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Vibrations during milling of hard-to-cut materials can cause low productivity, inferior quality and short tool life. It is one of the common issues in the machining of hard-to-cut materials employed in aerospace applications, such as titanium alloys. This paper presents an analysis of the vibration signals in the 3 axes of movement during titanium end milling, under diverse cutting parameters, manipulating spindle speed and feed rate. Signals were obtained using a triaxial accelerometer and processed in MATLAB. The analysis was conducted in the frequency-domain and the time-frequency domain. The results show that high-frequency vibration could occur in any direction with different amplitudes. Response on each axis depends on spindle speed, feed, and type of milling. A frequency component continually appeared in each axis regardless of cutting conditions and is located near the natural frequencies. Finally, the triaxial accelerations were compared for the milling cases with a new and a worn tool. Results highlight the importance and need for continuous monitoring of vibration in the 3 axes, instead of only using a single-channel signal, providing experimental data which could expand knowledge relating to the milling of titanium alloys.

Recubrimientos monocapa de nitruro de hafnio fueron depositados en buriles de acero rápido, mediante técnica de deposición física en fase vapor mediante pulverización con magnetrón (magnetrón sputtering). Se usó buriles sin recubrir como sistemas de referencias, en el mecanizado por arranque de viruta del acero AISI1020, midiendo las temperaturas generadas. Se caracterizó la resistencia al desgaste de las herramientas evaluándolas mediante microscopia electrónica de barrido, y las superficies obtenidas en el acero mecanizado mediante un rugosímetro. Se evidenció que el uso de recubrimientos monocapa de nitruro de hafnio en buriles de acero rápido disminuye el desgaste adhesivo de la herramienta y la transferencia de energía generada durante el proceso de corte. Además, el recubrimiento ofrece ventajas en su aplicación en el corte por arranque de viruta de metales ferrosos, al aumentar la vida útil de la herramienta, mejorar la calidad del producto, y disminuir los tiempos y costos del proceso.

In this study, AISI 1020 steel was machined by chip removal, in dry conditions, using ASSAB 17 tool bits with Hafnium Nitride (HfN) monolayer coating, deposited as a thin film via magnetron sputtering physical vapor deposition (PVD) technique, and uncoated tool bits, used as reference system. The surfaces of the machined steel were evaluated and characterized using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The use of monolayer HfN coating on the tool bits was demonstrated to improve the surface finish of the workpiece and reduce cutting process time and cost.Keywords: Monolayer, Surface roughness, Machining, Cutting Tools, Hafnium Nitride. ResumenEn este trabajo, se realizó el mecanizado por arranque de viruta del acero AISI 1020, en condiciones de ausencia de lubricación; utilizando buriles de acero rápido ASSAB 17, con recubrimiento monocapa de Nitruro de Hafnio (HfN) depositados como película delgada, mediante la técnica de deposición física en fase vapor (PVD) magnetrón sputtering y con buriles sin recubrir, usados como sistemas de referencias. Posteriormente se evaluaron las superficies obtenidas en el acero mecanizado, caracterizándolas mediante microscopia de fuerza atómica (MFA) y microscopia electrónica de barrido (MEB). Se evidencio que el uso de recubrimientos monocapa de HfN sobre los buriles de acero rápido, mejoran el acabado superficial del material mecanizado, reduciendo los tiempos y costos del proceso de corte.

Among the diverse challenges in machining processes, chatter has a significant detrimental effect on surface quality and tool life, and it is a major limitation factor in achieving higher material removal rate. Early detection of chatter occurrence is considered a key element in the milling process automation. Online detection of chatter onset has been continually investigated over several decades, along with the development of new signal processing and machining condition classification approaches. This paper presents a review of the literature on chatter detection in milling, providing a comprehensive analysis of the reported methods for sensing and testing parameter design, signal processing and various features proposed as chatter indicators. It discusses data-driven approaches, including the use of different techniques in the time–frequency domain, feature extraction, and machining condition classification. The review outlines the potential of using multiple sensors and information fusion with machine learning. To conclude, research trends, challenges and future perspectives are presented, with the recommendation to study the tool wear effects, and chatter detection at dissimilar milling conditions, while utilization of considerable large datasets—Big Data—under the Industry 4.0 framework and the development of machining Digital Twin capable of real-time chatter detection are considered as key enabling technologies for intelligent manufacturing.

The main purpose of coatings is to increase the lifetime of cutting tools, to perform continuous and economical material removal process, reducing the frequency of sharpening or replacement of the tool, which contributes to increase quality of product. Therefore, hafnium nitride (HfN) single layer coatings were deposited on High-speed steel by Magnetron Sputtering physical vapour deposition (PVD). The machining on AISI 1020 steel samples were carried out in a computer numerical control (CNC) machine, using coated and uncoated tools, the temperature of the different components were measured (steel bar and tool), due to continuous temperature measurement help to predict tool wear and the quality of finished piece [1] . In order to evaluate wear resistance and performance, not only temperature data were compared, the tool wear morphological analysis for flank wear was carried using Scanning Electron Microscopy (SEM), and work pieces roughness were checked through their surfaces in an Atomic Force Microscopy (AFM). In most of the parameters evaluated differences between the tools were identified, and results reveals that on HfN coating, occurs less wear, due the proportionality between the energy transfer and the tool deterioration, also the coating improves surface finish of the machined part; all of them are reflected in changes on process temperatures. The use of single layer HfN coating on cutting tools could increase their lifetime, improve the quality of the work piece, and even reduce process time and cost.

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