Surface Grinding Machine Research Articles

Strategy and computational examination of surface grinding machine with predictive diagnostic performance system during operation

Strategy and computational examination of surface grinding machine with predictive diagnostic performance system during operation

Анализ процессов в гидравлической системе плоскошлифовального станка с возвратнопоступательным движением стола, влияющих на качество обработки и эффективность работы привода

Based on the research carried out, the authors conduct a system analysis of the hydraulic system of a surface grinding machine. There was described the dependence between the hydraulic system of the working table moving and quality, effective and tolerance. During the study there were made the analysis of hydraulic circuits of the grinding machines in the different executions. There was described the different solutions of the surface grinding machines, using the reciprocating table moving. We make short description of the principles of working of hydraulic system and most significant properties, advantages and disadvantages. There were described all of work principle, starting from the simple system with mechanical elements of control till complicated system with flow control regulation with using electronic control system. It was shown signal supply diagram, also for proportional control system.

Reprint of: Explainable AI (XAI)-driven vibration sensing scheme for surface quality monitoring in a smart surface grinding process

Local Interpretable and Model-agnostic Explanation (LIME), an explainable artificial intelligence (XAI) approach is adapted to identify the globally important time-frequency bands for predicting average surface roughness (Ra) in a smart grinding process. The smart grinding setup consisted of a Supertech CNC precision surface grinding machine, instrumented with a Dytran piezoelectric accelerometer attached to the tailstock quill along the tangential direction (Y-axis). For every grinding pass, vibration signatures were captured, and the ground truth surface roughness values were recorded using a Mahr Marsurf M300C portable surface roughness profilometer. The roughness values ranged from 0.06 to 0.14 microns over the complete set of experiments. Time-frequency domain spectrogram frames were extracted for each of the vibration signals collected during the grinding process. Convolutional Neural Networks (CNNs) were modeled to predict the surface roughness based on these spectrogram frames and their image augmentations. The best CNN model was able to predict the roughness values with an overall R2-score of 0.95, training R2-score of 0.99, and testing R2-score of 0.81 with only 80 sets of vibration signals corresponding to 4 experiments with 20 trials each. Although the data size is not large enough to guarantee such performance metrics in real-world scenarios, one can extract statistically consistent explanations underlying the relationships these complex deep learning models capture. The LIME methodology was implemented on the developed surface roughness CNN model to identify the important time-frequency bands (i.e., the superpixels of a spectrogram) influencing the predictions. Based on the identified important regions on the spectrogram frames, the corresponding frequency characteristics were determined that influence the surface roughness predictions. The important frequency range based on LIME results was approximately 11.7 to 19.1 kHz. The power of XAI was demonstrated by cutting down the sampling rate from 160 kHz to 30, 20, 10, and 5 kHz based on the important frequency range and considering Nyquist criteria. Separate CNN models were developed for these ranges by only extracting time-frequency contents below their corresponding Nyquist cut-offs. A proper data acquisition strategy is proposed by comparing the model performances to argue the selection of a sufficient sampling rate to capture the grinding process successfully and robustly.

Explainable AI (XAI)-driven vibration sensing scheme for surface quality monitoring in a smart surface grinding process

