CBN Tools Research Articles

Analysis, modelling, and optimization of force in ultra-precision hard turning of cold work hardened steel using the CBN tool

The machinability of high-performance materials such as superalloys, composites, and hardened steel has been a big challenge due to their mechanical, physical, and chemical properties, which give them inherent complex machining characteristics. Additionally, majority of machinability tests conducted on these materials have been carried out on conventional and less precise lathes based on Taguchi, composite, and other designs of experiments that do not exploit all the possible combinations of cutting parameters. This work reports an investigation on ultra-precision hard turning (UHT) of cold work hardened AISI D2 steel of HRC 62, based on the full factorial design of experiment, carried out on an ultra-precision lathe. A theoretical analysis of the force components generated is reported. Modelling of the process, based on the resultant force, is also reported through a machine learning model. The model was developed from the experimental data and statistically evaluated with validation data. Its average MAPE values of 1.47%, 4.81%, and 10.66% for training, testing, and validation, respectively, attest to its robustness. The excellent coefficient of determination values, R2, also justify the model’s robustness. Multi-objective optimization was also conducted to optimize material removal rate (MRR), resultant force, and vibration simultaneously. For sustainable and efficient UHT, optimal cutting velocity (158.8 m/min), feed (0.125 mm/rev), and depth of cut (0.074 mm) were proposed to generate optimal resultant force (224.8 N), MRR (2603.6 mm3/min), and vibration (0.03 m/s^2) simultaneously. These results can be beneficial in planning UHT processes for high-performance materials.

Molecular dynamics simulation of the influence of nanocutting parameters on microstructure of AISI M2

Molecular dynamics simulation has become the main analysis method of ultra precision machining of various materials. In this research, molecular dynamics method was used to explore the influence of nanocutting parameters on amorphous atoms, atomic coordination numbers, atomic strain and dislocations of AISI M2 workpiece. LAMMPS was used to construct the molecular dynamics model for CBN tool cutting AISI M2. The polycrystalline model of the workpiece contained 12 grains and iron, chromium and tungsten atoms. The polycrystalline model of the tool contained 3 grains and boron and nitrogen atoms. Tersoff, EAM, Morse and L-J potential energy functions were used to characterize the interaction between atoms. The following results were obtained through 8 groups of simulation experiments: (1) Both cutting speed and cutting depth promoted the amorphous transformation of workpiece atoms. (2) Under the extrusion of the tool, atoms with high coordination numbers were produced in the contact area between the tool and the workpiece. (3) The cutting depth was positively correlated with the average strain of workpiece atoms. Large strain atoms mainly occurred in the cutting area and gradually extended into the workpiece. (4) 1/2 < 111> dislocation was the most common dislocation form in nanocutting. This research plays a rich role in molecular dynamics simulation of nanocutting polycrystalline alloys.

A predictive wear model in grinding using single-layer electroplated cBN tools

Wheel wear is a complex phenomenon significantly affecting grinding performance. While microscopic grit observation can detect various wear mechanisms, a predictive model is required to anticipate the total wear behavior under diverse grinding conditions. This study incorporates all wear mechanisms, including pullout, attrition, and fracture, into an analytical model aimed at determining improved grinding conditions. The grinding particles are approximated as standard constitutive geometries to model the wheel surface topography and the grit height reduction obtained from the wheel surface roughness is correlated with wear. The present model introduces an innovative approach to tracking and predicting wheel wear performance, eliminating the need for time-consuming grit micro-observation. Numerous grinding tests employing different tools were conducted, revealing strong agreement between the experimental results and the model predictions. The Application of this approach for predicting prolonged tool life is also demonstrated. Finally, the paper discusses how these findings contribute to a deeper understanding of the fundamental wear mechanisms in the grinding process.

