Through-feed Centerless Grinding Research Articles

Evaluating the optimized lubri-cooling technique for various cutting conditions in through-feed centerless grinding process

Evaluating the optimized lubri-cooling technique for various cutting conditions in through-feed centerless grinding process

Application of optimized lubri-cooling technique in through-feed centerless grinding process of bearing steel SAE 52100

Application of optimized lubri-cooling technique in through-feed centerless grinding process of bearing steel SAE 52100

Dynamic Rounding Stability in Through-Feed Centerless Grinding

The through-feed method in centerless grinding allows manufacturers to produce cylindrical parts at much higher levels of productivity than can be achieved with in-feed grinding, so it has been extensively employed in industry. However, its rounding mechanism is not yet well understood due to the complexity of the through-feed process. This paper presents the fundamental parameters, such as material removal rates, forces, and so on in the through-feed grinding, and analyses on the grinding system with feedback loops, including regenerative functions and the machine dynamic functions. Further, the characteristic roots of the system, representing the number of waves and the growth rates of the harmonics in roundness, are identified at each grinding position from entry to exit. To evaluate the grinding process stability, a rounding stability index (RSI) was proposed. It was demonstrated that the analytical tool modeled in this paper can identify the optimum operational conditions by the RSI for achieving desired grinding productivity and accuracy. Finally, the model is verified with grinding tests, and the nm-order roundness obtained by the tests is shown.

A novel approach to roundness generation analysis in centerless through-feed grinding in consider of decisive parameters of grinding gap by use of 3D kinematic simulation

Grinding gap geometry based on setup conditions and its effect on roundness generation is a complex phenomenon in through-feed centerless grinding process. The objective of this paper is to introduce a suitable solution for the use of simulation in through-feed centerless grinding, to assist in the selection of acceptable set-up conditions for centerless grinding and their effect on roundness quality. A qualitative assessment of geometrical influence parameters is carried out by means of a kinematics simulation based on a non-linear 3-dimensional model of the centerless grinding process. The novel aspect of the model analysis is the determination of the grinding gap with two new decisive parameters in centerless through-feed grinding and their effect on geometrical rounding stability. The ratio of the finishing to roughing length and ratio of the finishing to roughing material removal rate are crucial to minimize roundness errors.

<b>Effects of different cutting strategies on G-ratio in through-feed center-less grinding

Grinding is the main manufacturing process used in finishing operations. Center-less grinding is widely used in the production of auto parts e.g. roller bearings, valve stem and stem of shock absorbers. Center-less grinding is used in large-scale production due to shorter time and higher flexibility. However, the set-up of the grinder is complex and slow, and depends on the operators’ ability. The choice of the best parameters in the process is important to define exactly the cutting strategy and to optimize the process. Current study analyzes the input parameters: feed rate and type of materials on the responses G-ratio, surface roughness, and roundness. Thus, stems of shock absorbers were used as work pieces on the shop floor. Cutting speed and grinding wheel type were constant. The input parameters comprised feed rate and type of materials (1025 and 1045). Responses were surface roughness, roundness error and G-ratio. Results demonstrated that the kinds of tested material was the parameter that most influenced G-ratio and surface roughness. Moreover, feed rate had little influence on the quality of the work pieces, mainly on roundness error.

Dynamic Model of Material Removal Process in Through-Feed Centerless Grinding Based on the Lagrange Equation

Due to the unfixed state of the workpiece and the dissimilarity between sections in through-feed centerless grinding, the positions and orientations of the workpiece keep changing in the grinding process, which are coupled with the workpiece roundness generation. In this paper the positions and orientations of the workpiece are described by the dynamic equations obtained from Lagrange equation. And the homogeneous coordinate transformation is applied to present the profiles of the workpiece, grinding wheel and control wheel in the reference frame. Finally the time varying profile of the workpiece is obtained for the investigation of the material removal process in 3D space. The material properties of the workpiece, the wheels and the workrest combined with the geometric relationship of their profiles are utilized to calculate the interaction between them, including the three forces along the axes and the three moments about the axes.

Simulation investigation of through-feed centerless grinding process performed on a surface grinder

This paper proposes a simulation method for investigating the through-feed centerless grinding process performed on a surface grinder, where a compact centerless grinding unit, composed of a guide plate, an ultrasonic elliptic-vibration shoe, a blade, and their respective holders, is installed onto the worktable of a surface grinder, and the through-feed centerless grinding operation is performed as the workpiece located on the guide plate is fed into the space between the grinding wheel and ultrasonic shoe. The geometrical arrangement of the grinding apparatus including the contact lines on the grinding wheel, ultrasonic shoe, and blade are analyzed firstly for building a 3-D simulation model. Then, the workpiece forming process and the effects of major process parameters such as the workpiece eccentric angle, the stock removal, the ultrasonic shoe tilt angle and the applied voltage amplitude on the machining accuracy (i.e. workpiece cylindricity and roundness) are clarified by simulation and experiments. The obtained results indicate that higher machining accuracy can be achieved under the conditions of larger workpiece stock removal, smaller ultrasonic shoe tilt angle and higher applied voltage amplitude, while the workpiece eccentric angle is at 6°.