Local Interpretable and Model-agnostic Explanation (LIME), an explainable artificial intelligence (XAI) approach is adapted to identify the globally important time-frequency bands for predicting average surface roughness (Ra) in a smart grinding process. The smart grinding setup consisted of a Supertech CNC precision surface grinding machine, instrumented with a Dytran piezoelectric accelerometer attached to the tailstock quill along the tangential direction (Y-axis). For every grinding pass, vibration signatures were captured, and the ground truth surface roughness values were recorded using a Mahr Marsurf M300C portable surface roughness profilometer. The roughness values ranged from 0.06 to 0.14 microns over the complete set of experiments. Time-frequency domain spectrogram frames were extracted for each of the vibration signals collected during the grinding process. Convolutional Neural Networks (CNNs) were modeled to predict the surface roughness based on these spectrogram frames and their image augmentations. The best CNN model was able to predict the roughness values with an overall R2-score of 0.95, training R2-score of 0.99, and testing R2-score of 0.81 with only 80 sets of vibration signals corresponding to 4 experiments with 20 trials each. Although the data size is not large enough to guarantee such performance metrics in real-world scenarios, one can extract statistically consistent explanations underlying the relationships these complex deep learning models capture. The LIME methodology was implemented on the developed surface roughness CNN model to identify the important time-frequency bands (i.e., the superpixels of a spectrogram) influencing the predictions. Based on the identified important regions on the spectrogram frames, the corresponding frequency characteristics were determined that influence the surface roughness predictions. The important frequency range based on LIME results was approximately 11.7 to 19.1 kHz. The power of XAI was demonstrated by cutting down the sampling rate from 160 kHz to 30, 20, 10, and 5 kHz based on the important frequency range and considering Nyquist criteria. Separate CNN models were developed for these ranges by only extracting time-frequency contents below their corresponding Nyquist cut-offs. A proper data acquisition strategy is proposed by comparing the model performances to argue the selection of a sufficient sampling rate to capture the grinding process successfully and robustly.

Real single grain grinding FEM simulation for case-hardened steel based on equivalent contact area analysis

Abstract Grinding is an indispensable phase in the gear production chain as it allows very stringent requirements characteristic of the automotive sector to be satisfied. The main goal of this finishing process is to ensure compliance with the surface integrity and dimensional tolerance specifications of the product. A single-grain grinding FEM model has been implemented to predict grinding load values based on real grain geometry using a set of Johnson & Cook coefficients able to represent the flow stress curve of a typical gear case-hardened steel 27MnCr5. Grain geometry acquired through computed tomography was imported into three-dimensional process simulation software DEFORM-3D. As the use of real grain geometry leads to time-consuming simulations, an equivalent defined geometry grain was implemented to compare cutting behavior and calculate maximum force values through real contact area analysis under the same process parameters. Calculated loads were subsequently compared with experimental results, showing good agreement with a maximum percentage difference less than 13% for two different grain geometries. Grinding force measurements were performed in a single-grain configuration on a CNC surface grinding machine adopting a wheel speed of 384 rad/s, feed rate of 8.6 mm/s and a depth of cut of 0.1 mm.

Evaluation of dual-ended readout GAGG-based DOI-PET detectors with different surface treatments.

Parallax error is a major issue in small animal positron emission tomography (PET) scanners which are used in preclinical studies or detailed scanning of human organs. Several methods have been proposed and investigated to reduce this radial artifact in PET images by estimating the depth of interaction (DOI) of 511-keV photons in the crystal. Among all, the dual-ended readout method seems to be very simple and effective as it does not have any fabrication and readout complications. In the past, some studies suggested that increasing the roughness of crystal lateral surfaces improves DOI resolution. In this paper, this was experimentally examined for four Ce:GAGG crystals with different surface structures. Four 1.2×1.2×20mm3 GAGG crystals with following surface treatment were examined: polished with optical finishing, fine grinding (using a fine surface grinding machine), fine cutting (no treatment), and coarse cutting (no treatment). These crystals were coupled individually to two SiPMs for dual-ended readout and placed in a coincidence detection circuit for electronic collimation of 511keV incidents. The crystals were compared in terms of energy response and DOI estimation capability. DOI function for each crystal was extracted and FWHM DOI resolution was calculated. DOI resolution for the polished crystal varied in the range of 0.54-4.14mm throughout the length of the crystal due to its nonlinear DOI function. The fine grinding crystal showed a linear DOI function within the dynamic range of (-0.75, 0.75), and its DOI resolution varied in the range of 1.24-1.50mm (1.37±0.13mm DOI resolution). The fine-cut crystal had almost a linear DOI function and a wider dynamic range of (-0.85, 0.85) and therefore the best performance with 1.2±0.08mm DOI resolution. However, for the crystal with the roughest surface (coarse-cut crystal), even though the dynamic range expanded to (-0.95, 0.95), its DOI function became nonlinear resulting in 1.24±0.28mm DOI resolution. This means there is an optimum surface roughness to provide the crystal with the best DOI capability. The pulse-height spectrum measured at each depth was used as a measure to compare the energy performance of the four crystals. The photopeak of 511keV was observed for all depths, all crystals. The photopeak position for the coarse-cut crystal had extensive depth dependency which results in poorer energy resolution unless the energy window is calibrated for each depth. This variation of photopeak for the fine-cut and fine grinding crystals was comparable with that of polished crystal. This paper reports 1.2±0.08mm FWHM DOI resolution for a fine-cut unpolished crystal. This resolution is as narrow as the crystal width, resulting in the complete elimination of parallax error in PET images. Results suggest that there is an optimum roughness for the best performance of the dual-ended method and further increase in the roughness, degrades DOI resolution. Thanks to the high light yield of GAGG, the energy performance of the fine-cut crystal is acceptable, and the depth dependency of the spectrum is negligible.

