Experimental and numerical investigation of difference in diameter enlargement and circularity of micro-holes drilled by flexural spindle head

Abstract

The flexural bearing or the flexural cartridge allows very nano-meter axial displacement movement, which is frictionless and noiseless. The repeatability of the mechanism obtained is achieved by bending of the load element. The bearing can operate under stringent conditions such as vacuum, elevated temperatures (0–40 °C), and moist conditions. Hence, due to these indigenous properties, these bearings are observed in applications such as linear bearing of linear compressor, flexural bearing electromagnetic linear actuator, and parasitic error-free mechanism. The endorsed capability of obtaining high-level positional accuracy along with repeatability leads to design and development of low-cost flexural cartridge for micro-drilling spindle head. This flexural cartridge provides a linear guideway while feeding inside the test specimen (in micro-drilling operation). The designed head dampens and nullifies the force, acting on the shaft carrying the micro-tool. The designed spindle head carrying the three-leg spiral flexural stack is assembled on the designed machine tool. The run out measured on the spindle shaft is 50 µm. Four test specimens, namely aluminum, brass, acrylic and mild steel, are drilled by three drills of diameter 1 mm, 0.8 mm, and 0.5 mm each. The main objective of the article is to understand the differential analysis of diameter enlargement and circularity between the experimental method and the numerical method. The answers predicted by the experimental method may have second possible value as it depends upon judgment of inscribing the circle/points in the computer-aided design (CAD) environment. This ambiguity is excluded by the MATLAB code, which gives one specific answer. The maximum difference in diameter enlargement for aluminum, brass, acrylic, and mild steel specimens are 3.8 µm, 11 µm, 24.6 µm, and 16.1 µm, respectively, whereas the maximum difference in circularity for the same specimens is 11.8 µm, 1.3 µm, 8.2 µm, and 16.8 µm, respectively. This difference is termed as the |error|.