Chip Flow Angle Research Articles

Optimization of geometry parameters and cutting parameters of threading tool based on neural network prediction model for chip flow angle of single-edged oblique cutting

Optimization of geometry parameters and cutting parameters of threading tool based on neural network prediction model for chip flow angle of single-edged oblique cutting

Effects of chip breaker groove and tool nose radius on progressive tool wear and behavior when turning GH3536 nickel-based superalloys

Nickel-based superalloys are typically challenging to machine and often exhibit severe tool wear during the turning process, thus attracting substantial research attention. This study not only explores the tool wear mechanisms when turning GH3536 nickel-based superalloys but also introduces a focus on the role of tool geometry configuration. Tools with different chip breaker groove structures and nose radii were investigated, with results indicating the tool wear mechanisms were predominantly abrasive and adhesive. For the 04HA chip breaker, which has a 9° rake angle and a "V"-shaped bottom, there is a single point of impact with the chip during cutting, while the 04VP3 chip breaker, with a 15° rake angle and a flat bottom, has two points of impact with the chip during cutting, increasing chip deformation and favoring chip breaking, thereby suppressing the formation of built-up edge. Additionally, changes in the nose radius influenced the degree of work hardening and consequently influence the severity of notch wear, with the nose radius also impacting the chip flow angle. Based on this finding, a theoretical mathematical model describing the initial chip flow angle was established and validated. Additionally, an examination of the effects of varying operating parameters on tool life was conducted, revealing that cutting speed was the most significant factor affecting tool life, followed by feed rate and depth of cut.

Machinability analysis during finish turning Ti6Al4V with varying cutting edge radius

ABSTRACT The effect of cutting edge radius (rβ) on the chip formation mechanism during the finish turning of Ti6Al4V is studied. An increase in rβ decreases the cutting to thrust force ratio and produces lower chip thickness due to the increase in plowing zone depth. Larger radius tools produce thinner loosely curled chips whereas tightly curled thicker chips are formed for the unprepared edge tool (36 µm). As rβ increases, the chip flow angle (β) increases and free-flowing chips with reduced up-curl but increased side and lateral curl and consequently larger resultant chip curl radius are produced. The chip serration height to overall chip thickness ratio increases whereas chip core thickness reduces owing to the increased plowing action as rβ increases. Chip segmentation analysis reveals increased serration height, thermal instability, and shear localisation in the shear zone due to the increased ploughing effect beyond ~60 µm edge radius.

The influence of parameters of linear flat bottom chip breaker on chip flow

The simulation model of cutting TC4 titanium alloy with a YG8 cemented carbide tool is established through ABAQUS. The minimum width of the chip breaker, anti-chip surface angle, bevel angle of chip breaker, and the change of chip breaker front angle at the tooltip are changed by controlling other chip breaker parameters unchanged. Orthogonal tests are established under different edge angles to analyze the influence of the relevant parameters of the chip breaker on the chip angle and the influence of the change of the chip breaker parameters on the chip angle under different inclination angles. The results show that the chip breaker parameters affect the chip flow direction. The larger the groove spacing is, the smaller the chip flow angle first decreases and then becomes stable. The chip flow angle increases with the increase of the anti-chip surface angle, bevel angle of the chip breaker, and chip breaker front angle. The larger the inclination angle is, the more obvious the influence of chip breaker parameters is.

Theoretical and experimental research of edge inclination angle effect on minimum uncut chip thickness in oblique cutting of C45 steel