Grinding burn limits: Generation of surface layer modification charts for discontinuous profile grinding with analogy trials

By means of surface layer modification charts, the occurrence of thermal impact and thus the risk of grinding burn can be detected. With the present work it was shown that surface layer modification charts for discontinuous profile grinding can be generated using analogy trials carried out on a surface grinding machine for investigation of different grinding conditions and varied tilt angles in profile grinding. The experimental and the analysis effort for the analogy trials prove to be significantly more time and cost saving. The results also suggest that system parameters such as the grinding wheel specification or the cooling strategy are taken into account by the specific grinding power. Thus, the experimental results of this work allow the assumption that the determined process limit is not or just to a low extent depending on the system parameters. This assumption is supported by the thermal process limit determined by Malkin and converted in surface layer modification charts. Malkin's limit, identified for different ground steels with surface and cylindrical grinding processes and thus different system and process parameters, corresponds to the results generated in this work at workpieces ground with a kinematically more complex process. The results reveal that there is at least a group of steel materials which seems to share a similar thermal process limit.

소형 레일표면 연마장치의 제어 변수에 따른 연마 영향 분석

소형 레일표면 연마장치의 제어 변수에 따른 연마 영향 분석

WARNING WARNING OF PERFORMANCE GRINDING WHEELS OF EXTRACTIVE MATERIALS

When grinding circles, the working surface of which consists of periodically protrusions and depressions, in the elastic system of the machine due to the interruption of the cutting process there are high-frequency oscillations of small amplitude, which facilitate the process of chip formation and contribute to the formation of a developed cutting microrelief. However, at certain ratios of lengths of the cutting projections and depressions and at certain their quantities, parametric resonance may occur, which is a prerequisite for a periodic change in the stiffness time of the elastic system of the machine. Parametric resonance has a negative effect not only on the specific wear of the diamond kkol, but also on the quality of the machined surface. This implies the need for further exploration of the effect of parametric resonance arising from intermittent grinding on the relative flow of diamond circles. In the article, using the calculated and experimental ways, identified The extreme nature of the dependences of the specific wear of discontinuous circles of superhard materials on the number of slots on the working surface of the tool and on the ratio of the extent of the cavity to the length of the cutting ridge of the circle. Also, using the computational and experimental ways the characters of the influence of the dimensions and number of structural elements from which the working surface of diamond discontinuous circles was formed, as well as the rigidity of cutting on the parametric stability of the elastic system of a surface grinding machine, were revealed. The nature of the influence of the size and number of structural elements from which the working surface of diamond discontinuous wheels is formed, as well as the cutting rigidity on the parametric stability of the elastic system of the surface grinding machine is revealed by calculation and experiment.

Analysis of the Grinding Characteristics of β-Ga2O3 Crystal on Different Planes

The (010) and (100) planes of a [Formula: see text]-Ga2O3 crystal were subjected to precision grinding tests with a resin bond diamond grinding wheel on a precision surface grinding machine. The grinding characteristics and surface grinding quality of the planes of the [Formula: see text]-Ga2O3 crystal were analyzed on the basis of grinding force, grinding force ratio, specific energy, and surface morphology. The (010) plane shows a larger grinding force and specific energy but a smaller grinding force ratio compared with the (100) plane. Under experimental conditions, the normal and tangential grinding forces of the (010) plane are 1.4–2.2 and 2.6–7.8 times that of the (100) plane, respectively. The specific energy of the (010) plane is 2.8–6.1 times that of the (100) plane, and the grinding force ratio of the (100) plane is 1.4–3.7 times that of the (010) plane. Under the same grinding conditions, the material removal methods for the two planes are evidently different. The (010) plane is mainly removed by brittle fracture and accompanied by a minimal broken area, whereas the (100) plane is mainly removed by cleavage layering and exhibits numerous block cleavage. The (100) plane is the strong cleavage surface, and the (100) plane demonstrates a higher surface roughness than the (010) plane under the same grinding conditions.

