Conventional Surface Grinding Research Articles

Influence of ultrasonic vibration on machining quality of down/up grinding in ultrasonic vibration assisted grinding of silicon carbide

Conventional surface grinding can be divided into up grinding and down grinding according to rotation direction of spindle. Nevertheless, the effects and differences of ultrasonic vibration on the two machining methods have been less reported. The influence of ultrasonic vibration amplitude on cutting force, surface roughness and surface topography were investigated in this paper by conducting tangential and radial ultrasonic vibration assisted down/up grinding comparison experiments on SiC. The results showed that the grinding force of down grinding was less than that of up grinding in conventional grinding, while the surface roughness was greater than that of up grinding. The grinding forces of both down grinding and up grinding were reduced to different ratios after applying different ultrasonic vibration, while the surface roughness increased. The grinding force of up grinding decreased and then increased with the increase of amplitude, while the grinding force of down grinding kept decreasing and the surface roughness decreased. The reasons for the differences in cutting forces and surface quality between the two grinding methods after the application of ultrasonic vibration are discussed. By observing the surface morphology, the percentage of ductile area on the machined surface decreases and then increases with the increase of amplitude.

Thermal investigations on eccentric sleeve grinding of fibre reinforced composites

Thermal driven damages are one of the major concerns while machining fibre reinforced polymer (FRP) composites. Though cutting of fibre-matrix system using abrasive grains exhibited promising outcomes, conventional surface grinding (CSG) still poses the barriers of undesired surface damages on FRPs. High magnitudes of grinding forces due to continuous interaction of cutting edges, particularly at higher levels of depths of cut, leads to successive accumulation of heat flux in CSG and thereby, the thermal damages on fibre-matrix system may get enhanced. Eccentric Sleeve Grinding (ESG) is a unique grinding strategy proposed for FRPs, which adopts a progressive-intermittent cutting scheme capable of reducing grinding temperature and thermally triggered damages. Main focus of this paper is to investigate the thermal aspects of eccentric sleeve grinding and develop an analytical model for grinding temperature in ESG. Considering the unique cutting scheme followed by abrasive grains during their interaction with FRP, a progressively distributed-moving heat source model is introduced. The model is capable of predicting grinding temperature on FRP surfaces, during CSG as well as ESG at various grinding conditions, and thereby illustrates the merits of proposed ESG scheme. A thermal flux model using a cylindrical surface source is also introduced to study the temperature generated at the grinding wheel during its interaction with FRP. This paper also presents an attempt of 3D grinding simulation, both in ESG and CSG mode, with realistic modelling of CFRP and grinding wheel using Composite Modeler in ABAQUS. Thorough experimental investigation, incorporating the measurement of grinding force and temperature, is also covered to demonstrate ESG process and its thermal performance on Carbon Fibre Reinforced Polymer (CFRP) composites. 30 % and 10 % reduction, respectively, in average and peak grinding temperature during ESG of CFRP and subsequent reduction in thermal damages opens great avenues for industrial applications.

Feasibility studies on wet grinding of carbon fibre reinforced epoxy polymer at minimum defect condition via eccentric sleeve grinding

Although surface grinding is reported to be capable of precision material removal in carbon fibre reinforced epoxy polymer composites (CFRPs), it is highly limited by deprived cutting temperature dissipation, tool wear and sensitivity to undesired cutting defects. Continuous engagement of abrasive grains and successive accumulation of heat at cutting interface in conventional surface grinding results in severe surface damages. Though the controlled application of cutting fluids exhibited improved surface integrity, entrapment of fluid droplets into the defective zones/cracks of fibre, matrix and its interfaces are shown to be stimulating further defect propagation. Present paper investigates the feasibility of improving cutting fluid application in CFRP grinding, establishing a minimum surface defect condition through eccentric sleeve grinding (ESG). The reduction of post-grinding surface defects through an intermittent-progressive cutting scheme in ESG is demonstrated and the efficacy of cutting fluids in such a grinding scheme is illustrated through the comparison of grinding forces and surface characteristics.