Milling of TiBbm2 Particle Reinforced High-Modulus Steel

TiB2 particle reinforced high-stiffness steel is one of the composite materials that aim to improve Young’s modulus by compositing TiB2 particles into a stainless steel base phase. This material is designed to exhibit higher rigidity and strength than conventional iron-based materials by using TiB2 particles as the reinforcing phase, and is expected to reduce the weight of high-load components in engines. For this reason, tool life is very short when machining this material. Therefore, high Young’s modulus steel containing TiB2 particles is known to be one of the most difficult-to-cut materials. The purpose of this study was to investigate how to extend tool life in the milling of high-Young’s-modulus steel. Cutting speed dependence of tool life was investigated by end milling using a binderless CBN tool with excellent hardness and bending strength. In addition, the tool damage mechanism was also investigated. The results showed that tools composed of binderless CBN tool have a longer life than conventional CBN tool. In this type of binderless CBN tool, the tool wear rate tended to increase with increasing cutting speed. In addition, the longest tool life was obtained at a cutting speed of 1.25 m/s, though wear rate increased at a boundary cutting length of 1300 m. The wear rate was found to increase with increasing cutting speed. Temperature measurement results indicate that the primary cause of tool damage was mechanical wear, as the temperatures were much too low for a reaction between cBN and Fe. Friction tests revealed scratch marks on the tool originating from crushed cBN particles produced by the crushing of the cutting edge. This indicates that wear is accelerated by the high frictional energy of the cBN powder rubbing against the flank face.

Special Issue on Abrasive Technology for High-Precision and High-Efficiency Machining of High-Performance Materials

The demand for high-precision and high-efficient machining of high-performance materials and components has increased in various industries such as optical, automotive, communication, life sciences, and medical sciences. Certain difficult-to-machine materials can be reliably machined using deterministic precision cutting processes. However, hard and brittle materials such as ceramics, carbides, hardened steel molds, glassy materials, or semiconductor materials, require precision abrasive technologies with super abrasives like diamond, cBN, or new tool materials for machining. However, machining high-precision components and their molds/dies using abrasive processes is considerably more difficult due to their complex and non-deterministic nature and textured surfaces. Furthermore, high-energy processes such as laser technology can assist abrasive technologies in ensuring higher precision and efficiency. Precision grinding and polishing processes are primarily used to generate high-quality and functional components, typically made of difficult-to-machine materials. Thus, the surface quality achievable by precision grinding and polishing processes becomes more important for reducing machining time and costs. This special issue features 10 papers on the most recent advances in precision abrasive technologies. These papers cover the following topics: - Ultrasonic grinding of micro holes using cemented WC tools - Drilling holes in CFRP aircraft using cBN electroplated ball end mill - In situ evaluation of drill wear using tool images - Grinding belt based on modified information entropy - Radial directional vibration-assisted grinding of Al2O3 ceramics - Chatter vibration suppression using fixed superabrasive polishing stone - Free abrasive finishing of internal channels with different cross-sectional geometries - High-quality machining of cemented carbide using PCD ball end mills - Fixed-abrasive machining with magnetic brush for Ti-6Al-4V ELI alloy - High-efficient polishing of polymer surfaces using catalyst-referred etching This issue will provide an understanding of the recent developments in abrasive technologies, leading to further research. We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts.

Double-Sided Deep Grinding of Gas Turbine Engine Blades with Highly Porous CBN Tools

Double-Sided Deep Grinding of Gas Turbine Engine Blades with Highly Porous CBN Tools

Surface quality prediction by machine learning methods and process parameter optimization in ultra-precision machining of AISI D2 using CBN tool

