Grinding Operations Research Articles

A gear grinding allowance stochastic simulation model

The paper proposes a method and technique that allow, using a minimum sample (3 units) from a batch (30 units) of real gears, to obtain stochastic information about the actual distribution of the gear grinding allowance both on the left and right flanks of the gear gaps for all gears in the batch. The proposed gear grinding allowance stochastic model is based on the representation of the distribution of the gear grinding allowance along the gear periphery as a superposition of a sinusoidal component with a random amplitude and a random component of the white noise type. The conditions for the equivalence of the stochastic characteristics of real (measured) and virtual (not actually measured) gears are formulated, namely the ratio between the amplitude of the sinusoidal component and the average amplitude of the high-frequency harmonic components of the gear grinding allowance distribution along the gear periphery. The gear grinding allowance stochastic model adjusted according to the proposed method makes it possible to predict the distribution of the gear grinding allowance on the left and right flanks of the gear gaps for a batch of gears and, taking into account the information obtained (replacing the experimental data), both evaluate the existing technology and optimize the gear grinding allowance value. As a result, it becomes possible to assess the quality of the technological process of manufacturing the gear, taking into account the effect random deformations to gear grinding allowance at the stage of their heat treatment (hardening), which is performed before the gear grinding operation. In turn, optimization of the grinding allowance (based on its actual distribution along the periphery of the gear) makes it possible to reduce both defects in burns (with increased allowance) and defects in unground teeth (with insufficient allowance).

State-of-the-art review of applications of image processing techniques for tool condition monitoring on conventional machining processes

AbstractIn conventional machining, one of the main tasks is to ensure that the required dimensional accuracy and the desired surface quality of a part or product meet the customer needs. The successful accomplishment of these parameters in milling, turning, milling, drilling, grinding and other conventional machining operations directly depends on the current level of tool wear and cutting edge conditions. One of the proven non-contact methods of tool condition monitoring (TCM) is measuring systems based on image processing technologies that allow assessing the current state of the machined surface and the quantitative indicators of tool wear. This review article discusses image processing for tool monitoring in the conventional machining domain. For the first time, a comprehensive review of the application of image processing techniques for tool condition monitoring in conventional machining processes is provided for both direct and indirect measurement methods. Here we consider both applications of image processing in conventional machining processes, for the analysis of the tool cutting edge and for the control of surface images after machining. It also discusses the predominance, limitations and perspectives on the application of imaging systems as a tool for controlling machining processes. The perspectives and trends in the development of image processing in Industry 4.0, namely artificial intelligence, smart manufacturing, the internet of things and big data, were also elaborated and analysed.

The Effects of Process Parameters on Workpiece Roundness in the Shoe-Type Centerless Grinding Operation for Internal Raceway of Ball Bearings

One of the most important indices of bearing raceway, roundness, has an important influence on the life and performance of the bearing. Currently, shoe-type centerless grinding (STCG) is a core process for the fabrication of the raceway surface. Some researchers have carried out studies in this field; however, the reason and extent of the influence of process parameters on the workpiece roundness in the STCG operation for the internal raceway of the 6208 ball bearings are not clear up to now. In this paper, new research on the effects of process parameters on workpiece roundness in the STCG operation for the internal raceway of the 6208 ball bearings is presented. The influence of the angular placement of the two shoes, as well as the technology parameters including the offset between the rotational centers of the workpiece and the magnetic drivehead (e), the normal feed rate (Snf), the speed of the workpiece (nw), and the grinding depth (af), on the roundness of the raceway surface were investigated both theoretically and experimentally to solve the difficulties in the STCG operation to ensure the roundness of the raceway surface. Based on the research results, a guideline for selecting initial process parameters is introduced to ensure the roundness of the bearing raceway in the STCG operation for the internal raceway of 6208_ball bearings on the 3MK136B grinder.

