Lo (34) orthogonal array was chosen to design the experiments, whereas grey relational analysis (GRA) was utilized for the multi-objective optimization of the micro ball end milling process with minimum dimensional deviation and minimum arithmetic mean roughness as objective functions. Furthermore, principal component analysis (PCA) was used to extract principal components and identify the corresponding weights for performance characteristics. In order to determine the significance of micro-milling parameters on overall machining performance, analysis of variance (ANOVA) was performed. The result of the study revealed that the proposed approach is adequate to address the multi-objective optimization of micro-milling parameters.
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Keywords:
Micro-milling; Graphite; Workpiece inclination angle; Optimization; Dimensional accuracy; Surface quality; Taguchi method; Grey relational analysis
*Corresponding author:
[email protected] (Kramar, D.)
1. Introduction
Micro-milling is extensively used for machining of inclined and free-form surfaces with very high precision, e.g. in mold manufacturing, automotive and aerospace industries, optics, biomedical industries, etc. Camara et al. [1] characterized the micro-milling process by the size of the cuttingedge diameter of the tool, which ranges from 1 pm and 1 000 ит. Among various applications of micro-milling, the mold making industry is one of the most important due to the rapid and accurate machining of high aspect ratio in the micro-domain [2]. The dimensional accuracy and surface roughness of the micro-parts manufactured with this micro-mechanical cutting process plays a major role in defining the quality of a die. In complex engineering environments, predicting product quality based on performance parameters represents a challenging task [3]. There are some problems associated with the micro-milling process primarily induced by excessive cutting forces and cutting tool vibrations that can deteriorate the part quality or limit the overall productivity.
These performance characteristics are highly...