Analytical Modelling of Cutting Force in End-Milling with Minimum Quantity Lubrication

Milling with minimum quantity lubrication (MQL) is a commonly used machining technique in the industry because of its advantage in lowering the cutting temperature and cutting force. Among its wide usage in machining, modeling for milling operations was particularly hard for its complexity. This paper proposed an analytical model for cutting force prediction in the end-milling process with MQL. The 3D milling operation was transferred into equivalent 2D orthogonal cutting at each rotational angle. Then the proposed model incorporated updated friction coefficients due to the MQL with boundary lubrication effect. Based on Oxley's orthogonal cutting model, the cutting force was calculated with an updated friction coefficient. Two sets of validations were done with experimental measurements using different cutting materials. The proposed model delivered reasonable accuracy for the force prediction with MQL, providing an adequate method for the industry. Based on the model investigation, the friction coefficient in cutting was also significantly affected by the droplet's layer thickness, which was presumably linearly correlated with the flow speed of the lubricant.