Determining the effect of the direction of installing the cutting edges of shredder roller blades on process parameters

This paper reports a study aimed at increasing the intensity of grinding of the stems of coarse-stemmed crops by establishing the influence of the orientation of the cutting edge of the cutter-shredder knives on the quality of the technological grinding operations. Analytical dependences of the planar movement of the roller-shredder were established and it was determined that for rollers with knives, the cutting edge of which is directed in the direction opposite to the direction of rotation: – exceeding the value of the vertical components of the total forces of resistance of the knives, which made it possible to increase the values of forces, and, as a result, more intensive destruction of the layer of plant remains; – exceeding the values of the driving force of the knives based on the dependence of the driving force on structural and kinematic parameters (roller weight, drum radius, blade height, blade inclination angle, acceleration). Experimental studies have established an excess of up to 20 % of the quality indicators of milling sunflower and corn stems with roller knives, the cutting edge of which is directed in the direction opposite to the direction of rotation. The average number of crushed pieces of corn stalks in the range of less than 50 mm is 13.6 % higher in the combined unit, the cutter blades of which are directed with the cutting edge in the direction opposite to the direction of rotation. It was established that with zero and 3.92 kN (400 kg) additional loading, an increase in speed from 7.45 km/h to 13.6 km/h leads to a decrease in the values of the average traction resistance. The highest value of traction resistance was set at a speed of 13.6 km/h and an additional load of 7.84 kN (800 kg). The lowest value of traction resistance was established at zero additional load and a speed of 22.0 km/h, which is 21.5 % less than at a speed of 7.45 km/h and 14.1 % less than at a speed of 13.6 km/h.

Digital Twin is an Effective Tool for Digital Transformation of Industrial Enterprises

The article presents the results of a study of digital transformation processes taking place on scientific and industrial enterprises using digital twin technology. The degree of introduction of digital technologies and the level of labor productivity in the developed countries and in Russia were considered. The concept, definition, properties and characteristics of digital twin technology were studied. The applied methods of digital design and modeling in the digital twintechnology were investigated. The author analyzes the features of creation, functionality, and the advantages of digital twin technology at various stages of the object's life cycle - during design, production and operation. Practical examples of digital twins application in the domestic industry are given: the design of a premium-class car of the 'Tuple' project, the optimization of technological grinding operations of product manufacturing, the introduction of a predictive prognostic system and monitoring of modern high-tech equipment of the combined-cycle unit of the Izhevsk CHP-1 PSU for monitoring the operational condition, reliable forecasting of technological processes, protection from incidents and accidents. The application of digital twin technology as a training complex to train the operational personnel of industrial facilities based on modeling of rarely encountered and critically dangerous operating modes of industrial facilities is investigated. The Russian market of digital design and modeling is studied and key leaders were identified. The top digital technologies to achieve technological leadership of domestic companies are summarized. As a result of the research, the key capabilities of digital twin technology and barriers constraining the processes of full-scale digital transformation of scientific and industrial enterprises are identified. Recommendations for the successful implementation and development of digital twin technology are proposed. The motivating factors of state support for the digital transformation of domestic business are summarized.

ELID Dressing Behaviors of Non-Abrasive Iron-Based Grinding Wheels

Non-abrasive iron-based grinding diamond wheels, lacking abrasive particles, negate the concern of detached passivated abrasives scratching the polished surface. During the Electrolytic In-Process Dressing (ELID) polishing process, α-Fe2O3 particles form on the oxide film surface of the iron-based grinding diamond wheel devoid of abrasives. These particles assume the role of the grinding diamond wheel for polishing. Therefore, the ELID electrolytic performance and the oxide film formation performance of the non-abrasive iron-based grinding diamond wheel significantly influence the formation of α-Fe2O3 particles and the subsequent ELID polishing performance. Our studies investigating the ELID dressing behavior of the non-abrasive iron-based grinding diamond wheel have analyzed the influence mechanism of the electric field, flow field, and pulse energy on its ELID dressing. Moreover, the roundness of the ELID dressing grinding diamond wheel, oxide film properties, and α-Fe2O3 particle content were measured, and plate glass was polished using the ELID non-abrasive iron-based grinding diamond wheel. The results illustrate that the non-abrasive iron-based grinding diamond wheel exhibits excellent ELID dressing performance. The diamond wheel’s roundness is less than 0.001 mm, the oxide film uniformly covers the surface, the content of α-Fe2O3 particles is evenly distributed, and the surface accuracy of the polished plate glass is approximately 0.5 nm. These findings provide a compelling case for the continued use and development of grainless iron-based grinding diamond wheels in precision grinding operations.

