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A novel aerosol evaluation cell was employed to measure particle number and mass concentration, with a size distribution from nano to micro scale. Different cooling/lubrication and airflow extraction scenarios were tested on a CFRP/Ti6Al4V case study, and the particle concentrations were measured to evaluate their effect on productivity and cost per hole, if current occupational exposure limits are respected. Aspects to achieve sustainable machining like tool life, consumption of coolant and energy, and standby time required to safely open the machine-tool doors were considered. LCO 2 delivered the best productivity and cost results as it improved the tool life by 40 % compared to MQL, while eliminating the need for standby time to evacuate particles. [ABSTRACT FROM AUTHOR]

The development of cutting tools requires the knowledge of tribological phenomena at the tool – workpiece contact area. This knowledge is in dearth particularly for difficult-to-cut alloys like gamma titanium aluminide (gamma – TiAl alloys). Therefore, this article is an attempt to plug the gap and aid the development of cutting tools for gamma – TiAl alloys. To this end, friction, adhesion, and coating wear between AlTiSiN coated cemented carbide tool and Ti-48Al-2Cr-2Nb (Near lamellar), Ti-48Al-2Cr-2Nb (Duplex), and the most used titanium alloy of Ti-6Al-4V (alpha – beta) were experimentally derived. A Pin-on-Cylinder (PoC) tribometer with contact conditions corresponding to commercial machining conditions was used with dry, flood(EML), and two MQL lubricants. Additionally, the heat generated and partitioned between the pin and workpiece was quantified to assess the thermal exposure to the coatings. The results showed that Ti-6Al-4V had approximately 50% higher apparent friction coefficient than the Ti-48Al-2Cr-2Nb alloys. Interestingly, the friction coefficients of Ti-48Al-2Cr-2Nb alloys were nearly consistent across the entire test matrix. Notably, the change in the microstructure from near lamellar to duplex did not elicit any qualitative or quantitative change in the friction profile of Ti-48Al-2Cr-2Nb alloys. The contact pressure proved to be the statistically significant property influencing friction evolution inversely for Ti-6Al-4V alloy and directly for Ti-48Al-2Cr-2Nb alloys. The results showed higher probability of coating wear in dry conditions as opposed to the flood and MQL lubricants. [Display omitted] [ABSTRACT FROM AUTHOR]

Drilling is a continuous cutting process where two or more cutting edges remove the material, to obtain the desired feature. During the chip evacuation, it generally rubs against the generated surface. Thus, the roughness obtained differs from other machining processes such as turning or milling. Therefore, surface roughness can be different from the analytically expected one. In this research work, an analysis of the cutting conditions where a level of roughness is expected to meet specific requirements has been carried out. 600 holes were made with two different tool geometries on steel without modifying the cutting conditions. When analysing the surface generated, certain variability in the roughness profiles obtained can be observed. External signals to the machine tool were acquired with sensors (cutting forces, vibrations, and acoustic emissions) as well as internal signals (spindle power, spindle torque in the Z-axis, spindle current and positions, speeds, accelerations, and jerk of the tool tip in the three axes of the machine). The most representative statistical features of the signals regarding roughness were selected using correlation analysis. Besides that, the hierarchical clustering of statistical features of the external and internal signals of the process was compared with clusters obtained using roughness parameters. Results show that clusters appear using signals highly related to the roughness parameters obtained from the measured profiles, confirming a mapping between the acquired signals during the machining process and the roughness of the holes. [ABSTRACT FROM AUTHOR]

Surface topography irregularities generated by broaching are analysed. Experimental tests were carried out on three workpiece materials: AISI 1045, Ti-6Al-4V, and Inconel 718, varying the cutting speed, rise per tooth, and rake angle. The experimental results combined with numerical simulation demonstrate that surface topography irregularities result from mechanical rather than thermal effects. Higher surface topography variations are obtained when the force magnitude increases, and when its direction is more perpendicular to the machined surface. Additionally, the Young's modulus of both the workpiece and tool materials plays a fundamental role in topography quality, reducing irregularities when the Young's modulus is increased. [ABSTRACT FROM AUTHOR]

A novel methodology to map the friction and normal stress distribution on the rake face using Partially Restricted Contact Length Tools in orthogonal cutting tests is proposed. The influence of cutting speed, feed and coatings on tool-chip friction when machining AISI 1045 is analysed. The results demonstrate that the new methodology can replace the more difficult to use and less robust split-tool method. They confirm two clearly different contact zones: i) the sticking region, governed by the shear flow stress of the workpiece and ii) the sliding region, where the friction coefficient is higher than 1. [ABSTRACT FROM AUTHOR]

