Conventional Grinding Process Research Articles

An Investigation of the Efficient-Precise Continuous Electrochemical Grinding Process of Ti-6Al-4V.

Titanium alloys have many excellent characteristics, and they are widely used in aerospace, biomedicine, and precision engineering. Meanwhile, titanium alloys are difficult to machine and passivate readily. Electrochemical grinding (ECG) is an ideal technology for the efficient-precise machining of titanium alloys. In the ECG process of titanium alloys, the common approach of applying high voltage and active electrolytes to achieve high efficiency of material removal will lead to serious stray corrosion, and the time utilized for the subsequent finishing will be extended greatly. Therefore, the application of ECG in the field of high efficiency and precision machining of titanium alloys is limited. In order to address the aforementioned issues, the present study proposed an efficient-precise continuous ECG (E-P-C-ECG) process for Ti-6Al-4V applying high-pulsed voltage with an optimized duty cycle and low DC voltage in the efficient ECG stage and precise ECG stage, respectively, without changing the grinding wheel. According to the result of the passivation properties tests, the ideal electrolyte was selected. Optimization of the process parameters was implemented experimentally to improve the processing efficiency and precision of ECG of Ti-6Al-4V. Utilizing the process advantages of the proposed process, a thin-walled structure of Ti-6Al-4V was obtained with high efficiency and precision. Compared to the conventional mechanical grinding process, the compressive residual stress of the machined surface and the processing time were reduced by 90.5% and 63.3% respectively, and both the surface roughness and tool wear were obviously improved.

Multiphysics simulations of uniaxial compression applied to various rock samples subject to microwave pretreatment

PurposeAmong the various applications involving the use of microwave energy, its growing utility within the mining industry is particularly noteworthy. Conventional grinding processes are often overburdened by energy inefficiencies that are directly related to machine wear, pollution and rising project costs. In this work, we numerically investigate the effects of microwave pretreatment through a series of compression tests as a means to help mitigate these energy inefficiencies.Design/methodology/approachWe investigate the effects of microwave pretreatment on various rock samples, as quantified by uniaxial compression tests. In particular, we assign sample heterogeneity based on a Gaussian statistical distribution and invoke a damage model for elemental tensile and compressive stresses based on the maximum tensile stress and the Mohr–Coulomb theories, respectively. We further couple the electromagnetic, thermal and solid displacement relations using finite element modeling.Findings(1) Increased power intensity during microwave pretreatment results in decreased axial compressive stress. (2) Leveraging statistics to induce variable compressive and tensile strength can greatly facilitate sample heterogeneity and prove necessary for damage modeling. (3) There exists a nonlinear trend to the reduction in smax with increasing power levels, implying an optimum energy output efficiency to create the maximum degradation-power cost relationship.Originality/valuePrevious research in this area has been largely limited to two-dimensional thermo-electric models. The onset of high-performance computing has allowed for the development of high-fidelity, three-dimensional models with coupled equations for electromagnetics, heat transfer and solid mechanics.

Laser-assisted surface grinding of innovative superhard SiC-bonded diamond (DSiC) materials

Silicon carbide (SiC)-bonded diamond materials, comprising approximately 50% diamond by volume, represent innovative composites with exceptional mechanical and thermal properties, including high hardness, wear and corrosion resistance, and elevated thermal conductivity. Despite these advantageous properties, the machining of these composites presents formidable challenges due to their extremely high hardness. Grinding with diamond tools is commonly employed among the limited viable machining methods. However, the efficiency of this process is hindered by high grinding forces, elevated temperatures, and significantly high tool wear. Additionally, the surface integrity, form, and dimensional accuracy of the workpiece are compromised by the effects of tool wear and high cutting forces. To address these technological constraints in the grinding of SiC-bonded diamond materials, a laser-assisted grinding process has been developed. Ultra-short pulsed laser radiations were effectively utilized to induce material ablation with controlled structural damages, enhancing the productivity and efficiency of the grinding process through reduced grinding forces, temperatures, and tool wear. Furthermore, this study investigated the influence of grinding tools' specifications, design variations, and parameters on key aspects such as grinding forces, surface quality, and tool wear. Substantial reductions of up to 70% in tangential grinding forces, 83% in normal grinding forces, and a modest improvement in surface roughness achieved. The surface integrity analysis revealed a damage-free ground surface when utilizing laser assistance. Furthermore, there was a substantial enhancement in the grinding ratio (G-ratio), achieving an increase of up to 247%, concurrently with a noteworthy improvement in the actual removal depth, reaching up to 99%, when compared to conventional grinding processes. Compared to the utilized segmented metal bonded diamond grinding wheel, the vitrified bonded diamond grinding wheel induced lower grinding forces and higher actual removal rates.