Optimisation of rail profile and grinding pattern in the curve section of a subway

During routine rail maintenance, rail grinding of sharp curves is challenging. In particular, setting up the grinding pattern is essential. A rail-grinding pattern optimisation method is proposed based on the mathematical relationship between the grinding pattern parameters and geometric parameters of the rail grinding profile. In this method, the design variables and constraints are reasonably selected, and a multi-objective optimisation function considering the wheel-rail contact stress, wheel-rail lateral force, and rail grinding amount is established. The optimisation model is solved using a chaotic microvariation adaptive genetic algorithm. The optimisation method is applied to the repairable grinding of a worn rail in a metro curve section. The results demonstrate that using this method can realise an ideal grinding pattern with the expected grinding effect in addition to high accuracy and high optimisation speed. The wheel-rail contact characteristics, wear characteristics, and train dynamic performance are significantly improved after rail grinding; this is significant for conducting grinding operations and improving the train’s curve-passing ability. Therefore, this study provides theoretical guidance for formulating rail-grinding patterns.

Double-sided deep grinding of gas turbine engine blades with highly porous CBN tool

The results of the implementation of high-porous cubic boron nitride (CBN) grinding wheels in the operation of double-sided deep grinding of the fir-tree profile of the locking element of the turbine blade are presented. The features of designing the working layer of the CBN wheel for this operation are described. Recommendations for the selection of the characteristics of diamond dressing rollers are formulated. The principles of organizing an efficient production process when introducing CBN grinding wheels are described. Keywords: deep grinding, part, gas turbine engine, working turbine blade, grinding wheel dressing, diamond profile roller, highly-porous CBN grinding wheels. d_i_volkov@rsatu.ru, boris_tsvetkov@mail.ru

Adaptive Impedance Control for Force Tracking in Manipulators Based on Fractional-Order PID

Force tracking control in robot arms has been widely used in many industrial applications, particularly in tasks involving end effectors and environmental contact, such as grinding, polishing, and other similar operations. However, these environments are not always precisely known. In order to address the force tracking control problem in unknown environments, this paper proposes a fractional-order PID adaptive impedance control strategy based on traditional impedance control. The unknown environmental information is estimated online using the adaptive impedance control algorithm, and the estimated parameters are used to generate reference trajectories to reduce force tracking errors. Fractional-order PID control is then introduced into the system to improve the control performance of the system model, and the theoretical proof of strategy stability is conducted. Finally, a comparison of four strategies was conducted through simulations: traditional impedance control, adaptive hybrid impedance control, adaptive variable impedance control, and the fractional-order PID impedance control proposed in this paper. The simulation results demonstrate that the strategy proposed in this paper exhibits robustness, virtually eliminates overshoot, and enhances response speed. In contrast, both adaptive hybrid impedance control and adaptive variable impedance control exhibit approximately 30% to 45% overshoot during interactions with the environment. Furthermore, in terms of force tracking error, the proposed strategy in this paper outperforms the above two strategies by approximately 29% to 60%, achieving excellent force tracking control performance.

Energy conservation and consumption reduction in grinding operations through ceramic media stirring mill: An industrial validation test

This paper demonstrates the feasibility of using a ceramic medium stirring mill to reduce the energy consumption of grinding operations through an industrial verification experiment. Compared with the original two-stage ball milling process, the cost of grinding power consumption is significantly reduced by about 50.16%, which provides a reference for the subsequent research on energy saving and consumption reduction in ball milling operations. The optimal grinding parameters were determined to be grinding concentration of 50%, material ball ratio of 0.6, 3:2:5 media ratio (10:15:20 mm) of 3:2:5, medium filling rate of 90%, as well as stirring speed of 110 rpm. Under the optimum grinding parameters, an iron concentrate with an iron grade of 68.18% and an iron recovery rate of 94.17% were obtained by two-stage magnetic separation. The successful case of ceramic medium stirring mill replacing two-stage ball grinding provides a feasible solution for energy conservation and consumption reduction in mines in China.