Simulation of intermittent grinding for Ti-6Al-4V with segmented wheel

Abstract Titanium alloy-Ti-6Al-4V, in spite of all its superior mechanical characteristics and functional acceptance, is categorized as a difficult-to-cut super alloy. Major concerns associated with conventional surface grinding of Ti-6Al-4V is its poor thermal conductivity, grinding burn, high tendency of hardening during machining as well as chemical affinity with wheel materials. Higher magnitudes of grinding force and temperature reported during conventional grinding may lead to adverse burning effects and associated concerns such as micro-cracking etc. on the ground surface. Present paper is a simulation study to showcase the capability of intermittent-segmented grinding to eliminate such concerns. A comparison of intermittent segmented cutting with conventional abrasive action in continuous mode is presented through a 3D finite element model in ABAQUS. The effectiveness of intermittent-segmented cutting to control grinding temperature well below the critical limit to avoid burning effects on Ti-6Al-6 V, with a significant reduction in grinding force is illustrated through the present simulation study.

Laser polished fused deposition poly-lactic acid objects for personalized orthopaedic application

Patient-specific surgical guides are increasingly demanded. Material Extrusion (ME) is a popular 3D printing technique to fabricate personalized surgical guides. However, the ME process usually generates deleterious surface topography which is not suitable for orthopaedic emergencies. We designed and optimized parametric combinations of a laser polishing approach as post process to improve the surface quality of ME-made poly-lactic acid (PLA) objects. In this study, we investigated the contribution of processing variables to the mechanical properties and the biocompatibilities in vitro of the ME-made PLA objects. Conventional surface grinding was conducted as comparison. The results demonstrate that the ME-made PLA samples exhibit good mechanical properties and favourable biocompatibility after being post processed using laser polishing. The post laser polishing, as a powerful tool in manufacture of ME-made PLA objects, will open a new approach with a great promise in its applications in personalized and timely management of medical emergencies.

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.

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.

Material removal mechanism in rotary in-feed grinding - Modeling and analysis -

The rotary in-feed grinding is the most promising process to ensure the controllability of wafer geometry including the thickness and flatness. This makes it be widely applied into manufacturing of mono-crystal wafers, such as silicon, silicon carbide, sapphire, lithium tantalate, and etc. Unlike the conventional surface grinding, however, the rotary in-feed grinding is a complex material removal operation in which the extent of interaction between the abrasives and wafer keeps varying during the wheel/wafer contact zone. Such characteristic property significantly influences the chip formation, the homogeneousness of surface topography, the variations in grinding forces and the power consumption in the radial direction of the wafer. In this paper, the grinding mechanisms including the geometry, statics and surface topography were theoretically analyzed on a proposed grinding model and organized as follows. Described in Section 2 is the geometric analysis which mathematically expresses the wafer profile and a variety of information regarding to the dimensions of chip formed. The results suggest that the chip cross section increases proportionally as increasing in the wafer radial distance. Based on the results of chip formation, the grinding forces respectively exerted on an individual abrasive, a single wheel segment and whole wafer are calculated in the Section 3. Also, the necessary grinding power and generated grinding heat are estimated by statics analysis. In the Section 4, the surface roughness and its variation in a radial direction of the wafer are then derived by taking into consideration of the distribution of abrasive protrusion in height-wise.

Analytical and experimental investigations on the mechanisms of surface generation in micro grinding

Micro grinding is an emerging technology for producing structured surfaces on hard and brittle materials. A micro pencil grinding tool (MPGT) consists of a layer of superabrasive grits, bonded to a solid cylindrical surface. Randomly distributed and geometrically undefined grits interact with the workpiece surface at random positions. These random grit positions and protrusions lead to a difference in the size of undeformed chips. This study presents an analytical method to understand the undeformed chip geometry, that considers grit kinematics. Kinematic simulation of grit trajectory paths in longitudinal direction showed a reduced number of active grits in micro grinding with an increase in speed ratio and with reduced tool dimensions. MPGTs with different diameters, grit sizes, and planar grit densities have been used to perform the experiments on a 16MnCr5 hardened steel material. The influence of maximum radial height grits on surface generation in micro grinding has been verified experimentally for up and down grinding modes. Microscopic observations of ground surfaces have shown the distinct differences between up and down grinding modes, which are similar to the surface generation in milling processes. Moreover, the formation of linear grooves with uniform depth and width unlike conventional surface grinding at lower speed ratios indicated the influence of individual grits on surface generation. Trajectory path simulation results have also shown the same observation.

