Sustainable and environmentally friendly longitudinal-torsional ultrasonic cryogenic cooling drilling system

Cutting fluid is widely used in the drilling of high-volume fraction composites, and the use of advanced ultra-precision machining technology to realize environmentally friendly, high-efficiency dry drilling is of great significance in promoting cleaner production. Longitudinal-torsional ultrasound-assisted drilling is considered a superior method for processing carbon fiber honeycomb sandwich panels (CFHSP). Intermittent cutting and high-frequency longitudinal-torsional ultrasonic vibration during the drilling process enhance machining quality and efficiency. However, prolonged high-frequency vibration in the ultrasonic machining system can lead to heating that directly impacts vibration stability. Therefore, an environmentally friendly longitudinal-torsional ultrasonic cryogenic cooling (LTUCC) system was developed, which adopts a novel mechanical structure to improve the longitudinal-torsional ultrasonic amplitude and heat dissipation efficiency. A high-power vortex tube cryogenic cooling device was designed, and a unique wireless power supply system was used to propose the design method of multiple transducers matching a single longitudinal-torsional composite hollow horn. The experimental results demonstrate that the LTUCC system exhibits superior vibration stability compared to conventional drilling, with a greatly improved longitudinal-torsional ultrasonic amplitude and high cooling efficiency. Under the conditions of a longitudinal ultrasonic amplitude of 16μm and an inlet working air pressure of 0.6MPa, the temperature decreased by 33.95K during continuous operation for 0.5 hours. Additionally, the length of the carbon fiber honeycomb burr was reduced by 34.7%, and the surface roughness of the CFRP hole wall decreased by 44.4%. The LTUCC system provides a feasible environmentally friendly drilling method.