Chip length control and adjustment through high frequency pulsed cryogenic jet cooling in turning aluminum alloys

Turning of ductile materials often results in continuous chips due to the lack of chip breaking. These chips have a negative impact on the sustainability of the machining process. Automation and recycling become more difficult, chips can damage the workpiece or machine tool and pose a risk to operator health. Several approaches are being investigated to address the issue of a lack of chip breaking. One of these is the pulsed supply of coolant. Studies have shown that the chip length can be controlled by pulsed high-pressure application of conventional metalworking fluids. This paper applies these findings to carbon dioxide based cryogenic jet cooling when turning aluminum alloys. Due to the typically high cutting speeds in aluminum machining, the coolant pulses are applied at high frequencies to create reasonably sized chips. The influence of the factors material, feed rate, pulse duration, pulse frequency and application angle on the probability of chip breaking and hence chip length is analyzed. The paper shows that pulse-induced chip breaking can be achieved. Depending on the parameters, the chip breaking probability per pulse ranges from 61.7 % to 100 % for EN AW2007 and from 11.7 % to 98.3 % for EN AW 6082. With a sufficiently high breaking probability, the chip length can be adjusted precisely.