Accurate prediction of cutting forces is essential for process planning and optimisation in modern machining. Mechanistic modelling is widely used for this purpose, but its accuracy is strongly affected by imprecise evaluation of uncut chip thickness and cutter-workpiece engagement. In addition, the choice of a suitable cutting force model and its identification methodology are non-trivial and directly influence cutting force prediction. This article introduces a general methodology for the modelling of uncut chip thickness in both conventional and high-feed milling. The approach is based on a parametric description of milling cutters combined with an algorithm for the computation of uncut chip thickness. This framework accounts for geometrical effects such as tool run-out, differential pitch and insert geometry, enabling a more reliable description of cutter-workpiece engagement than classical approximations. The methodology is coupled with mechanistic cutting force models and validated experimentally through instrumented high-feed milling tests of Ti-6Al-4V titanium alloy. An inverse identification strategy is developed to determine cutting force model coefficients from measured forces, including a quantitative correction of tool angular shift between simulation and measurement. In addition, the influence of the transition uncut chip thickness on the fractional model is investigated. Finally, the variability of identified coefficients is analysed across tool revolutions and cutting conditions. Sensitivity analysis demonstrates how this variability impacts simulated forces, providing a criterion for assessing the relevance and robustness of cutting force models. The proposed methodology thus offers a systematic framework for accurate force prediction and critical evaluation of mechanistic models in milling.

In modern manufacturing, accurately predicting cutting forces is essential for the design and control of machining operations. Common mechanistic models of cutting forces rely on a precise description of the local uncut chip area. However, in milling, the specific trajectories of cutting edges create challenges in modelling this quantity. Existing analytical models are typically limited to 2D contexts or assume circular tooth trajectories, which are mostly valid for cylindrical end mills. These assumptions limit their applicability to high-feed milling, especially due to low lead angles and complex insert cutter geometries producing non-circular paths. This article presents a new three-dimensional analytical model for evaluating the local uncut chip thickness in high-feed milling. It relies on closed-form expressions derived from geometric analysis and Taylor expansions to approximate the uncut chip area and cutter-workpiece engagement, even in regions where conventional models fail. The model applies to linear-path milling and accounts for tool run-out and differential pitch. Compared to a Newton-Raphson numerical method, it achieves a relative error below 5% while being 3 to 9 times faster, enabling efficient integration in force models. Beyond its computational efficiency, the explicit formulation enables analysis of geometric influence, such as sensitivity to feed per tooth or tooth count-capabilities not easily accessible with purely numerical approaches. This work contributes a rigorous and interpretable alternative for improving cutting force prediction in high-feed milling.

The applications of advanced ceramics such as Silicon carbide (SiC) or Silicon-SiC (Si-SiC) are widely developed in electronic, automotive and aerospace. The grinding of such hard and brittle materials remains challenging in terms of efficiency, accuracy and surface integrity. Grinding process involves the simultaneous interaction of multiple cutting edges with random geometries. The grain engagement is used to analyse and model the forces generated. The uncut chip thickness is difficult to determine in the case of grinding due to the uncertainty of the grain shapes, sizes and positions. This study presents a new method to simulate the interaction between each grain of the grinding wheel and the workpiece through the evaluation of the uncut chip thickness. Firstly, the real 3D topography of the electroplated diamond grinding wheel is measured using a focus-variation microscope. Then, the uncut chip thickness for each grain is calculated using this tool topography. The results coming from the simulation are used to evaluate forces generated during the grinding process. Finally, the results from the simulation are compared with experimental measurements on SiC material grinding.

In machine-tools, geometrical defects are unavoidable. They can greatly affect the dimensional accuracy of the final workpiece if not corrected. Software compensation strategies are less expensive than mechanical adjustments and they provide great improvement in volumetric accuracy. In this study, different compensation methods are compared in a 3-axis milling applications: Numerical Controller (NC) internal compensation tables, modification of the programmed tool-path (G-code) and modification of position feedback signals. The latter is the main purpose of this work, because it shows great potential and is not linked to one particular type of NC. It communicates with a custom software application that processes the position data and generates corrected signals according to a geometric model based on the rigid body assumption. The NC is then induced to perform volumetric error correction based on its default programming. The compensation methods are compared based on their ability to bring out or correct imposed geometric errors. The highlighted solution shows performances comparable to the G-code modification by correcting more than 96% of the imposed geometric errors without affecting the numerical chain from the program generation to its execution on the machine. It is also independent of the NC or the motors control cards.

