Grinding Characteristics Research Articles

Analysis of coupled vibration characteristics of PMS grinding motorized spindle

Field-path-kinetic coupling and the multi-body dynamics models were established and the finite element method (FEM) was used to study the coupled vibrations of motorized spindle. The results show that the frequency is mainly 1 fr at low speeds, fractional-octave and 1fr at high-speed only the bearing force. The orbit of bearing transitions is from a more pronounced circle to an approximately circular shape, while the rotor changes from a rule to a random pattern. The front bearing is more obvious than the rear and the orbits are always round; the radius of the orbit at the front bearing gradually increases as the speed increases. The result is the vibration displacement changes more significantly close to the spindle end and the amplitude increases accordingly. The experimental results show that operating conditions are closer to the normal, the influence of unbalanced magnetic pull can be neglected, the bearing selection and assembly are reasonable.

Vibration Characteristics of PMSM Grinding Motorized Spindle

This paper presents electromechanical vibration characteristics in parallel misalignment of a shaft by analyzing the vibration of PMSM grinding motorized spindle. The unbalanced magnetic pull (UMP) of the PMSM grinding motorized spindle is established as electromechanical model based on the Maxwell stress tensor, which is used to the spindle to cause the electromechanical vibration and calculated under different eccentricities through FEA (Finite Element Analysis). It increases with increasing eccentricity under no load and on load and is maximum value when mixing eccentricity. Applying a Jeffcott rotor model to analyse the dynamic characteristics of the spindle with UMP excitation and mass imbalance. The number of pole-pair is 6 and the number of slots is 36 for the PMSM grinding motorized spindle, the vibrations of 1fr, 2fr and 3fr are generated and the limit cycle is more complicated at 4500rpm. Simulated results agree well with the experimental results, and it indicates the electromechanical vibration with the shaft eccentricity and the UMP is obviously on the shaft.

The Cement Mechanical Activation Effective Application Field Determination

Of all the known methods for increasing the cement activity, mechanical grinding is distinguished in the work. For mechanical grinding, technological characteristics of grinding in an electromagnetic field are established (mill - linear induction rotator, LIV). The value of the increment of activity is determined depending on its initial (initial) value. To determine the estimated value of the cement consumption, the methods provided by the state standard of the Russian Federation were used. The experiments, as well as the measurement of the compressive strength (R), were carried out in accordance with the GOST requirements. The cement mechanical grinding effective application field in electromagnetic field is determined by comparing the costs and savings. The costs are calculated as the cost of electricity needed for grinding. The savings are the cost of the established difference between the cement consumption for the initial activity of cement and the actual value, which is able to provide the concrete with a given design strength. The results describing the field of the cement mechanical grinding effective application are presented in tabular form and graphically. When determining the area of ​​ the mechanical grinding effective use, the conclusion that it is necessary to adjust the technological grinding regimes depending on the initial activity of the cement, as well as on the chemical composition of the clinker (manufacturer) was confirmed. The prospects for the research on mechanical grinding technology are associated with obtaining grinding regimes depending on the initial size and composition of the clinker. The area of ​​effective application of mechanical activation should be determined each time depending on the physical and mechanical cement properties.

A novel high-shear and low-pressure grinding method using specially developed abrasive tools

In this work, a novel grinding method using a special abrasive tool was first proposed to achieve high tangential grinding force and low normal grinding force. The abrasive tool was developed with flexible composites to remove workpiece materials under “high-shear and low-pressure” grinding mode. The concept of the high-shear and low-pressure grinding method was introduced in detail. Grinding tests were carried out on a precision grinder with the developed abrasive tool for single crystal silicon specimens. The results showed that the grinding force ratio between tangential force and normal force for the proposed grinding method was ranged between 0.9 and 1.3, which was three times larger than that of the conventional grinding method. It was verified that the developed abrasive tool possessed the grinding characteristics of high tangential grinding force and low normal grinding force. After grinding of silicon specimens for 120 min, the value of surface roughness decreased from 429.20 to 32.91 nm under the selected grinding conditions. The surface quality of the silicon specimens was greatly improved after grinding.

