Cutting Force Variation Research Articles

Method for Increasing the Energy Efficiency of the Gear Teeth Cutting Process by Smoothing the Cutting Force Variation

The energy efficiency in metal cutting is, sometimes, very low. Recent studies show that the energy consumed for detaching chips represents only about 15% of the total energy involved in material machining. The available solutions for energy optimization in cutting processes mentioned are the improvement of manufacturing equipment, the optimization of processes, and appropriate production scheduling. Already-performed research shows that to increase energy efficiency, the cutting force must be reduced, for example, by reducing the depth of the cut and by increasing the feed rate. However, this is applicable when the cutting force is quasi-constant during the process, which is not the case for gear teeth cutting when the cutting force significantly varies. The present paper proposes a new solution for energy efficiency increase in gear teeth cutting, namely, the smoothing of the cutting force variation during the machining process, by keeping the area of the detached chip section quasi-constant during the cutting process. This can be reached by replacing the constant rolling feed, currently used in gear teeth cutting, with a rolling feed that varies after an appropriate law. An algorithm dedicated to implementing this solution has been developed. It uses graphical modeling in CATIA to find the variation in the detached chip area. Original MatLab R2018a applications were developed (i) to identify the analytical form of the law that approximates this variation and (ii) to find the variation law of the feed during the rolling motion, if imposing a constant area of the detached chip. The algorithm was successfully applied in the cases of toothing with a rack tool (by slotting) and with a pinion cutter (by slotting and turning). A technical solution for method implementation in practice is also presented.

Characterizing Rock-Breaking Performance of PDC Cutters via Stability Metrics and Energy consumption in FDEM Simulations

As oil production increasingly transitions from shallow to deep formation, the need for efficient PDC cutters to drill through deep hard rock becomes paramount. Currently, there is a lack of effective methods for optimizing cutter shapes and their cutting parameters. This study addresses this gap by developing a rock-breaking mechanism model for PDC cutters and proposing a Stability Index (SI) based on cutting force variations during the cutting process. Using the FDEM method, we simulated the rock-breaking processes of planar, stinger, and machete cutters under various cutting depths and angles. SI and Mechanical Specific Energy (MSE) were employed as evaluation metrics to analyze the rock-breaking characteristics and determine the optimal cutting parameters for each cutter type. The results indicate that at shallow cutting depths, cutting force changes are minimal, predominantly causing plastic damage to the rock, resulting in lower stress and reduced wear on the PDC cutters. Conversely, at greater cutting depths, significant fluctuations in cutting force occur, leading to brittle failure and the generation of large cuttings. This sudden increase in cutting force can accelerate rock breaking but also increases the risk of cutter wear. Our findings suggest that the planar cutter offers stable performance with high cutting force requirements, optimal at a cutting depth of 1.5 mm and an angle of less than 20°. The stinger cutter, requiring lower cutting forces, performs best at a cutting depth of 2 mm and an angle of 20°. The machete cutter exhibits characteristics similar to the stinger cutter at shallow depths and the planar cutter at deeper depths, making it suitable for drilling at a depth of 2 mm and an angle of less than 10°. By balancing SI and MSE, this study provides a comprehensive approach to optimizing PDC cutter performance, enhancing drilling efficiency while minimizing cutter wear.

Comparative analysis of cutting characteristics of simulated and bovine cortical bone

Simulated bone is widely used for surgical simulation, medical training, and especially for medical cutting device testing due to its mechanical properties similar to those of natural bone. However, studies on its cutting characteristics are still limited, especially for the simulated cortical bone. The cutting characteristics of natural cortical bone are often influenced by viscoelasticity and bone fiber structure that affect chip formation, as well as the variation of cutting forces at different cutting speeds or different depths of cut. In this work, orthogonal cutting experiments were performed on simulated cortical bone to investigate chip formation with cutting force variations and compared with bovine cortical bone. Experimental results show that the simulated cortical bone is similar to bovine cortical bone in viscoelasticity. Simulated bone has a relatively homogeneous composition with a simple hierarchy. Therefore, the difference in cutting force at small and large cutting depths is less significant than in natural cortical bone. In addition, because the glass fibers in simulated bone are randomly distributed, they do not accurately reflect the anisotropic properties of natural cortical bone. These findings can contribute to an in-depth understanding of the behavior of simulated bone during the cutting process and guide the improvement of simulated bone to better emulate the cutting characteristics of cadaveric bone for better application in the medical field.

