Flat Grinding Research Articles

Modeling of Dynamic Links which Characterize Static Properties of Grinding Wheel and Workpiece during Flat Grinding Process

The article considers the results of theoretical and experimental studies of the process of external grinding on the basis of the developed dynamic model. It uses the description of an equivalent dynamic link that converts a standard signal in the form of Gaussian white noise to a random process. For the settings of the forming filter, the results of statistical processing of profilograms of the working surface of the grinding wheel are obtained. The constructed forming filter makes it possible to characterize the statistical properties of the grinding wheel and workpiece. The developed mathematical model of the operation of flat external grinding can be used to assess the quality characteristics of machined parts and systems of automatic process control when solving the problem of intensification of production.

Effect of tooling surface on friction conditions in cold forging of an aluminum alloy

Abstract Friction during cold forging of aluminum was analyzed with a ring with boss compression test (RCT-B) and an optimum spike forging test (O-SFT). The tool surface was treated with three methods: flat grinding, bead blasting, and lapping-plus-polishing. With the RCT-B test, friction factors for oil lubrication and dry conditions were determined by using platens after bead blasting and lapping-plus-polishing. Because of friction anisotropy, the factors could not be determined directly with flat ground platens because the data was beyond the range of calibration curves. Anisotropic friction was also observed with the O-SFT method. Finite element simulations were performed to better understand the anisotropic friction results.

Structural-Technological Methods for Reduction of Thermal Stress in Grinding

A study has been made of temperature fields occurring in a workpiece in the process of its flat grinding. The author has obtained relations making it possible to calculate the rate of heating and cooling of the machined workpiece at any point of it with account of the machining regime and of the intensity of the heat flux and the time of its action, and also the dependence of the stresses in the workpiece on the time of action of the heat source and its temperature. It has been established that by changing the structural parameters of the cutting surface of the wheel and the relation between the velocity of motion of the workpiece, the velocity of motion of the wheel, and the grinding depth, one can control the time of action of the heat flux on the workpiece and reduce thermal stress of the process.

The Effect of the Operating Speed and Wheel Characteristics on the Surface Quality at Creep-Feed Grinding Titanium Alloys

The paper dwells upon flat creep-feed grinding of grooves in Ti6Al4V workpieces. Those were machined with high-porosity silicon carbide wheels of I, H grades at a speed of 20-30 m/s. Machined surfaces were analyzed using a Versa 3D electron microscope. The paper demonstrates the formed morphology of ground surfaces along the workpiece. Higher-speed grinding results in greater concentrations of silicon on the machined titanium alloy surface. Altering the characteristics of the abrasive tool does not have a significant effect on the concentration of silicon on machined surfaces. The paper analyzes how the grade of wheel and the grinding speed affect Ra surface roughness parameter. The article demonstrates the difference in grades of wheels along the surface, at the stage of constant length of arc and the stage of exit.

Energy efficient rotor design for HIGmills

Extensive research with HIGmill grinding rotors has shown that flat grinding discs in stirred media mills in hard-rock applications experience poorer process performance compared to castellated rotors. The first industrial size equipment to benefit from this is Kevitsa Cu-Ni mine, where the energy improvement from flat to castellated discs was 28–50%. This observation was investigated further through different size pilot scale units, which clearly confirmed a step change shift in the specific grinding energy versus the product particle size at 80% passing. The design of the rotors was further developed and fine-tuned with DEM (Discrete Element Method). The validated results have allowed the castellated rotor design to be applied as a standard to allHIGmills.

Determining surface roughness of machining process types using a hybrid algorithm based on time series analysis and wavelet transform

In this paper, the surface roughness of the machined workpieces are estimated using a hybrid algorithm based on time series analysis and wavelet transform and differences between contact method with this method are presented. The suggested method is based on the exact recognition of the surface dynamic properties in lapping, external grinding, flat grinding, turning, and horizontal milling processes using the largest Lyapunov exponent parameter in time series analysis. This method has the unique ability to reduce image noise and remove image curvature which are produced due to reflection of light or surface geometric curvature in the mentioned machining process. Also, in order to select the appropriate length of the captured images and increasing accuracy of estimating the surface roughness, the image entropy criterion in image processing is used. The results show that the estimated surface roughness are considerably close to the measured surface roughness by the contact method.

Influence of cutting parameters on surface hardening of 52100 steel in flat grinding process

Grinding is a finishing operation widely used in the production of mechanical components that need high tolerance, less form errors, and excellent surface quality. Using the correct cutting strategy in grinding can generate better results by minimizing the amount of cooling fluids, improving surface roughness and decreasing cutting forces. The main aim of this work was to produce analyses of the surface roughness, shear strengths, and microhardness related to the variation of cutting parameters. Thus, a grinding wheel of silicon carbide with 254 mm of outer diameter and width of 25.4 mm was employed to carry out flat grinding tests on 52100 hardened steel. Shear strengths, surface roughnesses, and microhardnesses were monitored with specific devices. The results showed that the most influential parameters were the feed rate and the depth of cut. Thus, the increase of the feed rate resulted in the rising of surface roughness values greater than 90%, considering the orthogonal plane and cutting direction. The process also generated higher microhardness values. Finally, the resulting microhardness also revealed the softening of the surface layer of the workpieces for cutting conditions with lower depth of cut and feed rate. Based on this, it can be concluded that the use of high feed rates generated higher values of microhardness. Thus, the use of correct feed rate values can reduce the burning of material without compromising the structure of the machined material.