A comparative study on the effect of chemical additives on dry grinding of magnetite ore

Dry grinding as an alternative to wet grinding is one of Sweden's strategic research areas to promote dry beneficiation. However, dry grinding has remained unpopular due to its higher specific energy consumption (Ec), wider particle size distribution (PSD), difficult material handling, and purported effects on downstream processes. In this work, the effects of the new additives (Zalta™ GR20–587, Zalta™ VM1122, and Sodium hydroxide) employed as grinding aids (GA) on dry grinding and product characteristics of a magnetite ore were studied in light of possible downstream effects. The grinding efficiency of Magnetite increased after using GAs in comparison without the GAs; however, an optimal dosage exists for each of the chemical additives investigated. Comparing to grinding without GA, Zalta™ VM1122, a viscosity modifier was selected as the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t, the PSD became narrower and finer (the P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects. Further, it was found that Zalta™ VM1122 resulted in similar zeta potentials and pH values for the product compared to grinding without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes such as flotation.

Application of pearling in modified roller milling of hull‐less barley and effect on noodles quality

The factors restricting the development of hull-less barley (HB) were the low flour yield in the roller milling and the poor quality of its products. In this work, the pearling combined with the modified milling flow was used to increase the flour yield by improving the separation efficiency of bran and endosperm. Moreover, HB flour was prepared by roller milling with different parameters, and the quality of noodles containing 50% HB flour was evaluated. Pearling 20% followed by roller milling was an effective way to improve the grinding characteristics of HB, which is illustrated mainly in flour yield and the β-glucan content of flour increase by 24.1% and 66.3%, and the total dietary fiber content of bran was improved by 82.7%. Under the same condition of pearling and milling, noodles with 50% HB flour had better texture properties and overall acceptability. Practical applications The pearling combined with the modified milling flow was helpful for the manufacturer to obtain barley flour with higher β-glucan, and more economic benefits can be gain because of the high flour yield. The change of kernel component with pearling rate also can provide a reference for the processing of highland barley rice. So, the research was useful on practical applications.

Performance evaluation of minimum quantity lubrication technique in grinding of AISI 202 stainless steel using nano-MoS2 with vegetable-based cutting fluid

Due to environmental issue and stringent rules over defilement and contamination of the environment, the demand for renewable and biodegradable cutting fluids is increasing. In this study, an eco-friendly minimum quantity lubrication (MQL) technique using vegetable oil–based cutting fluid (rapeseed oil) by varying MQL flow rate and MQL pressure was investigated in the grinding of AISI 202 stainless steel. In addition to explore the cooling capabilities of rapeseed oil, nano-MoS2 was added to the rapeseed oil to prepare different concentrations (0.5 wt% and 1.0 wt%) of nanofluids. The main objective of this experiment is to examine the performance of different grinding environments (dry, flood, pure MQL, and nanofluid MQL) with respect to grinding characteristics, namely, grinding forces, surface morphology, surface roughness, and temperature. Experimental results revealed that NFMQL grinding with vegetable oil was performed much superior as compared with the dry, wet, and pure MQL machining. The lowest specific normal force and tangential force are observed to be 9.2 N/mm and 0.76 N/mm respectively under 1.0 wt% concentration of MoS2 nanoparticles at oil flow rate of 120 ml/h and air pressure 90 psi under MQL grinding condition, which decreased by 43% and 33%, respectively, as compared with dry conditions. Furthermore, the application of nanofluid also leads to the reduction of surface roughness and surface temperature. MQL application with MoS2 nanofluid helps in effective flushing of chip material from the grinding zone, thereby improving the lubrication and cooling capabilities during the grinding of the AISI 202 stainless steel. In summary, appropriately chosen minimum quantity lubrication parameters can enhance the lubrication and cooling properties of the oil film and improve the grinding characteristics.

