Surface Generation In Machining Research Articles

Tribological aspects of nano-particle fluid based cooling and lubrication in milling process

The introduction of different additives into the cooling and lubrication systems in the metal cutting process, contributed to improving the machining process sustainability. Different types of additives can help to reduce friction, reduce wear of contact surfaces, improve heat dissipation from the cutting zone, etc. With the development of nanotechnology, great focus has been placed on the investigation and using of nano-particles, nano-additives and nanofluids in industry. In this paper, the effects of using the nano-particle based cooling and lubrication fluid are investigated. There are performed comparison effects of standard cooling and lubrication fluids versus nanofluids based cooling and lubrication on cutting process performance. Molybdenum disulphide particles are used as nano-particles, which dispersed in a standard cooling and lubrication fluid. As workpiece was used alloyed tool steel. Milling process performance indicators was analysed based on Taguchi experimental plan, for different cooling and lubrication condition and process parameters. Cutting forces component in three perpendicular axes, and machined surface parameters were measured. Experimental analysis has shown that the use of nano-particles, which mixed in a standard cooling and lubrication fluid, significantly contributes to the reduction of cutting forces, friction coefficients, more efficient cutting and generation of machined surfaces.

Effects of Cutting Edge Radius on Surface Integrity in Machining of Nickel-Based Cast Superalloy: An In Situ Imaging Approach

Abstract Cutting edge radius is a crucial factor affecting surface integrity during metal machining, which determines product performance. However, the exact mechanism of how the cutting edge radius affects machined surface has not yet been understood, especially lacking in situ evidence during the material removal process. In this article, effects of cutting edge radius on surface roughness, subsurface deformation, and work hardening of nickel-based cast superalloy are studied through an in situ imaging approach. Based on continuous high-speed filming and digital imaging correlation (DIC) techniques, detailed chip formation and quantitative subsurface plastic deformation under various cutting edge radii are analyzed, and the formation of built-up edge (BUE) is observed when using a large edge radius. Furthermore, when the cutting edge radius is greater than the uncut chip thickness (h), the thickness of plastic deformation increases dramatically. On the other hand, the machined surface roughness can be improved when the cutting edge radius is between 30% and 60% of h. The sharp cutting tools or the cutting edge radius higher than 60% of h result in a poor surface quality on the machined surface during nickel-based cast superalloy machining. The effects of cutting edge radius on machined surface generation are systematically categorized as cutting with chipping, cutting with significant plowing, and cutting with plowing accompanied by BUE formation.

Influence of Feed Rate Response (FRR) on Chip Formation in Micro and Macro Machining of Al Alloy

In this paper, the investigation of chip formation of aluminum alloy in different machining strategies (i.e., micro and macro cutting) is performed to develop a holistic view of the chip formation phenomenon. The study of chip morphology is useful to understand the mechanics of surface generation in machining. Experiments were carried out to evaluate the feed rate response (FRR) in both ultra-precision micro and conventional macro machining processes. A comprehensive study was carried out to explore the material removal mechanics with both experimental findings and theoretical insights. The results of the variation of chip morphology showed the dependence on feed rate in orthogonal turning. The transformation of discontinuous to continuous chip production—a remarkable phenomenon in micro machining—has been identified for the conventional macro machining of Al alloy. This is validated by the surface crevice formation in the transition region. Variation of the surface morphology confirms the phenomenology (transformation mechanics) of chip formation.