High-quality machining is a crucial aspect of contemporary manufacturing technology due to the vast demand for precision machining for parts made from hardened tool steels and super alloys globally in the aerospace, automobile, and medical sectors. The necessity to upheave production efficiency and quality enhancement at minimum cost requires deep knowledge of this cutting process and development of machine learning-based modeling technique, adept in providing essential tools for design, planning, and incorporation in the machining processes. This research aims to develop a predictive surface roughness model and optimize its process parameters for ultra-precision hard-turning finishing operation. Ultra-precision hard-turning experiments were carried out on AISI D2 of HRC 62. The response surface method (RSM) was applied to understand the effect of process parameters on surface roughness and carry out optimization. Based on the data gained from experiments, machine learning models and algorithms were developed with support vector machine (SVM), Gaussian process relation (GPR), adaptive neuro-fuzzy inference system (ANFIS), and artificial neural network (ANN) for the prediction of surface roughness. The results show that all machine learning models gave excellent predictive accuracy with an average MAPE value of 7.38%. The validation tests were also statistically significant, with ANFIS and ANN having MAPE values of 9.98% and 3.43%, respectively. Additional validation tests for the models with new experimental data indicate average R, RMSE, and MAPE values of 0.78, 0.19, and 36.17%, respectively, which are satisfactory. The RSM analysis shows that the feed is the most significant factor for minimizing surface roughness Rɑ, among the process parameters, with 92% influence, and optimal cutting conditions were found to be cutting speed = 100 m/min, feed = 0.025 mm/rev, and depth of cut = 0.09 mm, respectively. This finding can be helpful in the decision-making on process parameters in the precision machining industry.

Effects of ultrasonic vibrations on brazing mechanism and evaluating grinding performance of CBN tools

Effects of ultrasonic vibrations on brazing mechanism and evaluating grinding performance of CBN tools

Analysis of Tool Wear and Calculation Results of Hardness Values in St 37 Steel Turning Using Characteristics

The development of lathe chisels is currently more advanced with the creation of carbide, CBN, ceramic, and inserts tool types. However, conventional chisel types, one of which is the HSS (high speed steel) chisel, are still used. ST 37 steel is a low carbon steel type that is easy to forge and easy to machine. The level of precision and surface roughness of the resulting workpiece must be in accordance with the needs. The higher the level of surface quality of the workpiece, the higher the level of precision. The research method we use is to find data, then the data obtained is graphed. From the results of the graph it can be concluded that for the depth of cutting the greater the rotation, the greater the depth. For wear, it can be seen that the wear will be greater if the speed is increased. The results of the hardness test at a medium rotational speed of 490 Rpm, the greater the number of examples, the greater the results of the hardness test experienced on the test material.

Cutting performance of binderless nano-polycrystalline cBN and PcBN milling tools for high-speed milling of hardened steel

Since difficult-to-machine materials are widely used in high-end equipment such as aerospace and marine components as well as precision molds, the development of high-performance cubic boron nitride (cBN) tools has been an important area of research. In this paper, we evaluate a new type of finer-grained, binderless end mill (binderless nano-polycrystalline cBN, BNNC) by comparing it to polycrystalline cBN (PcBN) end mills for high-speed machining of hardened steel. First, the process of tool preparation based on the above novel cBN is described and high-speed milling experiments were designed. Then, the cutting performance of the BNNC and PcBN tools during high-speed milling is analyzed and compared in four aspects: the cutting force coefficients, the friction coefficient of the rake face, the milling temperature and the tool wear. In addition, the wear mechanism of the two types of end mills was analyzed by energy dispersive X-ray (EDX). Afterwards, the trend of cutting temperature was further investigated by 2D finite element simulation. Finally, grey correlation analysis was applied to describe the correlation between the above factors and tool wear. This study shows that compared with PcBN end mills, BNNC end mills have longer tool life under the same cutting condition and are more reliable at high temperatures, which exhibit great application potential.

Optimization and prediction of CBN tool life sustainability during AA1100 CNC turning by response surface methodology

