Precision Cylindrical Grinding Research Articles

Research on geometric error modeling and compensation method of CNC precision cylindrical grinding machine based on differential motion theory and Jacobian matrix

Research on geometric error modeling and compensation method of CNC precision cylindrical grinding machine based on differential motion theory and Jacobian matrix

Material removal monitoring in precision cylindrical plunge grinding using acoustic emission signal

A mathematical model of the acoustic emission signal during a grinding cycle is proposed for the monitoring of material removal in precision cylindrical grinding. Acoustic emission signals generated during precision grinding are sensitive to forces in grinding and present opportunities in accurate and reliable process monitoring. The proposed model is developed on the basis of a traditional grinding force model. Using the developed model, a series of experiments were performed to demonstrate the effectiveness of the acoustic emission-sensing approach in estimating the time constant and material removal in grinding. Results indicate that acoustic emission measurements can be used in the prediction of material removal in precision grinding with excellent sensitivity.

Estimation of the Time Constant of Precision Plunge Grinding in Dwell Period Based on Acoustic Emission Measurement

Our previous work presented a method for estimating the time constant of grinding system in infeed period. To monitor the precision cylindrical plunge grinding process in dwell period, an estimation of the time constant of grinding system in the dwell period, using acoustic emission signal, is presented in this paper. Acoustic emission signals generated during precision grinding are sensitivity and present challenges for accurate and reliable process monitoring. Experiments demonstrate the results of the acoustic emission sensing approach in estimating the time constant in the dwell period of cylindrical plunge grinding.

Design of MK1432/H CNC Precision Cylindrical Grinding Machine

MK1432/H CNC precision cylindrical grinding machine is suitable for precision grinding IT6 to IT5 cylindrical or conical revolving workpiece, the table of the rail bed for the paste with plastic rail, the first holder of the rotating dial tone from the motor frequency speed, with Germany's Siemens 810D CNC two-axis system, built-in PLC, liquid crystal display. Servo motor is 1FK6 series; configure automatic measuring instrument line detection, automatic grinding work to achieve closed-loop cycle, ensuring high machining dimensional accuracy. Machine bed using a large round hole, fin-shaped reinforcement plates, Bench points up and down the table, you can grinding conical, bed and table in the guide rail for the laminating, the friction coefficient is small, table driven by a servo motor directly to the Deputy move the ball bar, smooth and reliable movement. Mainly used in automobile, motorcycle parts factory and other machinery manufacturing industry, for the grinding disc type, short axis, and taper shank type etc. parts.

Estimation of the Time Constant of Plunge Grinding of C45 in Infeed Period with Properties of Mechanical Materials Based on Acoustic Emission Measurement

To monitor the precision cylindrical grinding process, an estimation of the time constant of grinding system, using acoustic emission signal, is presented during infeed period in this paper. Acoustic emission signals generated during precision grinding are sensitivity and present challenges for accurate and reliable process monitoring. Experiments demonstrate the results of the acoustic emission sensing approach in estimating the time constant. This estimation of the time constant can be used to analyze the properties of mechanical materials of the workpiece with the same grinding conditions.

Application of the Minimum Quantity Lubrication (MQL) technique in the plunge cylindrical grinding operation

