External 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.

Design, preparation and characterization of iron nitride magnetic abrasives

In order to effectively polish the surface of the titanium alloy workpiece, a novel type of iron nitride magnetic abrasives was designed, prepared and characterized. Theoretically, first-principles were used to analyze the effects of phase compositions of iron nitrogen compounds on the mechanical and magnetic properties of the abrasive, and ε-Fe3N and γ′-Fe4N were determined as the grinding phase compositions with the simultaneously improved properties of hardness, ductility and magnetism. In the experiments, the core-shell structured iron nitrogen compounds were prepared by nitriding the iron powders of about 250 μm with ammonia at 600 °C, and the effects of nitriding time, ammonia pressure and cooling method on the product were investigated. The composition, morphology, magnetic properties and mechanical properties of the product were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), magnetometer and nanoindenter, respectively. Under experimental conditions of ammonia pressure of 0.2 Mpa, nitriding time of 3 h and water quenching, the abrasive was obtained with the external grinding phase of ε-Fe3N and γ′-Fe4N in a thickness of 35.10 μm and the internal ferromagnetic phase of α-Fe. Its magnetic saturation intensity and hardness were 148.5 A m2 kg−1 and 8.15 GPa, respectively. Grinding with this abrasive, the surface roughness of Ti–6Al–4V alloy plate was effectively reduced from 0.305 μm to 0.077 μm.

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.

Synthesis of lunberger stochastic observer for estimation of the grinding operation state

The technique of constructing Lunberger stochastic observer for the operation of circular external grinding is considered in the article, which makes it possible to obtain optimal estimates of the output parameters of the technological system. To build Lunberger stochastic observer, a program has been developed that allows solving the Riccati equation of the object and the filter. The calculation of the Kalman-Buсy filter coefficients for the steady-state mode of the process of grinding the camshaft journal is performed. This allows us to evaluate the state of the system in real time, and even in the case of measuring only one coordinate, the filter gives estimates of all coordinates, and the maximum estimation errors do not exceed 10%.

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.

Forecasting the surface roughness of the workpiece in the round external grinding

The article gives an analysis of the influence of technological factors on the parameters of the surface roughness during the machining of workpieces with the abrasive tools, based on the use of the modern mathematical apparatus of the theory of probability. It is shown that when processing with abrasive tools, the formation of surface microrelief is directly related to the mechanism of material removal in the area of contact between the workpiece and the tool. The main parameters of the contact zone are its dimensions and parameters of the material removal processes, which are characterized by the probabilities of removal or non-removal of the material. The obtained dependences take into account the parameters of the state of the working surface of the tool and can be used to calculate the basic parameters of the surface roughness in round external grinding. The made estimation of the influence of technological factors on the roughness of the surface of the workpiece being processed allows for the selection of the most significant ones, the changes of which must be taken into account when designing grinding operations.

Obrabialność stali 3H17M w procesie szlifowania zewnętrznych powierzchni cylindrycznych

Obrabialność stali 3H17M w procesie szlifowania zewnętrznych powierzchni cylindrycznych

Finite element analysis of burr formation and an automatic online micro-deburring method in precise end-face grinding process

A new approach is presented in this article for modeling and analysis of precise end-face grinding burr formation. The aim of this approach is to develop an automatic online deburring method that utilizes a precision motion control mechanism and effective deburring tools. Servo valve cores widely used in aerospace industry were employed as the workpiece in this study. After precision external grinding process, as a rule, the way of end-face grinding is adopted to get qualified working edges; the precision of these edges are generally required to be micron level or higher. However, after end-face grinding, the outside circle of the working edges will have burrs whose heights range from a few to dozens of microns, and the manual offline burr removal method currently adopted is not only uneasy to control accuracy but also easy for the working edges of the workpiece to lose its integrity and lead to a high rejection rate. In this article, the burr modeling and analysis procedure were used to get the corresponding formation mechanism of burr, and the online precision burr removal equipment was designed reasonably. Therefore, the effective removal of arising micro-burr from end-face grinding and the accuracy of the working edges were very well guaranteed, so as to improve the production efficiency.