The aluminium alloy (AA1100) was familiar with automotive flexible shaft coupling applications due to its high strength, good machinability, and superior thermal and resistance to corrosion characteristics. Machining tool life drives the prominent role for deciding the product quality (machining) act aims to productivity target with zero interruptions. The novelty of this present investigation is the focus on increasing tool life during the complexity of CNC turning operation for AA1100 alloy by using CBN coated insert tool with varied input parameters of spindle speed (SS), feed rate (f), and depth of cut (DOC). Design of experiment (L16), analysis of variance (ANOVA) statistical system adopted with response surface methodology (RSM) is implemented for experimental analysis. The turning input parameters of SS, f and DOC are considered as factors and its SS (900, 1100, 1300, and 1500 rpm), f (0.1, 0.15, 0.2, and 0.25), and DOC (0.1, 0.2, 0.3, and 0.4 mm) values are treated as levels. The investigational analysis was made with the ANOVA technique and the desirability of high tool life with input turning parameters was optimized by RSM, and sample no 11/16 was predicted as high tool life and performed with extended working hours compared to other samples. The RSM optimized best turning parameter combinations are 0.1 mm DOC, 0.2mm/rev to 0.25mm/rev f, and 1300 rpm–1500 rpm SS, facilitating a higher tool life of more than 20min.

Active brazing of cBN micro-particles with AISI 1045 steel using ceramic reinforced Ag-based fillers

cBN micro-particles have been brazed to medium carbon steel substrate using a new formulation of low-temperature, ceramic reinforced Ag-Cu-Ti alloy and evaluated for their wear resistance in developing cBN brazed tools. TiN and TiB2 microparticles were added as reinforcements independently in different proportions to Ag-Cu-2Ti (Ag-Cu-2wt%Ti) filler alloy and cBN tools were brazed. Wear characteristics of the ceramic reinforced alloys showed that the TiB2 added Ag-Cu-2Ti alloy exhibited excellent abrasion resistance with an improvement of 91–95 % over the commercial Ag-Cu-2Ti alloy. Conversely, the wear performance of the TiN added Ag-Cu-Ti alloys was poor owing to the weak bonding of TiN microparticles by the alloy matrix. The results were compared with 5 wt% TiB2 and TiN added Ag-Cu-5Ti alloys. However a significant improvement in the mechanical properties was not observed and the wetting on cBN was lower for reinforced Ag-Cu-5Ti alloy. Tensile tests showed that the Ag-Cu-2Ti-5TiB2 alloy demonstrated higher tensile strength (305.89 MPa) when compared to the Ag-Cu-2Ti and Ag-Cu-2Ti-5TiN filler materials. Low and high impact dynamic joint strength tests were further carried out on the 2 and 5 wt% reinforced Ag-Cu-2Ti and Ag-Cu-5Ti alloys. TiB2 added Ag-Cu-2Ti alloy displayed sufficient joint strength with TiN added Ag-Cu-2Ti alloys performing marginally better. Bearing in mind the excellent mechanical properties of the Ag-Cu-2Ti-5TiB2 filler and its appreciable joint strength, Ag-Cu-2Ti-5TiB2 filler can be used as an efficient filler material in developing cBN brazed tools for grinding applications.

Comparative Evaluation of Coated Carbide and CBN Inserts Performance in Dry Hard-Turning of AISI 4140 Steel Using Taguchi-Based Grey Relation Analysis

Dry hard-turning is a vital manufacturing method for machining hardened steel due to its low cost, high machining efficiency, and green environmental protection. This study aims to analyze the effect of various machining parameters on cutting forces and surface roughness by employing RSM and ANOVA. In addition, multi-objective optimization (Grey Relation Analysis: GRA) is performed to determine the optimum machining parameters. Dry hard-turning tests were carried out on AISI 4140 steel (50 HRC) using coated carbide and CBN inserts with different nose radii. The results show that the cutting force components are greatly affected by the cutting depth and cutting speed for both cutting inserts. As the level of cutting depth and cutting speed rise, the cutting forces also increase. However, the feed rate was the main factor in surface roughness. A low feed rate and high cutting speed lead to good surface quality. According to the results, CBN inserts exhibited better performance compared to carbide inserts in terms of minimum cutting forces and surface roughness. The lowest radial force (Fx = 55.59 N), tangential force (Fy = 15.09 N), cutting force (Fz = 30.49 N), and best surface quality (Ra = 0.28 µm, Rz = 1.8 µm) were obtained using a CBN tool. Finally, based on the GRA, the (V = 120 m/min, f = 0.04 mm/rev, a = 0.06 mm, r = 0.8 mm) have been chosen as optimum machining parameters to minimize all responses simultaneously in the machining of AISI 4140 steel using both carbide and CBN inserts.

