Tool Rake Face Research Articles

Fundamental tribological effects in lubricated cutting processes

Using cutting fluids has the potential to increase tool life and workpiece quality by reducing loads during cutting. However, cutting fluids lead to additional costs and environmental impacts. To effectively utilise cutting fluids, it is important to gain insights into their working mechanisms, in particular via direct observations of the tribology at the contact surfaces. This paper presents methods to investigate lubrication in cutting, focusing on a new approach for accessing the distribution of cutting fluids at the tool's rake face. This technique of visualising a lubricating film between chip and rake face allows to deeply understand tribological effects.

Effect of rake face surface of cutting tool on tool crater wear

Tool wear is complex to predict due to the intricate environment of a machining process. However, there are a confrontational effect of tool wear on the machining process in terms of deprived surface finish, reduced dimensional accuracy and increased power consumption. In this study an attempt is made to examine the effect of rake face surface of the cutting tool on tool crater wear. For this, three different types; uncoated, coated and structured rake face cutting tools were used and cutting test were performed of plain carbon steel (AISI/SAE 4140). The cutting speed of 283 m/min, feed rate of 0.1 mm/min and depth of cut of 0.1 were used. Results show, structured rake face of the cutting tool benefitted most in supressing the tool crater wear. Energy-Dispersive X-Ray analysis (EDXA) analysis confirms reduction in iron transfer on tool rake face in case of coated and structured cutting tool. Micro − hardness test was also performed and the values in case of coated and structured cutting tool was found to be suffice. This study can be a benefit for cutting difficult to cut material where crater wear formation is unavoidable.

The relationship between adhesion morphology and cutting force in orthogonal cutting of 6061-T6 aluminum alloy

Due to the sticky and soft characteristics of aluminum alloy, it is easy to form adhesion on the tool rake face during cutting process. In this work, the orthogonal cutting tests for 6061-T6 aluminum were carried out at cutting speeds of 20–300 m/min and feed rates of 0.05–0.3 mm, and the relationship between adhesion and cutting force has been explored. A slip-line model was used to separate the edge force of cutting edge to obtain the pure friction force of tool rake face, thereby obtaining the average friction coefficient. Adhesion morphologies were observed under the scanning electron microscope (SEM) and compared with the average friction coefficients. It was found that different adhesion morphologies correspond to different friction coefficient ranges. Simultaneously, the relationship between the temperature and normal stress on the tool rake face and the adhesion morphology and friction coefficient was investigated. The results showed that the temperature is the major factor of adhesion evolution and friction coefficient change. Combining the tool rake face temperature and the adhesion morphology, it was noted that the reduction of the friction coefficient is not only owing to the self-lubrication caused by thermal softening, but also due to the decrease of the total shear force caused by the incomplete contact. Finally, the relationship between the friction coefficient of tool rake face and the cutting force and specific cutting energy was discussed, with the conclusion that the friction coefficient has an impact on the cutting force and specific cutting energy by changing the shear angle.

Analytical prediction of cutting forces in cylindrical turning of 304 stainless steel using unequal division shear zone theory

In order to establish a more accurate prediction model of turning forces, this paper proposed an analytical model for cylindrical turning with the consideration of the effect of the main cutting edge angle and the nose radius. Meanwhile, the unequal division shear zone theory in orthogonal free cutting is extended and applied to the oblique non-free cutting in the interaction between the chip units. To take into account the real tool nose geometry, the tool nose involved in the cutting is discretized into a series of cutting edge units. The geometrical parameters associated with the cutting edge units are analysed by using the coordinate transformation approach. Then, the improved oblique cutting model is applied to each cutting edge unit to acquire the component forces along the tool rake face. Finally, the resultant cutting forces in the turning process are calculated by the numerical integration method. To verify the effectiveness of the proposed model, the turning force experiment of 304 stainless steel was carried out by changing the cutting conditions, the main cutting edge angle, and the nose radius. Through the comparative analysis between the measured results and the calculation values of the proposed model, it was found that the analytical prediction of cutting force is in good agreement with the experiment.

