Material Removal Process Research Articles

Predictive Modeling and Analysis of Material Removal Characteristics for Robotic Belt Grinding of Complex Blade

High-performance grinding has been converted from traditional manual grinding to robotic grinding over recent years. Accurate material removal is challenging for workpieces with complex profiles. Over recent years, digital processing of grinding has shown its great potential in the optimization of manufacturing processes and operational efficiency. Thus, quantification of the material removal process is an inevitable trend. This research establishes a three-dimensional model of the grinding workstation and designs the blade back arc grinding trajectory. A prediction model of the blade material removal depth (MRD) is established, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS). Experiments were carried out using the Taguchi method to investigate how certain elements might affect the outcomes. An Analysis of Variance (ANOVA) was used to study the effect of abrasive belt grinding characteristics on blade material removal. The mean absolute percent error (MAPE) of the established ANFIS model, after training and testing, was 3.976%, demonstrating superior performance to the reported findings, which range from 4.373% to 7.960%. ANFIS exhibited superior outcomes, when compared to other prediction models, such as random forest (RF), artificial neural network (ANN), and support vector regression (SVR). This work can provide some sound guidance for high-precision prediction of material removal amounts from surface grinding of steam turbine blades.

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.

Analysis of material removal process when scratching unidirectional fibers reinforced polyester composites

AbstractIn this study, the micromechanical scratch behavior of unidirectional glass fiber reinforced polyester (GFRP) using several wear conditions was highlighted. Single-indenter scratch tests (SSTs) were carried out on GFRP composite material perpendicular (SST⊥) and parallel (SST//) to fiber direction. Damage modes dominating the material removal process (MRP) and friction exhibit significant sensitivity to both attack angle and normal load. From findings, damage modes and apparent friction coefficient substantially accentuate when increasing the attack angle. The inspections of the damage state at different testing conditions using a scanning electron microscope (SEM) reveal the dominating modes governing the MRP through the different phases. The response surface methodology (RSM) was adopted to develop a mathematical model based on the measured data. The RSM approach was found very promoting for predicting friction evolution versus attack angle and normal load. The proposed model reveals good ability not only in predicting apparent friction coefficient but also in detecting separately its ploughing and adhesive component. To emphasize the correlation between friction coefficient and MRP, the wear maps have been drawn up.

The Additive-Subtractive Process Chain - a Review

In recent years, metal additive manufacturing developed intensively and became a relevant technology in industrial production of highly complex and function integrated parts. However, almost all additively manufactured parts must be post-processed in order to fulfil geometric tolerances, surface quality demands and the desired functional properties. Thus, additive manufacturing actually means the implementation of additive-subtractive process chains. Starting with the most relevant additive processes (powder-based PBF-LB, LMD-p and wire-based WAAM and LMD-w/WLAM), considering intermediate process steps (heat treatment and shot peening) and ending up with post-processing material removal processes (with defined and undefined cutting edges), this paper gives an overview of recent research findings with respect to a comprehensive scientific investigation of influences and interactions within the additive-subtractive process chain. This includes both the macroscopic geometric scale and the microscopic scale of the material structure. Finally, conclusions and future perspectives are derived and discussed.

A theoretical and experimental investigation into surface generation in ultra-precision diamond milling

Ultra-precision diamond milling (UPDM) provides a promising generation of high-quality surface up to sub-micrometric form accuracy and nanometric surface roughness. Prior to its machining process, the investigation on surface generation would be beneficial to achieve desired quality with reduced cost and boosted productivity. However, few studies discussed this issue so far. In this study, a theoretical and experimental investigation into surface generation was carried out in UPDM. Firstly, a geometric model was built up considering the material removal process between the milling tool and the workpiece. Secondly, surface generation process was elaborated according to the developed model. Finally, UPDM experiments were performed on a typical brass material at different cutting conditions and surface texture parameters were characterized according to ISO 25178-2. Autocorrelation function (ACF) analysis was employed for a detailed evaluation of surface generation. The results showed that the static factors (cutting parameters) as well as the dynamic factors (material effects and spindle vibration), which were associated with the cutting conditions, yielded a great influence on surface generation. Surface texture characterization indicated that there was a good consistence between simulation and experiment, demonstrating the feasibility of the proposed method. ACF analysis indicated that, with the increased feedrate/step ratio, surface generation approximately achieved a transition from the periodical surface (dominated by cutting residuals) to the random surface (determined by multiple components). Significantly, this study draws up a fundamental understanding toward surface generation in UPDM.