The use of Preston equation to determine material removal during lap-grinding with electroplated CBN tools

Grinding executed in a lapping configuration is an alternative finishing process benefiting from both grinding and free-abrasive machining, while minimizing the heat effect impact. Electroplated tools can be effectively used in different abrasive processes, including high-speed grinding, however, the assessment of machining performance over time is a key factor in their correct use to achieve satisfactory technological results. In conventional grinding, bigger grain-coverage provides better results due to the higher bonding strength of grains. In lap-grinding, fracturing and crushing of the abrasive particles initially covered by the plating result in a suspension which is typically dosed continuously in free-abrasive machining. Due to this, the process transforms from two-body (grinding) to three-body abrasion (free abrasive machining) which may result in reduced grinding performance approaching asymptotically a specific value while improving surface finish. The main aim of the presented study is the evaluation of electroplated CBN tools used in lap-grinding of 40H alloy steel workpieces whose hardness was 54 HRC. The obtained results and observations of the working surface of CBN wheels and workpieces allowed for the identification of the wear characteristics for three nickel plating thicknesses corresponding to 35%, 50% and 65% of the nominal CBN crystal size and for specific process parameters. The surface roughness Ra parameter decreased gradually from the initial value 1.9 μm to the values below 0.7 μm for bigger B107 grains and for all plating thicknesses. For smaller B64 grains, the surface roughness and waviness parameters reached similar values to those obtained for the larger B107 grains at corresponding processing times. The lowest value of Ra parameter below 0.4 μm was obtained for B64 grains and for the thinnest plating but with a 50% reduction in material removal comparing to B107 grains. The Preston equation was employed to calculate the material removal as a function of time under variable process conditions in the machining zone due to the tool wear. This attempt extended the range of the material removal modeling, despite the fact that the electroplated wheels were subject to wearing down resulting in the gradual reduction in the efficiency, as well as in the change of the working conditions in the workpiece-tool contact zone.

Cutting performance of the nanotwinned cBN tool in nano-cutting of Ni-Cr-Fe alloy

As nickel-based superalloys are broadly used and difficult to machine material, it is challenging to achieve high machining efficiency while improving surface quality and enhancing tool life. Aiming at the cutting of Inconel-718 type nickel-based superalloys, a new type of tool in which the cBN tool incorporated naontwinned structures is proposed. The mechanical properties of cBN tool materials with the introduction of nanotwinned structures are studied by uniaxial tensile simulations of nanotwinned cBN (nt-cBN) and single-crystal cBN (sc-cBN) nanosheets. Compared with the sc-cBN materials, the introduction of nanotwinned structures improved the properties of strength, toughness, and stiffness of cBN materials. The tool performance of the nt-cBN tool and the sc-cBN tool have been studied when cutting a simplified nickel-based superalloys (Inconel-718) model using the molecular dynamics method. Tool wear mechanisms of nt-cBN tools are investigated by calculating and visualizing tool temperature, Von Mises stress, and shear stress distributions. The results show that the wear resistance performance of the nt-cBN tool has improved during high-speed cutting, with less plastic deformation of the tool, less diffusion wear, less adhesion wear, and especially the wear of the flank surface is significantly reduced. As a new type of tool for machining difficult-to-machine materials, nt-cBN tools have promising research prospects.