Structural changes in Ti1-xAlxN coatings during turning: A XANES and EXAFS study of worn tools

Structural changes in Ti1-xAlxN coated tool inserts used for turning in 316L stainless steel were investigated by XANES, EXAFS, EDS, and STEM. For coarse-grained fcc-structured Ti1-xAlxN coatings, with 0 ≤ x ≤ 0.62, the XANES spectrum changes with Al-content. XANES Ti 1s line-scans across the rake face of the worn samples reveals that TiN-enriched domains have formed during turning in Ti0.47Al0.53N and Ti0.38Al0.62N samples as a result of spinodal decomposition. The XANES spectra reveal the locations on the tool in which the most TiN-rich domains have formed, indicating which part of the tool-chip contact area that experienced the highest temperature during turning. Changes in the pre-edge features in the XANES spectra reveal that structural changes occur also in the w-TiAlN phase in fine-grained Ti0.38Al0.62N during turning. EDS shows that Cr and Fe from the steel adhere to the tool rake face during machining. Cr 1s and Fe 1s XANES show that Cr is oxidized in the end of the contact length while the adhered Fe retains in the same fcc-structure as that of the 316L stainless steel.

Improving dry machining performance of surface modified cutting tools through combined effect of texture and TiN-WS2 coating

In this research work, investigation on different surface modification techniques on cutting tools such as TiN-WS2 coating (T2), textured cutting tool (T3) and TiN-WS2 coated textured tool (T4) in dry machining of Ti-6Al-4V has been carried out and compared with commercial tool (T1). The presence of (002) orientation corresponding WS2 was observed in the diffraction pattern and this in turn was said to provide lubricity properties to the coatings. The cutting force generated during machining was reduced by 14 % for T4 tool when compared to T1. The T4 tool showed an increase in the shear angle by 7.5 % and decrease in coefficient of friction by 47 %. The prime mechanism attributed to the better performance of cutting tool was reduced tool-chip contact length. The T4 tools showed a 13 % reduction in tool-chip contact length when compared to commercial tools. The tool life of the T2, T3 and T4 tools was improved by 35 %, 29 % and 43 % respectively in comparison to commercial tools. The TiN-WS2 coatings, through its effective lubricity properties have said to nullify the effect of coating affinity between the tool and workpiece as evidenced by the absence of built-up edge on the tool rake face while machining using TiN-WS2 coated tool. The combined effect of TiN-WS2 coatings and surface textures have resulted in better machining characteristics, suggesting it as a suitable surface modification for dry machining of Ti-6Al-4V.

Shaping of the Fresnel lens array on roller molds by 6-axis diamond machining

The Fresnel lens arrays are rapidly developing with the increasing demand for better optical performances and capabilities. For the roll-to-roll embossing of optical films, direct diamond machining of the Fresnel lenses on roller molds has been realized by installing an additional goniometer on the 5-axis ultra-precision machine tool in the previous study. However, this method owns two shortcomings, i.e., the communication delay between the machine tool and the goniometer and the poor positioning accuracy of the goniometer. In this paper, a 6-axis diamond shaping method is proposed to fabricate the Fresnel lens array on the roller periphery by utilizing a commercial 6-axis ultra-precision machine tool. It is ensured that the side cutting edge of the diamond tool matches the Fresnel lenses profiles during shaping. Also, the tool rake face is always perpendicular to both the roller tangent plane at the cutter location point and the cutting velocity relative to the roller via the synchronized rotations of the A-, B- and C-axes to avoid the tool–workpiece interference. The process to calibrate installation errors is introduced and utilized. The tool path is generated according to the cutting tool geometry, the lens parameters and the machine tool configuration. Experiments are carried out by machining the designed Fresnel lens array on a roller mold, which consists of lenses with different feature heights. The surface qualities of the lens arrays are evaluated and the influence of the block time to run the CNC code are also analyzed. The experimental results verify that the proposed method is effective and flexible for machining of the Fresnel lens array on roller molds.

