Rake Face Research Articles

Multi-Criteria Optimization of Al2O3-ZrO2(Y2O3)-based Self-lubricating Composite Cutting Tools for Increasing Shear Angle, and Wear Resistance in Machining Processes

Abstract In the present investigation, self-lubricating cutting tools were fabricated by adding various elements such as NiCr, Ag, Mo, SrSO4, and CaF2 to Zirconia Toughened Alumina in order to overcome the difficulties that occurred in dry machining. Three significant process parameters; cutting speed (50, 125, 200, and 275 m/min), feed rate (0.1 and 0.2 mm/rev), and depth of cut (0.1 and 0.2 mm) were selected for the machining process. The performance measures such as chip thickness ratio, shear angle, and tool wear, were investigated. The experimental runs were conducted with Taguchi L8 mixed-level orthogonal array. Technique for Order of Preference by Similarity to Ideal Solution is a multi-criteria decision-making method used to determine the best alternative from a set of options. Turning experiments have been performed on the AISI 4340 steel workpiece with various combinations of machining parameters. The findings revealed the incorporation of SrSO4 and Mo at 10Wt.% and CaF2 at 5Wt.% (i.e., self-lubricating cutting tool-4) achieved better mechanical properties and wear resistance due to the formation of a self-lubrication layer on the rake face of the cutting tool. A confirmation experiment is executed in order to verify the outcomes in the end. Finally, there is a noticeable improvement in the outcomes compared to the base cutting tool, i.e., chip thickness ratio is 35.77%, shear angle is 27.31%, and tool wear is 58%. The mechanism for improving performance measures is discussed in detail.

Finite element simulation and experimental investigation of in-situ laser-assisted diamond turning of monocrystalline silicon

While the effectiveness of in-situ laser-assisted diamond turning (In-LAT) for promoting the ductile machinability of monocrystalline silicon has been demonstrated, the underlying cutting mechanisms remain inadequately understood. In this study, we investigate the fundamental mechanisms involved in the In-LAT of monocrystalline silicon by finite element (FE) simulations and experiments. Specifically, a FE model of In-LAT of monocrystalline silicon is developed, which incorporates a Drucker–Prager constitutive model to address the brittle fracture of the material, as well as temperature-dependent materials properties to address the thermal softening effect. Furthermore, experiments of In-LAT of monocrystalline silicon are conducted with the self-developed In-LAT device, including tapering cutting and end face cutting. Simulation results demonstrate that In-LAT significantly increases the critical depth of cut for the brittle-to-ductile transition of monocrystalline silicon in tapering cutting mode by 72.2% compared to conventional cutting, accompanied with significantly reduced cutting forces, continuous chip profile and reduced surface brittle damage. The promotion of ductile machinability of monocrystalline silicon under In-LAT is attributed to the reduction and dispersion of stress in the cutting zone, which is in contrast to the significant stress concentration at the rake face and cutting edge in conventional cutting. And simulation results also provide an optimal temperature field of 900 K for the In-LAT of monocrystalline silicon, above which the excessive plastic flow accompanied by thermal accumulation results into deteriorated surface roughness. These findings provide valuable insights for understanding the cutting mechanisms of In-LAT and the parameter optimization for In-LAT application.

Finite element investigations for chip scraping during orthogonal cutting process with micro-textured tools

Compared with the conventional tool (CT), the micro-textured tool (MTT) has the advantages of reducing cutting forces, lowering cutting temperatures and inhibiting tool wear. However, the chip scraping phenomenon generated in the cutting process has negative effects and degrades cutting performance when using the MTT with grooves perpendicular to the cutting edge. Due to the difficulty in observing and characterizing chip scraping in situ by experiments, its mechanism and influence on specific cutting forces and tool wear are not fully understood. To this end, finite element (FE) method is employed for simulating the cutting process with MTT. The simulation model is validated by comparing the predicted and measured specific cutting forces. The average prediction error of specific cutting and feed forces is 12.4 % and 18.8 %, respectively. The simulation results indicate that chip scraping mainly results from the discontinuity, non-uniformity and high contact stress state of the tool-chip interface. The minimum specific cutting force is achieved when the advantages of micro-texture and the chip scraping effects are balanced. The MTT rake face wear is subdivided into a severe and a sliding wear zone. This partition characteristic is closely associated with normal contact stress and temperature distributions. The work in this paper contributes to improving the understanding of chip scraping, optimizing micro-texture and cutting parameters, and promoting MTT applications in the manufacturing industry.