An Experimental Investigation of the Effects of Dressing and Grinding Parameters on Sustainable Grinding of Inconel 738 Used for Automated Manufacturing

The significant effect of the dressing process on the surface of the grinding wheel (GW) and the need to provide an optimal dressing condition are the requirements of reduction machining time and energy consumption in the sustainable grinding process. In this study, for the first time, the results of changes in the parameters of the dressing process and changes in the topography of the grinding surface on the surface roughness of the Inconel 738 have been presented using single-edge and four-edge diamond dressers. The use of minimum quantity lubrication (MQL) and wet condition are other variables in this study to reduce the consumption of cutting fluid and prevent its destructive effects on the environment. The results indicate that the MQL technique increases the grinding performance of Inconel 738 by reducing ground workpiece surface roughness and decreasing the coolant–lubricant consumption comparing to the conventional wet grinding process. Additionally, it has been found from the experimental results that applying a single-edge dresser generates finer topography on the grinding wheel and, consequently, has a better surface finish in the grinding process compared to the multipoint diamond dressing tool with the same dressing and grinding parameters. In other words, increasing the dressing feed rate during dressing of the grinding wheel using a multipoint dresser makes a finer wheel surface topography and as a result decreases the surface roughness of the ground workpiece compared to a single-edge dresser. With multipoint diamond tools, the grinding performance during the life of the dressing tool also tends to remain more consistent, which is a definite advantage in automated production. Therefore, application of a multipoint dresser leads to a reduction in dressing time and increased production capability.

Thermal analysis of ultrasonic vibration-assisted grinding with moment-triangle heat sources

AISI 9310 steel has garnered increasing attention for its superior mechanical properties in the manufacturing of transmission gears for helicopters and accessory transmission systems in aero-engines. The ultrasonic vibration-assisted grinding (UVAG) technique is a new potential method to machine tooth surface given the periodically changing trajectory between abrasive grains and the workpiece, contributing to enhancing heat transfer and thus solving sudden burns. The accurate prediction of grinding heat and the proposal of the associated control strategy are desired to ensure the machining quality. Combined with the separation coefficient model and the chip volume distribution of UVAG processes, a new moment-triangle (MT) heat source model was established. Subsequently, comparative analyses on grinding temperature with conventional grinding and UVAG process were performed using the conditional triangular heat source model and the proposed MT heat source model. Results show that the MT heat source model has a lower prediction error with an average error of 7.13%, which is improved by 7.33% compared with that of the triangular heat source model. The prediction accuracy for the maximum grinding temperature can be raised by 13.39% when the MT heat source model is applied in place of the other one under UVAG processes. In addition, the heat source model transits from triangular into uniform heat source gradually as the ultrasonic amplitude increases, and the transition rate is positively correlated with the ultrasonic amplitude. On this basis, the desired controlling strategy is proposed to enhance the machining performance of ultrasonic grinding processes and effectively reduce heat generations during grinding by increasing the ultrasonic amplitude, reducing the depth of cut and decreasing the workpiece speed.

Key technologies for laser-assisted precision grinding of 3D C/C-SiC composites

Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.