Improved chip control on PCD tools by positioning of brazed chip breakers

A brazed chip breaker capable of controlling the chip curling and flow is proposed on the rake face of a polycrystalline diamond (PCD) tool to obtain ideal chip shape of aluminum alloy materials. Two new position parameters, the breaker-point distance and the rotation angle of chip breaker, are proposed for positioning the chip breaker on the rake face of PCD turning tool. Influences of two position parameters of the chip breaker on the chip curling and chip flow direction are studied through finite element simulations and cutting experiments. The appropriate breaker-point distance can improve the up-curling and back-flow of the chip, and control the chips flow to the tool flank face to form a C-shaped chip. After setting the appropriate breaker-point distance, increasing the rotation angle of chip breaker can promote the trend of side-curling and side-flow of the chip, which is beneficial to the formation of short helical chip. Based on the chip-breaking criterion and the geometric relationship between the chip breaker and tool rake face, the equations of two position parameters of chip breaker are established, and effective chip breaking can be achieved within the reasonable range of chip breaker position parameters calculated by the established equations. The proposed chip breaker which position parameters are convenient to measure and install can be brazed on turning and drilling tools to obtain needed chip shape of aluminum alloy materials. • Proposed two position parameters of chip breaker for PCD turning tools. • Derived a set of equations to determine the effective range of the two position parameters. • Analyzed the influence of the position parameters on the chip curl, chip flow direction and chip shape.

MACHINE LEARNING-BASED MODELING AND OPTIMIZATION IN HARD TURNING OF AISI D6 STEEL WITH ADVANCED AlTiSiN-COATED CARBIDE INSERTS TO PREDICT SURFACE ROUGHNESS AND OTHER MACHINING CHARACTERISTICS

In recent times, mechanical and production industries are facing increasing challenges related to the shift towards sustainable manufacturing. In this work, the machining was performed in dry cutting condition with the newly developed AlTiSiN-coated carbide inserts coated through scalable pulsed power plasma technique, and a dataset was generated for different machining parameters and output responses. The machining parameters are speed, feed and depth of cut, while the output responses are surface roughness, cutting force, crater wear length, crater wear width and flank wear. Abrasion and adhesion were found to be the two dominant wear mechanisms. With speed, the tool wear was found to increase. Cutting force was found to increase rapidly for higher speed ranges (70, 80 and 90[Formula: see text]m/min). But reduction of cutting force was observed in both low and medium ranges of cutting speed (40, 50, 55 and 60[Formula: see text]m/min). With higher values of feed and depth of cut, higher cutting force was also noticed. With the variation of depth of cut, the machined surface morphology and machined surface roughness were found to deteriorate. With higher feed and depth of cut values, more surface damages were observed compared to low values of feed and depth of cut. Both the feed rate and tool–chip contact length contributed significantly to the formation of crater on the tool rake surface. At high speed, continuous chips were observed. Both chip sliding and sticking were observed on the tool rake face. The data collected from the machining operation was used for the development of machine learning (ML)-based surrogate models to test, evaluate and optimize various input machining parameters. Different ML approaches such as polynomial regression (PR), random forests (RF) regression, gradient boosted (GB) trees and adaptive boosting (AB)-based regression were used to model different output responses in the hard machining of AISI D6 steel. Out of the four ML methodologies, RF and PR performed better in comparison to the other two algorithms in terms of the [Formula: see text] values of predictions. The surrogate models for different output responses were used to prepare a complex objective function for the germinal center algorithm-based optimization of the machining parameters of the hard turning operation.

Effect of volcano-like textured tools on machining of Ti-6Al-4V alloy: a numerical and experimental analysis

Higher temperature and lower thermal conductivity between the tool-chip contact face easily result in adhesion and wear on the tool surface which negatively affects the tool life and the machining quality of the workpiece in the machining Ti-6Al-4V alloy process. To address these problems, the investigation, combining the simulation and experiment, introduced the volcano-like textures of different diameters with excellent anti-adhesion performance on the tool rake face. Deform-3D software with updated Lagrangian formulation was used for numerical simulation, and the thermo-mechanical analysis was performed using the Johnson-Cook material model to predict the cutting forces, cutting temperature and tool wear. In machining experiments, volcano-like textures (VT) with different diameters were fabricated by fiber laser on the rake face of cemented carbide tools close to the main cutting edge. Experiments in machining Ti-6Al-4V alloy were carried out with the textured tools and non-textured tool under rough machining, semi-finishing and finishing conditions. Then, cutting force, cutting temperature and tool wear were investigated. The results showed that textured tools generally perform better than non-textured tool. The cutting force of VT1 was reduced by 31.2% and 50%, respectively, compared with the non-textured tool under semi-finishing and finishing conditions. With the refinement of machining, the cutting performance of the textured tools is improved, and the service life of the tool is extended. Therefore, the investigation can provide a basis for the surface texture design and optimization of the carbide tool.