Diamond machining of additively manufactured Ti6Al4V ELI: Newer mode of material removal challenging the current simulation tools

Single point diamond machining (SPDM) produces smooth machined surfaces that other production methods cannot match. While the mechanics of machining of cast alloys with SPDM is well-explored, the realm of SPDM for additively manufactured parts remains largely uncharted. This work reveals new insights into the surface generation process of an additively manufactured titanium alloy, specifically, a Ti6Al4V Extra Low Interstitials (ELI) alloy workpiece. Our examination of the chip morphology unveiled a distinct mode of chip removal, previously unrecorded in existing literature. During SPDM of additively made Ti6Al4V ELI workpiece, identification of numerous pores and discontinuities in the chips flowing on the tool rake face, indicating periodic intermittent cracking during the material's plastic flow was seen. To examine this phenomenon, a finite element analysis (FEA) model was developed. While the FEA model can well explain the machining mechanics and chip morphology of SPDM of cast Ti6Al4V ELI reported in the literature, it failed to describe the chip morphology that are obtained during machining of additively made workpiece in this work. This disparity underscores the need for innovative simulation approaches tailored for additively manufactured components. The experimental observations in this study highlight a unique form of chip formation in contrast to conventional Ti6Al4V alloy machining processes. At lower feeds, there was a presence of short, discontinuous chip formation with tearing at the outer periphery. Conversely, at higher feeds, a long, continuous ribbon-like chip formation was observed. In addition, some typical additive manufacturing defects appear on the machined surface and chips. Through optimisation of the SPDT parameters, a surface roughness (Ra) value of about 11.8 nm was achieved on additively manufactured Ti6Al4V ELI workpiece. This work provides a fresh perspective on the mechanics of SPDM for additively manufactured components, offering a stepping stone for subsequent studies.

Analytical model of modified diamond tools temperature by focused ion beam in dry diamond turning

The contact process between the chip and the rake face is directly affected by the temperature of the rake face, and then tool wear and machining quality is indirectly influenced by it. In this study, a temperature prediction model for the rake face of modified diamond tools during dry turning of the 6061 aluminum alloy was established based on the moving heat source method. The shear heat source, rake face chip friction heat source, cutting edge-workpiece ploughing effect heat source, cutting edge workpiece roll burnishing heat source, and flank face workpiece elastic recovery heat source were considered by this model during the dry diamond turning, simultaneously considering the non-uniformity of heat source intensity and heat distribution ratio, as well as the influence of ion implantation on the temperature of the tool rake face. The experimental results indicate that this model successfully predicts the temperature of the modified tool rake face, and it is found that an increase in dose will promote a decrease in the temperature of the rake face. Theoretical analysis reveals that modified cutting tools have the characteristic of reducing the temperature of the rake face, revealing the essence of the influence of “modification” on the temperature of the rake face from the perspective of the cutting mechanism, and providing a theoretical basis for optimizing modification parameters.

A cutting tool architecture designed to address the parasitic mechanisms consuming excess power during machining and manufacturing operations-A review-based study towards sustainable manufacturing.

Metal cutting has been extensively studied over the years for improving its efficacy, yet, parasitic mechanisms like chatter and tool wear continue to generate higher forces and energy consumption with poor surface integrity. To address these parasitic mechanisms, a single-point turning cutter design is proposed based on the physics-of-machining including chatter theory to achieve reduced power consumption during the cutting of various metallic alloys like Al-6061, Ti-6Al-4V and others used by critical sectors such as aerospace and automotive. The current work focuses on aspects of machining that effectively reduce parasitic forces feeding into cutting power. The proposed cutter amalgamates features such as optimum side and end cutting edge angles, smaller nose radius and textured rake face into the cutter-body. Such a design is further proposed for use with a mechanochemical effect on a recently discovered plastic flow mode called sinuous flow, which has been reported to bring down cutting forces significantly. Experimental and analytical tests on the cutter design features validate reduction of cutting forces and through that alleviate the tendency to chatter as well as bring about energy savings for cutting of Al 6061. The potential for reduced real-time power consumption makes this design-framework significant for multipoint milling cutters too. It will greatly facilitate frugal manufacturing to account for sustainability in manufacturing operations.