Investigation on surface roughness in axial ultrasonic vibration–assisted milling of in situ TiB2/7050Al MMCs

The surface roughness is one of the important parameters of surface quality evaluation. In the field of aerospace and industry, many attempts have been made to reduce the roughness of machined surface and improve the performance of parts. An advanced manufacture technique, ultrasonic vibration–assisted milling, can reduce the surface roughness, which is widely used to cut the materials that are difficult to machine. In this work, the theory of the machined surface generation is analyzed and the effect of cutting parameters and the ultrasonic vibration on the machined surface is investigated by ultrasonic vibration–assisted milling of in situ TiB2 particle–reinforced aluminum matrix composite. Firstly, the motion trajectory of cutting tool and machined surface topography generation is analyzed theoretically. Then, theoretical model of the number of vibration per cutting arc length and the transient angle is built to analyze the generation of the surface topography. Finally, experiments with and without ultrasonic vibration are carried out for the theoretical analysis of the machined surface generation and the surface roughness. The results show that regular micro-dimples are produced on the machined surface due to the addition of ultrasonic vibration and the theoretical model could be applied to explain the influence of ultrasonic vibration on the surface topography and roughness. Besides, in this study, the assistance of ultrasonic vibration can improve the surface quality in certain cutting conditions of cutting speed below 65.94 m/min and the vibration frequency of 20 kHz.

Evolutions of grain size and micro-hardness during chip formation and machined surface generation for Ti-6Al-4V in high-speed machining

Machined surface with ultrafine grained microstructure can be obtained through severe plastic deformation in high-speed machining (HSM) process. The aim of this paper is to investigate the evolution of grain size and micro-hardness during HSM of Ti-6Al-4V alloy using the finite element method (FEM) and user subroutine VUSDFLD of Abaqus/Explicit. Firstly, a FE model to simulate the cutting process of Ti-6Al-4V is proposed. The proposed cutting simulation model is verified by high-speed machining experiments in terms of cutting force and chip morphology. Secondly, a novel user subroutine VUSDFLD based on equations of Zener-Hollomon and Hall-Petch is developed to simulate the modifications of grain size and micro-hardness in chip formation and machined surface generation under different cutting speeds. Parameters in the equations of Zener-Hollomon and Hall-Petch are modified for Ti-6Al-4V for simulation of the change of grain size and micro-hardness during HSM. Lastly, the simulation results of the microstructure evolution in chips and machined surfaces are compared with experimental results obtained by optical microscopy, scanning electron microscopy (SEM), and measurement of micro-hardness. The comparison results show that the evolution of grain size and micro-hardness of Ti-6Al-4V in HSM can be accurately predicted by the modified Zener-Hollomon and Hall-Petch equations. This research indicates that smaller grain sizes are produced into both chips and machined surfaces due to more severe deformations with increasing of the cutting speed. The findings validate that HSM is a reliable approach to generate refined grains if proper machining parameters are selected. HSM can also be applied as a novel material test method to study the relationship between microstructure evolution and deformation parameters.

Tool damage and machined-surface quality using hot-pressed sintering Ti(C7N3)/WC/TaC cermet cutting inserts for high-speed turning stainless steels

A Ti(C7N3)/WC/TaC cermet cutting tool was developed using a hot-pressed technology. A standard orthogonal array was used to investigate the cutting performance of this newly developed insert in the high-speed turning of 17-4PH martensitic and 321 austenitic stainless steels. The effects of the cutting parameters on the tool life and surface quality were analysed to examine the performance of the inserts based on Taguchi method. The mechanisms of tool damage and machined-surface generation and their relationships were also thoroughly discussed to understand the machinability of different stainless steels. The used cutting parameters are as follows: a cutting speed of 350∼400 m/min for 17-4PH steel and 300∼350 m/min for 321 steel and a feed of 0.10 mm/r and a depth of cut of 0.30∼0.35 mm, which is considered to be a notably efficient parameter for machining stainless steel. The crater wear and flank wear prevailed in the machining of 17-4PH martensitic stainless steel, whereas the flank wear was serious and edge chipping occurred in the machining of 321 austenitic stainless steel. There were some pits on the machined-surfaces of 17-4PH steel and some material side flow on the machined-surface of 321 steel, which is related with the e material properties of these two stainless steels.