Flat grinding model, considering internal dynamics of the process

The article considers the results of theoretical studies of the process of flat external grinding on the basis of the developed dynamic model. In order to take into account the influence of the statistical properties of the current deviations of the radius vectors of the grinding wheel and the thickness of the work piece, in addition to the input signal, a random process with the same stochastic characteristics as that of the current deviation of the radius vector of the grinding wheel and the billet topography is fed to the input of the system model. The corresponding random input signal can be obtained by means of a shaping filter. The output coordinate of the shaping filter according to its statistical parameters corresponds to the parameters of the components of the dynamic system characterizing the processes of the grinding wheel effect on the work piece during the grinding process. The developed mathematical model of the operation of flat external grinding can be used to determine the estimates of the quality characteristics of machined parts and systems for automatic control of the process of flat external grinding when the model is supplemented by dynamic links characterizing the statistical properties of the grinding wheel and work piece.

Simulation of workpiece surface roughness after flat grinding by electroplated wheel

The stochastic nature of grinding wheel topography together with grinding process parameters and kinematics have great influence on the surface roughness of workpiece. This paper aims to achieve a method of kinematics simulation of flat grinding process using MATLAB to predict the surface roughness of workpiece based on the topography of the electroplated Cubic Boron Nitride (CBN) wheel. Grain distribution, protrusion height and size are varied for each simulation. Based on trajectory of spherical grain forms in flat grinding kinematics, a 3D simulation of surface roughness is resulted. Suggestions are made for the improvement in accuracy of predicting workpiece profile.

Contact ability optimization of the surface of titanium parts with different stiffness during flat grinding by highly porous wheel

In order to improve the contact performance properties, we present optimization of flat grinding of titanium parts in accordance with two parameters: the relative bearing length of the profile and the relative bearing part of the parts’ surface that allow to assess the quality of the surface at the micro- and macro-scale. It is established that in order to achieve the set goal, grinding should be carried out with a minimum lateral feed ratesΠ= 2.0 mm/double pass, and the remaining technological parameters are selected depending on the rigidity of the parts and the direction of its variation.

Deviation from flatness of surfaces after combined peripheral grinding

A new method of combined flat peripheral grinding is examined, which allows to carry out simultaneously preliminary and final machining of the planes without replacing the coarse with the fine-grain grinding wheel, to eliminate the auxiliary time for the tool replacement, to correct it and set the grinding equipment in order to accomplish the given size. An experimental multifactor model which relates the surfaces flatness deviation with independent factors of the combined grinding process is established on the basis of which it is possible to assign the cutting conditions that provide the required flatness with the greatest possible longitudinal and cross-feed of the blank.

Стохастическая модель процесса абразивной обработки. Динамика плоского шлифования

Стохастическая модель процесса абразивной обработки. Динамика плоского шлифования

Mathematical model for determining rational machining conditions for flat grinding with the wheel periphery on machines with a rectangular table

A mathematical model is presented for determining the rational machining conditions for flat grinding operations by the rim of a wheel on machines with a rectangular table consisting of a linear objective function and linear inequality constraints. As the objective function, the equation, determining the main machining time, was used. And constraints which are related to the functional parameters and parameters determining the machining quality and the kinematic capabilities of the machine were used as inequality constraints.

Стохастическая модель процесса абразивной обработки. Кинематика плоского шлифования

Стохастическая модель процесса абразивной обработки. Кинематика плоского шлифования

Design of Grinding Operations on the Basis of Modeling with Application of Artificial Neural Network