Experimental study and simulation analysis of the fracture mechanism in AFRP milling

The finite element model of aramid fiber reinforced polymer (AFRP) was established using the finite element analysis software, and milling simulation analysis was carried out. The influence of cutting speed and tool diameter on cutting force was obtained. Based on the motion law of the milling cutter, a fiber cutting mechanical model was established, and the influence of shear force and transverse pressure on the quality of the fiber section was analyzed. The milling experiment on AFRP specimens was carried out, and the milling appearance and cutting force variation of cutting speeds at 18.850–31.415 m/min and tool diameters of 1 –5 mm were studied. The results show that the diameter of a 5 mm milling cutter has a neater cutting fiber section and fewer burrs than the diameter of a 1 mm milling cutter, but inadequate sharpness can easily cause serious entrance burrs. Due to the influence of the feed motion, the milling tool feeding direction (X direction) is 42.456% higher than the Y direction cutting force, which can easily cause tool fracture. Increasing cutting speed can reduce cutting force to a certain extent and improve cutting quality. Therefore, choosing a large-diameter milling cutter with a large rake angle or relief angle for high-speed cutting can effectively improve the quality of the AFRP milling entrance and section.

Rock breakage and temperature variation of naturally worn PDC tooth during cutting of hard rock and soft rock

Although experiments and simulations of new polycrystalline diamond compact (PDC) tooth cutting have been conducted, the rock breakage and temperature variation of the worn PDC tooth cutting are still unclear. Thus, naturally worn PDC teeth removed from a worn PDC bit were used to determine the rock breakage and temperature variation of hard rock and soft rock using force sensors, high-speed photography, and thermal infrared instruments. The effects of wear on cutting force, temperature variation, and cutting chips were studied. The results indicate that the cutting force variation is different in granite and sandstone. The temporary increasing time of the sandstone cutting force is 0.04–0.063 s, which is less than for granite cutting (0.04–0.075 s). Greater wear of the cutter increases the time for the cutting force to increase from zero to an extreme value. The maximum cutting force of granite is 6.7 times greater than that of sandstone; the temperature increase of the PDC tooth in cutting granite is seven times greater than in cutting sandstone. As the wear increases, there is extreme fluctuation in the cutting force and temperature variation, which is attributed to the periodic removal of larger flake cutting chips. The relationship between the wear and the mechanical specific energy per unit mass (MSEP) and the coefficient of friction (COF) is discussed. It was found that as the wear increases, the cutting temperature and the MSEP quickly increase, and the COF decreases. This study is helpful in comprehensively understanding the rock breakage and heat generation of naturally worn PDC teeth in deep wells, which is beneficial for estimating the PDC cutter life and failure.

Numerical and experimental investigations on the laser assisted machining of the TC6 titanium alloy

In order to improve the machinability of difficult-to-machine materials in aviation, laser-assisted cutting technology has received extensive attention. This method of machining allows the workpiece to obtain a localized high temperature prior to cutting in order to benefit from thermal softening. A 3D transient laser heating model was developed for the finite element method to predict the preheating temperature of the cutting layer. The effect of cutting parameters (cutting speed, feed rates, depth of cut) on the magnitude, frequency and amplitude of the cyclic cutting forces was investigated both in conventional machining and in laser assisted machining. It is founded that the laser assistance decreases the flow stress of the material, magnitude of cutting forces and the amplitude of cutting forces. But the frequency of circulating cutting forces increase comparing with the CM (conventional machining). In addition, this paper considers the effect of the LAM (laser-assisted machining) technique on reducing the magnitude of cutting force fluctuations, which results in a flatter machined surface profile and reduces the number of surface defects. A chip morphology different from that of CM is created due to the influence of the cutting force by the temperature field in LAM. Furthermore, a “transitional chip” is discovered, which is a transition from a continuous chip to a segmented chip. The completely thermal-mechanical coupled orthogonal cutting model was established to reveal the evolution mechanism of shear band formation with laser assistance. The results show that shear bands can be formed faster and with less stress in LAM compared to CM. The model can effectively predict the shear angle and keep the prediction error within 10 %. The shear band formation processes in both machining methods were uncovered according to the models. The developed model is very useful for understanding the chip formation process and the cutting force variation in laser assisted machining.