Fundamental Investigations Into Burr Formation and Damage Mechanisms in the Micro-Milling of a Biomedical Grade Polymer

The demand for micro-machined polymer components has been rapidly growing for a number of years in various diverse applications. These polymer components often require high surface finishes and excellent dimensional accuracies, meeting these specifications requires a deeper understanding of material behavior and cutting performance during micro-machining. A lack of published literature relating to polymer machining increases the production challenge as cutting strategies employed are often based on trial and error with heuristic solutions developed. This work explains material behavior and machining outcomes by focusing on the study of the various damage mechanisms encountered during the micro-machining of a biomedical grade polymer. The importance of the material removal mechanism is highlighted with up-milling shown to produce a superior surface finish on average. The role of speed and feed in the generation of machined surfaces is examined with suboptimal settings shown to produce unwanted thermal influences and significant material deformations.

Reducing Shaping Burr by Beveling Exit Edge of 45C8 Steel

Production of high precision components needs constant attention to both the generation of machined surfaces without a burr and undertaking deburring operation. A machining process usually produces burr. In shaping, burr formation occurs when the cutting tool exits the workpiece. Absence of necessary back up support around an edge is the possible reason behind it. Several research works have been done on burr formation mechanism, its minimization, and deburring. A number of experiments is performed in this work on medium carbon steel (45C8) flats in dry condition to note the effects of burr formation on the workpiece with beveled exit edge. The experimental result shows that at 15o edge bevel, negligible burr formation is obtained. Analysis of variance is conducted on the experimental results to find out the relative influence of each process parameter on burr height observed. The regression analysis is also done with the experimental data and the regression equation gives fairly good estimate of experimental results.

Machined surface generation using wavelet filtering

The surface geometry of a workpiece after machining is a major concern in the industry. Thus, it is important to generate its geometry, reconfiguring and modifying it by a wavelet-based filtering technique with confocal laser scanning microscopy (CLSM). This technique is well-suited to construct the three-dimensional surface of a machined workpiece. The problem of noise on the surface always occurs when treating the raw height data (HEI: Height Encoded Image) acquired by CLSM. The noise occurs in constructing the surface height image (HEI) due to an electronic and photographic image process and must be filtered. In this paper, a wavelet-based filtering algorithm is used to eliminate noise in the shape features of the surface on a micro scale so as to realize an accurate geometry for further topographic analysis. The filtered surface patterns enable us to predict the machined surface and analyze surface characteristics in varied shapes of different levels. Also, to consider the tilting that inevitably occurs in mounting a specimen on the table, the surface is compensated and flattened in the x and y-directions simultaneously. This newly developed technique combines CLSM and wavelet filtering generates various micro machined surfaces over a wide range of surface resolutions on a micro scale

Surface Roughness and Cutting Force of Inconel 718 Machined by Different Cutting Tools

Given the stringent operating conditions to which super alloys are subjected to in aerospace, nuclear power and gas turbine industries, their efficient machining and generation of machined surfaces with high integrity assumes a lot of importance. Therefore, this paper presents an experimental investigation on the surface roughness and cutting force of Inconel 718 machined with several different kinds of cutting tools. Both single-factor and orthogonal experiments were carried out with cemented carbide, cermet and CBN tools. The effects of cutting tools and cutting parameters on the surface roughness and cutting force are investigated and the optimal cutting conditions are recommended.

Dynamic surface generation modeling of two-dimensional vibration-assisted micro-end-milling

An integrated model is proposed to simulate the surface generation in two-dimensional vibration-assisted micro-end-milling (2-D VAMEM). The model includes the developed submodels as dynamic cutting force model, machining system response model, and machined surface generation algorithm. The effects of feed rate on cutting force and surface roughness are investigated through simulations. It is found that the cutting force increases while the surface roughness decreases with the increment of the feed rate when the feed per tooth is smaller than the tool edge radius. The trials have been carried out to evaluate and validate the proposed model and the simulation results. The integrated model contributes to the comprehensive understanding of the process of machined surface generation in 2-D VAMEM and will assist the machining operators to select optimal machining parameters.