ВЛИЯНИЕ СТРУКТУРЫ И ТВЕРДОСТИ АБРАЗИВНОГО ИНСТРУМЕНТА НА ПОКАЗАТЕЛИ ШЛИФОВАНИЯ БЫСТРОРЕЖУЩЕЙ СТАЛИ

The operation of flat mortise grinding of high-speed steel blanks are presented. The regularities of changes in the components of the cutting force, the grinding coefficient and the arithmetic mean deviation of the profile of the treated surface during grinding with circles of different hardness and structure are determined. Recommendations on the choice of characteristics of the abrasive tool, modes of finishing and rough grinding of high-speed steel are given.

Impacts of Clinker Storages Heat Transfer, Its Effect on Vertical Roller Cement Performances: A Case Study of Cement Grinding Operations in Nigeria

Operational data indicates that vertical roller cement mills (VRCM) consumed lesser energy when compared to horizontal/ball mills. A case study of a vertical roller cement mills was carried out in Nigeria which was experiencing a lower production output and a higher energy consumption. This research was to investigate reasons behind the low production output on the VRCM. A thorough analysis was carried out on the clinker storage facilities and the heat transfer across the composite cylindrical clinker silo walls (off – spec and main clinker) both silos having the same design but with different dimensions and with different application purpose. The off-spec clinker silo has a design capacity of 1,800 tons and main clinker silo a design capacity of 60, 000 tons and both silo stores hot clinker that left the kiln clinker cooler at approximate temperature of 95oC. The analytical results shows that the rate of heat transfer across the main clinker composite walls was 728 kW and the rate of heat transfer across the off-spec clinker composite walls was 217.15 kW. Numerical simulation was also carried out using ANSYS simulation package and the results obtained were in good agreement with the results obtained theoretically. The ratio of heat loss on the main clinker composite walls to off-spec clinker composite walls was 3.35:1.

Effectiveness of Copper Minerals Liberation from the Gangue through Application of HRC Press in Copper Ore Processing Circuits

The article concerns investigations over benefits of application of HRC devices into sulphide copper ore processing plant. High pressure comminution appears to be very effective technology in hard ore processing circuits, especially in terms of energy consumption. This can be particularly observed in downstream grinding and beneficiation operations. A series of pilot-scale crushing tests in HRC roller press for various levels of operating pressure, were performed. HRC crushing effectiveness along with downstream grinding process course for each crushing product were also under analysis. The investigations were supplemented by analysis of flotation process effectiveness and impact of the process of high-pressure comminution on environment (dust emission). The results of investigation show that operating pressure level influences the obtained comminution results (comminution degree, yield of finest particle size fractions). The grinding effectiveness, measured through production of the finest particle size fractions was significantly influenced by the operating pressure. The results show that higher values of operating pressure (4.0 and 4.5 N/mm 2 ) are not as efficient within this scope as the pressure 3.5 N/mm2. Dust emission is also correlated with the operating pressure value.

Multiscale simulation of volumetric wear of vitrified alumina grinding wheels

Wear of vitrified alumina wheels is a major research issue. Although extensive experimental work has been presented in the scientific literature, wheel manufacturers and grinding users are still unable to predict the expected grinding ratio of their operations. This work presents a novel multiscale approach that integrates the mechanical behavior of vitrified bonds with the stochastic nature of grain location. The new multiscale model integrates a DEM microscale model (μSM) and a randomization of the μSM (RμSM) of the wheel. The μSM simulates the stress field in the region of the wheel in contact with the workpiece, while RμSM accounts for the actual and random location of the alumina grits. This approach drastically reduces computational time and effectively determines the actual number of grains lost under a set of given grinding conditions. The model successfully predicts the detachment of complete clusters of abrasive grains from the bonds, with a large degree of agreement with experiments considering the deviation introduced by the micro-cutting edges that modify the hypothetical spherical geometry of the Discrete Elements (DEs). This is the first model to predict the volumetric wear of grinding wheels. The results will be useful for informing the future analysis of grinding operations affected by volumetric wear.

