Increase In Material Removal Rate Research Articles

Scale effects on surface texture characterisation of ultra-precision diamond milling

Surfaces with nanometric texture, machined by ultra-precision diamond milling (UPDM), have wide applications for their functionalities. Surface texture characterisation is crucial for their quality evaluation and it would vary in the measurement data processing under various scales, which is termed scale effects. However, the scale effects have not been comprehensively studied. In this work, we focus on the scale effects on surface texture characterisation of UPDM. Firstly, a series of experiments were conducted at different material removal rates to produce surfaces with nanometric texture. Secondly, a discrete wavelet transform (DWT)-based method was employed for surface filtering and surface texture parameters (Sa, Sq, and Sz) were evaluated according to ISO standards. Thirdly, power spectral density (PSD) analysis and surface filtering comparison were performed to realize a scale observation. Furthermore, the effects of the filtering scale, the sampling scale, and the subarea scale on surface texture characterisation were investigated. Finally, the results showed that surface topographies were governed by various machining factors which resulted in multi-scale topographical components. The PSD analysis enabled discrimination of the multi-scale topographical components to the underlying machining factors. The DWT-based method achieved a relatively small deviation (<4%) for surface filtering as compared to the zero-order Gaussian regression filter. The filtering scale affected the filtered topographical components and it visualised and differentiated those components with the machining mechanisms. The sampling scale determined the filtered components to yield an impact on the characterisation results and Sz was more sensitive to this effect than Sa and Sq. The subarea scale influenced the probability distributions and statistical values of surface texture parameters within its contained components and it indicated that the increased material removal rate resulted in a deterioration of surface uniformity.

Mechanochemical grinding diamond film using titanium-coated diamond active abrasives prepared by vacuum micro-evaporation coating

The outstanding hardness and wear resistance of diamond materials pose significant challenges in their grinding processes for semiconductor substrate materials. To overcome this, a mechanochemical effect-based approach is used, which employs a grinding wheel comprising titanium (Ti)-coated diamond abrasives. A uniform Ti coating is vacuum-evaporated onto micrometer-scale diamond abrasives. The coating layer forms a diamond-TiC-Ti structure extending from the diamond matrix to the Ti coating direction. The material removal rate (MRR) of the DF is significantly increased as a result of the protruding active Ti coating on the diamond abrasives reacting with the DF at the interface contact locations. Increasing the grinding speed from 300 rpm to 700 rpm under a fixed grinding pressure of 300 N results in an MRR increment from 32 nm/min to 913 nm/min. Similarly, maintaining a grinding speed of 600 rpm while increasing the grinding pressure from 300 N to 600 N leads to an MRR increase from 388 nm/min to 1662 nm/min. The primary mechanism behind material removal is the reaction between the Ti coating and the DF, as well as the graphitization of the DF.

Optimization of Process Parameters for End Milling Operation on EN-31 Using Taguchi-Grey Relation

A material with exceptional levels of abrasion resistance, compressive strength, and hardness is known as bearing steel, also known as EN-31 high-grade carbon alloy steel. It has several uses, including the bulk manufacturing of roller bearings, taps, gauges, ejector pins, swaging dies, etc. The lowest surface roughness (Ra) and highest material removal rate (MRR) are sought for this alloy steel in order for it to be used successfully in a range of applications. In the experiment, a L9 Taguchi orthogonal array design was used to CNC end mill EN-31 steel using a bullnose end mill carbide tool with inserts. This study presents a way for enhancing process factors such as cutting speed, depth of cut, feed rate, and tool corner radius that result in desirable output responses. Taguchi and Taguchi-Grey analyses are used to show the best input values that reduce surface roughness and increase MRR. The lowest level of surface roughness could be attained using the operating parameters of 3000 rpm cutting speed, 500 mm/min feed rate, 0.25 mm depth of cut, and 1.00 mm tool corner radius, while the highest level of material removal rate could be attained using 3000 rpm cutting speed, 2500 mm/min feed rate, 0.25 mm depth of cut, and 1.00 mm tool corner radius.