Influence of shielding gas on machining and wear aspects of AISI 310–AISI 2205 dissimilar stainless steel joints

Abstract In this article, the effect of shielding gas combinations on gas tungsten arc-welded dissimilar AISI 310 steel and AISI 2205 steel joints was investigated. Two gases such as nitrogen and carbon dioxide were substituted in argon shielding gas and its corresponding improvement in the mechanical, microstructural, machining, and wear aspects of the dissimilar AISI 310–AISI 2205 joints was studied. Weld bead studies, tensile, and weld region microhardness were conducted. X-ray diffraction studies revealed joint intermetallics, and microstructural evaluation was conducted. Machining studies were conducted using drilling experiments. Using local analysis and global analysis, the cutting force variations in the feed direction and cutting direction were studied. Wear tests revealed that the variations in traction force, specific wear rate, coefficient of friction and tribo wear mass loss were studied. A considerable improvement in wear characteristics of AISI 310–AISI 2205 joints was observed by substituting CO2 and N in shielding gas.

Modeling and Stability Analysis of Robot-assisted Thin-walled Milling

Thin-walled machining has played an important role in automotive and aerospace domains. Due to physical characteristics of the flexible structure, the thin-walled machining is prone to the deformation and the onset of chatter. To solve the problem, a robot is considered to support the flexible workpiece while cutting. This paper studies finite element dynamic modeling and stability analysis of the robot-assisted thin-walled milling system. It is divided into three submodels: thin-walled workpiece, robot, and cutting process. The finite element method (FEM) is adopted to obtain a realistic dynamic model of the workpiece and allows analysis of any location. The robot dynamics is linearized to a 1-degree-of-freedom (DOF) mass-spring-damper system for model reduction. The cutting force variation and the regenerative effects involved in the cutting process establish time-periodic and time delay terms in the milling model. The semi-discretization method (SDM) is used for the stability analysis. Simulation results show a significant improvement in the milling stability from the robot support in any location, leading to higher productivity.

Using the finite element analysis to study the cutting speed influence on temperature and internal stresses in the turning process

The tendency to use the approach ing of finite element method in the turning simulation is becoming increasingly pronounced. The cutting process study based on this type of method requires the identification and knowledge of the geometric tool parameters that define the whole process. This simulation method aims to establish and describe the entire development process, characterized by trying to identify and present the optimal solution or close to an optimal realization and practical development of the entire cutting process. This study aims to draw up tabular analysis reports based on performing a series of simulations on the C45 material using the finite element approaching on DEFORM 2D. During the performed simulations, the same input values of the cutting conditions will be kept, except in the case of the cutting speed, whose modification is the object of the study. In this context, the cutting speed change influences the effective stresses distribution, the temperatures, and the cutting force variation in the cutting process. These issues were followed, and a package of own conclusions and points of view could be operationalized immediately.

Micro-end-milling of carbon nanotube reinforced epoxy nanocomposites manufactured using three roll mill technique

