Analytical and Experimental Study of Grinding Forces with Flap Wheels

Analytically, the dependences for calculating the grinding forces with flap wheels are obtained. The forces were defined as the sum of the forces associated with dispersion and friction of the cutting and plastically deforming petal grains against the workpiece. The dependencies take into account the change in the depth of penetration of the grain into the workpiece material along the length of the arc of the contact of the circle with the workpiece. Numerical modeling and experimental study of forces have been carried out. The discrepancy between the calculated and experimental values of the forces does not exceed 20%.

Effect of Graphene nanoplatelets (GNP) reinforcement on grindability of zirconium diboride ceramics

The grindability of graphene nanoplatelets (GNP) reinforced ZrB2 was studied using resin bonded diamond grinding wheel under dry and wet conditions. A comparative study of grinding forces was performed at selected wheel surface speeds and depth of cuts for surface grinding. ZrB2-GNP showed lower normal grinding forces due to the reduced hardness. The presence of GNP reinforcement in ZrB2 resulted in lower tangential forces and reduced specific grinding energy due to the role of GNP as solid lubricant. The measured forces showed good correlation with the micro cutting model for ZrB2 and ZrB2-GNP under dry condition. The tangential forces showed same trend as normal forces at different depth of cuts and wheel surface speeds for both ZrB2 and ZrB2-GNP with average force ratios of 0.3 and 0.35 respectively. The presence of porosity in ZrB2 increased the normal grinding forces during wet grinding. Scanning Electron Microscope (SEM) images of the grinding chips indicated a mixture of both the ductile mode and the brittle mode of material removal with predominantly brittle fractured chips. Energy Dispersive Spectroscopy (EDS) confirmed the presence of GNPs in ZrB2-GNP grinding chips. The topography of the grinding wheel showed higher wheel loading after the dry grinding than that of wet grinding. The wet grinding resulted in relatively lower surface roughness (Ra values) compared to that of dry grinding.

Laser Assisted Micro Grinding of Titanium

Laser assisted micro-grinding (LAMG) is an emerging area of research in the field of high-quality micro-job fabrication and performance improvement. Conventional micro grinding (CMG) by micro pencil grinding tool suffers drawbacks such as tool deflection, higher cutting force and poor surface finish. In the present work, authors have attempted to investigate the performance of LAMG and CMG in the fabrication of micro-channel on Titanium material. Surface of workpiece was structured with the help of air assisted nanosecond-pulsed fiber laser scanning prior to the CMG at the different values of laser power by keeping scanning velocity constant. During the study, the CMG forces were recorded and after the processes surface roughness of the fabricated microchannels was measured. Results have shown reduction in the magnitude of the normal and tangential force by 31 % and 44 %, respectively, in LAMG compared to the CMG. In addition to that better surface finish was observed in LAMG than CMG. The surface roughness of micro-channel and grinding forces were found to be dependent on the power density of laser. Increase in the laser power deteriorates the surface finish and reduces the magnitude of grinding forces. High grinding forces in the CMG led to the dynamic deflection of the grinding wheel which produced the vibration in the process. The excessive vibration in CMG processes exploited the surface finish of the micro-channel. Such vibration was not observed on the LAMG process; as a result, better dimensional accuracy and surface finish of the channel was found.

Digital light processing-based additive manufacturing of resin bonded SiC grinding wheels and their grinding performance

In this study, an additive manufacturing process based on digital light processing was employed for a quick, flexible, and economical fabrication of resin bonded SiC grinding tools. The grinding wheel has been fabricated using laboratory manufacturing processes that utilize ultraviolet-curable resins and conventional abrasives. Also, desirable geometries and features like integrated coolant holes, which are difficult or even almost impossible to manufacture by conventional processes, are easily achievable. Grinding experiments were carried out by different process parameters, and with two different grinding wheels, i.e., with and without cooling channels with different concentrations (25 wt.% and 50 wt.% grains) to evaluate the grinding efficiency of the produced tools. Grinding forces, tool wear, tool loading, and ground surface quality were measured and analyzed. The wear rates of the grinding wheels with cooling channels were generally less than those without cooling channels, particularly in the deep grinding processes with large contact areas. Grinding tests on a hardened steel have shown that the integration of cooling lubricant channels almost prevents the wheel loading. In addition, by increasing the cutting speed (from 15 to 30 m/s) and decreasing the feed rate (from 10 to 2 m/min), the grinding wheel wear was significantly reduced. Furthermore, surface grinding of aluminum resulted in surface roughness values (Ra) in the range of 1 μm to 2.5 μm, while a Ra of about 0.2 μm was achieved by grinding hardened steel (100Cr6) with the same grinding conditions. Using the higher SiC-grain concentration (50 wt.%), it was determined that the surface roughness was 50% finer. Additionally the tool wear was significantly reduced (up to 30 times depending on the process parameters). The wear characteristics of the grinding wheel were analyzed through a novel image processing system. Significant correlations were found between the wear flat of grains and the increase in grinding forces due to the tool wear.