Drilling-induced damage suppression on CFRP/Ti-6Al-4V stacks using textured drills

ABSTRACT Minimizing the drilling-induced damage on the walls and sub-surfaces of the drilled holes is a challenging but demanding task, especially on hard-to-machine materials such as CFRP/Ti-6Al-4 V stacks. In general, these stacks are highly preferred in aerospace structural applications. This paper analyzes the surface integrity of the drilled CFRP holes when they are stacked above the Ti-6Al-4 V alloy, by incorporating the laser-based marking of micro-textures on the flank and rake faces of the drill, which enables the micro-pool lubrication between the cutting-edges and work material. Comparative experimentations were conducted under MQL conditions. Considering the flank face micro-grooved drill, consistently lower thrust forces were observed across the entire range of cutting speeds and feeds, achieving reductions of up to 17 to 20%. Furthermore, the tool life study was performed, which reveals a substantial 26% enhancement in tool life with the flank face grooved drill, emphasizing its significant advantages for enhanced machining performance.

Research on effect of ultra-high pressure coolant supplied from flank face in end milling of Ti-6Al-4V supported by CFD simulations

In end milling of difficult-to-cut material such as Ti-6Al-4V, thermal wear is one of the main reasons leading to short tool life. High temperature occurred at the cutting zone during cutting process advances adhesion wear and diffusion wear at rake face, accelerates thermal plastic deformation. Furthermore, high temperature could also accelerate flank wear and promote adhesion wear at flank face. Consequently, machining precision of tool will degrade. Ultra-high pressure coolant (UHPC) is one of the well-known cooling/lubrication methods to solve this problem. In this paper, effect of UHPC on end mill flank face have been studied. To accomplish this, we designed an end mill with flank face coolant supplied from a close distance. The influence of coolant nozzle's direction has been studied by computational fluid dynamics (CFD) simulations. The result explains how the direction of the coolant nozzle impact on flow condition on the tool surface. The end mill was manufactured based on simulations by additive manufacturing. Experimental results including flank wear, surface roughness and cutting temperature demonstrate advantages of UHPC in end milling compared to dry cutting and flood coolant. The micro morphology of the worn areas on flank face and rake face further supports the advantages of UHPC.

A novel approach of composite turning for compacted graphite iron using minimum quantity lubrication and liquid nitrogen jetting by a developed setup

Compacted graphite iron (CGI) has high mechanical strength, and low thermal conductivity and content of sulfur, becoming a difficult-to-machine material. The tool life for machining grey cast iron (GCI) is 10–20 times of that of CGI, which greatly affecting the mass production in engine industry. To overcome this challenge, the influence of different spray positions on cooling and lubrication efficiency is analyzed based on the boundary layer theory, and a novel approach of composite turning with MQL lubricating flank face and liquid nitrogen (LN2) jetting cooling rake face is proposed. In virtue of boundary layer theory, negative graded pressure forms during the movement between the workpiece and cutter, resulting in that the MQL oil flows quickly to the contact area on flank face, which improves the lubrication effect. LN2 jetting is employed to cool rake face, effectively avoiding the accumulation of cutting heat on the tool and workpiece. The effects of four different cooling methods, including cutting fluid, MQL, LN2, and MQL + LN2, on the surface roughness, tool wear, and cutting force of cutting CGI and grey cast iron (GCI) were studied. According to the failure criterion of a cutting tool for the wear length of 200 μm on a flank face, the cutter life of cutting length is 2886 and 3884 m, correspondingly by cutting fluid and MQL + LN2, and the cutter life is increased by 34.6 %. In addition, the cutting force during turning CGI is 75.1 and 61.8 N by cutting fluid and MQL + LN2, respectively, and the cutting force is decreased by 17.7 %. The developed setup and findings provide a new turning method to cut a difficult-to-machine material for the use in mass production of the engine industry.