Carbon nanotubes (CNTs) have been applied as nano-fillers to improve mechanical, thermal and electrical properties of polymers. Despite near net shape techniques could be used to manufacture nanocomposites, micromachining processes are still necessary to attain high surface quality and dimensional accuracy. Besides, micromachining of nanocomposites could be a potential approach to produce micro-features/components, following the miniaturisation trend of modern manufacturing. Therefore, micro-machining of these relatively new materials needs to be investigated. A comprehensive investigation on machinability of nanocomposites will be presented in terms of chip formation, cutting force, tool wear, surface morphology and surface roughness. Three controlled quantitative factors are investigated at different levels, including filler loading, cutting speed and feed per tooth (FPT). Micro-slotting is performed on an ultra-precision desktop micro-machine tool using uncoated carbide micro-end mill. The additions of multi-walled carbon nanotube (MWCNT) have shown significant effects on the machinability of these epoxy-based nanocomposites including a dramatic reduction in cutting force and machined surface roughness with accelerating tool wear compared with a neat polymer. The irregular cutting force variations when micro-milling epoxy/MWCNT nanocomposites at feed rates below minimum uncut chip thickness (MUCT) (lower than 2 μm) indicating by their fluctuations that different from those in higher feed rates. It possibly shows the impact of size effects that are illustrated by the observations of chip formation, surface morphology, cutting force profiles as well as specific cutting energy calculation.

Identification method for the dynamic cutting force variation of a high energy efficiency milling cutter

The dynamic cutting force of a high energy efficiency milling cutter is an important indicator for evaluating the stability of the cutting energy efficiency. The existing cutting force analysis focuses on the main characteristics and influencing factors of the cutting force variation in the cutting process, ignoring the influence of the variation of the cutting layer parameters with the cutter tooth error in different cutting stages, and the dynamic cutting force variation is uncertain. In this research, the analytical model of the instantaneous cutting volume of a milling cutter was developed in order to obtain the time-frequency characteristics of the instantaneous cutting volume with the cutter tooth error. According to the sudden changes of the cutting force and the milling vibration, the variations were studied in different cutting stages. The dynamic cutting behavior sequences such as the instantaneous cutting volume, milling vibration, and dynamic cutting force were constructed to characterize the mapping relationship between the dynamic cutting behavior of a milling cutter. Based on these approaches, the identification method for the dynamic cutting force variation of a high energy efficiency milling cutter was proposed. The effectiveness of the method was verified by the results of the milling experiment and the dynamic cutting behavior response analysis. The results showed that the proposed method could effectively identify the variation and its control variables for the dynamic cutting force in the cutting process, and the method could provide a scientific basis for constructing the dynamic cutting force model of a high energy efficiency milling cutter.

Study of temperature and stresses using finite element analysis in turning of C45 material

Parts machined by high cutting speeds can often exhibit high fatigue strength, increased micro-hardness in the surface layers and plastic deformations, due to the tool cutting edge radius associated with the induced stresses. The changing of rake and clearance angles has an important influence on the chip formation, cutting forces, residual stresses, temperatures in both the workpiece and the tool. International research on the influence of geometric parameters of the tool on the entire cutting process, are of particular importance to understand this process development. The approach of this study, considers the parametric realization of the cutting tool profile - a coated TiC turning chisel, which will be used in the finite element simulation of the orthogonal turning process. Deform 2D application, which is a powerful simulation engine was chosen and allows the correct simulation of the cutting process in real machining conditions. Deform 2D enables the automatically meshing and remeshing generation and also the optimization whenever needed and wherever is required a high accuracy, thereby reducing the overall difficulty of the problem and the computational requirements. Using Lagrangian discretization, the machining process was simulated and made possible to observe and present a series of conclusions and own points of view regarding the temperature distribution at the tool tip and in the workpiece, the effective stresses distribution and the cutting force variation under the rake and clearance angles influences.

A MICROSTRUCTURE-BASED MECHANISTIC MODEL FOR BONE SAWING: PART 2 - ACOUSTIC ENERGY RATE PREDICTIONS

Abstract Part-2 of this paper is focused on modeling the acoustic emission (AE) energy rate as a function of the specific cortical bone microstructures (viz., osteon, interstitial matrix, lamellar bone, and woven bone) and the depth-of-cut encountered by the bone sawtooth. First, the AE signal characteristics from the sawing experiments (in Part-1) are related to the pure haversian and pure plexiform regions of the cut. Using the cutting force predictions from Part-1 as input, the AE energy rate is then modeled in terms of the energies dissipated in the shearing and ploughing zones encountered by the rounded cutting edge. For this calculation, the rounded edge geometry of the sawtooth is modeled as a combination of (i) shear-based cutting from a negative rake cutting tool; and (ii) ploughing deformation from a round-nose indenter. The spread seen in the AE energy rate is captured by modeling the variations in sawed surface height profile, tool cutting edge geometry, and porosity of the bone. The model calibration and validation protocols are similar to those used in Part-1. The validated AE model is useful for process planning both in terms of its ability to predict AE energy rate trends and cutting force variations, based on the differences in the underlying bone microstructures.