A Short Literature Review on Turning and Milling of Cobalt Alloys

Among the existing machining processes, turning and milling are characterized as the most used and consequently are considered the most important. Machining moves a market estimated at around 10% of gross national production. Many industrial components and parts are subjected to severe operating conditions, in corrosive environments, high temperatures what causes wear. With the development of industries, there is a need for steel alloys with different properties, to meet different purposes. Cobalt alloys, as well as others, arose from the need to develop metals that would meet the growing demand in applications with high temperatures and high working stress in gas turbine components. Due to their high mechanical and thermal resistance, these alloys are difficult to machining, a situation that requires in-depth studies to reduce process costs and improve the surface quality of machined parts. Machined surfaces may have different textures depending on the process. Turning and milling generate grooved profiles due to tool/part interaction. In many cases, roughness is used as an output parameter to control the process. Another important factor is the wear of cutting tools, which must be selected according to the material properties of the workpiece, machine tool and other parameters that influence its wear. Controlling the useful life of the tool is a decisive factor when you want to avoid loss of productivity, with fewer stops for changes, consequently, you have a more effective and economical production. The present study presents a brief review of the literature regarding turning and milling of cobalt alloys, regarding the optimization of machining parameters, tools used and the use of lubri-cooling techniques, with the objective of reducing the roughness of the parts, the tool wear, improve surface integrity and contribute to the sustainability of manufacturing processes when machining difficult-to-cut materials. In this review, a comparative analysis of the results is presented, indicating the gaps in research such as classification and processing of alloys, formation of carbides with non-uniform distribution, which impairs the performance of the tools. Some suggestions for future work indicate the absence of studies on the use of diamond and CBN tools, clarify the interaction medium lubricant-coolant-coating of the tools-alloy chemical composition and cutting parameters, in addition to dynamic analyzes in the cutting of hardened materials.

Experimental and Simulative Investigation of Thermomechanical Loads in the Cutting Zone by Machining X30CrMoN-15-1 Steel with CBN tools

Experimental and Simulative Investigation of Thermomechanical Loads in the Cutting Zone by Machining X30CrMoN-15-1 Steel with CBN tools

Tool wear characteristics analysis of cBN cutting tools in high-speed turning of Inconel 718

Nickel-based superalloy is a critical material for turbine engine components in the aerospace application, but the poor machinability and low machining efficiency have further hampered it to be used widely. Cubic boron nitride (cBN), having extreme hardness and chemical inertness, is the potential candidate to process superalloys. In this paper, we systematically investigated the tool wear characteristic of cBN at different cutting speeds in dry turning of Inconel 718 by experiments and FEM simulations. The FEM model with initial flank wear land (VB) was established and validated. Effects of cutting speeds (200–400 m/min) on cBN tool life and wear mechanisms were systematically investigated. Effects of tool flank wear on cBN tool cutting edge temperature field and Inconel 718 machined surface layer stress distribution were analyzed by FEM simulations.

Tool Wear of Cubic Boron Nitride in Cutting Sintered Steel

In the powder metallurgy method, after sintering, it is often necessary for the sintered steel machine parts to be machined by the metal removal process for dimensional accuracy. In this case, it is imperative that the tool materials have good wear resistance. Polycrystalline cubic boron nitride compact (cBN) seems to be an effective tool material because it has good heat and wear resistance. In this study, in cutting sintered steel with cBN tools, various cBN tools have been used in cutting experiments to identify an effective combination of binding phase and cBN content. As a result of experimentally examining the wear progress of the CBN tools, a cBN tool having a binder phase of (Al2O3-Al) and a cBN content of 60% was effective for wear resistance.

Research on the effect of cutting parameters on the machinability of polycrystalline Fe-Cr-W alloy by molecular dynamics simulation

Molecular dynamics simulation has become a major theoretical analysis method for ultra precision machining of various materials. Large Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) is used to construct a molecular dynamics model for cutting polycrystalline Fe-Cr-W alloy with CBN tool. The geometric parameters of the tool model are: the rake angle is −10°, the clearance angle is 7°, and the tool tip radius is 1.5 nm, including 8570 atoms. The size of the workpiece model is 24 nm × 10 nm × 10 nm, including 203,893 atoms. Ovito is used to visually analyze the influence of cutting parameters on the machinability of workpieces. The results show that the extrusion of the tool on the workpiece makes the atoms of the workpiece move and become chips and machined surfaces. Excessive cutting speed and depth will produce large hydrostatic stress, large cutting force, high cutting temperature and deteriorate the machined surface.