Obrabialność żeliwa sferoidalnego ADI w procesie szlifowania zewnętrznych powierzchni cylindrycznych

Obrabialność żeliwa sferoidalnego ADI w procesie szlifowania zewnętrznych powierzchni cylindrycznych

Surface roughness modeling based on laser speckle imaging

Surface roughness is an important parameter in measuring the roughness of surface formed by laser irradiation on the workpiece. Speckle images of rough surfaces in different classes and different surface roughness values are obtained by constructing a set of laser speckle image acquisition systems. First, the texture features of speckle images including coarseness, contrast and direction are extracted using Tamura texture theory. Then, the interactions these three features with the surface roughness are analyzed. Based on the analyses of their monotonic relations, the surface roughness functions, including flat grinding, external grinding and mill grinding craftworks, are established respectively between the texture coarseness feature of the speckle image Fcrs and surface roughness Ra. Through the establishment of surface roughness function for the above three classes of workpieces, the value of surface roughness can be computed directly. However, before obtaining the value of surface roughness, the classes of processing technic should be determined because of the inconsistency of function expressions for different classes. And based on the specific connection and related dependencies between Tamura texture features and workpiece class, Bayes network is proposed to describe this uncertainty relation among different classes. Through network structure learning and parameter learning, a model for reasoning is found which can be used to determine the class of workpiece after obtaining texture coarseness feature Fcrs. Thus, not only can the value of surface roughness be measured, also the class of work-piece can be recognized. Experiments are conducted to confirm the feasibility of the proposed model for measurement. The detection results indicate that high precision and accuracy are achieved for both workpiece class recognition and roughness measurement.

Effective cutting conditions in abrasive machining

Effective cutting conditions are considered in relation to the requirements on the product, for the example of external and plane grinding by the periphery of the wheel. Any technological constraint may be expressed as a region in parameter space. In solving various technological problems, the relevant factors may be analyzed in terms of the satisfaction of particular constraints. The outcome is a region corresponding to a particular constraint in the space of control parameters.

Evaluation of different methods of cooling-lubrication in cylindrical grinding of advanced ceramic dip

The current work presents a study of alternative methods of cooling-lubrication for the external plunge grinding of advanced ceramics using diamond wheels. These two alternative methods, which are intended to reduce cutting fluid expenses, are commonly referred to as the optimized cooling-lubrication method and minimal quantity of lubrication (MQL). The techniques were evaluated by process monitoring and by the assessment of output variables such as tangential cutting force, G ratio, roundness errors, surface roughness, microstructure and residual stresses measured by X-ray diffraction. The obtained results showed that the two proposed techniques can replace the conventional cooling-lubrication method, i.e., flood coolant. In particular, optimized cooling-lubrication method reduced wheel wear and produced workpieces with the best geometric and dimensional finishes, while MQL significantly reduced the amount of fluid employed in the process without harming the workpiece quality.

Force required in centerless external grinding of superhard powder composites

Force required in centerless external grinding of superhard powder composites

Stainless steel processing: external grinding of pipes – wet or dry?

Stainless steel processing: external grinding of pipes – wet or dry?

Grinding-Hardening Experiments and Grinding Force Analysis in Infeed External Grinding for 45 Steel

The grind-hardening method suitable for external grinding is proposed in this paper and the experiments are carried out on MI432B grinding machine.The hardened layer of the workpiece with cut depth 0.3mm and speed 0.2 m/min is analyzed.The result indicates the metallurgical structure of the hardened layer is martensite and the top hardness value is 754 HV(about 620 HRC).At the same time,the grinding force,one of the most important factors of grind-hardening process is modeled, and the measurement method is provided with elastic core clampers.The measurement result shows that the values of both the tangential force and the normal force increase when the cut depth increases,and the top value is 146 N and 656 N with the cut depth value of 0.4 mm respectively.