The minimum uncut chip thickness (MUCT) is an important phenomenon observed both in orthogonal and oblique cutting. Rounding the cutting edge influences the initiation of the cutting process and chip formation. In a previous study, the authors presented a theoretical analysis and experimental validation on the effect of edge inclination angle λs in the range of 0° to 60° on hmin in radial-free turning of C45 steel. The current work investigated the MUCT hmin in oblique cutting process of C45 steel, for extremely high value of edge inclination angle λs. In this research, a special technique based on milling tool machine using a special tool and sample is presented. Enabled model tests in the unprecedented range of angles λs not used in research to date. The samples were machined using a cutting speed vc = 0.063 m/min. Vertical feed of edge fv was determined by association on the applied sample slope (τ = 0.60–0.85 mm/m) and cutting speed vc. as fv = 37.8—53.5 μm/min. MUCT hmin parameter was measured using compensation for the effects of deformation, based on profilogram analysis. The machining experiments were carried out using a tool with rn = 185 μm. It was found that in the range of angles of 50° ≤ λs ≤ 85°, the MUCT decreases from hmin = 12 μm for λs = 50° to hmin = 4 μm for λs = 85°. Increasing λs by 35° resulted in up to threefold reduction in MUCT. The analysis of the experimental results of hmin for the range of studied λs angle confirmed authors previously reported theory for extreme values of λs. In optimization procedure based on LSM, chip flow angle coefficient was determined as k = 0.75 and critical value of rake angle γcf = -64.8°. This feature provides prediction of results with great accuracy to experimental value. The findings from this study opens the possibility of developing new tools for finishing operations in the field of oblique cutting with high values of λs angle. In addition, the results introduce new area for research on improving the surface quality based on lowering the effect of MUCT on surface roughness and explaining some aspects related to surface wear in the friction process.

Cutting Force in Drilling with Flat Bottom Drill

Flat bottom drills at a point angle of 180 deg. have recently been applied to not only drilling on inclined surfaces but also flat bottom holes in terms of the dimensional accuracy and the process efficiency. Controlling the cutting force, the tool damage, and the surface finish, the corner shape is a critical parameter in the design of the flat bottom drill. The paper discusses the effect of the corner radius on the cutting forces and the surface finish in drilling with flat bottom drills. The typical differences in the cutting force are confirmed during the edge engagement. Then, the cutting force is simulated with a chip flow model, in which the chip flow angle is determined to minimize the cutting energy. The cylinder surface finishes and the burr formations are associated with the chip flow direction and the uncut chip thickness at the end of the lip.

An analytical cutting force model of quasi-intermittent vibration assisted swing cutting based on predictive machining theory

Quasi-intermittent vibration assisted swing (QVASC) method was aimed to improve the cutting machinability of difficult-to-machine materials. Inherited the intermittent cutting characteristics of the elliptical vibration cutting (EVC) technology, this method reduces the impact of residual height on the machined surface quality. But there is still a lack of in-depth research on cutting force modeling of QVASC. Based on the conventional cutting force model, a cutting force prediction model in QVASC processing, which considers the time-variable characteristics of QVASC, adopts the non-equidistant shear zone model and regards the workpiece material properties, tool geometry, and cutting conditions as the input data are proposed in this paper. Using the micro-element method, the proposed model decomposed the cutting edge to calculate the cutting force and the cutting force value by superimposing them. It finally predicts the chip flow angle. Experimental results show that when the cutting velocity increases, the average cutting force and the Z -direction increases by 20%, the average cutting force and the Y direction decreases by 17%. The average cutting force along X direction remains unchanged; the depth of cutting became larger. Besides, the average cutting force X decreased by 18%, Y decreased 21%, and Z increased by 13%. As the feed rate increases, the X direction is increased by 26%, and the Z direction is reduced by 22%, while the cutting force in the Y direction is unchanged. After comparing and verifying the measured value and the predicted value, the minimum error of the prediction model reaches 4.01%, which validates the force model of QVACS.

Regularization of mathematical model for chip flow angle catastrophe

Regularization of mathematical model for chip flow angle catastrophe

Research on the plastic flow characteristics of metal material in mechanical scratching

The plastic flow characteristics of the metal material in mechanical scratching is determined on the important parameters of the negative rake angle, the material deformation amount, the scratching force, the groove quality, and the tool wear. However, the chip flow angle and the plastic flow direction of the metal material in the cutting or mechanical scratching are often derived from the approximate solution according to the metal cutting theory and assumptions. Meanwhile, there is no theoretical model of the plastic flow characteristics suitable for the mechanical scratching the metal material with diamond wedge scratching tool (irregular triangular pyramid tool). Therefore, the unit plastic flow vector (PFV), the working negative rake angle, and the chip flow angle (CFA) theoretical model are established in this paper. And the evolution law of plastic flow angle of the unit PFV and CFA under the influence of the multi-scratching factors was also studied. It can be known that the PFA is related to the elevation angle of the scratching tool, but independent on the speed and material, while the CFA is related to the above multi-scratching factors. Meanwhile, the evolution law of theoretical PFA is consistent with the experimental value, and the maximum deviation is 6.687°, which verifies the theoretical model. In addition, compared with the CFA, the PFV can directly reflect the material plastic flow direction on the contact surface.

