Titanium alloys are used in various industries due to their superior mechanical strength and corrosion resistance. However, titanium is classified as a difficult-to-machine material due to its low thermal conductivity that consequently causes poor tool life. In this study, cryogenic+MQL milling was performed to improve the machinability of Ti-6Al-4V; a cryogenic coolant and a minimum quantity fluid were sprayed simultaneously. The machinability was analyzed according to the cooling and lubrication conditions, focusing on the cutting force and tool wear. When the minimum quantity fluid was injected using two nozzles during cryogenic machining, the cutting force remained low despite the increase in machining distance due to the effective lubrication. The average cutting force at the long machining distances (82-86 passes) was 14.8% lower than that under the wet condition. The tool wear progressed without chipping, and the flank wear length was 55.5% lower than that of the wet machining because the cryogenic cooling and minimum quantity lubrication reduced the tool temperature, friction, and thermal shock.
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Design and Development of a Real-Time AI-Based Tool Failure Prediction System for Machining Difficult-to-Cut Materials Mi-Ru Kim, Hoon-Hee Lee, Min-Suk Park, Wang-Ho Yun Journal of the Korean Society of Manufacturing Technology Engineers.2025; 34(4): 225. CrossRef
The tower crane is widely used in construction and transportation engineering. To improve working efficiency and safety, input shaping methods have been applied. Input shaping is a method of reducing residual vibration of flexible systems by convolving a sequence of impulses with unit step command. However, input shaping is based on the linear system theory in which its control performances are degraded, in case of nonlinearity and unmatched dynamics of the control systems. In this paper, a new optimal reference input shape design method based on minimizing cost function is suggested and applied, to a simple cart-pendulum system which is a simplified model of tower cranes. Since pendulum dynamics is nonlinear, analytic solution does not exist. To overcome this problem, in this paper, a machine learning approach is suggested to find optimal reference input shape for the cart position control. The feasibility of the proposed design method is verified through some simulation examples by using MatLab.
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Compacted graphite iron (CGI) has been widely used in the automobile industry because of its good mechanical properties. CGI has better strength as compared to grey iron due to its internal structure. It includes graphite particles, which enhance the adhesion between graphite and iron. However, the material characteristics can negatively affect the machinability. In this study, cryogenic milling was performed for CGI450. It is well known that cryogenic machining is effective in improving the machinability. The process included spraying liquid nitrogen as a cryogenic coolant, and the influences on machinability were experimentally investigated with a focus on the cutting force and surface roughness. When liquid nitrogen was sprayed, the cutting force was slightly increased due to the cold-strengthening effect. On the other hand, surface roughness was dramatically decreased by 44.7% as compared to dry milling because brittleness of work material was increased by cryogenic coolant spraying.
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Tool life assessment of high strength cast iron alloys in dry face milling operations Alcione dos Reis, Gustavo Henrique Nazareno Fernandes, José Aécio Gomes de Sousa, Luiz Leroy Thomé Vaughan, Feliciano Cangue, Álisson Rocha Machado, Wilson Luiz Guesser Journal of Manufacturing Processes.2024; 111: 180. CrossRef
Study on the Effect of MQL Spraying Condition on the Machinability in Titanium Cryogenic Machining Dong Min Kim, Heung Bum Park, Byung-Gook Kim, Hoon-Hee Lee, Young Ha Hwang, Ki Hyuk Kim, In Su Shin, Do Young Kim Journal of the Korean Society for Precision Engineering.2023; 40(4): 261. CrossRef
FEM (Finite Element Method)-based numerical analysis model, which is known as CAE (Computer Aided Engineering) technology, has been adopted for the visual/mechanical analysis of machining process. The essential models for the FEM analytical model are the plasticity model of workpieces, friction model, and wear rate model. Usually, the outputs of the FEM analytical model are the cutting force, the cutting temperature, and chip formation. Based on these outputs, the machining performance can be virtually evaluated without experiments. Nowadays, there are emerging machining technologies, such as cryogenic assisted machining and CFRP machining. Therefore, FEM technique can be one of the good candidate to virtually evaluate emerging developed machining technologies.
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Post-machining Deformation Analysis for Virtual Machining of Thin Aluminium Alloy Parts Soo-Hyun Park, Eunseok Nam, Myeong Gu Gang, Byung-Kwon Min International Journal of Precision Engineering and Manufacturing.2019; 20(4): 687. CrossRef
The surface roughness and cutting forces are the important factors for the machine-part quality during the hard-turning process. The aim of this paper is to optimize hard-cutting conditions via implementation of response surface methodology (RSM). The experiments were conducted for the hard-turning process with the Box-Behnken design. The validation of the surface roughness and cutting forces was performed with the obtained 2nd order polynomial regression model. The results showed that the surface roughness was strongly dependent upon the RPM. The diminution of the cutting force was attributed to the low feed rate and the depth of cut. On the basis of the RSM, optimized cutting conditions of RPM, feed rate, and depth of cut are 3440, 0.0352 [mm/rev], and 0.03 [mm]. In this optimal cutting condition, the surface roughness can be around Ra= 0.202 μm.
Cryogenic machining uses liquid nitrogen (LN2) as a coolant. This machining process can reduce the cutting temperature and increase tool life. Titanium alloys have been widely used in the aerospace and automobile industries because of their high strength-to-weight ratio. However, they are difficult to machine because of their poor thermal properties, which reduce tool life. In this study, we applied cryogenic machining to titanium alloys. Orthogonal cutting experiments were performed at a low cutting speed (1.2 – 2.1 m/min) in three cooling conditions: dry, cryogenic, and cryogenic plus heat. Cutting force and friction coefficients were observed to evaluate the machining characteristics for each cooling condition. For the cryogenic condition, cutting force and friction coefficients increased, but decreased for the cryogenic plus heat condition.
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Study on the Machinability of Cryogenic Milling for Compacted Graphite Iron Jisoo Kim, Do Young Kim Journal of the Korean Society for Precision Engineering.2022; 39(1): 13. CrossRef
Determination of Flow Stress and Cutting Force Prediction of Ti-6Al-4V Material for 3D Printer using S-K Constitutive Equation Dae-Gyoun Park, Tae-Ho Kim, Eon-Chan Jeon Journal of the Korean Society of Manufacturing Process Engineers.2018; 17(6): 68. CrossRef
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