Evaluation of Contrived Wear Methodology in End Milling of Inconel 718

Abstract Tool wear plays a decisive role in achieving the required surface quality and dimensional accuracy during the machining of Inconel 718-based products. The highly stochastic phenomenon of tool wear, particularly in later stages, results in difficulty in predicting the failure point of the tool. The present research work aims to study this late-stage wear of the tool by generating consistent wear conditions and thereby decoupling the late-stage wear from the wear history. To do so, a multi-axis grinding operation is employed to create artificial tool wear that replicates the topology of natural wear occurring in the process. In order to evaluate the imitating ability of the proposed methodology, microscopic images in different wear states of naturally and contrived worn tools were analyzed. The methodology was validated by comparing the resulting process forces measured during end milling with the natural and contrived worn tool for different path strategies. Finally, a qualitative finite element (FE) analysis was conducted, and specific force coefficients for worn tool segments were determined through simulation.

Polygonal concave wear and irregular packing behavior of grinding balls for vertical grinding mill

Grinding balls are an indispensable grinding medium in vertical grinding mills, grinding ore powder to target size. Some were severely worn and unrounded by iron ore from Anshan, China, during grinding operation in the vertical grinding mill (VTM-1500, Metso Outotec). Their service failure behavior was explored, based on classifying the wear shapes of the recovered grinding balls, combined with the ore-media operating behavior. The wear mechanism of the unroundness, invagination and the special-shaped reduction was verified by the three-dimensional (3D) wear sizes and position relationships of grinding balls. The main wear model of grinding balls was polygon wear, including pentagon shape and quadrangle shape. The minor wear form was abnormal wear, containing biconvex spindle contour wear and single pit contour wear induced by free wear distribution. Both mainly occurred on the packing protective surfaces, resulting in several normalized final shapes along with the wear progress. This investigation provides a theoretical basis for understanding the interaction behavior among slurry and grinding balls.

Progress in grinding performance by additive manufacturing of grinding wheels integrated with internal venturi cooling channels and surface slots

Among the most promising features of additive manufacturing are tool or form-free manufacturing and the ability to create intricate geometries that are difficult or even impossible to fabricate with traditional methods. These advantages can be employed to produce enhanced grinding tools. Efficient coolant fluid delivery into the cutting zone of the grinding operation has been a challenging problem since high frictional contact in the arc zone deteriorates the resin bond and lessens the grinding performance. This research study was dedicated to assessing the influence of internal cooling along with surface structures on the grinding performance of resin-bonded grinding wheels fabricated via additive manufacturing. This research introduced a novel structure that benefits from internal venturi shape cooling channels to provide exceptional fluid velocity in the tool and workpiece interaction zone. The grinding wheels have been produced employing vat photopolymerization. Grinding experiments with and without internal cooling were conducted on an aluminium plate to study the impact of introduced structures on the main aspects of grinding performance, such as cutting forces, surface roughness, tool wear, and dimensional accuracy. Two different grinding scenarios comprising shallow (10 μm depth of cut) and deep grinding (100 μm depth of cut) were carried out to reveal the influence of the material removal rate on the grinding experiments. The measured grinding forces revealed that integrating internal cooling channels and surface slots in a grinding tool could significantly reduce the grinding forces, which was more pronounced in the case of using venturi channels. Measured tool wear and dimensional accuracy together with calculated grinding ratio revealed that using cooling channels could participate in a notable increase in tool life and material removal ability, especially for venturi channels, due to improved cutting conditions, by which higher dimensional accuracy was obtained as well for the ground parts. Besides, it was discovered that the cooling channels could improve the surface quality of the ground part, which was less noticeable with the venturi channel grinding wheel. Furthermore, the optical and confocal microscopy detection confirmed that internal cooling channels could reduce chip loading on the grinding wheel surface, decrease the required number of dressing intervals, and cause effective promotion of tool life.

A melting pre-bonding method for fabrication of mechanical-robust superhydrophobic powder coatings