Grinding characteristics during ultrasonic vibration assisted grinding of alumina ceramic in selected dry and MQL conditions

Ultrasonic vibration assisted grinding (UAG) has proven to lower the forces and improve the ground surface quality while shaping difficult to grind materials such as ceramics. A systematic study of UAG of alumina ceramic using a metal bonded diamond grinding wheel has been performed here. Taguchi’s L18 array based experimentation has been performed to study the effect of UAG parameters. During UAG, the vibration amplitudes of 6 and 12 microns have been used and the frequency has been kept at 20 kHz. From these experiments, optimum parameters for UAG have been identified using Grey relational analysis. Mathematical models generated using regression analysis have been found to correlate the experimental data with good accuracy. A comparison of the grinding forces and roughness of the surfaces generated in dry and minimum quantity lubrication (MQL) conditions in both conventional grinding and optimal condition in UAG has been performed to identify the beneficial effects of providing vibration to the workpiece. The surface quality has been evaluated using 3D roughness data, 3D plots and SEM images of the ground surface. By examining nature of the ground surface and kurtosis (Sku) values of the surface profile, it has been concluded that UAG reduces brittle fracture and facilitates material removal by ductile mode for alumina. The desired condition of least machining forces and highest surface quality has been achieved during the combination of UAG and MQL.

Thermal effect on oxidation layer evolution and phase transformation in grinding of Fe-Ni super alloy

This article is devoted to investigate thermal damage and its influences on phase transformation and surface characteristics in grinding of Fe-Ni super alloy. From the oxidation analysis, it was found that higher thermal effect could cause a worse subsurface damage layer and higher Oxygen proportion. In terms of the phase transformation, the results show that the volume fractions of martensite and austenite increase while that of ferrite decreases with elevated grinding temperature, which lead to an increment of surface hardness. Based on these analyses, the thermal induced phase transformation can be reduced by increasing work speed and decreasing depth of cut.

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.

Grinding of alumina ceramic with microtextured brazed diamond end grinding wheels

Brazed monolayer diamond grinding wheels have advantages of a high abrasive bonding strength, high protrusion, and a large chip disposal space. However, it is difficult to prepare ordered and fine-grained brazed diamond grinding wheels. This study presents a new method for grain-arranged, brazed diamond grinding wheels with microtextures with similar performance to ordered and fine-grained brazed diamond grinding wheels. First, coarse diamond grains (18/20 mesh) were orderly brazed to fabricate the end grinding wheels. Next, a series of microtextures were ablated on the diamond grains using a pulsed laser, and two types of textured end grinding wheels—TG-G (ablated microgrooves only) and TG-GH (ablated microgrooves and microholes)—were prepared. Then, an experiment involving the grinding of alumina ceramics was performed, and the grinding characteristics and grinding mechanism were analyzed. The results indicated that compared with untextured diamond end grinding wheels (TG), the textured diamond grinding wheels (TG-G and TG-GH) significantly reduced the grinding force and the roughness of the machined surface. The local stress concentration at the microtextures promoted the formation of microcracks in the diamond grains of TG-G and TG-GH, and the self-sharpness of the grinding wheel was significantly improved. The brittle fracture mode of ceramic materials in grinding included intergranular fracture and transgranular fracture. Ironing pressure action was a key material-removal mechanism. It had an important influence on the cutting force and plasticity characteristics of the TG machined surface. For the surfaces processed by TG-G and TG-GH, the effect of ironing was weakened, while shearing played a more important role. The TG-GH grinding wheel ablated with microgrooves and microholes was superior to the TG-G grinding wheel ablated with only microgrooves, with regard to the grinding force, roughness, and self-sharpening.

Structural design and fabrication of polycrystalline diamond micro ball-end mill

Since cemented carbide has been used as a micro-lens array mold, its processing method and micro-tool is one of the research priorities. In order to achieve high-quality milling of cemented carbide micro-lens array, the design and fabrication of the 0.5-mm diameter polycrystalline diamond (PCD) micro ball-end mill were studied. Based on the space vector, the mathematical model of the plane cutting edge of the PCD tool is established. According to the three processing characteristics of milling, grinding, and milling grinding, the double-edged conical surface micro ball-end mill, spherical micro ball-end mill, and single-edged hemispherical micro ball-end mill were designed respectively. Based on the line-face contact model of the grinding wheel and the movement principle of the CNC tool grinder, the grinding principles and methods of the rake face and the flank face are proposed. The high precision grinding of PCD micro ball-end mills are realized. The micro-groove milling experiment of cemented carbide was conducted; the milling performance of three PCD micro ball-end mills was studied. Considering the surface morphology and roughness of the micro-groove machining, a single-edged hemispherical PCD micro ball-end mill can avoid the phenomenon of chip blocking and depositing and can also fully exert the grinding characteristics of PCD materials to obtain relatively better processing quality.