Mechanism for segregation of cutting fluid and scrap for industrial application

Nowadays, metal removal or machining processes on metallic work pieces are frequently seen to obtain the appropriate surface roughness and dimensional precision. Turning, milling, facing, boring, and other processes could be used. Cutting fluids are designed to help in the material removal process because they have anti-rust qualities to stop the work piece from rusting and because they stop the work tool from overheating in machines like milling, drilling, and lathes, among others. To save operating costs, it is planned that both the material removed during this machining process and the cutting fluid will then be reused. In this article, a segregation method is thus suggested. If the scrap is allowed to flow without separation, it shortens the lifespan of the supporting mechanical equipment since it interferes with the functionality of those parts. Magnetic separation, centrifugal separation, and conveyor belts are the most popular existing technologies used today to separate scrap and fluid, although they are expensive to operate. A mechanism with high efficiency and low cost is thus suggested.

Surface generation modelling and form maintenance strategy in maskless fluid jet polishing of structured array surface

Structured array surfaces are extensively utilized in the fields of functional optical components and molds. However, high surface form accuracy of these surfaces is usually needed to implement superior performance, leading to great challenges in manufacturing. In this study, fluid jet polishing (FJP) was utilized to polish the cylindrical array surface. The effect of abrasive size and jet pressure on the form maintainability was elucidated by combining computational fluid dynamics (CFD) simulation. The abrasive trajectory and abrasive impact information were analyzed to reveal the material removal process. Tool influence functions (TIF) at different positions were simulated to model the surface generation process and provide a theoretical basis for the optimization of polishing parameters. A surface form maintenance strategy was proposed to achieve high form accuracy together with excellent surface quality by controlling the feed rate of the nozzle. A series of experiments were conducted to validate the effectiveness of the form maintenance strategy. The results revealed that the form error agreed well with the requirement after polishing with the designed feed rate. This study paves a new way for the polishing of structured array surfaces with a good surface form control.

The Effects of Plasma Pre-Cracking on Drilling of Hard Rocks: A Single Insert Cutting Experiment

AbstractThis paper studies the effects of plasma-induced cracks on rock cutting to support the concept of a plasma-integrated drag bit for accelerated geothermal drilling through hard rocks. For this, a single polycrystalline diamond compact (PDC) drilling technique is used in cutting granite to compare thrust and cutting forces between plasma-treated and untreated rock samples. The cracks are produced using underwater plasma at 80 J per pulse. This energy level does not produce visible damage to the rock. The cutting tests are conducted at a cutting speed of 12.7 m/min and four feed rates of 0.127, 0.201, 0.267, and 0.414 mm/s to represent actual drilling scenarios. The results show a general trend of reduction in both thrust and cutting forces for these feed rates, but the magnitude of reduction highly depends on the feed rate. The maximum force reduction of around 50% is found at the 0.267 mm/s feed rate with statistical significance. Cases with a higher force reduction are also found to have rougher surface topography, which indicates more excessive fracturing and, thus, a cracks-accelerated material removal process. This study provides initial evidence of using underwater plasma to increase the downhole drilling rate of hard rocks.