An efficient method to obtain essential oil from Asarum heterotropoides via homogenate-microwave-assisted hydrodistillation and evaluation of Fusarium species inhibition activity in vitro compared to its main components

An improved method was investigated to obtain the essential oil from the roots and rhizomes of Asarum heterotropoides (RRAH) via homogenate-microwave-assisted hydrodistillation compare to conventional grinding process and the RRAH essential oil, methyleugenol, 3,4,5-trimethoxytoluene, and 3,5-dimethoxytoluene all had inhibitory effects on Fusarium species, with methyleugenol exhibiting the greatest inhibitory effect on them. We systematically explored some of the parameters that may affect the yield of essential oils. The maximum yield of the RRAH essential oil was 27.98 ± 1.4 mL/kg under the optimized conditions (22000 r/min homogenization speed, 3 min homogenization time, 460 W microwave irradiation power, 23 min microwave irradiation time and 23 mL/g liquidsolid ratio). Methyleugenol was the main component of RRAH essential oil (41.13%) analysed by GCMS. Studies on antifungal activity suggest that methyleugenol has potential and broad application prospects in the direction of preservative-related fields such as slow-release microencapsulation in the future.

Influence of cryogenic grinding surface on fatigue performance of carburised 27MnCr5

Automotive transmission components are subjected to cyclic loads and, thus, must have a reliable fatigue performance. Since fatigue cracks nucleate at the surface, it is necessary to guarantee that its surface integrity accomplishes the required specifications. Typically, those components are finished by wet grinding after carburising heat treatment. However, there is an increasing demand to reduce pollutants and hazardous lubricants in the industry, and eco-friendly finishing operations have been highly encouraged. To this end, it is necessary to understand the effect of these novel finishing processes on surface integrity and, consequently, on fatigue behaviour. This study aims to assess the surface integrity and the fatigue performance of cryo-ground surfaces of 27MnCr5 steel, extensively used in fabricating shafts and gears for gearboxes. Fatigue specimens for pure torsion tests were initially case-hardened and afterwards finished using two different cryogenic grinding conditions applying liquid N2 and, as a reference, using the conventional wet grinding process. First, the surface integrity was analysed in terms of texture, residual stresses, microstructure, and microhardness. Second, the batches of specimens were tested under pure torsion fatigue. Surface residual stress relaxation was also measured during fatigue tests. Finally, fracture surfaces were observed to identify crack initiation sites and establish correlations with the surface integrity. Specimens produced by cryogenic and conventional wet grinding did not show microstructural defects or hardness reductions in the carburised layer. All conditions induced compressive residual stresses, and they barely relaxed during fatigue tests. Compressive residual stresses induced by cryogenic grinding were 10–20% lower than those generated by conventional wet grinding. This decrease resulted in a minor reduction of the fatigue resistance (4–6%) compared to the wet grinding. Importantly, this study demonstrates that with a slight geometrical radio correction in the design of the mechanical components (around 2.2%), cryogenic grinding generates pieces with the same fatigue strength as conventional grinding. Therefore, it confirms that cryogenic cooling could be a potential solution to replace pollutant coolant/lubricant fluid in grinding operations.

Experimental study on ultrasonic vibration-assisted grinding of hardened steel using white corundum wheel

The combination of ultrasonic vibration-assisted grinding (UVAG), the ultrasonic vibrating method, and the conventional grinding (CG) process is proposed to improve the grindability of hardened steel in the CG process. Comparative investigations on grinding force, temperature, and specific grinding energy for both grinding processes were conducted. In addition, the morphologies of the wheel wear and ground surfaces were also studied. Findings show that compared with the CG processes, the normal and tangential grinding forces in UVAG are reduced greatly by 16.44% and 17.44%, respectively. The UVAG process decreases the specific grinding energy by 8.30% owing to the increase of the maximum undeformed chip thickness and the grinding temperature by 19.01% due to the improvement of the coolant heat transfer capacity in the grinding arc zone. Meanwhile, the promising grain sharpness of wheels can be guaranteed from the enhanced cooling function on the grinding arc zone and the grain’s micro-fracture caused by ultrasonic impacting actions.

