This study proposes an air-cooling method that utilizes the stable, low temperature air layer near the factory floor to improve energy efficiency and machining accuracy in machine tools. Environmental measurements confirmed that the air near the floor exhibits minimal temperature fluctuations, forming a stable thermal environment. A simplified structural model was developed to evaluate heat exchange between the floor and air layer, and a CNC lathe equipped with an air-cooling structure was designed. CFD and thermal fluid simulations demonstrated improved cooling performance and reduced variation in machining diameter. Experimental validation confirmed that the system-maintained machining accuracy even under varying ambient temperatures. These findings indicate that the proposed air-cooling method is an effective alternative to conventional water-cooling systems, offering both energy savings and high-precision machining. This approach contributes to sustainable manufacturing by leveraging naturally stable thermal conditions within the factory environment.

This paper presents the design of a position control system for the rotary axis of five-axis machine tools by roller gear cam, with a focus on robustness against frictional fluctuations to enable high-speed and high-precision motion. A prototype rotary table drive system is first modeled precisely using a mathematical model that incorporates nonlinear friction characteristics. Next, the proposed control system is designed by combining a feedforward nonlinear friction compensator and the model error compensator to mitigate modeling error based on the aforementioned model. The proposed control system is applied to a prototype rotary table drive system that simulates the rotary axis of a five-axis machine tool. Experimental results demonstrably show that the position error can be robustly reduced at the reversal point of a sinusoidal position command, even in the presence of modeling errors.

This study aims to improve the efficiency and precision of milling WC-Co based cemented carbide (WC-Co) using the chemical vapor deposition (CVD) diamond-coated carbide tools. Five types of WC-Co materials with varying WC grain sizes and Co contents are machined at cutting speeds of 100 m/min and 400 m/min. Tool flank wear width (VB), wear morphology, cutting forces, and tool flank temperature are evaluated to clarify the effects of microstructural and compositional differences. The results show that coarse- and medium-grained materials exhibit reduced VB at the higher cutting speed of 400 m/min, while fine-grained and high-Co-content materials show increased VB under the same condition. Abrasive wear dominates at the low cutting speed of 100 m/min, whereas adhesive wear becomes prominent at the high cutting speed of 400 m/min. Based on the measured cutting forces and tool flank temperatures, the influence of WC grain size and Co content on tool wear behavior is discussed in relation to the cutting speed-dependent wear mechanisms. These findings provide useful insights for optimizing cutting conditions in high-efficiency and highprecision milling of cemented carbides.