Removal mechanism of the chemical products layer on single-crystal sapphire surface in magneto-rheological polishing with Fe3O4/SiO2 core-shell abrasives

Chemical reactions will occur on sapphire surface in the magneto-rheological polishing (MRP) process with Fe3O4/SiO2 core–shell abrasives, resulting in a chemical products layer, which is easily removed due to its low hardness. In this paper, the specific mechanical removal mechanism of this chemical products layer was investigated by analyzing scratch morphology and scribing forces obtained from computer simulation and scratching experiment. The results showed that the tangential force plays a major role in the material removal process, the shearing action of abrasives dominates the material removal of the chemical products layer on sapphire surface. During scribing process, the chemical products layer is plastically deformed firstly and then removed when the shear stress exceeds its material yield strength. The materials on both sides of scratch flow outward plastically cause ridges under the continuous extrusion process. The material on the bottom of scratch is destroyed and removed under the continuous severe extrusion and shearing process, resulting in an uneven “jag-like” morphology. Both normal and tangential forces increase fluctuatingly with scribing distance, and the average depth and width of scratch increase with scribing velocity. Therefore, the material removal mechanism of sapphire in MRP process is the combination of chemical reaction of surface material and the synthetic action of plastic deformation and shearing removal of chemical products layer.

Two-step electropolishing of internal surfaces of 316L stainless steel made by laser-based powder bed fusion

Investigating electropolishing (EP) effects on the material removal process of laser-based powder bed fused internal surfaces is crucial for the application of EP in the polishing of complex internal structures. This study aims to electropolish various internal surfaces of 316L stainless steel fabricated by laser-based powder bed fusion (L-PBF). Un-sintered powders and sintered area on top, face up, side and face down internal surfaces were characterized. Based on the material removal characteristics of different surface features, a two-step EP was proposed using different potentials and polishing time for L-PBF internal surfaces after parametric study in a developed EP system which is capable of circulating electrolytes in high-speed. Material removal process and anodic dissolution of L-PBF internal surfaces were then discussed based on experimental results and impedance analysis. The comprehensive characterizations of morphology, roughness and cross sections with microstructure differences in consideration are important for analyzing the evolution of L-PBF surfaces during polishing. The study demonstrates the high efficiency of the two-step EP in polishing various L-PBF internal surfaces.

Optimization techniques for energy efficiency in machining processes-a review.

Metal working process is one of the main activities in mechanical manufacturing industry; it is considered as a major consumer of energy and natural resources. In material removal process, the selection of cutting parameters and cooling or cutting liquid is necessary to save energy and achieve energy efficiency as well as sustainability. During the last two decades, the number of publications in this field has rapidly increased and has shown the importance of this research area. This review paper identifies and reviews in detail a total of 166 scientific studies which exhibit original contributions to the field and address multiple energy efficiency challenges. The recently developed models of energy consumption and different materials used in the machining process are presented. Therefore, this study describes various techniques for modeling and optimizing machining operations such as turning, milling, and drilling. Modeling techniques, experimental methods, multi-objective and single-objective optimization methods, and hybrid techniques optimization are presented in a detailed manner compared to previous review papers where only energy models are discussed. It can help practitioners and researchers to select the most appropriate approach for the desired experience and to highlight the progress of these methods in terms of machining energy efficiency. Additionally, this paper provides a review of different cutting fluids adopted in machining processes. This paper assists researchers and manufacturers in making advantageous technical decisions that have substantial economics in terms of energy saving.

Real-time path correction of industrial robots in machining of large-scale components based on model and data hybrid drive

Industrial robots are increasingly used in machining of large-scale components due to advantages of high repeatability, large workspace and low cost. Nevertheless, applying industrial robots to high-accuracy machining of large-scale components remains a challenge, where the major hurdle is the insufficient manipulator stiffness due to joint flexibility. When the robot is performing a machining task, joint flexibility-induced position errors between motor and link called joint position errors (JPEs), as the main source of robot deformations, make the robot deviate from the desired path. For most industrial robots, due to the lack of link-side encoders, it is difficult to obtain the JPEs by direct measurement and compensate them in the controller, which deteriorates the path accuracy of the robot during machining greatly. To address this problem, this paper presents a real-time path correction approach of industrial robots based on JPE estimation and compensation with requiring only motor-side measurements and external wrenches. The proposed approach is divided into three steps. First, to estimate the actual link position of the robot in real-time, the dynamics of a manipulator with joint flexibility called flexible dynamics (FD) is introduced. Second, by taking both FD and disturbance dynamics into account, a novel link state estimator called flexible-dynamics based disturbance Kalman filter (FDBDKF) is developed, and thus JPEs can be estimated in real-time. Third, a data-driven locally weighted projection regression (LWPR)-based JPE prediction and compensation method is developed to further improve the compensation accuracy of the JPEs. Simulation and experimental results, obtained on a 6-DOF industrial robot, demonstrate the feasibility and effectiveness of the proposed approach. Experimental results show significant improvement (>80%) in the path accuracy of a simple material removal process corrected using the proposed approach.