Tool condition monitoring: unscented Kalman filter for tool flank wear estimation in turning of Inconel 718

This article presents flank wear estimation during the turning process of Inconel 718 in dry cutting condition using unscented Kalman filter (UKF). A discrete flank wear model is developed where two components of flank wear due to abrasion and diffusion are considered as state variables and the cutting force is taken as the output variable. The proposed model can be implemented for online tool wear monitoring and the UKF predicts the actual states of tool flank wear in real-time by measuring the cutting force variation. The simulation result of flank wear estimation using UKF is compared with the extended Kalman filter (EKF) under a similar cutting environment. The error of estimation for UKF is obtained less than that of EKF indicating better accuracy of UKF than EKF for tool condition monitoring of the proposed model. Hardware experiments are performed to validate simulated results of both UKF and EKF on the proposed model correlating the cutting force and flank wear components.

Optimization of Cutting Process Parameters in Inclined Drilling of Inconel 718 Using Finite Element Method and Taguchi Analysis.

Nickel-based superalloys are famous in the demanding applications. Inconel 718 is one of the most commonly used nickel-based superalloys due to its extraordinary inherent properties. Inconel 718 is a suitable material for high temperature applications due to the properties such as anti-oxidization, high hot hardness, high creep, and fatigue strength. Drilling operation is one of the most widely used manufacturing operations in almost all industrial sectors. However, drilling operation is very complex in nature due to the presence of intricate geometry of the drill bit. In conventional drilling, cutting is performed by the combined action of the chisel edge and the two or more cutting lips. In depth analysis of the cutting process shows that chisel edge starts with an indentation at the center of the twist drill. Then away from the center, chisel edge performs orthogonal cutting with negative rake angle. Whereas, cutting action at the cutting lip is oblique in nature, and force analysis involves the use of element formulation due to involvement of radius. It is rarely found in the literature where drilling operation at different inclination angles is conducted and analyzed. The presented study numerically investigates the cutting performance of drilling operation, when operated at different inclination angles. The study revealed cutting force variation at different inclination angles due to the different tool workpiece engagement for each inclination. The magnitude of thrust force increased when inclination angle is changed from 30° to 60°. It can be linked with the higher chip load initially in this case as compared to the 30° inclination angle. The cutting temperature was affected by spindle speed (53.7%), followed by feed rate (33.31%) and inclination angle (3.44%).

Preliminary investigation on ultra-precision diamond turning of titanium alloys using thermoelectric cooler fixture

The low thermal conductivity of titanium alloys causes an accumulation of high cutting heat at the tool/workpiece interface and thus deteriorates surface integrity of the machined surface in ultra-precision machining (UPM). In response of this underlying source causing the poor machinability of the materials in UPM, in this study, a novel fixture composed of thermoelectric cooler (TEC) is firstly developed and applied into single point diamond turning (SPDT) of titanium alloys, aiming to dissipate the cutting heat in the machining process. The TEC contacted with workpiece during the whole turning process and caused a dissipation of cutting heat from the workpiece. By using the fixture with TEC device, the cutting force variation and surface roughness involved in SPDT were reduced. This study presents the preliminary results of application of TEC fixture on UPM of titanium alloys and shows the feasibility of the use of TEC device in UPM area, suggesting a new approach to resolve the problematic high cutting heat of titanium alloys in UPM.