Mechanism of Electrochemically Assisted Friction and Wear Behavior of GaN in KMnO4 Slurry

Electrochemically assisted friction and wear behavior of gallium nitride (GaN) in a KMnO4 slurry was investigated to optimize the composition of the chemical mechanical polishing (CMP) slurry, and the material removal effect of GaN was visually evaluated by using the coefficient of friction (COF) curve and wear area. The results showed that the surface oxidation of GaN was effectively enhanced by KMnO4 and electrochemical assistance. The average COF and wear area of GaN increased with stronger oxidation of the environmental media, which improved the removal of the GaN surface material. Under acidic conditions, the oxidation of KMnO4 for GaN surface was significantly stronger than that under neutral and alkaline conditions, and the GaN surface was effectively oxidized and corroded when the initial mass fraction of KMnO4 was 5 wt%. When the chemical and mechanical actions reached a synergistic effect, the oxide layer generated on the GaN surface was immediately removed by the Si3N4 ball and SiO2 abrasive, which led to a large increase in material removal rate (MMR); the COF curve tended to stabilize, and the average COF increased. The experimental results of the electrochemically assisted CMP of GaN were consistent with the friction and wear test results.

Defect-Engineered MnO2 as Catalyst for the Chemical Mechanical Polishing of Silicon Carbide Wafer

Chemical mechanical polishing (CMP) of SiC wafer is challenging due to its extreme hardness and inertness. Catalyst assisted CMP is a cost-effective approach to increase material removal rate (MRR) without sacrificing surface quality. Herein, oxygen-deficient α-MnO2 was prepared by mechanochemical synthesis and the effect of catalyst physiochemical structure on the CMP performance of Si-face SiC wafer was systematically studied. The addition of 1% α-MnO2 catalyst increased MRR by 38.8% to 1.11 μm h−1, much higher than commercial γ-MnO2. The synergy of phase structure, oxygen vacancy and surface area & porosity contributed to the high catalytic activity. α-MnO2 is an outstanding oxidation catalyst due to its stable framework, large tunnel size, rich surface area and porosity, which can facilitate the adsorption, activation and transfer of guest species and intermediates and therefore affects the reaction pathway and reaction kinetics. Mechanochemical synthesis generates nano MnO2 particles with rich oxygen vacancies. The presence of more surface oxygen vacancies can improve oxidizing activity of MnO2 catalyst, facilitating the oxidation of C species on wafer surface. The use of defect-engineered α-MnO2 catalyst is promising for overcoming the present bottlenecks of long processing time and high cost of current CMP of SiC wafer.

Parameter optimization in the enhancement of MRR of titanium alloy using newer mixing method in PMEDM process

The addition of powders in electrical discharge machining (EDM) reduces the breakdown strength of the liquid dielectric, thereby enhancing the occurrence of early spark, and aids in machinability. Challenges occur in the sustainability of the powder mixed electrical discharge machining (PMEDM) process in terms of homogeneity of the powder-dielectric mixture and adverse effects of these powders on the impellor of the pump, maintaining the concentration of the powder–dielectric mixture for a wide range of powders at varied size. In this investigation, an attempt is made to address these challenges and limitations in performing PMEDM process by developing a newer mixing method for PMEDM. The Taguchi L18 orthogonal array has been selected to study the material removal rate (MRR) of titanium grade 5 alloy. Gap current, duty factor, pressure of the powder mixed dielectric fluid, type of powder, and concentration of the powders have been considered as the process variables. The results found to be satisfying with increase in MRR. The confirmation experiments indicate considerable increase in MRR. This newer system is capable of performing sustainable manufacturing method irrespective of the nature of the powder and the particle size of the additive powders, that are permissible in the inter-electrode gap as it restricts the size of the powder, added in the PMEDM process.