Geometric errors in a machine tool structure are mainly responsible for the volumetric error in the workspace. They occur at the attachment of each link between axis joints, but also along each axis in their joint frame. Reducing the impact of these errors is a key factor in guaranteeing the functional requirements of high value-added parts. Unlike mechanical correction, software compensation strategies are often chosen for their ease of implementation and versatile nature. In this study, a correction method by modifying the position measurement in real time is introduced and compared to compensation tables. The reaction response of the numerical controller (NC) to the modification of its position feedback is studied, and a 5-axis machining experiment to validate the proposed solution is performed. The principle of the experiment is to impose a virtual volumetric error in the workspace by modifying a machining program, then to test separately the ability of compensation tables and the proposed method to correct the chosen virtual geometric errors. The aim is to obtain a corrected workpiece similar to the one machined with a nominal program. In this way, it is not necessary to identify the geometric errors of the machine’s structure to test the performance of software compensation methods. The machined workpieces feature geometries that are easy to control, but the tool paths generated to produce them were complex enough to challenge the compensation methods. The ability of the proposed solution to correct the virtual volumetric error introduced by a modified machining program is evaluated at 98

In modern manufacturing, machining remains a vital process for complex mechanical components. In particular, the aerospace industry extensively employs high-feed milling techniques to machine complex geometries from nickel-based superalloys. This study focuses on the analysis and modeling of high-feed milling for Inconel 718 in 2.5-axis machining. Its objective is to develop a generalized model of high-feed milling that enables the prediction of surface topography. The proposed model integrates crucial geometric parameters of the tool and its exact kinematic within the machine, along with tool and machine deflections caused by cutting forces. A key novelty of this research lies in its capability to determine surface topography and its quality based on a generalized model, representing significant progress in the field of high-feed milling. To validate the model, experimental efforts are measured to characterize the cutting forces and system deflections during machining. The developed approach demonstrates its ability to model surface topography and to predict surface roughness. It also highlights the influence of tool and machine deflection on surface quality. This research contributes to the advancement of the application of high-feed milling in aerospace manufacturing by enhancing machining capabilities and improving part quality.

Aeronautical parts located in hot engine zones may be made of Inconel 718: a material known for its poor machinability. This results during machining in high levels of thermo-mechanical loading, located in machined subsurface. This loading may affect the surface integrity and residual stresses may lead to part distortion in some cases. Certain geometric features, such as scalloped housings or thin walls on turbomachinery, are obtained by flank milling. This study demonstrates that residual stresses during Inconel 718 flank milling can lead to part distortion and proposes a methodology to characterize involved phenomena. Instrumented machining of beam-type workpiece allows to quantify these geometric deviations and the stresses introduced into the subsurface by the milling process. The specimens are characterized before and after the finishing operation: distortion is assessed by measuring the straightness of the specimen and its stress state using the XRD method. The studied parameters are the cutting conditions, such as cutting speed, feed and flank wear. It is therefore possible to conclude which parameters have an impact on specimen distortion and on the stress level in the work material, then the approach to use perform the reduction of workpiece distortion. (c) 2024 The Authors. Published by Elsevier B.V.

Inconel 718 is a challenging alloy to machine, commonly employed in the aeronautic and energy industries. There is a continual need to enhance our understanding of its cutting processes to improve its machining applications. This research presents an in situ analysis of the kinematic and thermal fields behaviour of a serrated chip, during orthogonal cutting in the primary shear zone. This study involves a specific self-designed optical system enabling the simultaneous acquisition of both a visible high-speed CCD camera and an infrared camera via a single × 25 magnification reflective objective. A particular attention is brought to evaluate the accuracy of the whole optical system to measure the thermomechanical fields in the unfavourable peculiar cutting conditions among such are high strain rates, texture evolution, strong thermal gradients, and very narrow observation window. The description of the digital image correlation technic within the visible range and the infrared images post-processing are both affronted, and their limitations exposed. To conclude, a deeper characterisation of the primary shear zone shape is done from the kinematic and the thermal point of views showing that, at least under the employed cutting conditions and for Inconel 718 alloy, the primary shear zone width exhibits no thickness despite the literature.