Cutting force model of longitudinal-torsional ultrasonic-assisted milling Ti-6Al-4V based on tool flank wear

The interaction mechanism between the tool flank wear and the cutting force, in milling Ti-6Al-4V, is of significance for its further development. However, the relationship between the tool flank wear and the cutting force should be further investigated under ultrasonic-assisted milling. In this study, the longitudinal-torsional ultrasonic-assisted milling (LTUAM) Ti-6Al-4V in dry cutting was evaluated by comparing with conventional milling (CM). With the consideration of the ultrasonic vibration on the chip flow angle, a novel cutting force model in terms of the tool flank wear was developed by discretizing the side edge to apply the oblique model. Wherein the stress evolution both on the shear plane and the flank plane was analyzed, as well as the swinging range of chip flow angle resulted from ultrasonic vibration. In addition, the coefficients of the cutting force were calibrated through the mechanical method. The model could predict the cutting force evolution with different flank wear bandwidth ( VB ), and optimize the machining parameters. The experimental results indicated the errors between the model and the test were 19.1 % and 12.9 % in the feed ( x ) and the normal ( y ) direction of the tool coordinate system ( o - xyz ), respectively. Through time-frequency transformation, the behavior of the cutting force both in CM and LTUAM was further explained. Besides, the growing amplitude was beneficial to restrain the flank wear apart from the overgrowing amplitude, while the growing helix angles resulted in the serious tool flank wear in LTUAM. For the machined surface texture, the cutter scratches parallel to the feed direction dominated the machined surface in CM while the LTUAM surface featured by the order wave textures.

FE-SPH hybrid method to simulate the effect of tool inclination angle in oblique diamond cutting of KDP crystal

Due to the soft and brittle characteristic, the potassium dihydrogen phosphate (KDP) crystal undergoes a complex process in diamond cutting, which makes the material removal mechanism is still a subject of controversy. In this paper, based on the machining model of oblique diamond cutting of KDP crystal, the effect of tool inclination angles in machining is numerically investigated by constructing a FE-SPH hybrid model, which combines the finite element (FE) method and smoothed particle hydrodynamics (SPH). Subsequently, oblique fly-cutting experiments with the same tool geometries and cutting parameters are performed, and the topographies of uncut shoulder and finally machined surface are measured by the atomic force microscope (AFM). Results show that the distribution of hydrostatic pressure clearly reflects the susceptibility of the processed surface to the cracks formation. With the consideration of hydrostatic pressure, the simulated results of cracks on the uncut shoulder and finally machined surface present a good consistency with the measured results in experiments. Moreover, the chip flow angle in simulation approximately follows the Stabler's chip-flow rule. As tool inclination angle increases, the width of interference zone decreases and the phenomenon of chip tearing is gradually relieved. Finally, the simulation results and experimental observations confirm that the roughness of finally machined surface is influenced by the average slope of uncut shoulder, the width of interference zone and the distribution of cracks.