Influence of different wet-blasting pressure on the surface integrity and tool cutting performance of hybrid CVD-TiN/TiCN/α-Al2O3/TiN coated tools

This paper investigates the effect of wet-blasting pressure on the surface integrity and tool cutting performance of hybrid CVD-TiN/TiCN/α-Al2O3/TiN coated tools. The hybrid TiN/MT-TiCN/α-Al2O3/TiN multilayer coating was deposited on the surface of the cemented carbide inserts by chemical vapor deposition (CVD) technique. Then the coated inserts were subjected to wet-blasting by aluminum oxide with varying pressure. The coatings were characterized by scanning electron microscopy, white light surface profiler, and X-ray residual stress diffractometer. The results indicate that the average residual tensile stress of the α-Al2O3 layer on the rake face of CVD-coated inserts gradually decreased with the increase of wet-blasting pressure. When the wet-blasting pressure reached 0.24 MPa, the residual tensile stress was transformed into compressive stress. It was accompanied by increased cutting edge roughness and cutting edge radius, reduced cutting edge coating thickness, and a change in rake face surface roughness. To understand the effect of the surface integrity change on the cutting performance of CVD-coated inserts, a case study designed for AISI 4340 steel machining under continuous and intermittent cutting conditions is performed. When the Al2O3 layer on the cutting edge is not peeled off by wet-blasting, the change of residual stress from tensile to compressive in the rake face of CVD-coated inserts can effectively improve the fracture failure resistance of inserts in continuous and intermittent cutting processes. When the Al2O3 layer on the cutting edge is peeled off by wet-blasting, the fracture failure resistance during intermittent cutting will be significantly reduced.

The cutting performance of saw blades with textured structures on the rake face, main flank face, and secondary flank face

The cutting performance of saw blades with textured structures on the rake face, main flank face, and secondary flank face

Finite Element Simulation of Orthogonal Cutting of H13-Hardened Steel to Evaluate the Influence of Coatings on Cutting Temperature

High cutting temperatures increase tool wear and reduce tool life. To achieve a longer tool life, coated carbide tools have been developed. In this study, the influence of tool coatings on the cutting temperature distribution during the orthogonal cutting of H13-hardened steel is investigated. Firstly, four coating materials, including TiC, TiN, Al2O3, and TiAlN, with the same coating thickness, are selected to evaluate the effects of coating materials on cutting temperature with finite element simulation. The maximum temperatures at the tool rake face and the temperatures at the coating–substrate interface are evaluated. It was found that the maximum temperatures at the tool rake face were the lowest and the highest when TiN and Al2O3 coating materials were applied, respectively. The TiAlN coating material had the best thermal barrier property. Then, the temperature distribution along the direction perpendicular to the tool rake face is investigated for TiAlN-coated tools with different coating thicknesses ranging from 3 μm to 10 μm. It is shown that the temperature gradient increases with the coating thickness. The coating thickness should be kept below 5 μm. Finally, cutting experiments validate the availability of the finite element model.

Enhanced steel machining performance using texture-controlled CVD alpha-alumina coatings: Fundamental degradation mechanisms

Cemented carbide inserts coated with CVD α-alumina, particularly those exhibiting a (0001) texture, have proven highly effective in steel turning. Despite the established superior performance of (0001) textured alumina coatings, the underlying reasons remain unclear. This study explores the influence of the crystallographic texture of alumina on wear mechanisms in various chip-tool contact zones on the insert rake face. The objective is to establish a fundamental understanding of the active degradation mechanisms and machining performance by relating coating texture to the orientation and deformation of individual Al2O3 grains. Two multilayered coatings, Al2O3 on Ti(C,N), featuring (0001)- and (112‾0)-textured CVD α-alumina, were assessed in dry turning of a bearing steel. The wear rate of the (112‾0) coating was double that of the (0001) coating. Worn coatings exhibit nano-terrace formation at the insert edge, likely due to chemical etching. In the sticking zone, plastic deformation leads to larger facets for grains oriented with the chip flow direction, while rounded surfaces result if this condition is not met. In the transition zone, both (0001) and (112‾0) textured coatings undergo increased plastic deformation accompanied by sub-surface dislocations. (0001) texture deforms more by basal slip creating a wavy coating pattern with steps present at larger misalignments of the lattice planes in neighboring grains while (112‾0) texture deforms by several slip systems creating elongated ridges and ruptured-like areas resulting in rougher surface. This difference in surface morphology is then inherited by the abrasion of submicron coating fragments embedded in the chip (more in (112‾0) texture) in the sliding zone resulting in an even rougher surface. Chemical reaction with the hot chip may also contribute to wear acting as an additional mechanism. This fundamental understanding contributes to the potential enhancement of steel machining using texture-controlled CVD alumina coatings, ultimately improving coated cutting tool performance.

