Investigation of high-frequency pulsed carbon dioxide based cryogenic minimum quantity lubrication for milling 1.4404 steel (AISI 316 L)

Carbon dioxide (CO 2 )-based cryogenic minimum quantity lubrication (cMQL) is a sustainable, high-performance alternative to conventional wet machining, particularly for milling difficult-to-cut materials. Due to the physical properties of CO 2 , flexible and precise dosing of this cooling lubrication strategy poses a challenge, that can be addressed using pulsed media application. While previous research using low pulse frequencies of around 1 Hz , has already shown promising results, it also indicates that higher pulse frequencies could further enhance the outcome. This paper presents a custom-made application system, capable of achieving pulse frequencies greater than 100 Hz , to demonstrate the impact of high pulse frequencies on the milling of 1.4404 steel with cMQL. To this end, the bending moment of the tool, the tool wear and the surface quality of the work piece are determined and compared to those of continuous cMQL, as well as wet and dry machining. The experiments show, that both cMQL strategies achieve lower bending moments and lower tool wear than wet and dry machining, while producing better surface quality in most cases. Additionally, the high-frequency pulsed application produces results that are at least equal to, if not superior to those of continuous cMQL in all metrics analyzed. These findings imply that high-frequency pulsed cMQL is functionally equivalent to continuous cMQL, while simultaneously offering the potential for flexible dosing and therefore further increases in sustainability.