Parametric study of indigenously developed electrochemical diamond cut-off grinding setup using Inconel 925

Electrochemical grinding (ECG) is a combination of electrochemical machining and conventional grinding processes, and when the diamond is used as an abrasive particle in a grinding wheel, the process is called electrochemical diamond grinding. This process is useful for machining newly developed and difficult-to-cut conductive materials. In this paper, the authors have performed an experiment on an indigenous developed electrochemical diamond cut-off grinding (ECDCG) setup for nickel-based superalloy (Inconel 925) by applying one parameter at a time (OPAT) method. The parametric study of material removal rate (MRR), surface roughness (Ra), and overcut has been done. It also includes morphological study of the machined surface. It was noticed that MRR improves, with increment in any machining parameters, while better Ra can be observed at the moderate value of supply voltage and electrolyte concentration. Moreover, it was also found that, the overcut has been decreased with increase in wheel speed and feed rate.

Analysis of surface roughness during Machining of AISI H-13 steel using EDDFG

Electric Discharge Machining (EDM) is well known AMP as it can easily machine the complex shaped, hard, and difficult to machine materials. EDM involves removal of material by thermal erosion, due to which recast layer may be formed and the surface quality may degrade. To reduce recast layer generation and improvement of surface quality, Electric discharge face grinding is developed. Electric discharge face grinding process is a HMP in which material removal occurs by mechanical abrasion as in conventional grinding process and thermal erosion as in EDM. Surface roughness is important aspect in analyzing the surface quality of the processed product. This paper shows the impact of input parameters viz. Ton, Ip, and Toff on ASR during machining of AISI H-13 steel workpiece. Influence of tool RPM on MRR is also studied. After performing experiments using ‘one parameter at a time’ strategy, it was found that by increasing tool RPM, MRR first increases then decreases. It was also found that by increasing Ton & Ip, ASR increases and by increasing pulse off time, average surface roughness first decreases then increases.

Effect of innovative finishing operations on the tribological performance of steel 27MnCr5

Transmission shafts used in the automotive sector must have a good tribological performance, and therefore an enhanced surface integrity. This paper aims to study the effect of eco-friendly innovative finishing operations (belt finishing, cryogenic grinding and dry grinding) on the surface integrity and tribological performance of steel grade 27MnCr5, and compare to the behavior of components produced by conventional wet grinding process. For that purpose, a total of seven finishing conditions were analysed: wet grinding as reference, two dry grinding conditions, two cryogenic grinding conditions and two hard turning+belt finishing conditions. The surface integrity (roughness, residual stresses, hardness and microstructural defects) of samples was assessed. Finally, the step-loading test method was used to determine the scuffing resistance of the samples. Tested innovative finishing operations led to higher scuffing resistance than conventional wet grinding. Results demonstrate that higher surface hardness and roughness leads to higher scuffing resistance, while the effect of surface residual stresses is not significant.

Study on the Influence of Amplitude on Ultrasonic Assisted Grinding of Hard and Brittle Materials

With the development of advanced manufacturing technology, ceramic matrix composite materials, a typically hard and brittle material, have been widely used in high-tech fields such as aerospace manufacturing. Due to the anisotropy of materials, the quality of conventional processing workpieces is poor, and the processing accuracy is difficult to guarantee. In this experiment, ceramic matrix composite materials are machined by ultrasonic vibration grinding with the CBN grinding rods. The influence of amplitude on the grinding force and the surface quality of the workpiece in the grinding process are analyzed by a series of experiments on ceramic matrix composites. The results show that, compared with the conventional grinding process, in the ultrasonic vibration-assisted grinding process, the grinding force is reduced by about 60%, and the surface quality is also improved significantly,the surface roughness Sa is reduced by about 25%.