Performance analysis of conventional and high-feed turning tools in machining the thermally affected zone after plasma arc cutting of low carbon manganese-alloyed steel

The service life of cutting tools significantly affects machining costs. Establishing end-of-life criteria is crucial to mitigate wear effects on part quality, machine integrity, and maximize tool utilization. This is particularly important in machining operations with materials featuring numerous surface defects, as observed in those processed by prior thermal cutting operations, leading to accelerated tool wear rates. This study compares tool life and wear mechanisms in conventional and high-feed turning of low carbon manganese-alloyed steel bushes, previously profiled by plasma thermal cutting. Machinability tests utilized Class P carbide tools with triangular geometry for conventional turning and rhombic geometry for high-feed turning, both coated for enhanced performance. Tool's end-of-life criterion was established per ISO 3685 standard. The machining parameters adopted include a standard cutting depth of 1.5 mm, varying cutting speeds (140, 160, and 200 m/min) and feed rates (0.2; 0.3; 0.4 mm/rev for conventional turning, and 0.5; 0.75; 0.82 mm/rev for high-feed turning). Analysis involved assessing tool wear rates by observing flank wear and analyzing it using scanning electron microscopy and energy-dispersive spectroscopy techniques. Machined surface quality was quantified by roughness measurements. Metallographic characterization of bushes post-cutting indicated thermal cutting effects on the cutting edge's microstructure, microhardness, and residual stress. Machinability test results showed superior wear resistance in the high-feed turning tool (wear rate about 13 % lower). Surface finish evaluation demonstrated that, when isolating the effects of tool geometry and feed rate, the average surface roughness increased at a similar rate with tool wear for both conventional turning and high-feed turning. Identical wear mechanisms were observed: abrasive on the flank and adhesive on the rake face. Thus, the superiority of high-feed turning over conventional turning is established under the evaluated machining conditions.

Research on bionic design of cylindrical milling cutter based on the curvilinear configuration of the rake face of beaver teeth

Research on bionic design of cylindrical milling cutter based on the curvilinear configuration of the rake face of beaver teeth

Study on milling behavior of TiAlN coated tool with variable distribution density micro-texture

Considering that after milling titanium alloy with a ball-end milling cutter, the wear degree of different areas of the rake face is different, which indicates that the tool-chip contact conditions in this area are different, and then the micro-texture action mode is different. To improve the effect of micro-texture, this paper establishes a mathematical distribution model of variable distribution density micro-texture based on the two-zone method, builds a variable distribution density micro-texture ball-end milling titanium alloy test platform, studies the influence of variable density micro-texture parameters on tool milling behavior, and optimizes the parameters based on the improved particle swarm optimization algorithm. The results show that the micro-texture with variable distribution density has a positive effect on the milling behavior of the tool. The micro-texture parameters of the stickiness area have the greatest influence on the milling behavior of the tool. A texture parameter is optimized, and the overall milling behavior of the variable density micro-texture TiAlN coated milling cutter is optimal. This study provides a theoretical basis for the design and preparation of variable distribution density micro-textured tools. Highlights Based on the two-zone method, the mathematical distribution model of the variable distribution density micro-texture of the rake face of the tool is constructed. The influence mechanism of micro-texture parameters on the milling behavior of a ball-end milling cutter is explored. The multi-objective optimization of the variable density micro-texture parameters was carried out, and the optimal parameter combination was obtained. It is verified that the variable distribution density of the micro-texture has a positive effect on the cutting performance of the tool.