Three-dimensional turning force prediction based on hybrid finite element and predictive machining theory considering edge radius and nose radius

Abstract Cutting force provides a basis for predicting tool wear and fracture, surface quality of component, as well as vibration and power demand of machine tools during the process of turning. Based on the finite element and mechanical analysis model, a three-dimensional (3-D) cutting force prediction model with consideration given to the edge radius and the nose radius of cutting tool is proposed in this paper. Firstly, combined with cutting force experiment, 3-D cutting simulation is performed in Deform to determine the appropriate Johnson-Cook (J-C) material constitutive model, and the two-dimensional (2-D) orthogonal cutting model is simulated by applying the determined J-C model. By observing the strain rate distribution in the shear zone, the shear angle is obtained, while the nonlinear regression model of shear angle, cutting speed and cutting thickness is conducted. Then, taking into account the impact of nose radius on the cutting process, 3-D oblique cutting is converted into equivalent orthogonal cutting using the chip flow angle and the equivalent cutting edge. The method used to determine the strain rate coefficient of the second deformation zone is redefined in the modified Oxley model, and the chip forming force is calculated. Based on the Waldorf slip line field model, the plowing force generated by the edge radius is predicted. Finally, the cutting force of 3-D oblique turning is obtained by means of coordinate transformation. The proposed model is validated by the excellent consistency between the theoretical predictions and the results obtained after referencing literature data and performing experiment of cutting 304 stainless steel and Inconel 718.

3D FEM simulation of chip breakage in turning AISI1045 with complicate-grooved insert

In order to solve the problem of low efficiency and high cost in designing inserts with groove, finite element simulation (FEM) method has been employed to directly simulate the chip breaking condition. However, the current methods tend to involve a large number of cutting experiments and a user subroutine program used for secondary development, causing inconveniency in engineering application. Here, we propose a high-efficient three-dimensional (3D) FEM method to analyze the chip breakage properties of complicate-grooved insert. For the simulation, a three-dimensional cutting simulation model is established by Deform 3D FE package, and the Johnson-Cook (J-C) material constitutive model and Cockcroft-Latham (C-L) ductile fracture criterion are adopted. To verify the validity of the model, the simulations and corresponding turning experiments of AISI 1045 steel are performed with complicate-grooved insert at several combination groups of cutting depth and feed rate. The estimated chip morphology, chip breaking process, and cutting force from the simulation are in good consistency with those from the experiments. Additionally, the comparisons between the simulations and corresponding turning experiments with complicate-grooved insert and flat rake insert are conducted. The results show that the chip breaking groove can significantly change the chip flow angle and the chip geometry and that the complicate-grooved insert can more efficiently promote chip breakage than the flat rake insert. Therefore, the 3D FEM method proposed can be used to effectively investigate the chip formation mechanism and chip breakage properties and has promising application prospects in complicate-grooved insert design and cutting parameter optimization.

Performance of textured tool in turning of Ti–6Al–4V alloy: numerical analysis and experimental validation

Development of advanced or new cutting tool has gained attention among the research community nowadays. Due to environmental obligation, researchers are working on hybrid machining processes without cutting fluids to improve sustainability. The effect of micro-dimple-textured tool on turning of Ti–6Al–4V alloy is assessed by considering cutting force, chip morphology and chip flow angle using finite element method (FEM) in the current study. The machining simulations are performed for both flat and textured tool using DEFORM software. The simulation results show that machinability of textured tool increased (maximum reduction 16, 30 and 12% in cutting surface roughness and chip thickness, respectively) as compared to the flat tool. The simulated results are validated by performing experimental runs, and significant coherence (error % < 10) is obtained.

Theoretical modeling and experimental verification of chip flow angle catastrophe in double-edged cutting considering non-linear effects

It is found that when linear double-edged cutting tool is employed and the control variables are continuously changed into certain critical values, the chip flow angle (CFA) will change abruptly, and the cutting force and cutting power will drop sharply when the catastrophe occurs. This provides a possibility to keep the cutting process in a low energy consumption state by controlling the catastrophe of CFA. The root cause of the catastrophe is the strong non-linearity of the system. To this end, a modified method for establishing a mathematical model of the CFA catastrophe in double-edged cutting based on the catastrophe theory is proposed in this paper. In this method, the non-linear empirical formulas of cutting process parameters fitted by the finite element analysis (FEA) results of orthogonal cutting are used to reflect the non-linear effects of material deformation mode in the primary shear zone and the tool-chip friction status in the friction zone on the cutting process. Moreover, the sudden change of the shear area is utilized to tell the non-linearity of cutting process caused by geometric factors, when control variables of the cutting process change continuously. As a consequence, the accuracy of predicted results derived from the established model are improved. With the derived cutting power function as potential function, a mathematical model (cusp model) of the CFA catastrophe consisting of potential function, manifold and bifurcation set is established by the aforementioned approach. And a set of critical cutting width of the CFA catastrophe and the CFA before and after the catastrophe are obtained under the condition that the end face of 6061-T6 aluminum alloy workpiece is turned transversely by different straight double-edged turning tools. In order to validate the model and the prediction results, a series of cutting experiments are completed to indirectly measure the critical cutting width and the CFA before and after the catastrophe. The end face of 6061-T6 workpiece is turned transversely by straight double-edged turning tools with different tool geometry. Comparing the experimental results with the predicted results, it is found that the two have good consistency.