Development of a new high-shear and low-pressure grinding wheel and its grinding characteristics for Inconel718 alloy

Nickel-based alloy has been widely used due to its outstanding mechanical properties. However, Nickel-based alloy is a typical difficult-to-machine material, which is a great constrain for its application in the manufacturing field. To improve the surface quality of the ground workpiece, a new high-shear and low-pressure grinding wheel, with high ratio of tangential grinding force to normal grinding force, was fabricated for the grinding of selective laser melting (SLM) manufactured Inconel718 alloy. The principle of high-shear and low-pressure grinding process was introduced in detail, which was quite different from the conventional grinding process. The fabrication process of the new grinding wheel was illustrated. A serial of experiments with different processing parameters were carried out to investigate the grinding performance of the developed grinding wheel via analyzing surface roughness and surface morphology of the ground workpiece. The optimal processing parameters of high-shear and low-pressure grinding were obtained. The surface roughness of ground workpiece was reduced to 0.232 μm from the initial value of 0.490 μm under the optimal grinding conditions. It was found that the initial scratches on the ground workpiece were almost completely removed after the observations with the metalloscopy and the field-emission scanning electron microscopy (FE-SEM). The capability of the newly developed high-shear and low-pressure grinding wheel was validated.

Optimization of Machining Parameters in Hard Turning of Automotive Gears with PCBN tool using Taguchi Method

Hard turning, a comparatively modern machining technology, can replace the conventional grinding process for finishing of parts made out of steel. Nowadays, industries prefer hard turning to grinding. This is due to some of the most distinctive features of hard turning over grinding, such as lower machining time and manufacturing cost, and the achievement of grinding equivalent quality characteristics on parts and machining can be possible in a dry environment, which eliminates the hazardous effect of cooling media used during machining on the environment and humans. However, in hard turning, machining parameters (cutting speed-vc, depth of cut-ap, and feed rate-f) are critical for achieving specified quality attributes and establishing a cost-effective setup. The influence of machining parameters on workpiece surface roughness (Ra) and tool flank wear (VB) has been investigated in this research using the Taguchi Design of Experiment (DOE) approach, as well as signal to noise (S/N) ratio, and Analysis of variance (ANOVA) techniques. The experiments have been carried out on automotive gear made of SAE-AISI 5120-compliant 20Mn5Cr5 alloyed hardened steel. The CBN cutting tool has been used for this research.

The Performance of Polycrystalline Diamond (PCD) Tools Machined by Abrasive Grinding and Electrical Discharge Grinding (EDG) in High-Speed Turning

Polycrystalline diamond (PCD) tools are widely used in industry due to their outstanding physical properties. However, the ultra-high hardness of PCD significantly limits the machining efficiency of conventional abrasive grinding processes, which are utilized to manufacture PCD tools. In contrast, electrical discharge grinding (EDG) has significantly higher machining efficiency because of its unique material removal mechanism. In this study, the quality and performance of PCD tools machined by abrasive grinding and EDG were investigated. The performance of cutting tools consisted of different PCD materials was tested by high-speed turning of titanium alloy Ti6Al4V. Flank wear and crater wear were investigated by analyzing the worn profile, micro morphology, chemical decomposition, and cutting forces. The results showed that an adhesive-abrasive process dominated the processes of flank wear and crater wear. Tool material loss in the wear process was caused by the development of thermal cracks. The development of PCD tools’ wear made of small-sized diamond grains was a steady adhesion-abrasion process without any catastrophic damage. In contrast, a large-scale fracture happened in the wear process of PCD tools made of large-sized diamond grains. Adhesive wear was more severe on the PCD tools machined by EDG.

Effects of grinding and dehydration on kaolin in a steam jet mill

AbstractSteam jet milling was applied for the first time to ultra-fine grind the filter cake (moisture content 23.80%) produced by a kaolin concentrator. The material was dehydrated and dried simultaneously during grinding, and the final ground sample met the moisture content requirement for powder products of <2%. The particle size of the ground kaolin samples decreased and the particle-size distribution was more concentrated, indicating that the steam jet milling was more effective for kaolin processing than the conventional dry grinding process. In addition, steam jet milling can improve the whiteness and decrease the crystal order of the samples, thus improving the kaolin properties in follow-up applications.