Mechanism of polishing lutetium oxide single crystals with polyhedral diamond abrasive grains based on molecular dynamics simulation

Lutetium oxide single crystal is an excellent laser crystal material with the advantages of low phonon energy, high thermal conductivity, and high laser-induced damage threshold. Polishing is an important method to achieve ultrasmooth, damage-free surfaces of lutetium oxide wafers. The diamond abrasive grains used in mechanical polishing are mainly in the form of blocks, flakes, and balls. In this study, the molecular dynamics simulation method is used to simulate the process of polishing a lutetium oxide single crystal with different shapes of polyhedral diamond abrasive grains, and the polishing force, subsurface damage, and material removal are analyzed. Results show that the compressive stress and thickness of the machined amorphous layer in the subsurface are minimum at the vertex contact position and maximum at the face contact position. The values at the sphere and edge contact positions are somewhere in between. In terms of material removal, polyhedral and spherical abrasive grains have a plowing effect on the material removal process. However, the vertices and edges of polyhedral abrasive grains can be more easily cut into the workpiece than spherical abrasive grains, so polyhedral abrasive grains are conducive to the removal of materials in specific cases.

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.

Material removal mechanism in magnetorheological foam plane finishing

The material removal process of magnetorheological foam plane finishing (MRFPF) method which considers various processing conditions was studied in this paper. A material removal rate (MRR) model based on the updating type of workpiece moving trajectory, magnetic field distribution, and polishing speed in the polishing area was established for MRFPF. In this model, MRR is generated by integrating the polishing pressure and speed over the time that polishing pressure on workpiece updating for 1 cycle with the relative error between theoretical and experimental results less than 11.63 %. Moreover, MRFPF can achieve much higher MRR and surface flatness improvement rate than that of magnetorheological finishing (MRF) under different processing conditions, which further indicates the effectiveness of MRFPF in planar finishing.

Study of the dynamics of material removal processes in combined pulse laser drilling of alumina ceramic

Combined pulse laser (CPL), one of the hybrid laser processing technologies, has proven to be a reliable tool for the high-quality and high-efficiency material processing. In CPL drilling, the nanosecond laser has been proven that it can improve the drilling performance of the millisecond laser by increasing the laser absorption or improving the sputtering of the melt. However, the dynamics of material removal processes regarding CPL drilling have not been systematically investigated. In this paper, a numerical model of the CPL drilling of alumina ceramic was built to reveal the dynamic processes of the energy absorption, phase transformation, and micro-hole deformation process. The millisecond laser absorption enhanced by the ablated keyhole was quantified and considered as saturation (100 %), thus improving the drilling efficiency. In addition, the shock wave generated by the nanosecond laser accelerated the removal of the melt with a sputtering velocity of up to 23.8 mm/ms, which was much higher than the recoil pressure generated by the saturation vapor pressure, ensuring the drilling quality. Also, the experimental results showed that well drilling quality (1.09° taper angle, 0.96 circularity) were obtained for 1 mm thick alumina ceramic with a material removal rate as high as 1.9 × 104 μm3/μJ. The analysis and summary of the CPL drilling mechanism helps to further improve the drilling performance and provide a new technological route for high-speed processing of ceramic substrates.

