ANALYTICAL DETERMINATION OF THE MICRORELIEF PARAMETERS FORMED AS A RESULT OF CENTERLESS GRINDING OF THE FULL SPHERE

При технологической подготовке операций чистовой и отделочной обработки деталей абразивными инструментами очень важными задачами являются прогнозирование ее результатов в зависимости от назначенных режимов и назначение режимов в зависимости от требуемого качества обработанных поверхностей. Имеющиеся многочисленные справочные материалы такого характера получены в лабораторных условиях, носят дискретный характер, не учитывают специфическую топографию поверхностей абразивных инструментов и множества других условий и поэтому недостаточно достоверны. На их основе возможно планировать технологический процесс только предварительно, а затем неизбежно требуется уточнять его параметры экспериментальным путем, что приводит к значительному удорожанию процесса подготовки производства. Наличие достоверной аналитической методики позволяет кратно снизить эти затраты, и поэтому она настоятельно необходима не только и даже не столько при выполнении научных исследований, сколько в реальном производстве. В статье аналитически определены параметры микрорельефа, образующегося в результате бесцентрового шлифования полной сферы. Уточнено влияние процесса выхаживания на формирование шероховатости сферы. Приведена методика расчета среднеарифметического отклонения микропрофиля сферической поверхности In the technological preparation of the operations of finishing processing of parts with abrasive tools, it is very important to predict its results depending on the assigned modes and the purpose of modes depending on the required quality of the processed surfaces. The available numerous reference materials of this nature were obtained in laboratory conditions, are discrete in nature, do not take into account the specific topography of the surfaces of abrasive tools and many other conditions, and therefore are not reliable enough. On their basis, it is possible to plan the technological process only in advance, and then inevitably it is necessary to refine its parameters experimentally, which leads to a significant increase in the cost of the production preparation process. The availability of a reliable analytical method allows you to multiply these costs, and therefore it is urgently needed not only and even not so much when performing scientific research, but in real production. In the article, we analytically determine the parameters of the microrelief formed as a result of centerless grinding of a full sphere. We determined the influence of the nursing process on the formation of the sphere roughness. We present a method for calculating the arithmetic mean deviation of the micro-profile of a spherical surface

A Reusable Unit Process Life Cycle Inventory Model for Infeed Centerless Grinding

Environmental impact minimization is an important aspect for improving the sustainability performance of manufacturing processes. Quantifying the environmental impacts of unit manufacturing processes requires systematic modeling of process life cycle inventories. This paper develops an inventory model for infeed centerless grinding based on the unit process life cycle inventory methodology. The developed model estimates the energy consumption, material losses, and consumable fluids, for a typical high-volume production setup. Process consumption data is estimated from parameters directly used for process setup as well as machine and tool specifications that can be easily obtained from technical documentation and product geometrical specification. The developed model is demonstrated using a case study involving the infeed centerless grinding of an Inconel 718 shaft on a Cincinnati Twin-Grip Centerless Grinding Machine.

Novel application of multitubular nozzle in through-feed centerless grinding process of bearing steel SAE 52100

Through-feed centerless grinding is a high-productivity machining process widely used for mass production of cylindrical parts and rotationally symmetrical parts in automotive and bearing industries. Grinding process is strictly related to large amount of heat generated in the cutting zone. This process characteristic makes pivotal and indispensable the effects of lubrication and cooling provided by metal working fluid (MWF). In this regard, this work aims to contribute to the study of MWF application in grinding process, analyzing the effects of the optimized technique developed for an eco-friendlier use of MWF by the application of a novel multitubular nozzle. The results obtained for the novel designed multitubular nozzle with compressed air outperformed the conventional nozzle system with lower oil volume employed.