Today's industrial transformation is taking advantage of the benefits of information and communication technologies (ICT) to evolve into a more decision-making environment in manufacturing. Efficiency, agility, innovation, quality and cost savings are the goals of this transformation in one of the most employed manufacturing processes as is the case of machining. Drilling processes are among the last operations in the different manufacturing stages of machined parts, where an undetected problem can lead to the production of a defective part. Data analysis of sensor signals gathered during drilling processes provides information related to the cutting process that can anticipate non-desired phenomena. This work illustrates the experimental setup for sensorial data acquisition in drilling processes, signal processing techniques and feature extraction methodologies for faster and more robust decision-making paradigms. [ABSTRACT FROM AUTHOR]

Accurate and fast prediction of cutting forces is important in high-performance cutting in the aerospace industry. Gamma titanium aluminide (γ-TiAl) is a material of choice for aerospace and automotive applications due to its superior thermo-mechanical properties. Nevertheless, it is a difficult to machine material. This article presents the prediction of cutting forces for Ti-48Al-2Cr-2Nb (48-2-2) γ-TiAl in milling process using orthogonal to oblique transformation technique. The novelty of this paper lies in reporting the orthogonal database of 48-2-2 γ-TiAl. Fundamental cutting parameters such as shear stress, friction angle and shear angle are calculated based on experimental measurements. Friction coefficients are identified for two different coating conditions which are AlTiN, and AlCrN on carbide tools. Predicted results are validated with the experimental cutting forces during end milling and ball-end milling operations for different cutting conditions. The simulated results showed good agreement with the experimental results, which confirms the validity of the force model. [ABSTRACT FROM AUTHOR]

Broaching is a unique machining process with high accuracy and surface quality, which is employed in mass and batch production for the manufacture of components with highly complex geometries. It involves the use of multiple-edged complex tools in which the cutting edges are arranged with an offset also known as "rise per tooth" that determines the depth of cut per tooth. This paper presents the state-of-the-art of both the experimental and modelling aspects of broaching, and identifies the most important features related to this machining process. This includes a critical assessment of specifically designed broaching setups and their applicability and/or limitations compared to the machines used in industry. Contributions from academia and industry are included to support a comprehensive report of recent advances, as well as a roadmap for future developments. [ABSTRACT FROM AUTHOR]

Abstract The machining of difficult-to-cut materials involves limitations leading to low productivity in conventional machining processes due to high cutting forces and tool wear rates. The ultrasonic assisted machining techniques have been reported to reduce these drawbacks significantly, enabling the increase of productivity when machining this kind of materials. In the case of the reductions on cutting forces and their control, they can lead to important improvements concerning achievable Material Removal Rates (MRR) on processes where the maximum cutting forces are limited due to part-tool deflections or the appearance of chatter vibrations. The present study analyses the cutting force reductions generated when ultrasonically assisted turning of Ti6Al4V. The obtained results were analyzed for identifying the most relevant parameters generating such force reductions. Finally, an empirical model was developed allowing the calculation of the cutting forces to be generated during ultrasonic assisted turning operations of Ti6Al4V. [ABSTRACT FROM AUTHOR]

This paper reviews recent advances in constitutive and friction data and models for simulation of metal machining. Phenomenological and physically-based constitutive models commonly used in machining simulations are presented and discussed. Other topics include experimental techniques for acquiring data necessary to identify the constitutive model parameters, and recent advances in modelling of tool-workpiece friction and experimental techniques to acquire friction data under machining conditions. Additionally, thermo-physical properties for thermal modelling of the machining process, and microstructure data for the chip and workpiece together with relevant experimental methods are discussed. Future research needs in each of the focused areas are highlighted. [ABSTRACT FROM AUTHOR]

Broaching is a specific process characterized by relatively low cutting speeds and uncut chip thicknesses. The latter is in the range of 0.1 to 0.25 mm in the roughing section of the tool but can decrease down to 0.0015 mm in the finishing one. This induces drastically different cutting behaviours compared to macroscale processes such as turning. The question of the scale effects in such conditions is thus clearly raising and especially the size and distribution of the microstructure. This paper proposes an investigation to assess the importance of the material heterogeneities on chip formation when broaching ferritic-pearlitic steels. [ABSTRACT FROM AUTHOR]

The finite element approach is often adopted to study the machining process. The Lagrangian and Eulerian formulations or even Arbitrary Eulerian-Lagrangian (ALE), one of their combinations, are the most employed in the current literature; each having their pros and cons. One of the most challenging issue in finite element modelling is the large strains during the cutting process that induce high deformation levels in the elements of the mesh. Remeshing contributes to decreasing mesh deformation but the criterion adopted to control it influences the results. The Coupled Eulerian-Lagrangian (CEL) method proposes to combine the Lagrangian and Eulerian formalisms without any element deformation problem. This paper studies its implementation in Ti6Al4 V orthogonal cutting. The results are then compared to an experimental reference, as well as more standard models: an ALE model developed with Abaqus, an implicit Lagrangian model developed with Deform and an explicit Lagrangian model developed with AdvantEdge. The comparison is mainly based on the cutting forces and the chip morphology. It shows that the CEL formulation is a competitive alternative to the more standard models. [ABSTRACT FROM AUTHOR]