Grinding Material Removal Research Articles

Effects of grinding mode on grinding performance of anisotropic CF/PEEK composites

AbstractGrinding could be used to enhance accuracy and quality of carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) composites. However, the grinding mode, namely up‐grinding (UG) or down‐grinding (DG), is usually neglected while unbefitting grinding mode choice may cause inferior surface quality. To investigate effects of grinding modes on grinding performance of anisotropic CF/PEEK, grinding experiments in UG and DG were carried out under different fiber orientation angles θ. Experimental results indicated that maximum grinding temperatures and normal grinding forces in UG were lower than DG regardless of the abrasive grit sizes. Material removal mechanisms of CF/PEEK affected by grinding mode were revealed by analyzing morphologies of surface, chip and grinding wheel. When θ = 0°, the dominant mechanisms in DG were extrusion fracture and fiber deformation, while they were interface shear debonding and bending fracture in UG. When θ = 90°, the dominant mechanisms in DG included interface layer separation and bending fracture, while they were shear and extrusion fracture of well‐supported fibers in UG. Thus, UG was more favorable for material removal, obtaining lower surface roughness values, fewer machining defects and less wheel wear than DG. This study will provide technical guidance for high‐quality grinding of carbon fiber‐reinforced thermoplastic composites.Highlights The effects of grinding modes (DG and UG) on the grinding performance of anisotropic CF/PEEK composites were investigated. Material removal mechanisms of CF/PEEK affected by grinding mode were revealed under different fiber orientation angles. The maximum grinding temperatures and normal grinding forces in UG were lower than DG. UG was more favorable for material removal in grinding, and could produce better ground surface quality than DG.

Robotic Grinding Process Monitoring by Vibration Signal Based on LSTM Method

In robotic grinding, the trajectory deviation of the robot will change the grinding force and then affect the grinding material removal. Therefore, grinding force and material removal monitoring is important for the machining quality of robotic grinding. In this paper, force and material removal estimation methods are proposed based on the acceleration signal. The dynamic model of robotic grinding is studied and the vibration force relationship can be obtained. Based on the vibration force relationship, the framework of the grinding force and material removal monitoring is established. In this framework, the peak value of the acceleration is firstly extracted by the signal process, and the Long Short-Term Memory (LSTM) network is used to train the vibration-force mapping model. Then the grinding removal can be calculated by the empirical formula. The experiments of robotic grinding are carried out. The real grinding force and the material removal can be estimated in time, which proved the effectiveness and potential of our method.

Vision and sound fusion-based material removal rate monitoring for abrasive belt grinding using improved LightGBM algorithm

Accurate material removal modeling is the basis for optimizing the surface quality and improving the performance of equipment components. In this study, a multi-sensor fusion method of vision and sound is used to monitor in-process grinding material removal rate (MRR). First, belt grinding experiments are conducted using different grinding parameters, and vision and sound signals are captured by industrial CCD cameras and an omnidirectional condenser microphone, respectively. Second, the features of the captured grinding spark images are extracted based on two aspects: color and texture, and those of the grinding sound are investigated in the time, frequency, and time–frequency domains. Moreover, the complementarity between the vision and sound signals and their sensitivity to different grinding parameters are discussed. Finally, based on feature-level fusion strategies, the Pearson correlation coefficient and the sequential backward selection algorithms are jointly used to select the optimal feature subsets. MRR prediction models are established using the selected feature subsets and an improved light gradient boosting machine (LightGBM) algorithm. The test results show that the error in the MRR prediction model of same-specification abrasive belts is less than 3 %, and the coefficient, R2, is as high as 99.2 %. The proposed method can be used to predict the MRR resulting from a single grinding parameter and multiple ones, using the same-specification abrasive belts. Compared to other prediction models, the improved LightGBM model is superior in terms of the time factor without reduction in the accuracy of the model.

An adaptive grinding method for precision-cast blades with geometric deviation

Precision-cast blades are core components in aeroengines, and their machining precision has a considerable effect on the performance of the aeroengine. In this paper, an adaptive grinding method for precision-cast blades with geometric deviation is proposed to improve the machining precision, machining efficiency, and automation level of precision-cast blade grinding. A scheme for adaptive grinding of precision-cast blades with geometric deviation is developed, a grinding process for precision-cast blades is formulated, and a robotic grinding system is constructed. An optimal model to match the blade measurement data to the design model is then established, and a corresponding optimal matching matrix is solved to determine a position reference for precision-cast blades. Further, the theoretical cutter contacts are extracted, and the machining allowance of the precision-cast blade profile is measured. An estimation model of grinding material removal (MR) of precision-cast blades based on a neural network algorithm is established, and the correctness of the model is verified. Finally, an adaptive grinding experiment is performed on the concave surface (CC) of a precision-cast blade to verify the accuracy of the proposed grinding method. The experimental results show that, after adaptive grinding, the machining allowance of CC is distributed in the range of − 0.05 mm to 0.05 mm, which meets the machining precision requirements of the blade.

