Material Removal Model Research Articles

Study of discharge characteristics and multi objective optimisation of machining parameters in ultrasonic vibration assisted micro electrical discharge machining

Micro-EDM is a non-traditional manufacturing technique that uses the heat energy of the plasma to remove material. When there is a sufficient electric potential between two electrodes, the dielectric in between becomes ionised, resulting in the formation of a plasma channel. The net discharge energy produced is the result of the current and voltage present at the inter-electrode gap (IEG). The current and voltage waveforms obtained from the oscilloscope are used to calculate the discharge energy. A small part of this discharge energy gets converted as plasma temperature, which facilitates material removal in micro-EDM. Because plasma is the only source of heat, its properties must be studied. In the present study, Optical Emission Spectroscopy is used to calculate the temperature of the plasma. This article explores the scope of a hybrid micro EDM process, where an ultrasonic vibration is integrated to the tool electrode. A systematic approach using Response Surface Methodology is employed for modelling and analysis of plasma properties and material removal in micro EDM. Two types of input parameters were chosen: Voltage and pulse on time being the electrical parameters, and Amplitude and Frequency as the vibrational parameters. Dielectric used is deionised water. A single spark experiment was performed on Nitinol Shape Memory Alloy and tool used was of same material. Ultrasonic vibration was provided to the tool using a piezoelectric actuator. It was found that electrical parameters have a significant impact in determining plasma properties and material removal properties. Vibrational parameters play a vital impact in enhancing the crater’s surface features.

Super hard and brittle material removal mechanism in fixed abrasive lapping: Theory and modeling

Currently, the problems of inefficient fixed abrasive lapping (FAL) for super hard and brittle material wafers (such as sapphire) with fixed abrasive pads (FAPs), restrict the development of the semiconductor industry. Most importantly, the mechanisms of FAL processes are still unclear, often analyzed based on the theoretical models of chemical mechanical polishing (CMP). However, the material removal models of CMP are specific to loose abrasives, do not effectively apply to the lapping processes for super hard and brittle material wafers with a FAP. In this paper, the spherical crown model modified by elastic-plastic mechanics and brittle-plastic transformation mechanism was applied to super hard and brittle material removal mechanism in FAL processes. In consideration of the influences of the yielding abrasives embedded in the FAP matrix and the matrix surface topography on the wafer-pad contact, a material removal model suitable for super hard and brittle material wafers lapped by FAPs was obtained. The loads applied on the fixed abrasives and the matrix asperities during the elastic-plastic-brittle deformation processes of wafers were analyzed, respectively. The model indicates that the back-off of the abrasives embedded in the FAP matrix intensifies along with the decrease of the matrix hardness and the increase of the abrasive size, respectively. The penetrating depth of the fixed abrasive can be raised by increasing matrix hardness, applied pressure, abrasive size, and decreasing abrasive number, as same as the elastic recovery of the super hard and brittle material slid by the abrasive after unloading. The pad matrix surface dressed by loose grains greatly affects the MRR of wafers. The predicted MRR of sapphire wafers based on the FAL model is consistent with experimental data. Finally, the keys to improving the processing efficiency of super hard and brittle material wafers are clarified in detail.

Profile prediction for ultrasonic vibration polishing of alumina ceramics

Ultrasonic-assisted polishing methods are widely used for the precision processing of hard and brittle materials such as glass and ceramics due to their excellent polishing performance. Most research has been focused on basic removal mechanisms of ultrasonic-assisted polished materials. Some investigators have studied the profile of surfaces after conventional mechanical polishing, but less research has been done on the profile of faces after axial ultrasonically assisted polishing. This paper has established a novel force prediction model for the ultrasonically assisted polishing, which is critical for geometrical accuracy and surface finish. Also a material removal model has been developed for this process using a spherical polishing head at different tilt angles. Pressure and velocity distributions have been calculated for multi-position contact areas. The experimental study of multiple trajectory polishing of alumina ceramics showed a good correlation between the experimental and simulated surface profiles. The ultrasonic polishing process parameters were optimized by applying the gray correlation analysis. The obtained results can be used not only select ultrasonic assisted polishing process parameters but also provide theoretical underpinning for surface polishing trajectory planning.

Multiphysics Simulation of the Shape Prediction and Material Removal Rate in Electrochemical Machining Process

ABSTRACT The electrochemical machining process involves electrical and chemical processes while removing materials from the workpiece. Electrochemical machining (ECM) lacks accurate models for predicting the shape and material removal rate during the ECM process. This limits the ability to optimise the process and predict the final product geometry, which is crucial for industrial applications. This research mainly focused on the modelling and simulation of material removal from the workpiece using COMSOL Multiphysics software. This research involves developing a mathematical model that describes ECM’s electrical, chemical, and mechanical interactions. The model is based on electrochemistry, fluid dynamics, and solid mechanics principles and will be solved using numerical simulation techniques. Various workpiece materials considered in this investigation include Aluminium, Nickel, Stainless Steel, and Tungsten, whereas copper is electrode material. The effects of the various parameters, such as workpiece materials, the voltage applied during machining, and electrolyte conductivity on the material removal rate are being investigated. In addition, the shape of the machined workpiece is also predicted. The results of this research provide a deeper understanding of the underlying physics of the ECM process and lead to the development of more accurate models for predicting the shape and material removal rate during ECM.