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.

Model and formulation in grinding mechanism having advanced secondary rotational axis

“Grinding Mechanism having Advanced Secondary Rotational Axis” is one of the newer plane surface grinding methods that has an uncommon abrasion mechanism. Unlike conventional methods, in Grinding Mechanism having Advanced Secondary Rotational Axis, there are two rotations of a wheel. The first rotation is the same as the conventional grinding methods, which is the circumferential rotation. The other rotation is the newly developed axial rotation, where the wheel rotates around itself perpendicular to its radial axis. In the grinding process, the grinding force, energy, power, and temperature are directly related to the material removal rate. In this article, the chip model in Grinding Mechanism having Advanced Secondary Rotational Axis was addressed and material removal rate was reformulated. The new chip ratio formula was adapted to the grinding force, energy, power, and temperature in the conventional plane surface grinding method. The chip formed in the conventional plane surface grinding method consists of two-dimensional xy plane. In Grinding Mechanism having Advanced Secondary Rotational Axis, on the other hand, the chips consist of three-dimensional xyz plane. The reason behind this is the second rotation obtained in Grinding Mechanism having Advanced Secondary Rotational Axis (axial rotational motion). The chip model was obtained from the combination of two rotations in Grinding Mechanism having Advanced Secondary Rotational Axis. As a result, the resulting chip model increased the material removal rate only slightly and this increase was negligible. Accordingly, an increase in grinding force, energy, power, and temperature was observed at negligible rates.

Rotary ultrasonic surface machining of CFRP composites: Effects of horizontal ultrasonic vibration

Abstract Carbon fiber reinforced plastic (CFRP) composites are popular in many industries due to their superior properties. However, many problems, including high cutting forces, high tool wear, high surface roughness, etc., are generated in conventional surface grinding (CSG) processes, due to the carbon fibers’ abrasive property as well as the inhomogeneous and anisotropic properties of CFRPs. Rotary ultrasonic surface machining (RUSM) with vertical ultrasonic vibration has been proven to be effective to reduce cutting forces. However, this process produces larger surface roughness than CSG because of vertical ultrasonic vibration. To solve this issue, RUSM with horizontal ultrasonic vibration is developed in this investigation. The comparisons between CSG and RUSM with horizontal ultrasonic vibration are conducted. The kinematic motions of abrasive grains in both processes are discussed and analyzed. Effects of input variables (including tool rotation speed, feedrate, and depth of cut) on output variables (including cutting forces and surface roughness) are also investigated in both CSG and RUSM processes. RUSM with horizontal ultrasonic vibration is proven to be an effective machining method for reducing cutting forces and simultaneously improving machined surface quality.

A Recent Investigations: Effect of Surface Grinding on CFRP using Rotary Ultrasonic Machining

Abstract The industrial scenario demands the product to be produced in higher surface finish with minimum tool wear. Grinding is predominantly known to provide excellent surface finish among other machining processes. The scope for improvement is always exists in the processes. In the meantime, Material Removal Rate (MRR) of the procedure ought not to be affected. Since, it directly affects the productivity of the process. The composite Carbon Fibre Reinforced Plastic (CFRP) has preferred properties involving high strength-over weight extent, high shortcoming restriction, high modulus-to-weight extent, etc. Due to the non-uniform and varying in magnitude, high gratings /abrasiveness and high strength ability of the reinforcement in CFRP composites, results in difficult to-cut (surface materials) in surface grinding shapes. The conventional surface grinding process on CFRP requires high cutting force at the same time material removal rate is low. In request to decrease and eliminate these intricacies, Rotary Ultrasonic Machining (RUM) is favoured for surface grinding of CFRP composites. In this paper, interdisciplinary reviews on CFRP composites have been done under the reaction of surface grinding of the composite using rotary ultrasonic machining. This paper will give the guidelines to future research in impacts on CFRP under RUM observational studies.