The understanding of phenomena related to machining processes in the aerospace industry is still the subject of study in the research community. This is due to the constrained geometric tolerances to ensure optimal performance and safety. Few studies have yet focused on the effect of the clamping sequence on part distortions during the machining process. Thus, the development of machining sequences, in particular the positioning of clamping points, still requires optimisation regarding the geometry to be machined. This contribution focuses on a first step of a study that aims to characterize workpiece distortions resulting from a multi-stage process in relation to the clamping, cutting forces and the initial ormachining induced stresses. To validate the approach, an in situ methodology for characterising the defects has been developed alongside a particular workpiece holder based on an industrial procedure is set up in order to observe and limit the part distortion along the whole process. The machining sequence is divided into two machining steps separated by unclamping and clamping operations. Frontal axisymmetric grooves are machined in turning on both sides of a thin Inconel 718 elementary disks. These operations are subject to in situ measurement on both side of the workpiece. A laser profilometer and laser point sensors are used between each pass and at each stage of the machining sequence operation. The collected data will be used in a next step to validate a numerical model that predicts the evolution of the distortions of the part during the entire machining process.

The radiometric calibration of an infrared camera is a crucial and unavoidable step to obtain an accurate temperature measurement. The calibration does the link between the sensor digital levels and the actual radiometric temperature. Although this step is critical and necessary to obtain meaningful measurement, it is a complex and time-consuming procedure, which requires many experimental data acquisitions and an algorithm to process them. This article proposes a method based on the radiance data processing allowing an easily and quickly radiometric calibration. Thanks to the proposed method, an integration time insensitive radiometric calibration is obtained from only two different observed steady and homogeneous thermal conditions (using a black body or equivalent).

In the thermography process, accurately determining emissivity is crucial to obtain precise temperature measurements as it enables the conversion of radiometric values to absolute temperatures. However, assessing emissivity is not a straightforward task as it depends on various other parameters. Traditional methods for measuring emissivity often involve costly materials and cannot be carried out simultaneously with infrared image acquisition. This article presents a method for obtaining pixel-wise emissivity using data from a multispectral infrared camera. Consequently, this method allows for direct emissivity measurement during infrared camera acquisition without the need for additional materials or experiments.

Burr size is a real issue in aeronautic for machining highly critical parts, such as broaching of turbine disks, it may affect the mechanical resistance of the part. However, the analysis and modelling of the burr formation and its accumulation is challenging due to the small concerned root area and the change of its shape after multiple cuts. In the state of the art, there is not much contribution on the burr mechanism during accumulation. To investigate this subject on nickel-based super alloy parts, an experiment with an in situ camera and LASER profilometer has been developed to follow the burr growth after multiple passes. Then, a phenomenological model of burr accumulation is formulated based on the description of a plastic hinge appearance during burr formations. It enables the modelling of burr height, root thickness and added material to the burr after each pass. Burr fracture occurrence is also discussed. This work proposes a new outlook on the burr formation mechanism and complete the models previously developed in the known literature.

Inconel 718 is widely used in aircraft industry due to its properties. Nevertheless, its mechanical and chemical properties make it hard-to-cut. As a consequence, additive manufacturing is developed in order to get near net shape part before machining. Thus, this article presents a study on the machinability of the Inconel 718 obtained by additive manufacturing compare to one from wrought bar. Firstly, the machinability in milling is investigated through microstructure observation and cutting forces analysis, then a tool wear observations for both material are realised. Thereafter, novel formulations of cutting force model in milling are developed associated to precise treatment and identification process. Thus, the cutting forces are modelled with a mechanistic approach fully parameterized, and furthermore the tool geometry as well as the local forces model consider tool flank wear effect. This study shows that additive manufactured Inconel 718 has a better machinability and that considering tool wear with tool geometry evolution improves the model precision.