Precision cylindrical grinding is used extensively in the manufacture of precision components in the metal-mechanical industry in general. Modern CNC grinding machines have improved this process with respect to the positioning and rigidity of the machine-workpiece-tool system, allowing the production of high precision parts with low dimensional tolerances. Besides the difficulties inherent to the process, awareness has grown in recent years regarding the environmental issues of cutting fluids. As a response, the industry has begun to seek alternative lubrication and cooling methods. Among the various existing techniques, Minimum Quantity Lubrication (MQL) has been considered as an alternative. This technique can be understood as a combination of conventional lubrication and cooling methods and dry machining, in which a small quantity of lubricating oil mixed with compressed air flow is delivered in the wheel-workpiece interface. The MQL technique is already widely employed in machining processes with tools of defined geometry (e.g. turning), in which produces very satisfactory results. However, the MQL technique has been little explored in grinding processes (non-defined tool geometry), in which the really effective heat removal methods are required due to the frictional heat generation in the grinding zone. Consequently, the aim of this study was to evaluate the plunge cylindrical internal grinding operation when using the MQL technique and the conventional cooling method. Roughness and roundness were the outputparameters. As a result, it was found that the best values of roughness Ra were obtained with the conventional lubrication method. The MQL technique applied as proposed was not able to flush the chips away from the grinding zone, leading to the highest Ra values. No significant differences were detected among the cooling methods when analyzing the roundness results. The workpiece fixture method selected was responsible for the overall unsatisfactory results.

In-process force measurement for diameter control in precision cylindrical grinding

This article shows the theory and implementation of a force measurement-based approach to controlling workpiece diameter in cylindrical grinding. A simple model proposed is used to relate infeed velocity to grinding force. The model is extended to accurately control the amount of material removed in outer diameter plunge grinding given the normal force, which may be monitored in real-time. The model incorporates the key parameters, including the structural loop stiffness, the plunge infeed velocity, and the wheel and workpiece properties. However, only the infeed velocity must be explicitly known. The contribution of this work is experimental validation that the lag between infeed and stock removal can be predicted using force feedback without a priori knowledge of the grinding system. This allows very accurate diameter control (0.25 μm of nominal), even in the presence of thermal drift, wheel wear, and machine error.

Process Requirements for Cost-Effective Precision Grinding

Costs in precision cylindrical grinding are compared for different abrasives, machines and grinding conditions. The analysis is for repeated batch production. Account is taken of machine cost and abrasive cost. Cost comparisons were based on extensive trials to assess re-dress life against workpiece quality requirements. Experiments show that different workpiece materials require different strategies to reduce costs. Easy-to-grind AISI 52100 and difficult-to-grind Inconel 718 materials were ground at conventional speeds and at high speeds. It is shown that wheel speed affects production rate through acceptable values of re-dress life, removal rate and dwell time. Advantages were gained using vitrified CBN at conventional speed and at high speed. For both materials, vitrified CBN wheels used at high speed, gave better quality at lower cost than conventional abrasives. Wheel costs became negligible and labour costs greatly reduced. Re-dress life trials, usually neglected, are shown to be essential to reduce costs and maintain quality [1].

The Application of Linear Motor in High-Speed Precision Cylindrical Grinding

The Application of Linear Motor in High-Speed Precision Cylindrical Grinding

Precision cylindrical face grinding

The mathematical models and experimental validations of precision cylindrical face grinding using a narrow ring superabrasive wheel are presented. The high pressure seal in diesel engine fuel systems demands the μm-scale form tolerance specifications and has driven the development of precision face grinding using the superabrasive wheel. Two mathematical models were developed: one was applied to predict the convex or concave face profile and another was used to simulate the abrasive trajectories, which become the cross-hatch grinding marks on the ground face. Cylindrical face grinding experiments were conducted. Experimental measurements of face profile and abrasive trajectories were used to validate the theoretical results. For high-pressure sealing surfaces, the height of face profile and grinding trajectories were two critical characteristics for design and manufacturing. Two design tools, a linear approximate solution for the profile height and an atlas for grinding trajectories, were developed to assist the selection of process parameters for the machine setup.