Edge surface grinding of CFRP composites using rotary ultrasonic machining: comparison of two machining methods

Edge surface grinding has been widely applied in achieving functional surfaces and repairing the damage surfaces of carbon fiber–reinforced plastic (CFRP) composites especially with complex three-dimensional features. The conventional surface grinding (CSG) usually generates surface damages, leading to reduced service life and load-carrying capability of the parts. Therefore, there is a critical need to develop a surface grinding process of CFRP composites in a high-quality and high-efficiency way. Rotary ultrasonic machining (RUM) surface grinding has been proven to be such a process. In addition, RUM edge surface grinding can be conducted by up surface grinding or down surface grinding. However, the difference between up surface grinding and down surface grinding with RUM has not been reported. In this paper, the comparison between up surface grinding and down surface grinding with RUM is studied for the first time. The effects of the grinding parameters on machining performance, including cutting force, surface roughness, and surface morphology characteristics, are experimentally studied. The results show that the cutting forces in up grinding are obviously larger than those in down grinding. Lower surface roughness is generated by down grinding when grinding parameters are kept unchanged. The reasons for the differences of cutting forces and surface integrity are discussed. Surface morphologies suggest clearly that brittle fracture is the predominant material removal mode in grinding of CFRP composites. The chip size of the resin, the fracture size of the carbon fiber, and the material removal scale are smaller in down grinding. Furthermore, compared with CSG, the advantages of RUM surface grinding are presented. This investigation will provide useful guidance for surface grinding of CFRP composites.

A study on the effects of machining variables in surface grinding of CFRP composites using rotary ultrasonic machining

Due to their excellent properties, carbon fiber-reinforced plastic (CFRP) composites are attractive in many industries, including aerospace, automobile, sports, etc. The structure of anisotropy and heterogeneity and the high abrasive resistance of carbon fibers make CFRPs difficult to cut in surface grinding processes. Many problems, including high cutting force, high tool wear, severe delamination, and high cutting temperature, are associated with conventional surface grinding processes. To reduce or eliminate these problems, surface grinding of CFRP composites using rotary ultrasonic machining (RUM) has been conducted. Machining variables play dominant roles in such a process. However, no investigations on effects of machining variables on output variables were reported. This paper, for the first time, reports effects of machining variables (ultrasonic power, tool rotation speed, feed rate, and depth of cut) on output variables (cutting force, torque, and surface roughness). The results revealed that the cutting force could be decreased by using higher level of ultrasonic power, higher level of tool rotation speed, lower level of feed rate, or lower level of depth of cut. Lower surface roughness could be achieved by a decrease of ultrasonic power, an increase of tool rotation speed, a decrease of feed rate, or a decrease of depth of cut. The machined CFRP surfaces’ morphology and the characteristics of damaged carbon fibers were, for the first time, analyzed and reported in such a process.

Rotary Ultrasonic Surface Machining of CFRP Composites: A Comparison with Conventional Surface Grinding

Rotary ultrasonic machining (RUM), a hybrid nontraditional process technology combining ultrasonic machining and grinding, has been proven to be a promising method for hole making of CFRP. Due to its advanced capabilities, RUM has been further extendedly applied in surface machining: rotary ultrasonic surface machining (RUSM). Carbon fiber reinforced plastic (CFRP) composites have found extensive applications in areas such as aerospace, automotive, and sports due to their superior material properties. CFRP components are usually near net shaped after molding processes, however, additional surface machining is still required to generate the final dimensions and functional surfaces of the advanced CFRP components especially with three-dimensional features. However, the investigations on RUSM of CFRP are very limited and there are no reported studies on comparisons between RUSM and conventional surface grinding (CSG) of CFRP. In this paper, for the first time, a comparative study between these two processes of CFRP in the aspects of axial and infeed-directional cutting forces, torque, and surface roughness is conducted. In order to better understand the material removal differences between these two processes, the kinematic motions of the abrasive grains are also analyzed and compared.