Modeling of the catastrophe of chip flow angle in the turning with double-edged tool with arbitrary rake angle based on catastrophe theory

It has been found experimentally that when planing or turning with double-edged tool with 0° rake angle, the chip flow angle will suddenly change with the continuous change of cutting parameters. This phenomenon, named the catastrophe of chip flow angle, is caused by the nonlinearities in non-free cutting process, but further study has not been conducted. To explore the mechanism of the catastrophe of chip flow angle, in this paper, a mathematical model (cusp catastrophe model) of the catastrophe of chip flow angle in the turning with straight double-edged tool with arbitrary rake angle is established based on catastrophe theory. Applying this model, the main characteristics of the catastrophe of chip flow angle are analyzed, and a set of critical conditions of the catastrophe of chip flow angle is predicted. To verify the predicted critical conditions of this model, a group of experiments on 6061 aluminum alloy with double-edged tool with given rake angle is designed. In this experiment, the continuous change of width of cut is achieved by turning the specially designed tapered end face of 6061 aluminum alloy, and the critical conditions of the catastrophe of chip flow angle are captured by analyzing the chip flow videos and the dynamic cutting forces. The agreement between the critical conditions predicted by the model and the experimental results is satisfactory.

A novel approach to thermal modeling based on three-dimensional analysis in turning Inconel 718 with round insert

The sharp increase of heat generated when processing difficult-to-machine materials is the main reason of short tool life and poor surface integrity. Temperature modeling plays a significant role in the mechanism of metal cutting, which can guide the optimization of cutting parameters. This paper proposes a modified three-dimensional analytical model of temperature prediction for oblique turning Inconel 718 with round carbide insert. The discretization of heat sources is indispensable to analyze the temperature rise due to the complicated geometry of uncut chip area. In this study, primary heat source (shear band) and secondary heat source (tool-chip interface) that divided into many increments through different discretization methods are considered to analyze thermal effects. For each increment of secondary heat source, the local contact length is calculated through a modified function considering global chip flow angle in oblique cutting. The local heat liberation intensities of primary and secondary heat sources are determined through analytical force prediction model. The variation of heat partition fraction with respect to immersion angle is given to study the characteristics of secondary heat source. Finally, a modified three-dimensional expression of temperature rises when turning with round insert considering semi-infinite medium is proposed based on classical thermal theory. The temperature distributions in chip, tool and workpiece can be determined through the proposed model. The results calculated through predictive model show good agreement with that given by finite element method (FEM) and experiments, which validates the correctness of the proposed model.

Model for the prediction of whirling vibrations in drilling processes through semi-discretization of the drill motion equation