レジンボンド極微粒ダイヤモンドホイールによる円筒鏡面研削技術の研究

The goal of this paper is a mirror grinding of ceramic cylinder with an extremely fine grit diamond wheel. An ultra precision cylindrical grinding machine and a truing and dressing device for it are designed and built. For a mirror grinding, a very fine infeed motion and a low vibration are needed to avoid sinking diamond grits into a bond material with an unexpectedly large force on individual grits. Therefore, the grinding machine has a hydrostatic wheel spindle and a hybrid infeed mechanism. The latter one consists of a ball screw and a DC servomotor for a rough feed, and four piezoelectric actuators for a fine feed. The piezoelectric actuators are mounted in the ball screw nut. Vibration amplitude of the wheel head was less than 0.1 μm and the minimum depth of cut was 0.01 μm/step. After truing and balancing a resinoidbonded diamond wheel (SD5000B) on the machine precisely, a mirror grinding of a partially stabilized zirconia cylinder was carried out. A peak-to-valley height of the ground surface was 53 nm and a maximum chipping length on the edge was 0.5 μm or below.

Development of precise cylindrical grinding by ball centers: effect of ball wear

In high-precision cylindrical grinding and precision measurement, it is known that accurate and inexpensive steel balls used in place of cone centers enable one to grind and to measure the workpiece accurately without the influence of the misalignments and geometrical deviations of the center holes. The purpose of this study is to explain the supporting characteristics of these ball centers. In this article, endurance tests were performed and ball wear was measured to investigate the effect of the wear on the rotational accuracy and the roundness of the workpiece. The main results obtained are as follows. (1) The rotational accuracy and the roundness of the workpiece remained at high levels during the endurance test of 3 hours regardless of the ball wear. Consequently, the wear had little effect on the accuracy. (2) The contact points between the ball and the holder gradually shifted to other points that were not yet worn. This averaging effect maintains the rotational accuracy at a high level. (3) Lubricating the supports every quarter hour reduced the ball wear to half. Moreover, the lubrication was effective in preventing the ball from exfoliating. Therefore, there is no need to be concerned about ball wear in ordinary circumstances.

Development of precise cylindrical grinding by ball centers: effect of dynamic stiffness on work profile

In high-precision cylindrical grinding, it is known that the accurate and inexpensive steel balls used instead of the cone centers enable accurate grinding of the work without the misalignments and the geometrical deviations of the center holes. The purpose of this study is to explain the supporting characteristics of these ball centers. In this article the work profile, supporting stiffness, and grinding force in grinding only are measured to investigate the stiffness effects on the ground profile. Moreover, the generation process of the work profile is addressed via both experimental and simulation analyses. The obtained main results are as follows: (1) The ball center enables detailed observation of the work profile, displacement, and grinding force during grinding. (2) The radial compliance of the work supporting system correlates well with the center hole profile. (3) The compliance has a strong influence on the work profile in grinding. (4) The amplitudes and the phases of the work profile components are formed at the beginning of the spark-out states.

ボールセンタを用いた精密円筒研削 続報 鋼球の摩耗の影響

In high precision cylindrical grinding, it is known that the accurate and inexpensive steel balls in place of the cone centers enable to grind workpiece accurately without influences of the misalignments and the geometrical deviations of the center holes. The purpose of this study is to explain the supporting characteristics of these ball centers. In this paper, endurance tests were performed and ball's wear was measured to investigate its effect on the rotational accuracy and the roundness of the workpiece. The obtained main results are as follows : (1) The rotational accuracy and the roundness of the workpiece were kept at high levels during the endurance test of three hours regardless of the ball wear. Therefore, the wear had little effect on the accuracy. (2) The contact points between the ball and the holder gradually shifted to other points, not worn yet. Then the accuracy average effect maintains the rotational accuracy at a high level. (3) Lubrication every quarter hour reduced the ball wear to half. Moreover, the lubrication prevented the ball from release effectively. Consequently, there is no fear for the ball wear in ordinary circumstances.