Novel Process Modeling of Magnetic-Field Assisted Finishing (MAF) with Rheological Properties

The performance of a magnetic-field-assisted finishing (MAF) process, an advanced surface finishing process, is severely affected by the rheological properties of an MAF brush. The yield stress and viscosity of the MAF brush, comprising iron particles and abrasives mixed in a liquid carrier medium, change depending on the brush’s constituents and the applied magnetic field, which in turn affect the material removal mechanism and the corresponding final surface roughness after the MAF. A series of experiments was conducted to delineate the effect of MAF processing conditions on the yield stress of the MAF brush. The experimental data were fitted into commonly used rheology models. The Herschel–Bulkley (HB) model was found to be the most suitable fit (lowest sum of square errors (SSE)) for the shear stress–shear rate data obtained from the rheology tests and used to calculate the yield stress of the MAF brush. Processing parameters, such as magnetic flux density, weight ratio of iron and abrasives, and abrasive (black ceramic in this study) size, with p-values of 0.031, 0.001 and 0.037, respectively, (each of them lower than the significance level of 0.05), were all found to be statistically significant parameters that affected the yield stress of the MAF brush. Yield stress increased with magnetic flux density and the weight ratio of iron to abrasives in MAF brush and decreased with abrasive size. A new process model, a rheology-integrated model (RM), was formulated using the yield stress data from HB model to determine the indentation depth of individual abrasives in the workpiece during the MAF process. The calculated indentation depth enabled us to predict the material removal rate (MRR) and the instantaneous surface roughness. The predicted MRR and surface roughness from the RM model were found to be a better fit with the experimental data than the pre-existing contact mechanics model (CMM) and wear model (WM) with a R2 of 0.91 for RM as compared to 0.76 and 0.78 for CMM and WM. Finally, the RM, under parametric variations, showed that MRR increases and roughness decreases as magnetic flux density, rotational speed, weight ratio of iron to abrasive particles in MAF brush, and initial roughness increase, and abrasive size decreases.

Experimental Investigation on Surface Characteristics of Nickel-Based Super Alloy in Powder Mixed Electric Discharge Machining

Abstract: Electrical discharge machining behavior of nickel based super alloy using titanium carbide powder mixed dielectric fluid turned into studied. Experiments were completed consistent with face centered central composite design. The addition of powder particles in suspension in the dielectric modifies some process variables and creates hard and brittle materials with nano surface finish, high tolerance and accuracy to achieve a material removal rate increase. The effect of input parameters such as current, pulse on-time and flushing pressure on the output responses like material removal rate and tool wear rate are evaluated. Dielectric fluid used in this experiment was kerosene mixed with titanium carbide powder.

Tribological and machining characteristics of AA7075 hybrid composites and optimizing utilizing modified PROMETHEE approach

In this research work an attempt was made to reinforce AA7075 composites with B4C and SiC particles through stir casting route. SEM with EDS mapping revealed that the reinforcement were uniformly over the composites and hardness reduces with the addition of SiC particles owing to the inverse hall petch effect. The results revealed that wear rate reduces with addition of SiC particles owing to the formation of mechanically mixed layer and protective oxide layer confirmed through SEM with EDAX mapping. Three distinct cracks were formed, when slides at different temperature as confirmed through worn surface morphology, pits cracks and plasticization of material were the other features observed. The used motor oil properties were analyzed and results divulged that the oil suitable for dielectric fluid. Increase in Material Removal Rate (MRR), reduction in Tool Wear Ratio (TWR) and Surface Roughness (Ra) was observed with the incorporation of powder particles owing to the bridging effect. Black spots, craters, micro pits, globules and micro crack are the distinct observed on the machined surface topography. The modified Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE) optimization technique was utilized to find the optimal parametric combination.

The Effects of Friction and Temperature in the Chemical-Mechanical Planarization Process.