On-machine angle measurement of a precision V-groove on a ceramic workpiece

The included angle of a V-groove on a large ceramic workpiece with a length of 500 mm is measured on an ultra-precision surface grinding machine. A pair of electronic dial gauges is mounted on the grinding wheel head to detect the ground flank surfaces of the groove. A calibrated artefact with identical material and nominal geometry but a shorter length of 100 mm is aligned side-by-side with the workpiece. The influences of machine scanning motion errors and thermal errors on the angle measurement are compensated through measuring the angular deviations of the V-grooves on the workpiece and on the artefact.

Performance assessment of a hybrid intermittent-progressive grinding strategy for bi-directional carbon fibre reinforced composites

In today’s era, fibre reinforced composites (FRCs) due to their superior mechanical properties are preferred over metals in various applications such as sports, automotive, aerospace, etc. Even though high-quality fabrication procedures for near-net FRC structures are reported, their employment in many of the functional applications demands machining operations to yield controlled geometric tolerances and surface finish. To meet surface integrity without severe damages, machining using abrasive grains may be a potential solution. However, owing to non-homogeneous and anisotropic nature of FRCs, continuous engagement of abrasive grains may lead to undesirable effects of grinding force such as fibre pull-out, fibre breakage, matrix failure etc. Intensity of these damages, which are sensitive to the type of fiber and fibre orientations, is observed to be proportional to the depth of cut maintained by the cutting edge. While grinding bi-directional and multi-directional carbon fibre laminate composites using conventional abrasive tools, the aforementioned surface defects become a serious concern. Present paper aims to investigate the performance of a hybrid grinding strategy for bi-directional carbon fibre-epoxy composites, introduced with a title “Eccentric Sleeve Grinding (ESG)”, combining the merits of both intermittent and progressive cutting, solely using a conventional surface grinding machine and non-super abrasive wheel. Cost-effective eccentric sleeves for grinding wheel assembly and associated control over cutting scheme have been adopted in the proposed technique to achieve minimal damage material removal. Eccentric sleeve grinding experiments on 0/90° bi-directional carbon fibre reinforced composite (CFRC) at a range of depth of cut has been carried out and assessed the machining performance using indices such as grinding force, grinding efficiency in terms of force ratio, grinding wheel wear and surface defects. Superior tribological behavior was observed in ESG through the enhancement of grinding force ratio, in addition to significant reduction in normal grinding force, grinding wheel wear and surface roughness. Microscopic analysis of composite surfaces after ESG could illustrate the effectiveness of progressive-intermittent cutting to yield a favorable surface topography, without severe damages as observed in conventional surface grinding at same depth of cut.

The Effect of Overlap Ratio and Silicon Carbide Wheel Grinder on Vibration Amplitude and Surface Roughness for Material OCR12VM.

This research aims to find out how big the effect of the overlap ratio and grit size silicon carbide wheel grinder to the vibration amplitude and surface roughness when grinding process and the corelation between the vibration amplitude and surface roughness. This research used the material hardened tool steel OCR12VM. This research using the surface grinding machine KGS818AH model and this research using a variation of process parameters namely 5 variations on the overlap ratio, 4 variations on grit size silicon carbide wheel grinder, 2 variations in the depth of the cut and this research using constant parameters namely constant spindle speed and constant longitudinal feed. The selection the type of abrasive and the selection process parameters (overlap ratio and grit size silicon carbide wheel grinder) can give a great impact on the increased vibration amplitude and surface roughness on material OCR12VM. The conclusion of this study is with increasing overlap ratio, the vibration amplitude and surface roughness will decrease and the finer the grit size silicon carbide wheel grinder, the vibration amplitude and surface roughness will be lower.