Theoretical and experimental investigation of material removal in semi-rigid bonnet polishing of binderless tungsten carbide

Binderless tungsten carbide (B-WC) has become a typical material for mold inserts due to its super mechanical and thermal properties. However, it is a typical hard-brittle material that is difficult to implement precision and high-efficiency polishing. This paper answers this challenge using a semi-rigid bonnet (SRB) tool, together with systematic theoretical and experimental investigation on its material removal. First, both polishing spots generation and uniform polishing experiments were conducted to demonstrate the polishing performance and material removal characteristic of SRB on B-WC substrates. Afterwards, the tool influence function model of SRB was established and verified experimentally, which enables the accurate prediction of surface generation during polishing. Finally, the surface and subsurface integrity of a B-WC substrate before and after SRB polishing was demonstrated. The results indicate that SRB is effective for fast polishing of B-WC with superior surface and sub-surface qualities. This discovery also paves the way for the application of SRB for the polishing of other hard materials. The developed material removal model can be a theoretical basis for the prediction of surface generation during the polishing process.

Abrasion behavior of TiO2 catalyzing H2O2 to synergistically remove single crystal 6H-SiC under ultraviolet irradiation

Ultraviolet photocatalytic-assisted chemical mechanical polishing technology can effectively improve the processing efficiency and surface quality of single crystal SiC. In this paper, the chemical mechanical synergy (CMS) effects of TiO2 catalyzing H2O2 to synergistically remove single crystal 6H-SiC under ultraviolet irradiation were investigated by means of friction and wear. The ball-on-disk friction and wear test was carried out under two conditions M-Ⅰ (UV light for 20 min) and M-Ⅱ (UV light only in the last 10 min). The results showed that under UV light irradiation, anatase TiO2 exhibited photocatalytic and abrasive effects (including mending effect, rolling effect, ploughing effect, polishing effect and protective film effect) during the friction process. The longer the irradiation time, the stronger the chemical reaction on the oxidation of SiC by TiO2 catalyzing H2O2; the higher the TiO2 concentration, the greater the material removal of SiC. At last, the material removal model of single crystal SiC under the condition of ultraviolet light on TiO2 catalyzing H2O2 was established, and the synergistic effect of mechanics and chemistry was analyzed intuitively.

Modeling of material removal in magnetic finishing based on Maxwell's stress tensor theory and its experimental validation

Magnetic finishing is an extremely suitable process for processing high quality surface aluminum alloy mirrors due to the low damage. Obtaining an accurate removal function is essential to achieve a controlled finishing of aluminum alloy mirror. In this study, the magnetic field between the magnetized abrasive particles was simplified by equivalent substitution method after modeling the geometry of the abrasive and simulating its magnetic field. Distribution of finishing pressure was calculated based on Maxwell's stress tensor theory. Distribution of the finishing pressure was uneven, and the finishing pressure in the center of the finishing area was about 10 times that of the edges. And the removal amount was calculated with Preston's equations. The experimental results of the removal amount show that the removal amount increases and then decreases as the magnetic abrasive content in the abrasive decreases. The removal amount has a negative correlation with the finishing gap. Stronger magnetic fields can increase the removal amount. After 10 minutes of machining, the surface roughness Ra of the aluminum plate decreased from 0.189 μ m to 0.030 μ m . The relative error is less than 7% compared to the simulation results when the finishing gap is 2-3 mm. The removal depth experimental results show that the maximum removal depth reaches 117 nm after 10 minutes of machining at 950r/min, with a relative error of 3.5%. This accurate removal function can provide a theoretical basis for achieving controlled magnetic finishing.