Dual-scale folding in cutting of commercially pure aluminum alloys

We examine a, hitherto, little-studied and curious machining chip morphology, with tell-tale signs of folding at two different length scales, that is common in cutting of certain ductile and highly strain-hardening metals like soft aluminum alloys, tantalum and niobium. This chip morphology does not appear in the usual catalogues of common chip types. The mechanics of formation of the “dual-scale folded chip” is studied in model material systems of commercially pure aluminum alloys (AA 1100 and AA 8040), that prominently exhibit this chip morphology. The flow, folding and associated plastic instabilities are investigated using micro/macro structure observations of the chip in a plane-strain cutting framework, with high-speed in situ imaging and image analysis of material flow; and force measurements. The smaller-scale folding is shown to develop in the primary deformation zone while the larger-scale folding occurs as the chip traverses the rake face of the tool. The resulting chip is composed of irregularly-spaced large folds, superimposed onto which are the quasi-periodic small folds. The representative wavelengths of the two folds differ on average by an order of magnitude, 0.1 mm vs. 2 mm. The observations reveal a direct coupling between the material flow and chip morphology, and how specific attributes of the dual-scale folded chip arise from the flow mechanism. Plastic buckling is found to play a key role in the folding at both length scales. The small-scale folds are characteristic of a sinuous plastic flow mode, while the large-scale folding is characterized by buckling and stick-slip along the tool rake face, triggered by adhesive pinning of the chip to the tool. Important consequences of the dual-scale folding are very large cutting forces, and force oscillations of large amplitude, despite the alloys being very soft, only ∼25 HV. The dual-scale folding is why many of these alloys are classified as “gummy” to machine. Since the dual-scale folded chip is associated with large cutting forces and poor surface quality, there is much to be gained by disrupting this flow type in practical machining applications. Methods for controlling the folding to improve machining performance with the gummy alloys are briefly discussed.

Research on tool wear morphology and mechanism during turning nickel-based alloy GH4169 with PVD-TiAlN coated carbide tool

Tool wear affects tool life, dimensions, etc. However, tool wear mechanism was mainly studied by the relevant references in the sharp wear stage, and tool wear morphology and mechanism were not completely understood in the initial and steady wear stage. Tool wear investigation of coated carbide tool is carried out during turning GH4169 in dry cutting. Tool wear microscopic morphology, tool wear curve, tool cutting force and tool wear mechanism are studied during turning GH4169 in the initial, steady and sharp wear stage. Tool wear mechanism in the sharp wear stage is further investigated by SEM, EDS, XPS and XRD. Doing so helps to test and improve the quality of the tool coating and substrate material, helps to gain a deep understanding of the difficult-to-machine characteristics of GH4169, and helps to guarantee the dimensional accuracy and surface quality of the workpiece. Results show that serious abrasive wear, tool nose wear and adhesive wear occurred in the whole wear stage. The tool wear rate of turning superalloy GH4169 is much faster, the cutting force increases, the tool substrate material was worn seriously. The main tool wear mechanisms are abrasive wear, adhesive wear, oxidation wear and diffusion wear. Severe abrasive wear occurred between the large amount of hard abrasive carbides in the workpiece material and the tool rake and flank faces. Ni, Fe, Cr, etc are mainly distributed in the relevant wear areas. WO3, Co3O4, Ni2O3, Fe2O3, etc indicate that oxidation wear occurred, Ni, Fe, Cr, Nb and Mo are detected across the cross-section, which means that diffusion wear has occurred.