Chemical-mechanical planarization (CMP) represents the preferred technology in which both chemical and mechanical interactions are combined to achieve global planarization/polishing of wafer surfaces (wafer patterns from metal with a selective layer, in this paper). CMP is a complex process of material removal process by friction, which interferes with numerous mechanical and chemical parameters. Compared with chemical parameters, mechanical parameters have a greater influence on the material removal rate (MRR). The mechanical parameters manifest by friction force (Ff) and heat generated by friction in the CMP process. The Ff can be estimated by its monitoring in the CMP process, and process temperature is obtained with help of an infrared rays (IR) sensor. Both the Ff and the MRR increase by introducing colloidal silica (SiO2) as an abrasive into the selective layer CMP slurry. The calculated wafer non-uniformity (WNU) was correlated with the friction coefficient (COF). The control of Ff and of the slurry stability is important to maintain a good quality of planarization with optimal results, because Ff participates in mechanical abrasion, and large Ff may generate defects on the wafer surface. Additionally, the temperature generated by the Ff increases as the SiO2 concentration increases. The MRR of the selective layer into the CMP slurry showed a non-linear (Prestonian) behavior, useful not only to improve the planarization level but to improve its non-uniformity due to the various pressure distributions. The evaluation of the Ff allowed the calculation of the friction energy (Ef) to highlight the chemical contribution in selective-layer CMP, from which it derived an empirical model for the material removal amount (MRA) and validated by the CMP results. With the addition of abrasive nanoparticles into the CMP slurry, their concentration increased and the MRA of the selective layer improved; Ff and MRR can be increased due to the number of chemisorbed active abrasive nanoparticles by the selective layer. Therefore, a single abrasive was considered to better understand the effect of SiO2 concentration as an abrasive and of the MRR features depending on abrasive nanoparticle concentration. This paper highlights the correlation between friction and temperature of the SiO2 slurry with CMP results, useful to examine the temperature distribution. All the MRRs depending on Ef after planarization with various SiO2 concentrations had a non-linear characteristic. The obtained results can help in developing a CMP process more effectively.

Effect of potassium persulfate on chemical mechanical planarization of Cu/Ni microstructures for MEMS

Electrochemical FABrication (EFAB) can fabricate complex metal microstructures. Planarization is crucial in EFAB in terms of flatness and surface quality. Accordingly, chemical mechanical polishing (CMP) was employed to planarize Cu/Ni microstructures. The oxidant K2S2O8 is critical in regulating the material removal rate (MRR) selectivity between copper and nickel. In the presence of the complexing agent ethylenediamine sulfate and corrosion inhibitors benzotriazole and sodium dodecyl benzene sulfonate, the MRR selectivity of 1 (∼47 nm/min) and satisfactory surface quality can be achieved by tuning the K2S2O8 concentration to 20 mM. A two-step planarization method was proposed. After lapping for 7 min and CMP for 21 min, the step height of the Cu/Ni microstructures rapidly decreases from 251 μm to −46 nm on average, and the surface roughness Sa of copper and nickel are significantly improved to 8.7 nm and 2.9 nm, respectively. For the CMP mechanism, as the K2S2O8 concentration increases, the copper corrosion is enhanced, and thus the copper MRR quickly increases; The nickel surface film gradually transforms from Ni(OH)2 to NiOOH, and the intermediate state can be removed relatively easily, and thereby the nickel MRR increases and decreases. This study may provide a feasible high-precision planarization method for EFAB.

Synthesis of Hierarchical Layered Quasi-Triangular Ce(OH)CO3 and Its Thermal Conversion to Ceria with High Polishing Performance.

Layered quasi-triangular Ce(OH)CO3 assembled from primary nanoparticles was synthesized via a solvothermal method and converted into CeO2 abrasive particles by calcination at 800-1000 °C. With the increase of calcination temperature, the primary particle size increased and the microstructure, mechanical hardness, and chemical activity of the CeO2 particles changed, thus affecting the polishing performance. The calcined products obtained at 800, 850, and 900 °C maintained the layered edge structure of the Ce(OH)CO3 precursor and had a relatively high specific surface area and surface Ce3+ concentration. The samples calcined at 950 and 1000 °C lost the layered structure due to the large-scale melting of the primary particles, and their surface chemical activity decreased. The polishing experiments on K9 glass showed that, with the calcination temperature rising from 800 to 1000 °C, the material removal rate (MRR) first increased and then decreased sharply. The initial increase of MRR was attributed to the increase of mechanical hardness of the layered quasi-triangular CeO2, and the subsequent decrease of MRR was related to the decrease in surface chemical activity and disappearance of the layered edge structure. The product calcined at 900 °C had the highest MRR and best surface quality after polishing due to the layered edge structure and optimal match of chemical activity and mechanical hardness.