Повышение эффективности производства во многом определяется этапом проектирования изделий и технологических процессов с использованием современных программных средств автоматизированного проектирования. Отсутствие универсальных математических моделей, описывающих шлифование, обусловливают необходимость поиска новых подходов и методов описания и формализации данного процесса. Сложность решения этой задачи обусловлена, прежде всего, многофакторностью процесса и вероятностным характером протекающих явлений. Создание универсальной математической модели процесса шлифования, позволяющей определять параметры инструмента и режима обработки, возможно на основе применения нейросетевого программирования. В статье предлагается для решения задачи в условиях неопределенности использовать искусственную нейронную сеть (ИНС), основная сложность работы с которой связана с построением и обучением сети. Для моделирования процесса шлифования построена ИНС, в качестве функции активации которой был использован гиперболический тангенс. Проведенные исследования показали возможность построения сети на 6 нейронах в скрытом слое. Оценка результатов работы нейронной сети, структура которой состоит из трех слоев: входной - 7 нейронов-рецепторов; скрытый - 6 нейронов; выходной - 6 нейронов - показала, что погрешность обученной ИНС лежит в диапазоне от 0,1 до 2 %. Построение модели включает следующие этапы: загрузка в систему обучающих массивов данных; расчет параметров будущей модели; анализ исходных данных и вывод информации о качестве обучающих массивов; создание структуры и обучение нейронной сети. Разработанная модель положена в основу системы автоматизированного проектирования режимно-инструментального оснащения операций плоского шлифования, состоящей из нескольких модулей: «Моделирование», «Создание моделей», «Архив моделей», «Анализатор», «Справочник», «Пользовательский интерфейс». Использование специализированной САПР операций шлифования с возможностями автоматизации выбора абразивного инструмента и параметров процесса, созданной на основе математической модели с использованием ИНС, способствует повышению качества и сокращению времени проектирования.

Sharp corner transitional trajectory planning based on arc splines in glass edge grinding

The sharp corners on final contours in flat glass grinding can cause broken wheel center trajectories. A corner transitional trajectory planning algorithm based on arc splines is proposed in this paper to control the wheel center trajectory G1 continuity and the grinding depth at a corner. The radii of arc splines are derived first to meet design requirements based on the geometrical features of a sharp corner. A three-phase feedrate planning scheme is introduced to generate the arc splines. Corner classification and treatment are presented to make the proposed algorithm flexible, and steps for algorithm application are summarized. Experimental results demonstrate that the proposed algorithm can achieve satisfactory shape accuracy at corners without any breakage, rounding, or flattening.

Повышение качества шлифования заготовок из камня

The problems of planning and experiment setting, measuring equipment, tools and equipment used are described. There are shown results of experimental investigations of granite grinding process. A simulator for the assessment of the topography of a surface worked in a blank is developed. A method of technological impact at processing a blank by grinding and a design of an adaptive device are offered. The 3D model of an adaptive device for the flat grinding of a surface in a stone blank is developed. The description of the device components and its operation principles are shown.

Моделирование процесса стохастического взаимодействия инструмента и заготовки на операциях шлифования

The interaction analysis of abrasive grain tip contact probability with the material, number, the form and length of single cuts at finishing processes of flat grinding is presented. It is shown that when passing a contact area of a blank with a disk a grain can cut material off, if it falls on one of protrusions of surface roughness, or will not cut it, if it falls on one of roughness cavities. The dependencies obtained in the work allow estimating the influence of a grinding mode and tool characteristics on the length of single cuts, defining basic parameters of a grinding process, watching regularities in the formation of micro-relief formation on the surface worked and forming its rated profile which can be obtained at the operation fulfillment. The example of the computation and formation of a theoretical profile of a surface micro-relief is shown.

Influence of rigidity of the hardened parts on forming the shape accuracy during flat grinding

At present time there is not information about the influence of rigidity of hardened steel parts on the parameters of flatness deviations: EFE max , EFE a , EFE q , which are called correspondingly greatest, arithmetic average and quadratic average. To model the variable rigidity of workpieces, an arrangement with the frame structure was used. It allowed to simulate the variable compliance of parts with constant sizes in the direction of longitudinal feed of grinding machine. Searching for models of multiple dispersion analysis was carried out using the D-optimal plan of experiment. They predicted that in rough grinding all parameters of flatness deviations increase with the growth of the part rigidity. In the subsequent grinding stages, the increase of part rigidity is accompanied by the favorable decrease of the flatness deviations. The compliance of low-rigid parts in the finishing stage of grinding should be reduced using additional technological devices.

Optimization of Conditions for Non-rigid Workpieces Flat Grinding by Elastic Deformations Controlling

The authors propose the technique for optimizing the conditions for non-rigid workpieces end surfaces flat grinding that guarantees obtaining the pre-defined quality requirements of the machined surface (surface roughness parameter Ra, absence of grinding burns, required flatness tolerance of end surface) while ensuring the maximum process efficiency.Mathematical models of the cutting force components, grinding ratio, and roughness of the machined surface (Ra parameter) are obtained by the full factorial experiment method. The input factors (grinding wheel hardness, depth of grinding, table feed speed and run) are considered as the grinding process optimization parameters. Mathematical models of the output factors are used to limit the range of optimization parameters allowable values. The resulted efficiency is an objective function. The optimization of parameters in the range of allowable values is carried out with the view of ensuring the maximum process efficiency.The required flatness admission is provided at the second optimization stage of the workpieces by controlling the elastic deformation extent.The varied parameters at controlling the maximum elastic deformation extent are cutting forces and attraction of the machine table magnetic field.The terms for providing of the required end surface flatness tolerance are determined for workpieces taking into account elastic deformation of the non-rigid workpieces under the magnetic field effect on the machine table and the radial component of the grinding force.