Modelling of material removal due to sliding wear caused by bulk material

Modelling of material removal due to sliding wear caused by bulk material

The ultrasonic vibration–assisted polishing material removal model of tilted cylindrical polishing tool based on BK7 glass

BK7 glass is widely used in various optical instruments as a common ceramic material. However, there are still several difficulties in the polishing process due to its material properties. Ultrasonic vibration–assisted polishing (UVAP) is used widely for its excellent material removal properties. However, there are few researches on the model of UVAP material removal for tilted. Therefore, this paper investigates this problem. A model of UVAP material removal was established for titled column polishing; The pressure distribution and velocity distribution in the contact zone were modeled by means of experiments and geometric analysis. A series of orthogonal experiments were conducted, and the experimental results showed that the coefficient of determination was above 0.9 after fitting the actual profile to the predicted profile. The results of the orthogonal experiments were also analyzed by ANOVA. The predict error of maximum removal depth was less than 13.12%. The error of material removal rate (MRR) was less than 9.24%. By power spectral density (PSD) analysis, it was found that the introduction of ultrasonic amplitude has a good effect on suppressing the medium and high-frequency errors on the machined surface. The novel model can be used to optimize machining parameters and provide theoretical support for complex parts polishing.

Controllable electrochemical discharge machining with energy–electricity regulation in glycol-based electrolytes

Electrochemical discharge machining (ECDM) is widely used for manufacturing owing to its ability to machine any material regardless of its properties. Insufficient knowledge regarding the gas film and process mechanism restricts further improvement of electrochemical discharge machining (ECDM). In this study, to control the machining process, ECDM was performed using glycol-based electrolytes and a novel energy–electricity regulation methodology was developed. Through the analysis of gas film quality and machining performance, the advantages of glycol-based electrolytes were verified and a material removal model was established. Subsequently, analyzes of electrical signals based on the experimental verification of multiple process parameters were presented to realize the quantitative regulation of electrical discharge machining (EDM) and electrochemical machining (ECM) in ECDM. The results indicated that in glycol-based electrolytes, the gas film is thin and stable, and there is no transpassive film on the workpiece. Therefore, the material removal process was enhanced with regard to effectiveness and uniformity, and the surface integrity was improved. Furthermore, by adjusting the EDM energy (E) to approximately 10n–14n μJ (where n represents the total pulse number) and ECM electricity (Q) to approximately 0.5n–1n μC, low wire relative wear ratio and small slit width can be achieved. Pentagram patterns were successfully fabricated on several typical metallic materials, which verified the universality of the proposed process.

Modelling of material removal in unidirectional abrasive flow machining process using classical indentation model

Modelling of material removal in unidirectional abrasive flow machining process using classical indentation model

Modelling of Material Removal in Unidirectional Abrasive Flow Machining process using Classical Indentation Model

Modelling of Material Removal in Unidirectional Abrasive Flow Machining process using Classical Indentation Model

A novel approach to robotic grinding guaranteeing profile accuracy using rigid-flexible coupling force control for free-formed surfaces

This paper proposes a novel approach to robotic grinding guaranteeing profile accuracy for free-formed surfaces. Based on the material removal model and the feed-drive ability of the robotic grinding system, hybrid constraints of material removal, force-amplitude and robot dynamics are determined simultaneously. The feedrate and contact force are planned simultaneously to guarantee maximum efficiency with the hybrid constraints. A novel rigid-flexible coupling force-control actuator is developed to restrict overshoot and improve the control accuracy of the grinding force. Experiments demonstrate that the proposed method significantly improves the profile accuracy, grinding efficiency and surface quality of free-formed parts.

Mechanical Behavior of Material Removal and Predictive Force Model for CFRP Grinding Using Nano Reinforced Biological Lubricant

Mechanical Behavior of Material Removal and Predictive Force Model for CFRP Grinding Using Nano Reinforced Biological Lubricant

Removal Modeling and Experimental Verification of Magnetorheological Polishing Fused Silica Glass

Compared to conventional polishing methods, magnetorheological polishing has no subsurface damage and a has good polishing effect, which is suitable for fused silica glass surface processing. However, the existing magnetorheological polishing material removal model has low processing efficiency and uneven removal, which cannot realize the deterministic processing of parts. The material removal (MR) model of fused silica glass is established by convolving the dwell time with the material removal function. The residence time is Fourier transformed. The consequence of process variable such as machining time, workpiece rotational frequency, machining gap and X-direction deflection on the MR of workpiece interface are analyzed. Experiments verify the validity of the material removal model. The surface precision PV value of the workpiece surface under the optimal process parameters was decreased from 7.959 nm to 0.609 nm for machining. The experiment results indicate that the established MR model can be implemented as the deterministic MR of the optical surface and ameliorate the surface accuracy of the workpiece surface.

Material removal characteristics and particle motions in abrasive water jet quantitative machining.

Abrasive water jet quantitative machining (AWJQM) is a method that enables the production of lightweight mirrors. Investigating material removal characteristics and particle motions in AWJQM is necessary to understand its erosion mechanism and improve its processability. A material removal model based on computational fluid dynamics was established in this study by integrating the transition condition of the brittle-ductile mechanism and the single-particle erosion model. Quantitative machining experiments were carried out to verify the material removal model, and experimental data were consistent with the simulation results. Further simulation experiments were carried out to explore the particle distribution under different working pressures or slurry viscosities. Results showed that operating parameters affect the workpiece surface profile by changing the flow field distribution and particle behavior.