Quantitative impacts of regenerative vibration and abrasive wheel eccentricity on surface grinding dynamic performance

In grinding, regenerative vibration and forced vibration due to grinding wheel eccentric rotation are main excited-vibration sources that interact with grinding material removal mechanism. In the paper, instantaneous undeformed chip thickness in down-grinding cutting phase may consist of two components, i.e. linear kinetic thickness and nonlinear dynamic thickness. Considering abrasive grit-workpiece interaction in the grinding contact zone, the grinding vibration system is presented by a new set of differential equations of two degrees of freedom (DOF) with a close-loop feedback control system models. Conventional grinding control parameters, including wheel spindle speed, work-speed in feed direction and radial cutting depth, are often regarded as linear constants in many existing simplified models. When considering time delay, they can be transferred to nonlinear variables, so the capability of prediction and the accuracy of solution of the grit-workpiece dynamic performance are improved. Based on quantitative comparison of force and vibration magnitudes, the influence of the eccentric rotation of abrasive wheel and the negative rake angle of working grit cutting edges on grinding performance are demonstrated in the paper.

Exploration on Wire Discharge Machining Added Powder for Metal-Based Diamond Grinding Wheel on Wire EDM Dressing and Truing of Grinding Tungsten Carbide Material

In this paper, the effects of material removal rate and abrasive grain protrusion on the metal-based diamond grinding wheel were studied to find the optimal parameters for adding powder and wire discharge. In addition, this kind of electric discharge method to add powder on the metal-based diamond grinding wheel on line after dressing and truing will be applied on tungsten carbide to study the grinding material removal rate, grinding wheel wear, surface roughness, and surface micro-hardness.

Analysis of Grinding Surface Creation by Single-Grit Approach

This paper presents some new research findings in the investigation of single-grit grinding in terms of surface creation. The investigation demonstrated that rubbing–plowing–cutting hypothesis of grinding material removal mechanism is valid in both experiments and simulations. A finite element model (FEM) was developed to simulate the material deformation during the grit interacts with the workpiece. It was found that the cutting mechanism is the more effective in the first half of the scratch where the grit penetrates the workpiece. The plowing is a prominent mechanism in the second half of the scratch where the grit is climbing up along the scratch path and uplifting the material at the front and the sides of it. This observation is very important to provide a greater insight into the difference between up-cut and down-cut grinding material removal mechanisms. Multipasses scratch simulations were performed to demonstrate the influence of plowing on the ground surface formation. Moreover, by analyzing the effects of grinding conditions, the shape of cutting edges, and friction in grinding zone on the grinding surface formation, some useful relations between grinding performance and controllable parameters have been identified. It has demonstrated that plowing has significant influences on ground surface formation and concluded that the influence of grit shape, friction, and grinding kinetic condition should be considered together for the plowing behavior control, which could provide a good guidance for the improvement of grinding efficiency.

Characterization of material removal in ultrasonically assisted grinding of SiCp/Al with high volume fraction

Due to the significant difference between the reinforcement grains and matrix phase, the machining of SiC particle-reinforced aluminum composites (SiCp/Al) is difficult and costly, especially for SiCp/Al with volume fraction higher than 50%. Ultrasonically assisted grinding (UAG), which has unique advantages in the machining of both ductile and brittle materials, is a promising solution of the machining of SiCp/Al. This study conducts both UAG and conventional grinding (CG) process on SiCp/Al with an electroplated diamond wheel. The study explores material removal mechanisms involved in UAG in comparison to that in the CG. It also investigates grinding forces, surface integrity, subsurface damage, and wheel wear. The study finds that material removal in grinding of SiCp/Al is dominated by SiC particle fracture that is induced in the grinding process. The ground workpiece is smeared with an aluminum layer, making it difficult to evaluate surface integrity. Compared with CG, UAG of SiCp/Al results in similar surface integrity in terms of surface roughness and subsurface damage, but a much lower grinding force (35–50% lower).