Исследование неравномерного абразивного воздействия при наружном круглом шлифовании

Исследование неравномерного абразивного воздействия при наружном круглом шлифовании

Design of Ball Screw Mechanism for Retro Fit of External Grinding Machine

To convert the existing grinding machine into a good working machine, a ball screw mechanism is designed and incorporated in the existing grinding machine by retrofitting process. Grinding machine removes material from the work piece by abrasion, which can generate substantial amount of heat. Therefore a coolant System is incorporated to cool the work piece, so that it does not overheat and go out of its tolerance. Grinding practice is a large and diverse area of manufacturing and tool making. It can also rough out large volume of metal quite rapidly. It is usually better suited to the machining of hard materials. Cylindrical grinding is also called center type grinding. It is used in the removing the cylindrical surface and shoulders of the work piece. The five type of cylindrical grinding are outside diameter (OD) grinding. Inside diameter (ID) grinding, plunge grinding, creep feed grinding and center less grinding.It is used in the industries for grinding the nozzle body. The grinding machine can be changed to automatic machine according to one of the latest technologies called PLC's controller. The manually operated grinding machine has some of the in-accuracies and disadvantages compared to new modern CNC grinding machines.Based on the case study of both manual and CNC grinding machine, the manual machine is converted into automatic machine for the better accuracy and efficiency. The main replacement of the machine parts are hydraulic cylinder and stepper motor by ball screw mechanisms and

Proposal of Purification Method of Grinding Coolant by Dissolution of Micro-Bubbles

In this study, the purification method of coolant by the micro-bubble dissolution is proposed. The micro-bubble dissolving device with the simple configuration is incorporated within the coolant supply system of an external grinding machine, and then, the effect of the purification method is examined experimentally on the ground surface roughness. From the results, the following are clarified: The dissolved micro-bubbles can rise up grinding debris by electrical adsorption, and then, the debris is concentrated on the coolant surface in the coolant tank. By this effect, the grinding debris, especially the grain fragments of the grinding-wheel, can be removed from the coolant. The coolant purification by the enough dissolved micro-bubbles reduces the density of grinding debris down to a fourth of the initial condition. This purification effect improves the ground surface roughness. The longer the dissolving duration is, the more the ground surface roughness is improved. Eventually, the improvement of the surface roughness reaches down to a half of that without the micro-bubble dissolution.

Extending the technological capability of turning operation

The main goal of this paper is to compensate the elastic deformations of the technological system in order to achieve maximum cross sectional accuracy and productivity of turning operation with minimum cost. This study was based on developing of mechanical adaptive system (MAS) for accuracy control by dynamic adjustment of the tool position during processing. The dynamic characteristic of components of the engine lathe technological system supplied with the proposed MAS was studied, and a mathematical model was obtained and presented as a system with one degree of freedom in the direction of Z-axis. The stable zones of operating were defined using Leonarion graphic method. The optimal cutting parameters correspond to stationary positions of equilibrium were obtained when processing heat resistant steel under the following conditions: feed rate, S, ranges from 0.07 to 0.39 mm/rev; depth of cut, t, ranges from 0.5 to 1.5 mm; and turning speed, υ, ranges from 0.55 to 1.45 m/sec. Experimental examination of the proposed system showed that the use of adaptive control may overcome the error appeared due to the elastic deformation of the technological system. The maximum circularity deviation of the processed, using the developed MAS, cylindrical surfaces did not exceed 40 microns, whereas 98 microns of maximum deviation was reached using usual cutter. The developed MAS can, in number of cases, replace the cylindrical external grinding processing by usual cutting on lathe machine tools, providing thus the rigid requirements on dimensional and form accuracy in cross sections. Keywords: Control systems, cross sectional accuracy, mechanical adaptive, productivity, turning

Control of circular external grinding by means of an acoustic signal

Control of circular external grinding by means of an acoustic signal