Materials such as titanium alloys, nickel alloys, and stainless steels are difficult to machine due to low thermal conductivity, work hardening, and built-up edge formation, which accelerate tool wear. Frequent tool changes are required, often relying on operator experience, leading to inefficient tool use. While modern machine tools include intelligent tool replacement systems, many legacy machines remain in service, creating a need for practical alternatives. This study proposes a method to autonomously determine tool replacement timing by monitoring machining process signals in real time, enabling automatic tool changes even on conventional machines. Tool wear is evaluated using current and vibration sensors, with the replacement threshold estimated from the maximum current observed in an initial user-defined interval. When real-time signals exceed this threshold, the system updates controller variables to trigger tool changes. Results show vibration data are more sensitive to wear, whereas current data provide greater stability. These findings indicate that a hybrid strategy combining both sensors can enhance accuracy and reliability of tool change decisions, improving machining efficiency for difficult-to-cut materials.

The purpose of this study is to evaluate the deformation behavior of 3D printed specimens using the small punch tensile test method. Traditional tensile tests for assessing mechanical properties require a significant amount of material to produce uniaxial tensile specimens. In contrast, the small punch test method only requires 10 x 10 x 0.5 mm (width x length x thickness) thin plate specimens, providing a substantial economic advantage in specimen sampling and production. This method is particularly beneficial when it is impossible to produce specimens of the same size as uniaxial specimens, as it allows tensile testing with just the minimum sample required. In this study, we utilized fused deposition modeling 3D printing and considered various 3D printing parameters, such as layer height and volume fraction, while manufacturing the specimens. We then compared and analyzed the effects of these variables on tensile strength as measured by the small punch tensile test. Furthermore, we focused on investigating the applicability of this method to the deformation behavior of 3D printed specimens. We also examined the impact of laminating conditions, including layer height, printing speed, and laminating direction, on the failure modes observed after the small punch tensile test.