A Systematic State-of-the-Art Review of Conventional MQL and Cryogenic – MQL in Milling Processes

Sammanfattning

This thesis is a systematic state of art research review (SOTA) focused on the heat removal performance of Cryogenic - MQL and conventional MQL in milling operations. The research aims to determine whether sufficient scientific evidence of the effectiveness and its magnitude on the heat removal for these methods is available. In total three experimental literature studies were analysed, one using Inconel 718 and two using Ti-6Al-4V. By utilizing qualitative research methodology with primary investigation questions, relevant knowledge acquisition about heat generation and heat removal, with controlled comparisons of cooling strategies, surface integrity, tool life, tool wear, temperature and cutting forces is enabled. The findings in this thesis indicates that Cryogenic - MQL provides superior thermal management compared to conventional MQL when machining difficult to cut alloys, with low to moderate cutting speeds. In the studies it was noted that there were significant improvements in reducing cutting forces, improving tool life and temperatures, enhanced surface integrity and improved chip formation. However, solely using MQL exhibited strong lubrication effectiveness, excellent surface finish and reduced frictional heat. Under lubricant dominated conditions or higher speeds, conventional MQL remained competitive. There was observed limitation on the cryogenic performance due to potential vapor barriers and oil freezing. It was concluded from this thesis that the Cryogenic - MQL is an effective heat removal method in milling operations, by outperforming conventional MQL particularly under thermally demanding conditions. Nonetheless, the MQL remains valuable and effective in reducing heat generation for it’s lubrication efficiency and sustainability. To fully optimize and validate the Cryogenic - MQL approach which indicates a strong potential, it is required for further research across broader operating conditions, industrial scenarios and nozzle configurations.