The effect of cryogenic machining of S2 glass fibre composite on the hole form and dimensional tolerances

Abstract

S2 glass fibre reinforced epoxy composites are widely used in aeronautical applications owing to their excellent strength to weight ratio. Drilling glass fibres can be cumbersome due to their abrasive nature and poor thermal conductivity. Moreover, the use of conventional coolants is not desirable due to contamination and additional costs for cleaning the machine part. An alternative is to use environmentally friendly coolants such as liquid nitrogen (LN2) which have been previously employed in machining metals and composites. The current study investigates the effect of drilling S2 glass fibre composite in a bath of LN2. The study aims to evaluate the effect of spindle speed, feed rate and the presence of cryogenic cooling on the form and dimensional tolerances of the hole (hole size, circularity, cylindricity and perpendicularity). Design of experiments and analysis of variance (ANOVA) were used to determine the contribution of the input parameters on the analysed hole quality metrics. Results indicated that drilling S2 glass fibre in a cryogenic bath increased hole size significantly beyond the nominal hole diameter. The hole circularity and cylindricity were reduced compared to holes drilled under dry condition under all cutting parameters due to enhanced thermal stability during the drilling process. The current study aims to provide the scientific and industrial communities with the necessary knowledge on whether cryogenic bath cooling strategy provides better hole quality output compared to dry drilling and other cryogenic cooling strategies which were previously reported in the open literature.

Assessment of Hole Quality, Thermal Analysis, and Chip Formation during Dry Drilling Process of Gray Cast Iron ASTM A48

“…The two-dimensional radial tolerance called circularity or roundness error indicates how close a component with a diametrical cross-section is to a true circle [7,29]. Figure 5 depicts the circularity varying f and n. In the current study, the circularity error decreased significantly with increasing both f and n. Circularity values decreased from 0.034 mm to 0.027 mm by increasing f from 0.013 m/min to 0.049 m/min at a constant n of 43 rpm.…”

The Effect of TiN-, TiCN-, TiAlN-, and TiSiN Coated Tools on the Surface Defects and Geometric Tolerances of Holes in Multi-Spindle Drilling of Al2024 Alloy

“…A 2 mm diameter ruby stylus was used for the measurements. The measurement was taken 1 mm below the top region and 1 above the bottom region of the inside each hole, similar to the previous studies [33]. Finally, circles were generated using the maximum inscribed circle for each measurement.…”

Performance evaluation of AlTiN coated carbide tools during machining of ceramic reinforced Cu-based hybrid composites under cryogenic, pure-minimum quantity lubrication and dry regimes

“…Cryogenic medium was the successful method in improving the surface roughness index compared to conventional method. Koklu et al 48 evaluated the influence of cryogenic medium while comparing it with dry condition. An improved surface quality and hole diameter was reached by cryogenically cutting condition.…”