Research on prediction method of surface roughness in weak magnetorheological shear thickening fluid polishing

A joint prediction method of “mathematical modeling and finite element calculation” is proposed to improve the prediction of machining quality in weak magnetorheological shear thickening fluid polishing of complex surfaces. The study proceeded in several steps. First, based on both impact energy model and material removal model, a numerical prediction model of surface roughness is established. Second, based on the multi-peak fitting method, the field-induced rheological properties of the polishing fluid are characterized and material properties of the flow field medium in the polishing zone are defined. Third, the numerical boundaries of polishing flow velocity and shear stress in the above prediction model are obtained. Fourth, the polishing experiments with parameters consistent with the above simulation model are conducted, and the initial surface roughness values are substituted into the above prediction model. The results show that the joint prediction method can effectively predict the machining quality of workpiece surface. The absolute error of Sa value of surface roughness is up to 10.6 nm, and the maximum relative error is 12.3%.

Effect of Robot Motion Accuracy on Surface Form during Computer-Controlled Optical Surfacing Process

Nowadays, large-aperture optical components are increasingly used in high-power laser systems, remote-sensing satellites, and space-based astronomical telescopes. Fabricating these surfaces with submicron-scale shape accuracy and a nanoscale surface finish has been a great challenge for the optical industry, especially for hard and difficult-to-machine materials. Thus, to achieve the high-efficiency and high-precision polishing of large-aperture aspherical optical parts, this study combined robotic machining technology with computer-controlled optical surfacing (CCOS) technology and investigated the effect of robot motion accuracy on the surface topography of workpieces during polishing. First, a material removal model considering the normal error of the polishing tool was developed based on contact mechanics, kinematic theory, and the abrasion mechanism. Next, in combination with the polishing trajectory, the surface morphology and form accuracy after polishing were predicted under different normal-error conditions. Then, preliminary experiments were conducted to verify the model. The experimental data agreed with the simulation results, showing that as the normal error increased from 0° to 0.5° and 1°, the peak-to-valley (PV) values of the surface profile of the optical element decreased from 5.42, 5.28, and 4.68 μm to 3.97, 4.09, and 4.43 μm, respectively. The corresponding convergence rates were 26.8%, 22.5%, and 5.3%. The root mean square (RMS) values decreased from 0.754, 0.895, and 0.678 μm to 0.593, 0.620, and 0.583 μm, with corresponding convergence rates of 21.4%, 30.7% and 14.0%, respectively. Moreover, a higher motion accuracy enabled the polishing robot to reduce the mid- and high-frequency errors of the optical element.

A Novel Toolpath for Robotic Adaptive Grinding of Extremely Thin Blade Edge Based on Dwell Time Model

High precision and high efficiency in robotic grinding of aero-engine extremely thin blade edges is a challenging problem. In this article, a novel toolpath planning method is proposed based on the derived dwell time calculation model and the developed interpolation algorithm. The dwell time of each cutter contact point is solved based on the matrix method by consideration of the revised material removal model and machining allowance distribution. To optimize the previous interpolation algorithm based on geometric intersection, an arc length and Taylor binary expansion optimization are proposed to plan cutter contact points according to the dwell time and the curvature changes of blade edges. Subsequently, the tool orientation is corrected based on a double-vector controlling method to avoid the processing interference. Simulation results show that the proposed interpolation algorithm has improved the path coverage by 17.6%, and its computational efficiency is 34 times higher than that in previous algorithm. The comparative robotic grinding experiment results show that the proposed toolpath has improved the surface profile accuracy of blade edge to 0.042 mm, and its machining accuracy is 14.3–46.2% higher than that of other methods.

Theoretical and experimental investigations on material removal characteristics of small-diameter aspherical silicon carbide mould with weak magnetization-enhanced force-rheological polishing

Multi-field composite polishing with non-Newtonian fluids is a potential technology for manufacturing optical moulds. However, the correlation between the micromaterial removal mechanism and the properties of magnetic shear thickening fluid (MSTF) for weak magnetization-enhanced stress-rheological polishing (WMESRP) is still unclear. In this study, we propose a weak magnetization- enhanced stress-rheological polishing (WMESRP). Based on non-Newtonian fluid dynamics, microscopic contact mechanics, and vector discrete methods, a multi-scale material removal model (MRR) was established. Under a series of fixed-point polishing experiments, the maximum change rate between the experiment and theory was obtained as less than 5.7%. In addition, comparative experiments revealed that polishing liquids containing polyethylene glycol inhibit excessive agglomeration of particle clusters, thereby achieving a smooth surface. The proposed WMESRP method can accomplish non-destructive processing of hard and brittle ceramic materials, which can be used in various applications.