In this work, a model for the prediction of drilling stability against low-frequency lateral vibrations, named as whirling in the literature, is proposed. These vibrations are lateral displacements of the tool that arise at frequencies near multiples of the rotation frequency of the drill. The appearance of whirling vibrations leads to the generation of lobe-shaped holes. In order to predict whirling vibrations, the motion equation of the drill is deduced taking into account the modal characteristics of the drill and the cutting and process damping forces that act on it. In this paper, forces that arise in two different regions of the drill are considered: (1) forces on the main cutting edges and (2) forces on the chisel edge. Different force models are presented for each region that include both the regenerative effect of the vibration on the cutting area and the process damping. An oblique cutting model and an orthogonal model are employed for the calculation of cutting forces acting on the main cutting edges and on the chisel edge, respectively. The cutting force model for the main cutting edges takes into account the cutting angle (inclination angle, rake angle, and chip flow angle) variation along the main cutting edges. For the chisel edge region, where the feed speed is no longer negligible with respect to the cutting speed, the dynamic cutting angles are employed for the force model development. Concerning the process damping force model, previous works in the literature consider a constant value of the clearance angle for the calculation of the process damping coefficient. However, in this work, the variation of the normal clearance angle along the main cutting edges is considered. It is shown that, depending on the clearance face grinding parameters employed, the clearance angle can double its value along the main cutting edges. Considering the force models and through the semi-discretization of the motion equation of the drill, the appearance of low-frequency lateral vibrations is predicted regarding the drill geometry and cutting conditions such as drill rotation speed and feed. In addition, given cutting conditions at which whirling vibrations are expected to occur, the model is able to predict the vibration frequencies that are excited. The drilling model and the stability predictions are experimentally validated by means of drilling tests with different drill diameters and cutting conditions. In comparing the experimentally obtained results and the predictions obtained by the model, it is concluded that the model can reasonably predict the appearance of whirling vibrations as a function of drill geometry and cutting conditions. Generated hole shape is also analyzed through the measurement of hole roundness and bottom surface geometry. It is observed that, when drilling in the presence of whirling vibrations, holes with lobed shape and polygonal bottom surface are generated. It is also noticed that both the number of lobes and the number of sides of the polygonal bottom surface are directly related to the vibration frequencies that arise.

Mechanistic modelling for predicting cutting forces in machining considering effect of tool nose radius on chip formation and tool wear land

Tool wear during machining has been seen to result in changes in tool geometry, which adversely affect the performance characteristic of the process. Various force models have been proposed to compensate for the tool wear and thus enhance the process performance. The study undertaken proposes a mechanistic model to predict the cutting forces based on three-dimensional cutting operations. The model has been developed for predicting forces due to chip formation and due to worn-out cutting tool including cutting tool nose radius. The force that has been predicted due to chip formation is a function of chip flow angle and equivalent cutting edge geometry. The prediction of force due to worn-out cutting tool is based on the actual chip-tool contact area and the rubbing force. The total force estimated has been further optimised to get accuracy in the model. Optimisation process is achieved by using a technique of order preference by similarity to the ideal solution. Results of the proposed force model have been experimentally validated as well as found to be in good agreement with the results of the force models proposed by Huang and Liang [39] and Chinchanikar and Choudhury [21]. Further, a regression equation has been developed in order to check the adequacy of the proposed model. The modelling approach proposed may be readily extended to other machining operations such as drilling and milling.

An analytical force mode applied to three-dimensional turning based on a predictive machining theory

Cutting forces play an important role in the three-dimensional turning processes and are commonly calculated by the mechanistic or empirical models which are considered time-consuming and impractical for various cutting conditions and workpiece-tool pair. Therefore, this paper proposes an analytical force model in three-dimensional turning based on a predictive machining theory, which adopts the non-equidistant shear zone model and regards the workpiece material properties, tool geometry and cutting conditions as the input data. In this model, the real cutting edge of the turning tool is decomposed into a series of infinitesimal cutting elements and the cutting action of which is equivalent to the oblique cutting process with the imposed condition that all chip elements flow in the same direction on account of the interaction between adjacent chip ones. Consequently, the cutting force components applied on each cutting element can be calculated using a modified version of predictive oblique cutting model and the total cutting forces are obtained by summing up the forces contributed by all cutting elements. Finally, the global and local chip flow angles are investigated under various conditions of tool geometry (edge inclination angle, lead angle, nose radius) and cutting parameters (depth of cut, feed, cutting velocity) in this model. Furthermore, a detailed parametric study is provided by the proposed analytical model of cutting forces in order to analyze the influences of cutting parameters and tool geometry on cutting forces, which are verified respectively by the experimental data. Good agreement shows the effectiveness of the proposed analytical model.