Wear of micro diamond tool in ultra-precision turning under dry and minimum quantity lubrication conditions

Minimum quantity lubrication (MQL) is an effective way to reduce the cutting temperature and tool wear. To reveal the effect of MQL on the wear of micro diamond tool, a calculation model for the cutting temperature of micro diamond tool under dry friction condition is established firstly by using the Fourier’s law of heat conduction. Regarding the boundary film as a layer of heat-conduction medium, a revised calculation model for the temperature distribution on tool rake face under MQL condition with different cutting fluids is further established. The predicted results indicate that low viscosity is beneficial to the wetting of cutting fluid on tool-chip contact interface, which can relieve the friction. The reduction of friction finally decreases the cutting temperature. Secondly, the cutting temperature–dependent wear volume of micro diamond tool is predicted by using the Usui wear rate model in response to different cutting fluids and different cutting distances. In dry cutting, the graphite wear of micro diamond tool prevails. However, the application of MQL can slow down the graphitization of diamond, so the wear of micro diamond tool visibly decreases. Finally, cutting experiments with different cutting fluids are performed to verify the established models. The experimental observations agree well with the theoretical prediction results. Such satisfactory consistency confirms that the cutting fluid with low viscosity can reduce the cutting temperature and inhibit tool wear effectively.

Crystal orientation and material type related suppression to the graphitization wear of micro diamond tool

According to the Hencky stress theorem and J-C constitutive equation, a cutting force model is established for the diamond turning process when using micro diamond tool, through which the stress distributions on tool rake face and flank face are calculated. A stress model is further developed to calculate the stress distribution on the cutting edge region by using the stress intensity factor theory of fracture mechanics, into which the influences of crystal orientation of rake and flank faces are integrated. With consideration of elastic modulus and defect density of diamond crystal, the critical stress for graphitization of diamond tool is also deduced in response to different crystal orientations and types of diamond material. Finally, cutting experiments are performed to validate the theoretical predictions. Results show that the experimental observations agree well with the theoretical predictions. Such satisfactory consistency confirms that the natural cape Ia diamond as tool material and the (100) crystal plane as tool faces can effectively inhibit the graphitization wear of micro diamond tool.

Built-up edge formation mechanisms in orthogonal cutting of wood-plastic composite

ABSTRACT This project aims to improve the machinability of wood-plastic composites by understanding chip and built-up edge formation, so as to help manufacturers optimize cutting performance and product quality. Chip formation and built-up edge were studied during orthogonal cutting of wood polyethylene composite with cemented carbide cutters under different conditions. During the orthogonal cutting process, segmental, ribbon, and element chips were generated. The cutting depth was found to have a great impact on the types of chips that formed. Additionally, a built-up edge was found during wood-plastic composite machining, with debris only attaching to the tool's rake face due to thermo-mechanical coupling. Such built-up edges hinder cutting stability and surface quality. Furthermore, variations in the accumulation of debris on the built-up edge corresponded to changes in cutting force and temperature. In fact, both cutting force and temperature proved to be inversely related to the rake angle and positively correlated to the cutting speed and depth. Therefore, to achieve better cutting stability and surface quality for wood-plastic composites, a larger rake angle and a reduced cutting depth are recommended because they reduce the accumulation of debris and the formation of built-up edge.

Machinability Analysis of Finish-Turning Operations for Ti6Al4V Tubes Fabricated by Selective Laser Melting

With the advent of additive manufacturing as an advanced technology for the fabrication of titanium components, there is a pressing need to investigate the machinability of parts produced using these techniques compared to components made with conventional wrought methodologies. The motivation for this study was to investigate the influences of machining parameters, especially cutting depth, on the machinability of selective laser melted (SLMed) Ti6Al4V tubes, by analyzing the cutting responses, including cutting forces, machined surface roughness and tool wear at varying cutting parameters. Generally, it can be inferred that specific cutting tools used to machine wrought titanium components can also be used for SLMed parts when carrying out finish-machining operations. Cutting forces in the machining of SLMed workpieces could be up to 70% higher than those in machining the wrought counterparts. In contrast, the tool-wear analysis correspondingly showed larger tool-workpiece engagement area on the tool rake face for tools used for machining wrought parts. Adhesion on the cutting edge in the form of built-up edge and attrition of the tool surface were found to be the two most dominant tool-wear mechanisms, and the oxidation condition of the tool surface in machining SLMed parts was more severe (about 8% and 21%). Vibration analysis was also carried out, but no significant difference between the SLMed and wrought workpieces was observed, and the quality of the machined surface was similar.