Improved dynamic cutting force modelling in micro milling of metal matrix composites Part I: Theoretical model and simulations

Cutting force modelling for micro machining is of great importance for better understanding of the cutting mechanics in the process. As precision machining of metal matrix composites (MMCs) is much more complex than machining homogeneous materials, the accurate prediction of cutting force is critical to control the cutting performance and tooling life. This paper presents an improved theoretical dynamic cutting force model in MMCs micro milling process by using straight flute PCD end mills. The theoretical model is modified and improved based on the conventional milling force modelling while taking account of various factors including tooling geometries, the material microstructure, size effect and chip formation in the cutting process. An innovative expression on dynamic cutting force in micromachining MMCs is presented through the multiscale modelling and analysis. The cutting force coefficients are further defined through instantaneous cutting force signals analysis. Simulation results under varied cutting process variables are presented against a series of MMCs micro milling trials, which indicate that the improved dynamic cutting force model can predict the cutting force accurately and reveal more details on the cutting force variations in the process due to the material inhomogeneous nature. In addition, the optimal process variables can be readily explored through the dynamic force modelling and simulations so as to further improve the cutting performance.

Machine learning-based instantaneous cutting force model for end milling operation

Cutting force is the fundamental parameter determining the productivity and quality of the milling operation. The development of a generic cutting force model for end milling operation necessitates a large number of experiments. The experimental data contains multiple outliers due to noise and process disturbances lowering prediction accuracy of the model. This paper presents a novel approach combining the mechanistic model and the supervised neural network (NN) model to predict instantaneous cutting force variation during the end milling operation. The approach proposes training of an NN model using datasets generated from the mechanistic force model instead of using experimental data. The methodology generates a large number of datasets for the training of an NN model without conducting rigorous experimentation. A set of NN architectures were developed, and an appropriate network was derived by comparing performance parameters. A series of end milling experiments were conducted to examine the efficacy of the proposed approach in predicting cutting forces over a wide range of cutting conditions.

Prediction of surface variation field in face milling via finite element model updating with considering force-deformation coupling

Effective prediction of surface variation is of great helpf for developing and controlling machining process to maintain surface quality during face milling of large-scale component with discontinuous surface. However, the simulation ranges of machined surface error in traditional finite element analyses are far less than those needed in characterization of large-scale face milling with multi-tooth cutter in order to maintain efficiency. To address this issue, this paper attempts to develop a numerical methodology to estimate the field data of machined surface error based on iterative finite element analysis integrated with cutting trajectory reconfiguration. Finite element model updating (FEMU) method is applied to analysis the cutting deformation in each cutting instant while considering both the cutting force variation in face milling and the locally geometrical differences of component. A flexible model is established to predict the residual cutting material in each cutting instant with considering the coupling effect between instantaneous cutting force and cutting deformation. And then a sub-iteration scheme is proposed to calculate the equilibrium deflection and the real residual material of flexible cutting system with a modified Newton-Raphson method. The proposed simulation methodology can be generally applied for predicting surface variation field in face milling of large-scale component with multi-holed surface, especially for flexible component.

Serrated Chips Formation in Micro Orthogonal Cutting of Ti6Al4V Alloys with Equiaxial and Martensitic Microstructures.

The formation of serrated chips is an important feature during machining of difficult-to-cut materials, such as titanium alloy, nickel based alloy, and some steels. In this study, Ti6Al4V alloys with equiaxial and acicular martensitic microstructures were adopted to analyze the effects of material structures on the formation of serrated chips in straight line micro orthogonal machining. The martensitic alloy was obtained using highly efficient electropulsing treatment (EPT) followed by water quenching. The results showed that serrated chips could be formed on both Ti6Al4V alloys, however the chip features varied with material microstructures. The number of chip segments per unit length of the alloy with martensite was more than that of the equiaxial alloy due to poor ductility. Besides, the average cutting and thrust forces were about 8.41 and 4.53 N, respectively, for the equiaxed Ti6Al4V alloys, which were consistently lower than those with a martensitic structure. The high cutting force of martensitic alloy is because of the large yield stress required to overcome plastic deformation, and this force is also significantly affected by the orientations of the martensite. Power spectral density (PSD) analyses indicated that the characteristic frequency of cutting force variation of the equiaxed alloy ranged from 100 to 200 Hz, while it ranged from 200 to 400 Hz for workpieces with martensites, which was supposedly due to the formation of serrated chips during the machining process.