Experimental Research on Material Removal Mechanism and Grinding Force of FeCoNiCrMo0.1 High Entropy Alloy (HEA)

High entropy alloy (HEA) is an advanced alloy material, which has a wide application prospect due to its excellent properties. However, the material removal mechanism and change rule of grinding force of HEA in the grinding process have seldom been studied. The main work of this paper is that the material removal mechanism of the FeCoNiCrMo0.1 HEA is obtained by analyzing grinding debris and subsurface microstructure after grinding, the theoretical grinding force model of HEAs in plane grinding process is established on the basis of the force of a single abrasive grain, and the experimental verification is performed. According to the experimental results, the influences of different grinding parameters on grinding force are discussed, the influences of different types of grinding wheels on grinding force are analyzed, and the grinding forces generated by grinding different FeCoNiCr HEAs are compared. The results indicate that the material removal mechanism of FeCoNiCrMo0.1 HEA is the plastic removal. With the increase of grinding speed and the decrease of grinding depth and feed speed, both normal and tangential grinding forces decrease. Under the same grinding parameters, the grinding force produced by electroplated CBN grinding wheel is greater, followed by resin-bonded CBN grinding wheel and vitrified CBN grinding wheel. The grinding force produced by grinding FeCoNiCrAl0.1 HEA is lower than that produced by grinding FeCoNiCrMo0.1 HEA under the same grinding conditions. The calculated value of grinding force model is consistent with the experimental value, which can scientifically reflect the variation law of HEA grinding force.

Study On Grinding Force of High Volume Fraction SiCp/Al2024 Composites

In view of the difficult machining characteristics of high volume fraction SiCp/Al composites, this paper researches the grinding force variation of grinding SiCp/Al composites with grinding rod. A diamond grinding rod with a diameter of 3mm is used to grind the SiCp/Al2024 composite with 60% volume fraction by the method of end face grinding. By measuring the tangential grinding forces and normal grinding forces after grinding, the theoretical model of unit grinding force is deduced. According to the experimental parameters of spindle speed, feed rate and grinding depth, this paper derives the theoretical model of grinding force based on SiCp/Al2024 composites. And it clarifies the influence mechanism of grinding depth and feed rate on grinding force and explores the variation of grinding parameters on grinding force under dry grinding condition. Then the variation rule of grinding component force ratio is obtaines. The related research and theoretical model have theoretical guiding significance for exploring the grinding properties of hard-to-machine materials.

Digital light processing based additive manufacturing of resin bonded SiC grinding wheels and their grinding performance

In this study, an additive manufacturing process based on digital light processing was employed for quick, flexible, and economical fabrication of resin-bonded SiC grinding tools. The grinding wheel has been fabricated using laboratory manufacturing processes that utilize ultraviolet-curable resins and conventional abrasives. Also, desirable geometries and features like integrated coolant holes, which are difficult or even almost impossible to manufacture by conventional processes, are easily achievable. Grinding experiments were carried out by different process parameters, and with two different grinding wheels, i.e. with and without cooling channels with different concentrations (25 wt.% and 50 wt.% grains) to evaluate the grinding efficiency of the produced tools. Grinding forces, tool wear, tool loading, and ground surface quality were measured and analyzed. The wear rates of the grinding wheels with cooling channels were generally less than those without cooling channels, particularly in the deep grinding processes with large contact areas. Grinding tests on a hardened steel have shown that the integration of cooling lubricant channels almost prevents the wheel loading. In addition, by increasing the cutting speed (from 15 to 30 m/s) and decreasing the feed rate (from 10 to 2 m/min) the grinding wheel wear was significantly reduced. Furthermore, surface grinding of aluminum resulted in surface roughness values (Ra) in the range of 1 µm to 2.5 µm, while a Ra of about 0.2 µm was achieved by grinding hardened steel (100Cr6) with the same grinding conditions. Using the higher SiC-grain concentration (50 wt.%), it was determined that the surface roughness was 50% finer. Additionally the tool wear was significantly reduced (up to 30 times depending on the process parameters). The wear characteristics of the grinding wheel was analyzed through a novel image processing system. Significant correlations were found between wear flat of grains and the increase in grinding forces due to the tool wear.

Measurements of Non-Grinding Forces and Power

Grinding forces and power are important parameters for evaluating grinding process performance, and they are typically measured in grinding experiments. Forces are typically measured using a load cell or a dynamometer, whereas power is measured using an electrical power sensor to monitor the power of the spindle motor. Direct readings of the measurements include the net grinding force and power components for material removal and non-grinding components such as the impingement of a grinding fluid. Therefore, the net components must be extracted from the direct readings. An approach to extracting the net grinding forces and power is to perform additional spark-out grinding passes with no down feed. The forces and power recorded in a complete spark-out pass are used as the non-grinding components. Subsequently, the net grinding components are obtained by subtracting the non-grinding components from the corresponding totals for actual grinding passes. The approach becomes less accurate when large depths of cut, particularly large depths of cut and short grinding lengths, are involved. A new experimental approach is developed in this study to measure the non-grinding force and power components and to extract the net components. Compared with the existing approach, the new approach is more accurate for grinding with large depths of cut or short grinding lengths. In this approach, two additional grinding passes on an easy-to-grind material, one with and the other without a grinding fluid, are conducted using the same setup and condition as those in the actual test material to measure the forces and power for obtaining the non-grinding components. Subsequently, these non-grinding components are used as the non-grinding components of the actual material and subtracted from the total force and power components of the actual material to obtain the net values. To illustrate the application of the approach, surface grinding experiments are conducted to collect the forces and power. The extracted net power is consistent with the power predicted with the extracted net forces.

The Study of the Flat Grinding Process of Workpieces of Composite Materials

The paper shows the results of the carried out examination of the grit of the processed surface and the intensiveness of the flat grinding of workpieces of composite materials. The processing has been carried out using of a special grinding tool with anti-frictional fillers produced in accordance with the microwave technology. The grit and components of grinding forces of workpieces of aluminomatrix composite materials with various carbon contents have been determined.