Determination of the Tool-Chip Contact Length for the Cutting Processes.

The thermomechanical interaction of the tool with the chip in the most loaded secondary cutting zone depends on the contact length of the tool rake face with the chip. Experimental studies of the dependency of the contact length on the cutting speed, the undeformed chip thickness, and the tool rake angle, performed by the optical method, are used for comparison with the contact length obtained by the FE modeling of the orthogonal cutting process. To determine the parameters of the constitutive Johnson–Cook equation, which serves as a material model of the FE cutting model that has a predominant influence on the contact length, a software-implemented algorithm was developed. This algorithm is based on determining the generalized parameters of the constitutive equation through finding the intersection of these parameter sets. The plurality intersection of the parameter sets of the constitutive equation is determined by means of the design of experiments and refined by subsequent multiple iterations. The comparison of the contact length values, obtained by simulating the cutting process using the generalized parameters of the constitutive equation as a material model with their experimental values, does not exceed 12% for a wide range of cutting speeds and depths of cut, as well as for the tool rake angle.

Fabrication of polygonal Fresnel lenses with a rotating cutting tool on three-axis ultraprecision lathes

Fresnel lenses are gaining wider applications due to their advantages of being lighter, thinner and suitable for increasingly complex and miniaturized optical systems. To increase the fill factor when combining multiple Fresnel lenses to form an array, polygonal Fresnel lenses have been designed and machined with the ultra-precision machine tools in industry. However, for the three-axis machine tool equipped with the X-, Z-, and C-axes, it is difficult to machine the straight edges of the polygonal Fresnel lens due to the lack of a Y-axis. Although the synchronized servo motions of the linear axis and the spindle can be utilized to fit the relative motion trajectory of the tool to a straight line, the cutting tool rotates relative to the workpiece and thus the tool rake face is not always perpendicular to the direction of the relative motion during machining. In this paper, a high-precision rotating platform is integrated into the three-axis ultra-precision machine tool to make the cutting tool track the rotation of the spindle and keep the tool rake face perpendicular to the direction of the relative motion at all times. Then the tool trajectory is generated and the influence of the tool nose radius is compensated. Finally, an experiment of cutting the hexagonal Fresnel lens is performed on a three-axis ultra-precision lathe, and the machined workpiece is inspected with a white light interferometer. The experimental results show that the profile accuracy of the machined polygonal Fresnel lens satisfies the requirements in industrial applications.

Effect of micro-grooved texture on cutting performance of tool under dry condition

To clarify the anti-adhesive properties of the textured tool, two types of micro-grooved textures were fabricated on the tool rake face. The cutting tests were conducted on aluminum alloys under no lubrication condition. Experimental results showed that the cutting force, tool–chip friction coefficient, and surface wear of the P_1 textured tool decreased. However, noticeable disadvantages were observed in samples with other textures. Detailed research indicated that the chip material (Al alloy) was easy to squeeze into and clog in the micro-grooved texture, due to low hardness and high ductility. In contrast, the cutting force, tool–chip interfacial friction, and wear of steel samples with T_1, T_2, and P_2 textures were all greater than that of the nontextured tool. The difference observed in these various textures signifies the importance of the small geometric size of the surface texture in the P_1 texture. Thus, an improvement of tool anti-adhesion with aluminum alloy material was obtained under dry cutting conditions.

The effects of micro-texture shape on serrated chip geometry in the hardened steel AISI D2 cutting process

Five micro-textures were processed on the rake face of PCBN tools: circular pits, elliptical grooves, transverse grooves, composite grooves, and wavy grooves. The effect of different micro-textures on cutting force, the cutting temperature, the micro-morphology of serrated chips, tool wear and surface roughness were investigated utilizing three-dimensional finite element simulation and cutting tests. The results indicates that micro-textured tools can lower cutting force when compared to non-textured tools, while cutting force varies significantly during the cutting process. Micro-texture can decrease the temperature in the adiabatic shear band, changes the temperature distribution of the rake face, reduce the serrated degree, and increase segmentation frequency. However, it is more prone to cracking. The wear resistance and the surface quality of machined surface of the elliptical grooves and wavy grooves micro-texture are better.