An investigation on machined surface quality and tool wear during creep feed grinding of powder metallurgy nickel-based superalloy FGH96 with alumina abrasive wheels

In this study, the machined surface quality of powder metallurgy nickel-based superalloy FGH96 (similar to Rene88DT) and the grinding characteristics of brown alumina (BA) and microcrystalline alumina (MA) abrasive wheels were comparatively analyzed during creep feed grinding. The influences of the grinding parameters (abrasive wheel speed, workpiece infeed speed, and depth of cut) on the grinding force, grinding temperature, surface roughness, surface morphology, tool wear, and grinding ratio were analyzed comprehensively. The experimental results showed that there was no significant difference in terms of the machined surface quality and grinding characteristics of FGH96 during grinding with the two types of abrasive wheels. This was mainly because the grinding advantages of the MA wheel were weakened for the difficult-to-cut FGH96 material. Moreover, both the BA and MA abrasive wheels exhibited severe tool wear in the form of wheel clogging and workpiece material adhesion. Finally, an analytical model for prediction of the grinding ratio was established by combining the tool wear volume, grinding force, and grinding length. The acceptable errors between the predicted and experimental grinding ratios (ranging from 0.6 to 1.8) were 7.56% and 6.31% for the BA and MA abrasive wheels, respectively. This model can be used to evaluate quantitatively the grinding performance of an alumina abrasive wheel, and is therefore helpful for optimizing the grinding parameters in the creep feed grinding process.

Effects of wheel speed on surface/subsurface damage characteristics in grinding of glass-ceramics

Glass-ceramic is widely used in optics and other areas because of its good physical and mechanical properties. However, the accompanying hard and difficult to machine characteristic brings great challenges to the commonly used grinding in industry. Previous researches on the removal mechanism of glass-ceramic are basically traditional low-speed scratch and low-speed grinding, ignoring the effect of the wheel speed on surface/subsurface damage. In this study, the effects of the wheel speed on the surface morphology, surface roughness, and subsurface damage of Zerodur glass-ceramics were studied at different wheel speeds based on a multi-step grinding process. Experimental and analytical results showed that increasing wheel speed can restrain the occurrence and development of brittle fractures due to the effects of strain rate and grinding temperature, resulting in fewer and smaller micro-pits and micro-cracks, and thus more signs of plastic flow are observed. In addition, the effects of wheel speed on surface roughness under the semi-finishing grinding stage are not as clearly defined as on that under the rough and finishing grinding stages. The smeared layers on the ground surface, which are related to the compound effects of the grinding temperature and semi-finishing grinding conditions, are recognized as the major contributor to the contradictory surface roughness results. Furthermore, the effect of wheel speed can prevent crack from nucleating and propagating, and then leads to a smaller depth of subsurface damage. Accordingly, there is a general trend toward subsurface damage depth with the increase of undeformed chip thickness, regardless of the grinding conditions. In a word, higher wheel speeds are easier to achieve ductile removal mode and conversely, the glass-ceramic is more prone to a brittle removal mode. The research is expected to provide guidance for grinding-induced damage control and the engineering application in high precision optical parts of glass-ceramic.

Effect of Freeze-Drying on Quality and Grinding Process of Food Produce: A Review

Freeze-drying is an important processing unit operation in food powder production. It offers dehydrated products with extended shelf life and high quality. Unfortunately, food quality attributes and grinding characteristics are affected significantly during the drying process due to the glass transition temperature (during drying operation) and stress generated (during grinding operation) in the food structure. However, it has been successfully applied to several biological materials ranging from animal products to plants products owning to its specific advantages. Recently, the market demands for freeze-dried and ground food products such as spices, vegetables, and fruits are on the increase. In this study, the effect of the freeze-drying process on quality attributes, such as structural changes, the influence of glass transition during grinding, together with the effect on grinding efficiency in terms of energy requirement, grinding yield, and morphological changes in the powder as a result of temperature, drying time were discussed. An overview of models for drying kinetics for freeze-dried food sample, and grinding characteristics developed to optimize the drying processes, and a prediction of the grinding characteristics are also provided. Some limitations of the drying process during grinding are also discussed together with innovative methods to improve the drying and grinding processes.