The rapid development of the coating industry has led to the exploration of novel functions beyond decoration and protection of traditional coatings. Superhydrophobic coatings bring about many potential benefits. e.g., water-repellency, self-cleaning property and corrosion resistance, etc. However, the durability of such coating remains an issue in the practical application. In the study, we proposed a melting pre-bonding method for synthesizing a durable solvent-free superhydrophobic powder coating with a high-water contact angle of 164.9°. With this method, the nano-micro polyester (PE)-SiO2 conglomerates were formed, which involved compaction, heating, and grinding operations to bond the SiO2 nanoparticles with the PE matrix. The resulting PE-5 %SiO2/PE composite coating retain its high WCA of beyond 150° after 150 abrasion cycles, presenting excellent abrasion resistance. The coating also has exceptional self-cleaning property and water bouncing behavior, as well as long-term durability when exposed to strong/weak acid/base corrosion media, NaCl solution, and UV radiation. This melting pre-bonding method increases the dispersibility and stability of nanoparticles in the fabricated superhydrophobic coating film under high-temperature melt-curing process, which is beneficial in achieving improved mechanical durability compared to the regular direct-blending method. The work endows powder coating with superhydrophobic property, promoting the development of functional coatings.

REGULARITIES OF VIBRATION FINISHING AND GRINDING PROCESSING AND DIRECTIONS OF IMPROVEMENT OF ITS INTENSITY AND QUALITY

The data on the labor intensity of manufacturing engineering products and the share of finishing and grinding operations in the total labor costs of their manufacture are presented. The list and the degree of mastering the technological operations of finishing and grinding processing, performed in the conditions of machine-building industries during the last years are given. The grounds are given for highlighting the method of vibration processing as the most promising for ensuring complete mechanization of the process of finishing and cleaning, as well as achieving high technological characteristics of the surface roughness of parts. An assessment was made of the influence of modes, the trajectory of the movement of the reservoir and the grain size of the granules of the abrasive medium on metal removal. It is indicated that the intensity and quality of vibration treatment is estimated quantitatively by the weight removal of metal and qualitatively by the roughness of the processed surface. It is indicated that the determining factor in this case is the speed of the oscillating movement of granules and parts, the difference of which represents the speed of vibration processing, depending on the speed of the oscillating movement of the medium. It is noted that in order to increase the productivity of the process, it is necessary to increase the speed of the medium by increasing the frequency and amplitude of the reservoir oscillations. The layer-by-layer transmission of a force impulse from the bottom of the reservoir to the bulk medium is considered. The physical meaning of increasing productivity by increasing the amplitude of the reservoir oscillations is indicated. The conditions for obtaining metal removal are indicated, which provide increased efforts for the interaction of granules with parts at high micro-cutting speeds. Experimental studies are described to determine the influence of the amplitude and frequency of oscillations on the results of vibration finishing and grinding. Graphic dependences of metal removal were obtained for various ratios of the sample weight to the weight of the medium granule. The dependence of metal removal on the ellipticity coefficient and the amplitude of the reservoir oscillations was obtained in a similar way. It is noted that the vertical component of the amplitude during in-plane oscillations of the reservoir is the determining factor of the complex influence of the parameters of the ellipse coefficient of the trajectory of the reservoir and its amplitude of oscillations. It has been established that when using a coarse-grained abrasive, the penetration of grains into the metal of the part occurs to a greater depth and larger metal chips are removed with a large metal removal. With a small grain size of the abrasive, small chips are removed with a small metal removal and a decrease in the height of micro-roughness.

Feasibility of granite processing waste as a fill material in geotechnical applications

India is the third largest granite producer worldwide, and an increasing trend in its export has been seen year by year. Granite is generally sold in dimensional and finished form. Large quarried granite blocks are processed to get a finished dimensional granite in processing industries. Processing comprises sawing, grinding and polishing operations. In processing operations, about 30 to 35 per cent of the mass of large granite blocks is left as fine Granite Processing Waste (GPW) in the form of slurry. Dumping of GPW is of major concern for the processing industries; it is often unscientifically dumped. Disposal of GPW in an unscientific manner causes adverse effects on humans and the environment. Delightful results are obtained in previous studies addressing its use in concrete, mortar building blocks and stabilization of expansive soils. GPW has the potential to serve as a fill material in geotechnical applications. However, a comprehensive characterization of GPW addressing its use as a fill material is significantly lacking. The current study intends to characterize GPW in light of its application as a non-conventional fill material in place of natural materials. Based on geotechnical and geoenvironmental tests carried out on GPW involving grain size analysis, Atterberg limits, hydraulic conductivity, swelling potential, compaction characteristics, surface morphology, chemical composition, elemental and mineralogical composition, pH and organic content analysis, it can be inferred that GPW is comparable to conventional fill materials.