Characterization of surface polishing with spindle mounted abrasive disk-type filament tool for manufacturing of machine tool sliding guideways

In order to expand the regional production of machine tools which utilize precision machined sliding guideways, cubic boron nitride (CBN) hard milling may be implemented as an alternative finish process instead of conventional surface grinding. While higher material removal rates can be achieved with a milling strategy, the use of a defined cutting edge leads to surfaces with asperities. These sharp peaks quickly wear down during sliding contact, resulting in unacceptable changes in the load bearing surface of the guide. Therefore, a post process to milling must be implemented to mitigate these features. This paper investigates the use of a spindle mounted abrasive disk filament tool for producing a functional surface similar to the ground surfaces. The optimal process parameters were investigated using 2D profile measurements, followed by comparison using areal analysis of ground, milled, and polished surfaces. It was found that polishing reduces both the height and volume of asperities on the milled surface, leading to contact characteristics which were more similar to those of the conventional ground surfaces currently used for sliding guideways.

Modelling and Simulation of Grinding Processes with Mounted Points: Part II of II - Fast Modelling Method for Workpiece Surface Prediction

Due to the importance of high surface quality of machined parts, considering its functional requirements, it is important to select a proper set of grinding parameters. Experimental trials are material, energy and time consuming. Therefore it is relevant for the industry to use a roughness model capable of simulating different grinding kinematics with different sets of parameters. This paper presents a fast and reliable method, for the NC-grinding process with abrasive mounted points, to reach this demand. In order to achieve this, numerical and empirical experiments were conducted proving the feasibility of the model for conventional, oscillating and tilt surface grinding.

Experimental investigation on the effects of different heat treatment processes on grinding machinability and surface integrity of 9Mn2V

This paper investigated the grinding machinability and surface integrity of premium thread gauge material 9Mn2V in conventional surface grinding by using seeded gel (SG) abrasive (3SG80KV) under different heat treatment processes. Serious meshy segregation of carbide, excessive amounts of retained austenite, coarse and inhomogeneous distribution of material structure were significant causes of grinding burn and grinding crack. In order to improve the abrasion resistance and mechanical properties of workpiece material, cryogenic and tempering treatment was added. After adopting cryogenic and tempering treatment for two times, the disappearance of the meshy segregated carbide and network carbide was eliminated, the amount of the retained austenite content was within 4 %, and martensite became much more fine and homogeneous. The grinding experiment results indicated that workpiece material 9Mn2V could provide superior grinding integrity with the occurrence of grinding burn and grinding cracks reduced by using this process.

Experimental study on grinding force and grinding temperature of Aermet 100 steel in surface grinding

This paper investigates grinding force and grinding temperature of ultra-high strength steel Aermet 100 in conventional surface grinding using a single alumina wheel, a white alumina wheel and a cubic boron nitride wheel. First, mathematical models of grinding force and grinding temperature for three wheels were established. Then, the role of chip formation force and friction force in grinding force was investigated and thermal distribution in contact zone between workpiece and wheel was analyzed based on the mathematical model. The experimental result indicated that the minimum grinding force and the maximum grinding force ratio under the same grinding parameters can be achieved when using a CBN wheel and a single alumina wheel, respectively. When the phenomenon of large grinding force and high grinding temperature appeared, the workpiece material would adhere locally to the single alumina wheel. Grinding temperature was in a high state under the effect of two main aspects: poor thermal properties of grinding wheel and low coolant efficiency. The predicted value of grinding force and grinding temperature were compared with those experimentally obtained and the results show a reasonable agreement.