A new through-feed centerless grinding technique using a surface grinder

This paper proposes an alternative centerless grinding technique, i.e., through-feed centerless grinding using a surface grinder. In the new method, a compact centerless grinding unit, composed of a guide plate, an ultrasonic shoe, a blade, and their respective holders, is installed onto the worktable of a surface grinder, and the through-feed centerless grinding operation is performed as the workpiece located on the guide plate is fed into the space between the grinding wheel and ultrasonic shoe. The ultrasonic shoe, produced by bonding a piezoelectric ceramic device onto a metal elastic body, is tilted at a small angle so as to provide sufficient force to control the workpiece rotational motion and to feed the workpiece along its axis by the ultrasonic elliptic-vibration. In this paper, the workpiece motion control tests were carried out firstly to make sure that the workpiece rotational speed and through-feed rate can be exactly controlled by the ultrasonic shoe which is essential for performing high-precision grinding operations. Then, the effects of major process parameters such as the workpiece eccentric angle, the stock removal, the ultrasonic shoe tilt angle and the applied voltage amplitude on the machining accuracy (i.e. workpiece cylindricity and workpiece roundness) were clarified experimentally. The obtained results indicate that: (1) the workpiece rotational speed can be adjusted by changing the applied voltage amplitude, whereas its through-feed rate can be adjusted by changing both the applied voltage amplitude and the ultrasonic shoe tilt angle; (2) the optimum eccentric angle is 6°, and a larger stock removal, a smaller tilt angle, or a higher applied voltage is better for higher machining accuracy; (3) the workpiece cylindricity and roundness were improved from the initial value of 16.63 μm and 14.86 μm to the final ones of 1.49 μm and 0.74 μm under the optimal grinding conditions.

New Models and Global Stability Charts to Avoid Principal Instabilities and Constraints in Throughfeed Centerless Grinding

AbstractThis paper presents new simulation models and global stability charts that have been developed to analyze the principal instabilities and constraints involved in the throughfeed centerless grinding process. In addition to a frequency domain stability analysis of the three characteristic instabilities of the process (geometric lobing, chatter and spinning), new models have been developed and implemented to analyze the other main restrictions, namely, process power, temperature and burning power, roughness, and final part geometrical tolerance due to machine compliance. As a result, new global stability charts have been devised where instabilities are plotted against different productivity rates by combining the two principal variables in the throughfeed process: regulating wheel speed and feed angle. The use of such charts has led to the development of new optimization strategies for throughfeed operation mode and their implementation in a web based SET-UP ASSISTANT software tool developed to improve machining accuracy and productivity in centerless grinding.

ELID Grinding Characteristics and Surface Analysis for Micro Fabrication of Advanced Ceramics

The present paper describes the highly efficient and precise ELID grinding method and presents a discussion on the ELID grinding process and the grinding characteristics of several kinds of ceramic materials. The following conclusions are obtained; (1) Good ground surface roughness and accuracy are achieved using the #4000 metal-bonded grinding wheel in through-feed centerless grinding for ZrO2 optical fiber ferrules. (2) Efficient and precise grinding of spherical lens molds with cup wheels using the ELID CG-grinding process was proposed and tested in the present study. (3) The ELID grinding method can be used to fabricate machined surfaces exhibiting desirable characteristics for hard AlN ceramics. The ELID ground AlN demonstrated a surface hardness and sliding characteristics that were superior to those of the polished series. These advantages may be attributable to the diffusion phenomenon of the oxygen element produced by the ELID grinding.

Precision, Stability and Productivity Increase in Throughfeed Centerless Grinding

Centerless grinding is a high precision manufacturing process commonly applied to the mass production of many industrial components. However, workpiece roundness is critically affected by geometric lobing and no practical tool has been developed to solve the problem in throughfeed working mode. Based on simulation methods previously applied to plunge grinding, a new software tool has been developed in this work. The software determines the optimal working configuration and can be used to reduce set-up time and improve three important features: 1) Precision, as the roundness error is rapidly corrected at the optimal configuration. 2) Productivity, since the workpiece stock can be significantly reduced. 3) Stability, because the process is less sensitive to the original roundness error of the workpiece.

An Adaptive Statistically Based Controller for Through-Feed Centerless Grinding

The purpose of this research is to develop a statistically based controller that is “self-tuning.” High volume manufacturing processes such as through-feed centerless grinding are best controlled with a statistical approach, but traditional methods of statistical control generally rely on fixed parameters that must be determined. These values must be precisely known and the true physical characteristics they model must remain constant throughout grinding, or traditional statistical control methods may break down. The mean and standard deviation of a process are measures of its accuracy and precision. The scheme developed here makes control decisions based on the real-time values of these quantities. This self-adjusting ability can compensate for changes in machine parameters as they occur.

A New Regulating Wheel Truing Method for Through-Feed Centerless Grinding

A new regulating wheel truing method for through-feed centerless grinding is presented. In conventional regulating wheel truing systems, a single-point diamond tool is traversed across the regulating wheel in a straight line. The interference between the regulating wheel and workpiece exists. This interference problem, a main source of error in precision through-feed centerless grinding, is due to the radius of curvature of the regulating wheel and workpiece. A new concept for regulating wheel truing is developed to eliminate the interference problem. In this new truing system, the rotary diamond truing tool has the same size as the finished workpiece, locates at the same center-height of the workpiece, and moves across the regulating wheel in the direction parallel to axes of workpiece and grinding wheel. A mathematical model is developed to calculate the surface profile for the regulating contact and to study the curved line of contact between workpiece and regulating wheel. An example is used to illustrate the model and to demonstrate that the interference between regulating wheel and workpiece has been eliminated.

Improving Workpiece Roundness through Centerless Grinding Cycle Optimization

In centerless grinding, achievable workpiece roundness is directly related to the cycle length selected for the grinding process. This paper proposes a systematic approach to minimize workpiece roundness error by optimizing the cycle length. In the paper, the transient characteristics of the rounding process is first investigated. It was found that minimum workpiece roundness error can be obtained when the initial roundness error is effectively suppressed but the lobing pattern is not yet fully developed on the workpiece surface. Then, a computer simulation method is introduced to optimize the grinding cycle length in terms of minimum workpiece roundness error for both plunge and through-feed centerless grinding processes. The concept of an average growth rate is introduced to assess the lobing stability in through-feed centerless grinding.