Evaluation of the Possibilities of Processing High-Alloy Corrosion-Resistant Steels during Grinding Operations

The issues of processing high-alloy corrosion-resistant steels by the method of centerless cylindrical grinding are considered in the article. Experimental data on changes in the parameters of roughness and hardness of a workpiece depending on the depth of cut, the speed and the design features of a control wheel are presented. The change in the microhardness of a part depending on the depth of cut is analyzed. Much attention is paid to the study of thermal stress of the grinding process. Images of temperature changes in the cutting zone depending on the grinding wheel characteristics are shown. Conclusions in the form of practical recommendations for improving high-alloy steel processing by the method of centerless grinding are formulated on the basis of the results obtained.

Multi-Objective Optimization of Process Parameters to Enhance Efficiency in the Shoe-Type Centerless Grinding Operation for Internal Raceway of Ball Bearings

In this article, new research on the multi-objective optimization of the process parameters applied to enhance the efficiency in the shoe-type centerless grinding operation for the inner ring raceway of the ball bearing made from SUJ2 alloy steel is presented. The four important input parameters for this process, which included the normal feed rate of fine grinding (Snf), the speed of the workpiece (Vw), the cutting depth of fine grinding (af), and the number of ground parts (Np), were investigated. The aim of the study was to find the most appropriate value set of process parameters in order to, simultaneously minimize the grindstone wear (Gw), maximize the material removal rate (MRR) and the total number of ground parts in a grinding cycle (N’p), while guaranteeing other technology requirements such as surface roughness Ra ≤ 0.5 (µm), oval level Op ≤ 3 (µm), etc. In order to solve the problem, based on the experimental data, in which the grindstone wear was measured online by a measuring system consisting of two pneumatic probes, the optimization of the target functions of Gw, N’p, and MRR and mathematical models that express the dependencies of outcome parameters Gw, Ra, Op, MRR, etc. on the process parameters were determined. Therefore, a global optimal solution of such a discrete and nonlinear multi-objective optimization problem was solved by using a genetic algorithm, presenting the most appropriate process parameters as follows: Snf = 15.38 (µm/s), Vw = 6.00 (m/min), af = 11.76 (µm), and Np = 20 (parts/cycle). In addition, the impact of the four process parameters (Snf, Vw, af, Np) on the wear of the grinding wheel (Gw), the oval level of parts (Op), and the surface roughness of parts (Ra) was evaluated. The discovered technology mode has been applied to the real machining process for the inner ring raceway of the 6208_ball bearing made from SUJ2 alloy steel, and the outcome showed a much better result in comparison with default setting modes, while still ensuring the technology requirements. The difference between the predicted values and the real values of the parameters Gw, Ra, Op, and MRR were controlled within 5% of the ranges.

Geometrical Optimization of Centerless Grinding Process by Profiled Workrest

This work presents a method to optimize centerless grinding geometrical configuration. It is based on the regulation of the horizontal axes of operating and rubbing wheels of the machine machine coupled with an opportune blade profile, allowing a continuous selection of workrest angle and workpiece height, without requiring blade substitution and/or manual interventions. The regulation of workrest angle and height cannot be done independently: their relationship is defined during blade profile design. In machines with two independent axes for regulating wheel and blade horizontal displacement, this regulation can be performed in process or in the setup phase and does not require manual blade adjustment/replacement. This results in optimal processing parameter choice leading to improved quality and shorter time of processing as well as reduced setup time.

Investigation of the Surface Roughness in Infeed Centerless Grinding of SCM435 Steel

This study was carried out to investigate the surface roughness in infeed centerless grinding process. The experiment was performed to determine the influence of several technological parameters on the surface roughness. The grinding wheel of Hai Duong Company, Vietnam, was used to machine the SCM435 steel. The experimental matrix was designed using central composite design (CCD). The machining parameters that were used as the input parameters in this study include the workpiece center height, dressing feed rate, regulating wheel velocity, and infeed rate. From the experimental data, an initial model of the surface roughness was built as a quadratic function. Further, a Box-Cox transformation was used to develop a new model from the initial surface roughness data with better accuracy than that of the initial model. The accuracy of the proposed model was verified by comparing the values of the mean absolute error, mean square error, and determination coefficients. This direct approach can be applied for the investigation of other factors during machining processes and can be used in the optimization of machining processes.