Understanding the dust generation and machinability characteristics during cryogenic drilling of carbon fiber-reinforced plastics

Carbon fiber-reinforced plastics are used across various industries, particularly in aviation, owing to their exceptional properties, necessitating secondary operations such as drilling, milling, and turning to achieve the desired shape. Machining of carbon fiber-reinforced plastics can induce thermal and mechanical damage in the laminate, resulting in the fragmentation of fibers and matrix into fine particles, creating powder-like chips that negatively impact operator health. In this study, particle dust contamination generated during the drilling of carbon fiber-reinforced plastics under dry and cryogenic conditions and using different cutting parameters was measured and evaluated. The results showed that, in general, dust formation was less at 1000 r/min, but the damage in the hole was greater. On the other hand, at low spindle speeds of 1000 rpm, while cryogenic machining increased the thrust force by 31–36% and torque by 19–162%, it also led to a reduction in dust generation by 18.26–38.91% at 1000 r/min and an improvement in roughness (6–12%). Interestingly, a significant increase in dust generation (58.5% to 249%) was observed under cryogenic conditions at higher spindle speeds of 9000 r/min, possibly due to liquid nitrogen vapor levitating additional dust particles into the atmosphere. The results indicate that while cryogenic machining can be considered an environmentally friendly cooling process, it can become the primary source of increasing mass concentrations of airborne particles when drilling at high spindle speeds.