斜面のボールエンドミル加工における工具挙動と仕上げ面生成機構の解析 (第1報)

By using a cutting model and energy method proposed in previous papers, cutting forces in various milling processes in which both cutting edges of spherical and cylindrical portions engage with the workpiece can be predicted, and distribution of cutting forces along the cutting edge also obtained. To clear the behavior of tool deflection and the mechanism of machined surface generation in milling along a contour line of an inclined surface, FEM model of a ball end mill is constructed by using geometrical data of cross section of the tool. The tool deflection and locus of tool axis during milling are analyzed by using the cutting force data predicted and the FEM model of a ball end mill. In the analysis, radial force components distributed along the cutting edge are applied to the FEM model and support condition of the tool is experimentally determined on the basis of a bending test of a cylindrical bar conducted on machine tool. Tool deflection and behavior of the tool axis during contour milling of inclined surfaces is measured by using an eddy-current type sensor and compared with the predicted results. The predicted results are in good agreement with the experimental results. It is shown that the tool deflection and behavior of the tool axis vary considerably with the feed direction of the tool. For milling an inclined surface where the left side of the feed direction is higher, the tool axis deflects to be drawn toward the inclined surface.

Multi-scale simulation of the nano-metric cutting process

Molecular dynamics (MD) simulation and the finite element (FE) method are two popular numerical techniques for the simulation of machining processes. The two methods have their own strengths and limitations. MD simulation can cover the phenomena occurring at nano-metric scale but is limited by the computational cost and capacity, whilst the FE method is suitable for modelling meso- to macro-scale machining and for simulating macro-parameters, such as the temperature in a cutting zone, the stress/strain distribution and cutting forces, etc. With the successful application of multi-scale simulations in many research fields, the application of simulation to the machining processes is emerging, particularly in relation to machined surface generation and integrity formation, i.e. the machined surface roughness, residual stress, micro-hardness, microstructure and fatigue. Based on the quasi-continuum (QC) method, the multi-scale simulation of nano-metric cutting has been proposed. Cutting simulations are performed on single-crystal aluminium to investigate the chip formation, generation and propagation of the material dislocation during the cutting process. In addition, the effect of the tool rake angle on the cutting force and internal stress under the workpiece surface is investigated: The cutting force and internal stress in the workpiece material decrease with the increase of the rake angle. Finally, to ease multi-scale modelling and its simulation steps and to increase their speed, a computationally efficient MATLAB-based programme has been developed, which facilitates the geometrical modelling of cutting, the simulation conditions, the implementation of simulation and the analysis of results within a unified integrated virtual-simulation environment.

An investigation of cutting forces and surface damage in high-speed turning of Inconel 718

Abstract Knowing the stringent operating conditions to which superalloys are subjected to in automobile, aerospace and gas turbine industries, their efficient machining and generation of machined surfaces with high integrity assumes a lot of importance. Therefore, this paper presents an experimental investigation into the effect of various process and tool-dependent parameters on cutting forces, an indirect measure of machined surface integrity besides a detailed microstructural analysis of the machined surface damage, in high-speed machining of superalloy Inconel 718. Accordingly, the effect of cutting speed, feed rate, depth of cut and tool cutting edge geometry on cutting forces, surface roughness and surface damage in high-speed turning of Inconel 718 using PCBN tools has been discussed. The input parameters were varied as: V = 125–475 m min −1 , f = 0.05–0.15 mm rev −1 , d = 0.50–1.0 mm and edge geometry as: 30° chamfer, 20° chamfer and 30° chamfer plus honed. The results show that the radial and feed force components are almost equal and the main cutting force component is two to three times that of feed and radial force components. The honed plus chamfered cutting edge was influential in reducing cutting forces significantly. It was noted that specimens showing larger cutting forces generated poor surface finish as well as extensive surface damage.