Material Removal Characteristics of Abrasive-Free Cu Chemical-Mechanical Polishing (CMP) Using Electrolytic Ionization via Ni Electrodes

Recently, various efforts have been made to reduce the environmental burden caused by semiconductor manufacturing by improving the process efficiency. Chemical mechanical polishing (CMP), which is used to planarize thin films in semiconductor production, has also been studied to improve its efficiency by increasing the material removal rate (MRR) while reducing its environmental burden. Previous studies have been conducted to electrolytically ionize chemical solutions used in abrasive-free CMP for improving the MRR. In this study, we analyzed the change in the chemical solution according to the variation in voltage applied to the nickel (Ni) electrode in abrasive-free Cu CMP and studied the tribological material removal characteristics. The experimental results revealed that electrolytic ionization of the chemical solution for abrasive-free CMP increases the amount of dissolved oxygen (DO). The static etch rate of the Cu thin film and MRR in CMP increased as the voltage applied to the Ni electrode increased. The frictional force and temperature during CMP also increased as the applied voltage increased. Therefore, the increase in MRR caused by the increase in the applied voltage in abrasive-free Cu CMP using electrolytic ionization is plausibly caused by the chemical reaction between the dissolved oxygen in the chemical solution and Cu.

Maximizing MRR of Inconel 625 machining through process parameter optimization of EDM

Past decade witnessed a growing trend of electrical discharge machining (EDM) process, laying a strong consideration on it. EDM is suitable for material subtraction from hard to machine materials by electric spark between work material and tool used as electrodes. Besides the reduction of material from workpiece in machining, the process leads to the removal of a certain amount of tool material as well. There is always a quest for achieving economy in machining through increased material removal rate (MRR) using optimum machining process parameters. In this paper an experimental exploration is presented for optimizing process parameters (factors) like time of pulse on (Ton), input current (Ip) and time of pulse off (Toff) to maximize MRR for subtracting material from Inconel 625 work part using Taguchi experimental design (DoE) and its analysis.

Experimental investigation on simultaneous machining of EDM and ECM with different electrode materials

In order to improve the machining efficiency and the surface quality of EDM/ECM, adding a small amount of sodium nitrate into deionized water as the working medium, a novel simultaneous machining approach of EDM and ECM (SEDCM) was developed. In this work, a comparative study was conducted on the SEDCM performance of TC4 alloy using different electrode materials viz. brass, copper and copper-tungsten alloy. In addition, the effects of process parameters, such as peak current, pulse on time and gap voltage on material removal rate (MRR), tool wear rate (TWR), surface roughness (Ra), and surface micromorphology were investigated. The results show that brass electrode provides the smallest MRR, the highest TWR and the worst surface quality. The copper electrode has the smallest average diameter of a single discharge craters and the best surface finish. The MRR and TWR of copper-tungsten electrode are similar to those of copper electrode. As peak current increases, TWR increases and Ra deteriorates for all the electrodes, as well MRR increases and then decreases for copper and copper-tungsten electrodes. Increase in pulse on time and gap voltage, MRR and TWR increases and then decreases gradually. At higher pulse on time and gap voltage, Ra becomes greater for three type electrodes.

Prediction and analysis of material removal rate and white layer thickness during wire electrical discharge turning (WEDT) process

This paper seeks to propose an analytical model for material removal rate (MRR) and white layer thickness (WLT) during wire electrical discharge turning (WEDT) process. This approach considers the predicted crater radius and depth (based on overlapping of craters) for the determination of MRR. The discharge energy (ranging from 4.217 J to 12.228 J) was utilized for the evaluation of the process responses. Besides, a detailed analysis of material removal is visually demonstrated with the aid of a high-speed camera captured at 15,000 fps. The images/videos from the camera help to visualize the material removal process at various discharge energies and input settings. A non-uniform increase in MRR at discharge energy ranging from 4.217 J to 8.475 J was observed, presumably due to the unpredictable wire vibration as confirmed from the high-speed camera. The white layer formation during the process was analyzed using SEM images. Beyond the discharge energy value of 10.276 J (approx.), substantial increase in molten pool formation causes the WLT to shift to a higher incremental slope. The predicted MRR and WLT values are in good agreement with the measured results with an absolute average error of 7.09% and 5.12%, respectively. A detailed EDS analysis confirms the variation in surface elemental composition before and after the WEDT process.