Estimation of the active grains load in different kinematic variations of the internal cylindrical grinding process

This article presents indexes referred to in literature and used when describing the working conditions of abrasive grains in internal cylindrical grinding processes: equivalent chip thickness heq, material removal rate Qw and the proper grinding material removal rate Q′w, as well as the average cross-section of the cut layer AD. From consideration of these indexes, it became apparent that there was a need to develop a new index which would synthetically combine all of the key grinding parameters, as well as the geometric structure of the grinding wheel active surface. A new index was defined, marked as SIQ (synthetic index of single abrasive grain material removal rate), in which the material removal rate Qw was related to the number of active grains on the grinding wheel surface and the converse speed ratio q = vs/vw. The work presents example calculations and charts detailing the changes within the SIQ index values for the following kinematic variations of internal cylindrical grinding processes: traverse grinding, reciprocating grinding, plunge grinding and plunge grinding with grinding wheel oscillations. The work includes an analytical and experimental example of how the SIQ index can be used to determine the grinding parameters within which the grain load remained at a similar level in various kinematic variations of the grinding process. The analyses performed show that application of the proposed index allows for: a comparison of various kinematic variations of internal cylindrical grinding, the selection of machining parameters in instances where the grinding kinematics may need to be altered, the necessity for maintaining the active grains load at the same level, determination of the changes of the active cutting vertexes load during the functioning of select machining parameters, and the comparison of grinding wheels with a variety of active surface geometric structures.

Application of acoustic emission sensor to investigate the frequency of tool wear and plastic deformation in tool condition monitoring

Abstract The metal cutting process initiates with the occurrence of plastic deformation of workmaterial and is followed by tear and removal of material from the workpiece. This process ultimately damages cutting tool and causes tool wear. An acoustic emission (AE) sensor has been employed to measure the signal frequency in machining. The AE signal component of tool wear and plastic deformation in turning are separated by simulating the process of tool wear by a grinding test where the workpiece of grinding test is the same tool-insert for tuning test, and the process of tool wear in turning is replicated by the process of material removal in grinding. The frequency of tool wear for this particular investigation is found to lie between 67 kHz and 471 kHz whereas for plastic deformation of workmaterial, it has a fluctuation within the range starting from 51 kHz to some value within 471 kHz.

Effect of different parameters on grinding efficiency and its monitoring by acoustic emission

Grinding efficiency is one of the most important considerations in the selection of grinding operation conditions because it has a significant impact on the productivity, quality, energy consumption and cost. Focusing on the core issues of grinding process, the paper presents some fundamental research findings in relation to grinding material removal mechanisms. The grinding efficiency is analysed by considering the rubbing, ploughing and cutting of a single-grit grinding. By analysing the features of acoustic emission in single-grit grinding tests, an evidence-based scientific foundation has been established for monitoring grinding efficiency using acoustic emission. Following the discussion of the energy consumption, temperature elevation and thermal stresses in grinding, the paper provides a logical depiction that explains why acoustic emission can be used for grinding thermal performance monitoring. As a result, a novel acoustic emission monitoring method is to monitor grinding temperature and grinding wheel wear status.

Experimental study on single grit grinding of Inconel 718

This article presents an important investigation of material removal mechanism in grinding utilizing single grit scratch tests. The investigation helps people to understand the abrasive cutting behaviour when the abrasive cutting edge shape alters during single grit grinding. The results provide fundamental knowledge of the grinding material removal process, which helps to improve grinding performance and quality. Cubic boron nitride grits of 40/50 mesh size were used to perform scratch tests on the alloy Inconel 718. The concepts of material pile-up ratio and actual material removal area were introduced to measure the material removal efficiency during grinding. It is found that pile-up ratio decreases and actual material removal area increases when the depth of cut increases, albeit the material removal mechanism is highly dependent on the abrasive grit cutting edge shape. The material removal mechanism along the scratch length shows different behaviours at the entrance and exit sides of the scratching passes. When a grit was moving along its scratch path, it pushed material forward resulting in high material accumulation at the exit side of the scratches. Consequently, cutting is more prominent at the entrance side of the scratch, whereas ploughing or pile-up is extremely high at the exit side of the scratches. The research finding provides crucial information for grinding process optimization.

Pose estimation and machining efficiency of an endoscopic grinding tool

In this research, a method was developed for estimating the amount of material removed in an endoscopic grinding process. A model was formulated for the estimation of the pose (position and orientation) and force on a modified PENTAX ES-3801 endoscope, based on geometric analysis of the endoscope bending section and input from an LVDT position sensor and load cell placed in line with the driving cable of the endoscope. The experimental and theoretical results showed that the pose and force of the flexible bending section can be predicted and monitored when subjected to varying machining loads. In most conditions, the estimated force, position, and orientation error were less than 0.5 N, 2.0 mm, and 3.0°, respectively. For estimation of material removal in grinding, the effective energy spent on removing material, energy wasted by chatter, and energy wasted by the transmission shaft had to be calculated. Grinding experiments were carried out on aluminum workpiece, and the amount of material removal was estimated and measured for comparison. The results suggested that it is possible to estimate the amount of material removed by a non-rigid machine tool with the method described.