Multiscale simulation on nanometric cutting of single crystal copper

Molecular dynamics (MD) simulation and finite element (FE) method have been successfully applied in the simulation of the machining process, but the two methods have their own limitations. For example, the MD simulation can only explain the phenomena occurring at nanometric scale because of the computational cost and nanoscale, while the FE method is suited to model meso-macroscale machining and to simulate macro parameters such as the temperature in cutting zone, the stress/strain distribution, and cutting forces. With the successful application of multiscale simulation in many research fields, the multiscale simulation of the machining process is becoming possible in relation to the machined surface generation including the surface roughness, residual stress, microhardness, microstructure, and fatigue. Based on the quasicontinuum (QC) method, this paper presents the multiscale simulation of nanometric cutting of crystal copper to demonstrate that a combined MD—FE technique can be applied to a multiscale simulation of the machining process. The study shows that the multiscale simulation is feasible, not withstanding that there is still more work needing to be done to make the multiscale simulation more practical.

Surface shape prediction in high speed milling

Chatter is one of the main causes affecting the surface quality of machined parts. Since it occurs when a machining process is unstable, it is important to select process parameters that promote stability. However, this condition alone is not sufficient to ensure good surface shape because the dynamics of the machining system as a whole also affects the resulting surface. Thus, even in the absence of chatter, significant movement of the tool or the part may occur causing surface defects. This effect is significant in high speed milling. In order to select optimal machining parameters, a computationally efficient simulator has been developed based on a novel machined surface generation model capable of accurate and reliable prediction of the surface shape. The programme written in MATLAB ® predicts the surface shape from which surface finish, waviness, form and position parameters can be determined. A test bench consisting of a relatively low frequency second order dynamic mode is used to hold a test sample. The results obtained on a machining centre show that the predictions favourably compare with experimental results.

FEM Simulation on Machined Surface Generation in Shaving Process.

Machined surface generation process in shaving, which is one of fine blanking process, was analyzed by using elastic-plastic finite element method in this paper. We employed two material fracture criteria. When the node in front of die edge comes close 2 μm to die edge, we assume that the node is separated to two nodes. And the ductile fracture criterion depends on equivalent strain and hydrostatic pressure is applied as a second criterion. As the result of analysis assuming a brass as the work material, the deformation process shows the same way as that of cutting process from the initial stage to the middle stage. In the end stage the deformation area moves from the line connecting the die edge and the chip free surface to the line connecting the die and the punch edges. Then deformation concentrates on that region. There remains small strain under 1.0 on the initial to middle stage where cutting like deformation is observed.

Dynamic Generation of Machined Surfaces, Part 1: Description of a Random Excitation System

With increasing emphasis on the adaptive control for the purpose of quality and productivity improvement, it becomes necessary to develop models which can correlate the surface finish parameters with the machining conditions as well as work-piece material characteristics. This paper presents a study that leads to the development of a model for the dynamic generation of three-dimensional texture of machined surfaces. In Part 1, the mathematical formulation of the random excitation system which is responsible for the random portion of a surface profile is developed. It is assumed that the random excitation system originates from the nonhomogeneous distribution of microhardness of workpiece material. Machining tests are also performed to verify the validity of such a model development. In Part 2, a procedure for the construction of three-dimensional topography will be developed and the relationship between the machining conditions and the surface finish parameters will be established.

Dynamic Generation of Machined Surfaces, Part 2: Construction of Surface Topography

In Part 1 of these two-part papers, a normal distribution model has been formulated to describe the random excitation system present during machining. Part 2 presents a methodology to dynamically generate the surface topography under the random excitation environment through computer simulation. The proposed methodology uses the tool vibratory motion along with the tool geometrical motion to construct the topography of a machined surface. Both experimental and simulation results confirm that when a small feed is used, the influence of the spiral trajectory of tool geometrical motion on the surface generation decays dramatically and the random excitation system, on the opposite, is strengthened playing a significant role in surface texture generation.

ダイヤモンド工具によるＡｌ合金の鏡面切削に関する研究 ＩＩ 摩耗バイトによる切削面形成メカニズム

ダイヤモンド工具によるＡｌ合金の鏡面切削に関する研究 ＩＩ 摩耗バイトによる切削面形成メカニズム