An eccentric sleeve grinding strategy for fibre-reinforced composites

Though Fibre Reinforced Composites (FRCs) can be manufactured with minimum damage using the state-of-the-art-innovative practices, inevitable machining operations on them during functional applications may invite further damages in matrix, fibre and interfaces. Surface grinding in its various capacities and hybrid forms has been demonstrated as one of the potential techniques for material removal in FRCs. However, effects of grinding forces on damages such as trans-laminar cracks in conventional grinding is proportional to the depth of cut for all fibre orientations. This paper introduces a new methodology referred to as eccentric sleeve grinding (ESG), with an intermittent progressive cutting strategy to minimize the machining defects on FRCs. Configuration of ESG will establish an eccentric grinding wheel rotation with cutting and non-cutting zones for abrasive grains, establishing a step-by-step cutting scheme without severe fibre-matrix fracture or fibre pull-out. A mathematical model for ESG is derived to assess the grinding forces and material removal, with experimental validation using conventional aluminium oxide wheel on bi-directional carbon fibre reinforced composite. The significantly lower magnitude of grinding forces, improved grinding force ratio and reduced surface roughness were observed in ESG, in comparison with conventional surface grinding for all the selected depths of cut from 20 to 100 μm. Microscopic topography studies on surfaces generated through conventional and eccentric sleeve grinding were clearly illustrating the effectiveness of the progressive cutting strategy in ESG. The ESG configuration presented in this paper can be adopted appropriately for minimal damage machining of FRCs, even using a traditional surface grinding machine.

GRINDING WHEEL MONITORING SYSTEM

It has been hypothesized that the change in the micro and macro geometry of the grinding wheel can be determined by a non-contact way by supplying jet of air through the nozzle of a pneumatic-electric-contact converter to the surface of the tool during operation. To confirm this hypothesis an experiment was did on a surface grinding machine. Various samples were machined, that led to self-sharpening of the tool. Grinding wheel monitoring system was developed for the experiments. System includes a device that provides the setting of the necessary working gap between the nozzle and the controlled wheel. A justification is proposed for determining the frequency of grinding wheel grinding during operation by accurately accounting for changes in the state of its surface without stopping the machining process.

Modeling and optimization of machining parameters during grinding of flat glass using response surface methodology and probabilistic uncertainty analysis based on Monte Carlo simulation

In this paper, the performance of diamond grinding wheels was investigated. The industrial diamond crystals with a size of 140/170 mesh were utilized. The microstructure of the grinding tool was observed using a Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Analysis Device (EDX). The experiments were designed using Box–Behnken method and optimum grinding parameters for glass were analytically determined. Experimental studies were carried out on a surface grinding machine in a flat glass factory. Grinding characteristics were examined with respect to surface roughness. The effects of grinding parameter on output responses were studied using analysis of variance (ANOVA). Probabilistic uncertainty analysis depends on Monte Carlo simulation was applied. Moreover, after the experiments using the optimized cutting parameters, the microstructure of the grinding wheels was analyzed. From results, the established model and optimization method could be employed for predicting surface roughness and this work is reliable and suitable for solving the problems encountered in machining operations. The lifetime of Cu-based grinding discs can be increased by adding Zn and Fe to the matrix material.

철도 전동소음 저감을 위한 자동화된 소형 레일표면 연마장치의 성능평가

철도 차량의 차륜과 레일의 불균형한 표면상태는 차량의 운영시에 상호접촉하여 전동소음(rolling noise)을 발생시키는 중요한 원인이 된다. 이러한 전동소음을 저감하기 위해서는 차륜과 레일 표면의 음향조도(acoustic roughness)를 측정·분석하여 기준치를 초과하는 경우에 차륜을 삭정하거나 레일표면 연마를 실시하는 등의 일정한 주기의 차륜 및 궤도의 유지보수가 필요하다. 따라서 본 연구에서는 레일표면을 미세하게 연마할 수 있도록 소형화 및 자동화된 연마장치를 개발하고 현장시험을 통하여 그 성능을 시험하였다. 특히, 시험궤도 레일의 단계적 연마를 수행하고 이에 따른 표면상태의 변화를 국제규정을 기준으로 비교하였으며, 연마 단계별 음향조도 레벨 분석을 통하여 레일 표면의 음향조도 변화에 의한 소음 저감 효과를 검증하였다.