Material removal monitoring in precision cylindrical plunge grinding using acoustic emission signal

A mathematical model of the acoustic emission signal during a grinding cycle is proposed for the monitoring of material removal in precision cylindrical grinding. Acoustic emission signals generated during precision grinding are sensitive to forces in grinding and present opportunities in accurate and reliable process monitoring. The proposed model is developed on the basis of a traditional grinding force model. Using the developed model, a series of experiments were performed to demonstrate the effectiveness of the acoustic emission-sensing approach in estimating the time constant and material removal in grinding. Results indicate that acoustic emission measurements can be used in the prediction of material removal in precision grinding with excellent sensitivity.

Grinding Surface Creation Simulation Using Finite Element Method and Molecular Dynamics

This paper presents some research results of the application of finite element method and molecular dynamics in the simulation of grinding surface creation. The comparison of these two methods shows that both methods could illustrate the material removal phenomena and provide useful information of grinding mechanics, but they have different feasible application arranges depending on the level of size scales. The investigation demonstrated that rubbing hypothesis of grinding material removal mechanism is valid at all size level even down to nanometre level. Further investigation areas are identified in the paper.

Simulation of Grinding Surface Creation – A Single Grit Approach

The paper presents an investigation of grinding material removal mechanism using finite element method. Understanding of grinding removal mechanism relies on the investigation of material removal by each individual grain. Although some analytical formulations have been developed to predict and to quantify the machining events in grinding, they do not illustrate every stage of abrasive actions. Finite element analysis provides good facility to present details of physical behaviour in grinding. In this research, material removal mechanism of grinding, namely rubbing, ploughing and cutting, is discussed with the variation friction coefficient. The major emphasis here is on the ploughing. Total force variation exerted during indention and sliding of a grain is also presented along its path.

Modelling of specific energy requirement during high-efficiency deep grinding

Grinding is a multi-point cutting operation. The specific energy or the energy expended for unit material removal in grinding is very high, typically one or two orders higher than the machining specific energy. Such high specific energy required in grinding can be attributed to the irregular and random geometry of the abrasive grits, which induce a lot of rubbing and ploughing actions along with the chip formation by shearing process. Also the effective angle in grinding is highly negative which is again responsible for such high-specific energy requirement in grinding. In grinding, a number of notable phenomena occur during the chip formation process, which actually consumes a significant percentage of energy. Such main energy consumers in grinding are: • Chip formation due to shearing • Primary rubbing • Secondary rubbing • Ploughing • Wear flat rubbing • Friction between the loaded chip and workpiece • Friction between bond and workpiece, etc. The present paper tries to analytically predict the specific energy consumed during high-efficiency deep grinding (HEDG) of bearing steel by monolayer cBN wheel. During the HEDG process, energy is spent mostly for shearing, rubbing and ploughing processes. The other energy consumers have insignificant role in such high-speed grinding process. So, models which take into account the processes of shearing, primary rubbing, secondary rubbing and ploughing process can reasonably be used to predict the energy requirement in such HEDG process. The total specific energy value obtained from the model has been validated with those experimentally observed values. A good trend matching of the modelled and experimental values have been observed and the root mean square error values have been found to vary between 7% and 11%.

Grinding Acoustic Emission Classification in Terms of Mechanical Behaviours

The material removal in grinding involves rubbing, ploughing and cutting. For grinding process monitoring, it is important to identify the effects of these different phenomena experienced during grinding. A fundamental investigation has been made with single grit cutting tests. Acoustic Emission (AE) signals would give the information relating to the groove profile in terms of material removal and deformation. A combination of filters, Short-Time Fourier Transform (STFT), Wavelets Transform (WT), statistical windowing of the WT with the kurtosis, variance, skew, mean and time constant measurements provided the principle components for classifying the different grinding phenomena. Identification of different grinding phenomena was achieved from the principle components being trained and tested against a Neural Network (NN) representation.

Partial-Ductile Grinding, Lapping, and Polishing of Aspheric and Spherical Surfaces on Glass

This paper discusses partial-ductile-mode grinding, lapping and polishing of aspheric and spherical surfaces on glass. Industrial manufacture of glass lenses usually involves three operations: grinding (known as milling in the optical industry), tapping, and polishing. The fracture mode of material removal is dominant in the grinding process. While these three operations have been successful for machining spherical lenses, aspheric lenses have been manufactured in the absence of the lapping process, because of the considerable amount of ductile mode of material removal in grinding. The parameters that helped identify and solve problems in manufacturing were surface roughness, micro-fractures and ductile streaks on glass surfaces, and interferometric fringes.

Surface Integrity and Wear Behavior of Ground Ceramics

The present study intends to cast some light upon the performance of ceramic parts ground with diamond and to determine the extent of improvement possible by an adapted finishing process. From the analysis of material removal in grinding, a model was derived which predicts the state of stress in the machined surface and thus the likely behavior of parts in service.