Study on the influence of waste residue of mixing station, slag and water slag on the strength of cement mortar

In their paper. In this paper, the influence of the waste residue of the mixing station on the strength of cement mortar was studied. And the influence of the different content of the waste residue of the mixing station, slag and water slag on the strength of cement mortar was studied to get the optimal proportion. The study showed that when the mass ratio of the waste residue of mixing station, slag and water slag is 3:3:4 and 3:2:5, the synergistic effect of the three materials can be fully exerted, the grinding characteristics of the waste slag of the mixing station can be effectively improved, and the hydration activity of the waste slag of the mixing station can be improved.

Influence of the Freeze-drying Conditions on the Physicochemical Properties and Grinding Characteristics of Kiwi

AbstractThe aim of this work was to study the influence of freeze-drying conditions of kiwi (Actinidia deliciosa) on physicochemical properties and grinding characteristics of dried fruits. Whole kiwi fruits were freeze-dried with the different pressure: 12, 20, 42, 63, 85, and 103 Pa. Dried fruit properties that underwent evaluation included color, texture, rehydration, total phenolics content, antioxidant properties and sensory analysis. Moreover, the grinding energy indices of dried kiwi were determined. The results showed that an increase in the pressure caused decreased lightness, but increased yellowness and greenness of freeze-dried kiwi. The force of kiwi penetration increased and the rehydration ability decreased with the increase in the pressure. The specific grinding energy of dried kiwi ranged from 10.1 to 13.6 kJ⋅kg−1, whereas the average particle size of kiwi powder changed from 0.331 to 0.337 mm. The highest values of these parameters were obtained for kiwi freeze-dried with the highest pressure.

An experimental assessment of the grinding characteristics of some native seeds used by Aboriginal Australians

Numerous plant seeds (the caryopsis or achene) from a wide variety of genera were traditionally ground for food by hunter-gatherer peoples, including over 200 varieties by Aboriginal Australians. In Australia, these seeds varied greatly in size, shape and hardness. Except for a broad distinction being made between grass and tree seeds, differences in the morphological and other characteristics of seeds — in particular their performance in seed-grinding — are rarely documented. A recent experimental examination of the efficiency of millstones using commercial proxies for difficult to obtain Australian native seeds has shown significant differences in workability and output of different types of seeds. This paper tests predictions as to whether the grinding characteristics of a number of widely used native seeds also vary significantly, the implications this has for the selection, treatment and use of seeds by Aboriginal people in Australia and elsewhere, and generates quantitative data which can supplement and explicate other experimental research. It also makes a preliminary assessment of whether domesticated seeds can provide useful grinding analogues for unavailable native seeds. Our findings have broad relevance for an understanding of prehistoric seed-grinding and species selection in Australia and other parts of the world.

Drying Kinetics, Grinding Characteristics, and Physicochemical Properties of Broccoli Sprouts

In this study, we studied the drying process, grinding characteristics and physicochemical characteristics of broccoli sprouts (BS). The seeds of broccoli were germinated at 20 °C for 3 and 6 days. Then, the seeds were air- and freeze-dried, and the Page model was used for prediction of drying kinetics of broccoli sprouts. It was observed that the drying time of BS decreased about twofold as the air-drying temperature increased from 40 to 80 °C. An increasing the air-drying temperature from 40 to 80 °C decreased the drying time by approximately twofold. Freeze-drying of sprouts took the longest drying time. Germination of seeds significantly decreased the value of grinding energy requirements, and the ground sprouts exhibited a different grinding pattern in comparison to ground non-germinated seeds. In terms of color parameters, the highest lightness and yellowness were found for freeze-dried sprouts. Redness and yellowness of sprouts increased with an increase in the air-drying temperature. The lowest total color difference was obtained for the freeze-dried sprouts. Higher drying temperature resulted in lower total phenolics content (TPC) and decreased antioxidant activity (AA). The highest TPC and AA were observed in air-dried sprouts (40 °C) and freeze-dried sprouts after 6 days of germination.

Quantitative evaluation of grinding wheel surface condition and effect of dressing condition on characteristics of grinding

Quantitative evaluation of grinding wheel surface condition and effect of dressing condition on characteristics of grinding