Deliberate Surface Treatment of Zirconium Dioxide with Abrasive Brushing Tools

Brushing with bonded abrasives is a flexible finishing process used to reduce the roughness of technical surfaces. Although industrially widespread, especially for the finishing of metallic surfaces, insufficient knowledge of the motion, the material removal, and the wear behavior of the abrasive filaments complicates predictions of the work result. In particular, the reliable finishing of ceramics with bonded diamond grains proves difficult due to increased material removal rates, quickly leading to undesirable changes in the workpiece geometry. Based on technological investigations with abrasive brushing tools, this article provides insights into the surface finishing of zirconium dioxide with a focus on finding compromises between reduction in the surface roughness and alteration of the workpiece shape.

Multi-Objective Optimization of Metal Removal Rate, Dimensional and Profile Accuracy during Drilling of ASTM A516 (Grade70) Steel

The aim of this research work is identification of optimum drilling parameters to increase material removal rate, dimensional and profile accuracy during drilling. ASTM A516 (Grade70) which is a boiler quality plate of 12 mm thickness was considered as the specimen for conducting the experiments. The experiment was done based on full factorial design using 18 experiments generated using Minitab Software. Two levels for tool material and three levels for feed-speed combination and cutting environment were considered. Two runs were carried out for each trial. The metal removal rate was calculated for each hole drilled. The mean result of the two runs of a trial was taken as the result of the trial. The drilled holes were then tested for their dimensional, profile accuracies. With these results in hand the Artificial Neural Network software was trained to predict the optimized input parameters for drilling a hole of required dimensional and profile accuracies and with required metal removal rate.

Investigating the effects of electrochemical discharge machining (ECDM) on the dimensional accuracy and surface integrity of the PDMS microchannel

In this study, the electrochemical discharge machining (ECDM) process was used to fabricate a microchannel on polydimethylsiloxane (PDMS), which is able to fabricate channels on the non-conductive materials at low cost and acceptable material removal rate (MRR). One of the main advantages of this method, in addition to much less time and cost, is the possibility of achieving high depths (up to 1000 μm). For this purpose, the effect of electrolyte concentration, rotational speed, feed rate, and machining voltage on the surface quality and surface roughness was investigated in the PDMS micromachining. It was found that the ECDM is capable of fabricating the channels with the surface quality similar to lithography. Also, with increasing the machining voltage and electrolyte concentration, the MRR increases and the possibility of mechanical contact between tool and workpiece decreases. Increasing the machining voltage and also the electrolyte concentration changes the machining regime from contact machining to electrochemical machining. Increasing the machining voltage from 38 to 42 V increases the channel cross-section by nearly 40%. Also, the surface roughness increases by 36% with increasing the voltage from 38 to 42 V. Changing the rotational speed from 0 to 10,000 rpm, due to the reduction in the thickness of gas film, reduces the side sparks and concentration of the sparks on the bottom of the tool, which reduces the surface roughness. The Response Surface Method was used to achieve a mathematical model between inputs and outputs. The model represented a Quadratic Equation to predict the outputs.

Digital twin-enabled machining process modeling

Considering the new generation of information technology, the digitalization and intellectualization of the machining process have become the major core in intelligent manufacturing. The complex and diverse requirements, as well as the processing sites force the machining sequence to move towards cyber-physical integration. This paper presents a multidimensional modeling approach for machining processes, by introducing Digital Twin (DT) technology. The method is oriented towards the design and execution phases of the machining process and is used to support intelligent machining. The working mechanism of modeling, simulation, prediction and control of machining process is described based on the interpretation of the modeling and application methods of machining process design, inspection process, fault diagnosis and quality prediction, as based on digital twin technology. Finally, key components of diesel engines are targeted as test objects, demonstrating increased material removal rate by 5.1%, reduced deformation by 22.98% and 30.13%, respectively, verifying the effectiveness of the applied framework and the proposed method.