Surface Texturing Potential on Carbide Insert in Reducing Aluminium Alloy Adhesiveness during Machining

Aluminum alloy is a widely used material which contributes greatly in numerous engineering applications. Aluminum alloy can be considered as having low strength and it is less likely to experience tooling difficulty. However, the complexity of machining aluminum alloy is related to its adhesive behavior, which capable to impede the machining operations where build-up-edge can be observed easily to occur. Since machining process generates a lot of energy due to friction and adhesive contact between tool and material, it is suggested to apply wet cutting method during machining of aluminum alloy to decrease the likeliness of aluminum alloy chip to adhere onto the tool surface. However, this method of machining is still having low effectiveness whereas the limitation of cutting fluid to enter the tool-chip sticking zone. Thus, the fabrication of textures on carbide insert rake surface is one of the predominant methods to enhance the sustainability of turning process with aluminum alloy workpiece. In this study, grinding process was utilized using Okamoto ACC52ST surface grinding machine to fabricate textures, where it is assumed that high effectiveness of lubricant can be retained and friction at tool-chip interface can be reduced. Turning process was conducted with the application of ROMI C420 lathe machine to investigate the adhesive behavior of aluminum alloy. It is observed that, the adhesive behavior of aluminum alloy was minimized with the application of textured carbide insert especially in wet cutting condition in general. Additionally, it can observed that, even at relatively high cutting speed and depth of cut, less adhesion behavior of aluminum alloy is obtained for textured carbide insert in wet cutting condition. This can be considered as a gain in productivity, whereas the adhesive behavior for non-textured carbide insert can only be reduced if only low cutting speed condition and wet cutting method are utilized.

OPTIMIZATION OF CYLINDRICAL GRINDING PROCESS PARAMETERS OF SS316L AUSTENTIC STAINLESS STEEL BY TAGUCHI METHOD

The main objective of this study is to optimize the cylindrical grinding parameters that can be utilized to predict optimal grinding parameters to achieve minimum surface roughness of a material. A SS 317L Austentic steel round rod of 80 mm x 168 mm was considered for cylindrical grinding in this study. Cutting speed, depth of cut and feed rate were chosen as input variables while Surface roughness (Ra) selected as output response. An L9 orthogonal array was selected for this study and S/N ratios were analyzed to study the surface roughness characteristics. Nine experiments were conducted in the surface grinding machine with different values of input parameters obtained from the orthogonal array. The surface roughness values were optimized in the optimization software (Minitab version 17) and the optimal solution was obtained for minimum response. Minimum surface roughness is achieved with 100 rpm cutting speed, 0.03 mm depth of cut and 1 mm/s feed rate. The confirmation experiments were conducted for the optimal solution obtained from Taguchi experiment and the results are verified.

Acoustic image-based damage identification of oxide aluminum grinding wheel during the dressing operation

Grinding is a finish process of parts that require high precision and tight dimensional tolerance, which owe high value-added. As the grinding process takes place, the cutting surface of the grinding wheel undergoes wear and then its cutting capacity is reduced. On the other hand, the dressing operation is responsible for restoring the cutting surface of the grinding wheel and, therefore, plays a key role in the grinding process. This work aims at obtaining acoustic images of the grinding wheel surface to identify its conditions during the dressing operation. Experimental tests were conducted with a single-point diamond dresser in a surface grinding machine, which was equipped with an oxide aluminum grinding wheel in which specific marks were intentionally made on its surface to simulate damages for identification. An acoustic emission sensor was fixed to the dresser holder and the signal were acquired at 5 MHz. The signal spectrum was investigated and a frequency band was carefully selected, which represented the conditions of grinding wheel surface. The root mean square values were then computed from the raw signal with and without filtering for several integration periods, and the acoustic images obtained. The results show that the proposed technique is efficient to identify the damage on the wheel surface during the dressing operation as well as its location.