Gear Hob Base Worm Modelling from a Straight Toothed Generating Rack

The precision of a gear realized by hobbing is mainly influenced by the precision of the base worm, the adequate form of the rake face and the number of resharpenings. Gearing theory states that the base worm of a gear hob must be of involute type. Despite of this, manufacturing technology often admits a convolute worm as gear hob base worm. Due to the rake face grinding technology, there appears a difference between the theoretical and the real surface. On the other hand, the profile modification of the cutting edges occurs due to the re-sharpening. As a result, the cutting edges cannot reproduce that initial basic worm surface from which the gear hob was derived. In our opinion, the computing of the generating surfaces of the basic worm is still an unsolved problem. This paper deals with the study of a worm derived from a straight toothed generating rack. The incidence of an involute worm and that developed from the generating rack is investigated.

Development of a numerical cutting model for understanding the chip formation in cryogenic machining

The aim of this study is to develop a finite element model of metal cutting that includes fluid structure interaction. The proposed model is used to improve the physical comprehension of the chip formation during cryogenic assisted machining. This is performed based on the coupled-Eulerian-Lagrangian formulation. An algorithm is also developed to ensure heat exchange between the fluid and the structure. It also allows decoupling the mechanical and thermal effects induced by liquid nitrogen. The titanium alloy Ti17 is used as a work material, and uncoated tungsten carbide is used as a tool under dry and cryogenic conditions with cutting speeds of 50 m/min and 70 m/min and feeds of 0.1 mm/rev and 0.2 mm/rev. Simulation is validated by comparison with the experimental results. Standard deviations of both forces and chip thickness are low; they stay under 15% and 35% of the average value, respectively. The chip formation, the cutting force and the temperature are studied. It is shown that cryogenic machining has a significant effect on the chip formation and the temperature distribution in the cutting zone. A remarkable temperature reduction by up to 500 °C is observed at the tool rake face. However, the tool tip temperature slightly decreases with the application of liquid nitrogen when compared to dry machining.

Performance of Liquid Nitrogen (LN2) on Machining Pure Titanium (Grade 2): A Comparative Study

The biggest challenge for manufacturing industries is machining super alloys due to their properties. Titanium grade 2 also comes under the category of difficult cut material. In this present investigation, the green manufacturing technology was applied to cut the titanium grade 2. The comparison study was carried out between dry and cryogenic machining. The turning trails were performed using TiN-coated carbide cutting tools. Cutting force measurements surface roughness as well as the tool wear studies were carried out with the Kistler dynamometer, SURFCOM and SEM analysis. From the responses, under cryogenic cooling 32.5% of main cutting force reduction was observed when contrasted to dry condition at a cutting speed of 282 m/min. The 24 % of improved surface quality was observed under cryogenic cooling approach, more fracture on tool rake face was observed under dry condition and the favorable chip formations were also noted under cryogenic cooling approach.

Wear characteristics and performance in side milling of Ti2AlNb intermetallic alloys with coated and uncoated end mills

Ti2AlNb intermetallic alloy is highly suitable for aerospace key component manufacturing due to its low density, exceptional temperature strength, high specific strength, and creep resistance. However, the poor machining quality and severe tool wear appear, because of their poor thermal conductivity and excellent high temperature strength performance. In this paper, the coated and uncoated end mills are performed to investigate the tool wear characteristics during side milling of Ti2AlNb intermetallic alloys. In addition, the milling forces, tool service life, tool wear morphologies and mechanisms are discussed in detail. Results indicate that the coated and uncoated end mills suffered severe tool wear in the side milling process, leading to a rapid increase in milling forces. The coated end mill exhibited a longer service life of tools than the uncoated end mill. The service life of coated end mill reaches 6 min, primarily limited by flank wear and accompanied by chipping, whereas the uncoated end mill had a service life restricted to 2 min due to tool tip breakage. Tool wear morphologies of coated and uncoated end mills include rake face wear and flank face wear. Typical characteristics (e.g., crater wear, built-up edge, chipping and adhesion) are observed on the rake face of the both coated and uncoated end mills. On the flank face of the coated end mill, the chip adhesion, micro-chipping, chipping and coating delamination are found, whereas only chip adhesion and micro-chipping appear for uncoated end mill. Furthermore, the primary mechanisms of wear for both coated and uncoated end mills are adhesive wear and oxidation wear, which occur on both the rake face and flank face.