Multi-objective optimization of high-speed turning parameters for hardened AISI S7 tool steel using grey relational analysis

Nowadays, die manufacturing industries prefer eco-friendly machining, i.e., high-speed turning for hardened AISI S7 tool steel followed by the conventional grinding process. The effectiveness of this eco-friendly turning depends on selection of appropriate process parameters, which decides the surface integrity of machined components. Hence, the first objective of present research work is to optimize the turning parameters for lower cutting force, machining temperature, surface roughness and higher material removal rate simultaneously using grey relational analysis (GRA). ANOVA utilized to identify the significant effect of each turning parameter on the response variables. Secondly, the effects of turning parameters such as tool nose radius (Rn), cutting speed (Vc), feed rate (Vf) and depth of cut (dc) on tool wear and finished surface topography were studied through scanning electron microscopy (SEM) and atomic force microscope (AFM). Optimal turning parameters for multi-performance responses were Rn: 1.2 mm, Vc: 450 m/min, Vf: 0.05 mm/rev and dc: 0.2 mm. The confirmation test was conducted on the optimal parameter level. According to ANOVA, depth of cut was the major influencing factor on all response variables. AFM and SEM micrograph indicated that excellent surface quality with lower surface roughness (Sa: 64.21 nm and Sq: 90.34 nm) was observed at higher cutting speed. Flank and crater wear were observed in cutting tool faces owing to thermo-mechanical loading. Different wear mechanisms like abrasion, adhesion, built-up edge formation and chipping hammering were found in the alumina-mixed ceramic insert at higher cutting speed and depth of cut.

An efficient material removal rate prediction model for cemented carbide inserts chemical mechanical polishing

Aiming at the defects of cemented carbide inserts surfaces produced in the conventional grinding process, a cemented carbide inserts chemical mechanical polishing (CMP) process is developed to reduce the insert rake face roughness for the improvement of cutting performance. Especially, an efficient material removal rate (MRR) prediction model for cemented carbide inserts CMP is established considering synthesized effects of multi-factors characteristics such as abrasive particles, the polishing pad, and cemented carbide inserts. Firstly, the contact mechanism between the cemented carbide insert and the polishing pad is analyzed by using the Greenwood and Williamson elastic model. Then the contact model between the abrasive particle and the polishing pad is established based on the Sneddon's hyper-elastic micro-contact mechanics, and the contact model between the abrasive particle and the cemented carbide insert is built by applying the elastic-plastic micro-contact mechanics. Finally, an efficient MRR prediction model is proposed. The experimental results show that when changing the polishing pressure and the polishing disk rotational speed individually, the MRR average error between the predicted value and the experimental value is 1.65% and 2.18%, respectively. This study demonstrates that the proposed model can contribute to CMP preparation of high-performance cemented carbide tools/inserts.

The effects of elliptical ultrasonic vibration in surface machining of CFRP composites using rotary ultrasonic machining

Compared with conventional surface grinding (CSG) process, surface machining of carbon fiber-reinforced plastic (CFRP) composites using rotary ultrasonic machining (RUM) with vertical ultrasonic vibration generates smaller cutting forces because of improved machining performance and more damages to the machined CFRP surface due to the intermittent knocking induced by vertical ultrasonic vibration. It is reported that surface quality can be improved when the ultrasonic vibration is parallel to the feeding direction. In addition, elliptical ultrasonic vibration can be formed by the combination of horizontal and vertical ultrasonic vibrations. However, the effects of elliptical ultrasonic vibration in RUM surface machining of CFRPs are still unknown. This paper will study the influences of elliptical ultrasonic vibration on the machining performance and machined surface quality in RUM surface machining of CFRPs. The comparisons of output variables (including cutting forces, surface roughness, and machined surface topography) between RUM surface machining with elliptical ultrasonic vibration and the CSG process as well as RUM surface machining with vertical ultrasonic vibration will be conducted under different levels of input variables (including depth of cut, feedrate, and tool rotation speed). The abrasive-grain trajectory and the tool-workpiece contacting modes in these three machining processes are analyzed. It is found that RUM surface machining with elliptical ultrasonic vibration produced smallest feeding-direction cutting force, smallest vertical-direction cutting force, best morphology of machined surface, and smallest surface roughness among these three kinds of machining processes.