Development of precise cylindrical grinding by ball centres—contact stiffness between ball and centre hole

In high precision cylindrical grinding it is cutomary to support the workpiece with dead-centres. Then, the geometrical deviations of cone centres and centre holes, and their misalignments have an influence on the roundness of ground surfaces. It is known that the misalignments and geometrical deviations of centre holes do not influence the roundness of ground surfaces with the accurate and inexpensive steel balls in place of cone centres. Few reports, however, are found which are concerned with the characteristics of the ball centres. In this paper, experiments on the axial and radial stiffness were performed, at the contact parts between balls and centre holes. The obtained main results are as follows. (1) The relationships between the elastic deformations and the loads exhibit hysteresis. (2) The axial and radial contact compliances are from 0.0025 to 0.006 μm N −1. In the ball centres, the stiffness is smaller than that of the cone centres, but the variances of stiffness are smaller than these. (3) The stiffness decreases according to the increase of the circumferential waviness of centre holes, and to the decreases of ball diameter and Young's modulus. (4) The ellipsoidal component of centre holes decreases the radial contact stiffness remarkably.

ボールセンタを用いた精密円筒研削 Ｉ 接触剛性について

It is customary to support the workpiece with dead-centers in high precision cylindrical grinding. Then the geometrical deviations of cone centers and center holes, and their misalignments have an influence on the roundness of ground surfaces. It is known that the misalignments and geometrical deviations of center holes do not influence the roundness of ground surfaces with the accurate and cheap steel balls in place of cone centers. But few reports concerned about the characteristics of the ball centers were found. In this paper, experiments on the axial and radial stiffness were performed, at the contact parts between balls and center holes. The obtained main results are as follows : (1) The relationships between the elastic deformations and the loads are hysteretic. (2) The axial and radial contact compliances are from 0.002 5 to 0.006 μm /N. In the ball centers, the stiffness is smaller than that of the cone centers, but the variances of stiffness are smaller than these too. (3) The stiffness decreases according to the increase of the circumferential waviness of center holes, and to the decreases of ball diameter and Young's modulus. (4) The ellipsoidal component of center holes decreases the radial contact stiffness remarkably.

鋼球を用いた精密円筒研削

Usually, a pair of cone centers have been used for supporting the workpiece in cylindrical grindings. Then, the roundness of ground surface is influenced by the form errors of cone centers and center holes, misalignments and lubrication. Although it costs much time and money, the center holes must be ground or lapped for the precise cylindrical grinding. The purpose of this paper is to establish a grinding method which makes precise cylinders easily and inexpensively. In the experimental apparatus, two holders press the workpiece through each balls. Both the holders and the workpiece have center holes. The experiments were conducted under following two conditions. First, the balls were fixed on the holder. Second, the balls were fixed on the workpiece. The latter was better than the former to finish the accurate cylinder. In the latter condition, 0.5μm out-of-roundness of the ground surface was obtained with the precise balls of0.7μm out-of-roundness.

Comparison of cone-centre and ball-centre for roundness in cylindrical grinding

In high precision cylindrical grinding it is customary to support the workpliece with dead-centres. The workpiece is rotated as a guide to the points o

An Analysis of a Special Hydrodynamic Bearing for Machine Tool Spindles

The paper deals with the analysis of a special hydrodynamic bearing incorporated in a precision cylindrical grinding machine developed at CMTI. The special bearing is an improvement of the earlier conical multilobe bearing developed at CMTI. The improvement effected is particularly in automatic preloading through hydrodynamic thrust bearing where the preload increases with increase in speed and thereby improving the performance of the bearing over a wide range of speeds. The initial axial clearance in the thrust bearing, taper on the thrust surface, the lobe depth in the conical bearing are the main controlling parameters.

Tools for the Workshop

A. A. Jones & Shipman Ltd., Leicester, have introduced a high precision cylindrical grinding machine for small batch work. Feed increments are in steps of 0.000005 in. (diameter reduction 0.000010 in.) and roundness accuracy is quoted as 0.000010 in. on dead centres; 0.000025 in. on live standard workhead centre. Maximum grinding diameter is 3 in. Swing over table 5 in. Capacity between centres 12 in.