Morphological characteristics of top soiling in the reclamation areas of post-coal mining at Kutai Kartanegara and Kutai Timur Regencies

This study aimed to obtain information about the impact of different morphological characteristics and genesis at some reclamation sites after coal-mining activities. Two coal sites were chosen as study areas, i.e. the Separi site, which is located in Kutai Kartanegara regency and the Bengalon site, located in Kutai Timur Regency. A descriptive research method was used to identify the morphological characteristics of reclamation sites at different times (chronosequence). The results showed that in-situ weathering, indicated by soil leaching caused by rainwater infiltration, led to the formation of the Ah horizon more than two years after the reclamation activity. The process of material removal and disposal (cutting, filling, transporting and levelling) from coal mining operations tends to accelerate the decomposition of parent soil material and promote the formation of pre-cambic horizons. The soils used (horizon A, B, and C) for the topsoil of the reclamation site were initially Typic Hapludults and Typic Dystropepts, although Typic Tropaquents and sandy parent materials were also used. Due to the impermeable layers of overburdening where water channels in the soil profile and deeper layers have not yet formed as human-made soil and landscape (artificial) cause rainwater to fail to infiltrate deeper layers so that with less heavy rain, the groundwater level will rise to the surface and the land will become waterlogged/flooded.

Prediction of Flank Wear during Turning of EN8 Steel with Cutting Force Signals Using a Deep Learning Approach

Currently, manufacturing industries focus on intelligent manufacturing. Prediction and monitoring of tool wear are essential in any material removal process, and implementation of a tool condition monitoring system (TCMS) is necessary. This work presents the flank wear prediction during the hard turning of EN8 steel using the deep learning (DL) algorithm. The turning operation is conducted with three levels of selected parameters. CNMG 120408 grade, TiN‐coated cemented carbide tool is used for turning. Cutting force and flank wear are assessed under dry‐cutting conditions. DL algorithms such as adaptive neuro‐fuzzy inference system (ANFIS) and convolutional auto encoder (CAE) are used to predict the flank wear of the single‐point cutting tool. The DL model is developed with turning parameters and cutting force to predict flank wear. The different ANFIS and CAE models are employed to develop the prediction model. Grid‐based ANFIS structure with Gauss membership function performed better than ANFIS models. The ANFIS model’s average testing error of 0.0074011 mm and prediction accuracy of 99.81% are achieved.

Multi-scale machining damages of CFRP circular cell honeycomb during end face machining

CFRP circular cell honeycomb is becoming increasingly important in aerospace due to its low density, high specific stiffness, impact resistance and microwave absorption performance. However, high-quality machining of CFRP circular cell honeycomb still represents a significant challenge due to its anisotropic, heterogeneity and discontinuous characteristics. This paper is presented to summarize the machining damage and analyze its cause. In this paper, the exit angle and MRR are defined to describe the effect of discontinuous structure on material removal process, the machining damage of CFRP circular cell honeycomb is classified based on the morphology and scale, the end face machining experiments are carried out to study the effect of machining method (milling and grinding), geometry of tools, exit angle and MRR on damage. The results show that milling produces larger tearing and less burr than grinding. The exit angle influences the curvature radius of fiber that determines fiber fracturing significantly, and side face burr occurs as exit angle and curvature radius of fiber increases. The MRR is larger in cut in and cut out stage of circular cell, tearing and delamination occurs respectively, but the chamfer or fillet of the grinding wheel tetrad material removal process and strength the stiffness of machining area, damage was suppressed. Considering the frequency and the size of damage may occur systematically, grinding wheel with chamfer or fillet is recommended to process CFRP circular cell honeycomb.

Modeling and simulation of surface generation in manufacturing

The paper describes the state-of-the-art in modeling and simulation of surface texture and topography generation at micro and nano dimensional scales. Three main classes of manufacturing processes used for the generation of engineering surfaces are considered: material removal processes, material conservative processes, and material additive processes. Types of modeling techniques for the simulation of surface generation are reviewed and discussed including analytical models, numerical multi-physics models, and data-driven methods. After presenting the application of those modeling techniques for the prediction of characteristics and geometry of surfaces generated by different manufacturing processes, their performance, implementation, and accuracy are discussed. Finally, a roadmap for the realization of a complete surface generation digital twin in manufacturing is outlined.