In-process workpiece elastic deflection is the major source of geometrical error when machining low-stiffness workpieces. It creates an undercut error which needs to be corrected by time-consuming and labour-intensive operations. For this reason, cutting process simulation is growing in interest. To do so, a model representing the workpiece flexibility is coupled with a model to predict the applied cutting forces. For a given tool-material set, these cutting forces depend on the cut section, which therefore depends on current deflection of the part during machining, but also on the level of tool wear. This research work focuses on developing a general coupling approach to tackle this challenge. The case study is the finish turning on thin Inconel 718 discs. The cutting forces are predicted by a mechanistic model taking tool wear into account. The wear effect is expressed using the cumulative removed volume. The workpiece stiffness is determined with a reduced model using a modal basis. When dealing with large workpieces, it results in a remarkable computing time reduction during the time domain simulation. Cutting tests with varying engagements are simulated in a dexel-based versatile framework and undercut errors are compared to experimental observations.

Machining thin workpieces is a challenging task as geometrical errors may result from the combination of several phenomena. Among these, elastic workpiece deformation and machining induced residual stresses may be predominant sources due to low part stiffness. There is a lack of studies trying to quantify the influence of machining induced residual stresses on the total geometrical errors. A thorough experimental methodology is developed to quantify the influence of both phenomena separately by comparing the workpiece shape and dimensions, in-situ, before and after machining, using laser sensors. The proposed methodology can also be used to quantify the geometrical errors linked to clamping or stress rebalancing following material removal. The case study is the finish turning of thin Inconel 718 workpieces using carbide tools. In the studied case, machining induced residual stresses are responsible for 3-32 % of the total geometrical errors depending on tool wear and cutting parameters.

As mechanical, physical and microstructural properties of metals can be significantly affected by the machining process, electrochemical properties and corrosion resistance are consequently altered. Manufacturers should control the impact of cutting conditions on surface integrity, as it will affect the component's functional performance and life. This study addresses the case of orthogonal cutting of oxygen-free high conductivity copper. A set of experiments was performed and a statistical analysis was conducted to reveal the relationship between the cutting conditions and the surface integrity in terms of residual stresses, microstructure, plastic deformation and hardness and the impact of those parameters on the electrochemical behaviour. The physical origins of the observed phenomena are explained. The results show that the surface performance can be controlled by selecting the appropriate cutting conditions (e.g. reducing the tensile residual stress and roughness by more than 75%), such that the electrochemical behaviour can be enhanced.

To reduce the size of exit burrs induced by broaching, it is possible to use a low value martyred part clamped to the functional one on the tool exit side. Thence, this research work deals with an in-situ analysis of the burr formation at a bi-specimens interface in orthogonal cutting configuration. New mechanisms of burr formation at the interface formed by Inconel 718 and cast iron specimens are identified. In addition, a post-machining study is carried out to quantify the burr size obtained with and without the martyred part.

This study presents a novel analysis of the machined subsurface layer formation dealing with strain hardening phenomenon which results from complex mechanisms due to cutting edge multiple passes in drilling. On the one hand, the hardened layer during drilling is characterized in relation with the local cutting geometry and thanks to a quick-stop device (QSD) to suddenly interrupt the operation. Micro hardness is used to determine the hardened thickness of the machined subsurface layers along the local cutting edge geometry. On the other hand, orthogonal cutting performed with a complex self-designed planing experiment is used to investigate in details the hardening accumulation aspects. Then, dedicated methodologies are proposed to quantify the strain hardening as well as the incremental plastic strain generated by consecutive tool passes. In addition to the subsurface hardness evolution, the work material strain is observed during the steady-state cutting process thanks to the high-speed camera. The digital image correlation technique is exploited to analyze not only the plastic strain remaining on the workpiece after the cut but also the effect of the incremental plastic strain generated by the consecutive planing passes as the cutting edges in drilling do. One of the outcomes is that the hardened layer thickness can reach from two to three times the cut thickness in drilling or in planing. As a consequence, this work demonstrates that the cutting process affects itself by hardening. Thus, the studied austenitic stainless steel in such a way that this last is never cut in its initial state.