Workpiece Roundness Research Articles

Modeling and experimental analysis of wheel-work interface in the cylindrical plunge grinding process

This paper presents a study of grinding wheel-workpiece interference in external cylindrical plunge grinding processes. This is to study the effect of workpiece surface memory on the workpiece roundness error after grinding. The study has been carried out theoretically on a model simulating cylindrical grinding process. The model takes contact stiffness, grinding wheel and workpiece wear into consideration. The proposed model was sued to predict the normal grinding forces in cylindrical grinding as a function of the previous height and number of waves of the initial profile.The new model has been validated by conducting experiments on a cylindrical grinding machine. Results indicate that the proposed model shows a good agreement with the experimental data obtained.The results of experiments indicate that the proposed modeling method is both feasible and reliable. The results showed that the theoretical model was effective studying the output of cylindrical grinding process. Normal grinding force, vibration level, and roundness error in cylindrical plunge grinding processes are dependent on the workpiece surface memory. Keywords: Plunge Grinding, Modeling, Roundness Error, Surface Memory.

Realization of Online Measurement Technology and its Application in the Intelligent Machining Cell

In view of the continuous unmanned machining of revolving workpiece, this paper has integrated the industrial robot with machine vision, mill-turning center and trigger online measurement systems into an intelligent machining cell. It has achieved the automatic loading and unloading material, automatic adjustment of the Machine Coordinate System (MCS) of workblank, automatic compensation of machining errors and workpiece diameter and roundness of the on-machine inspection. In order to ensure the accuracy of continuous unmanned machining of the intelligent machining cell, the main factors that affect the accuracy of online measurement system and the corresponding solutions are analyzed. On this basis, a machining instance is made to verify the validity of the trigger online measurement technique’s application in continuous unmanned machining of the revolving workpiece. The results of this study show that the intelligent machining cell can ensure stable unmanned machining with high precision for several hours.

Experimental Study on Roundness of High-Speed Cylindrical Grinding for 20CrMnTi Alloy Steel

In order to reduce the roundness error of cylindrical grinding of shaft parts for 20CrMnTi alloy steel, the related experiments of high-speed cylindrical grinding are carried out and the influence of grinding parameters on roundness is analyzed. Based on the analysis of experimental data the conclusions are as follows: The influence of grinding wheel speed on work-piece roundness is not apparent, but the influence of work-piece speed and grinding depth on roundness is very significant. Based on high-speed grinding experiments the prediction model of cylindrical grinding for 20CrMnTi alloy steel is established by using of regression analysis method of least square. Based on the analysis of the roundness prediction model of cylindrical grinding the conclusions are as follows: The roundness error of cylindrical grinding parts will become lager with the increase of work-piece speed, grinding depth and grinding wheel speed.

A study about microhole machining characteristics of plastic mould steel

In this study, the effect of number of the tool cutter flute on machining characteristics was investigated through precision machining of the plastic mould steel, an injection moulding material; the roundness of the machined workpiece was measured using the three-dimensional measuring machine. Also, the surface roughness of its cross-section was measured after the wire cut electric discharging machining. Cutting characteristics appeared to be low in the four-flute condition than in the two-flute condition due to its hardness, and got better as the spindle rotation count and the tool feedrate became lower. The roundness measured was shown to be better under the four-flute condition, which was the same as the cutting force component. The roughness of the machined surface was about 50% better under the four-flute condition than under the two-flute condition.

An analytical investigation on the workpiece roundness generation and its perfection strategies in centreless grinding

Continuous improvement of the component roundness accuracy through computer numerical control centreless grinding in high productivity is one of the most important issues particularly for modern automotive and bearings manufacturing. For instance, the process is towards 0.1–0.3 µm roundness accuracy in grinding the engine valve rod because of the increasingly stringent energy efficiency requirement in automotive engines. The characteristics of the computer numerical control centreless grinding process make it challenging, that is, how to assure the workpiece roundness generation in a predictable, producible, highly productive and scientific manner. In this article, a simulation-based industrial feasible approach is presented to model and control the workpiece roundness generation and its perfection strategies in computer numerical control centreless grinding. The kinematics of the workpiece in the process is presented according to the workpiece profile and its geometric configurations. Taking into account the workpiece geometric movements, contact and loss effect and grinding restrictions, a time-domain dynamic model is developed to provide the dynamics description of the workpiece, the grinding wheel and the control wheel in the process. The roundness generation of the workpiece is further predicted using this model. The effects of multiple factors on the workpiece rounding process are discussed and the influences on final roundness errors are investigated.

Estimation algorithm of minimum dwell time in precision cylindrical plunge grinding using acoustic emission signal

This work presents an investigation of the minimum dwell time during the precision cylindrical-plunge grinding process. According to the model of acoustic emissions proposed in earlier work, two estimation algorithms of the dwell time, focused on the size error and the surface roundness of the machined workpiece, are deduced from the models of the material removal and the surface roundness, respectively. Based on the proposed estimation algorithms, an on-line estimation method of the minimum dwell time is developed using the measurement and analysis of the acoustic emission signal. A series of experiments of grinding C45 steel are conducted to confirm the validity of the proposed estimation algorithms and determine the model coefficient. The ability of the estimation algorithms to predict the minimum dwell time is deemed necessary for optimal control of the grinding process. In addition, the proposed model provides a new approach to estimate the machined qualities of a workpiece such as the surface roughness and size error using the dwell time of the grinding process.

Workpiece roundness profile in the frequency domain: an application in cylindrical plunge grinding

In grinding, most control strategies are based on the spindle power measurement, but recently, acoustic emission has been widely used for wheel wear and gap elimination. This paper explores a potential use of acoustic emission (AE) to detect workpiece lobes. This was achieved by sectioning and analysing the AE signal in the frequency domain. For the first time, the profile of the ground workpiece was predicted mathematically using key frequencies extracted from the AE signals. The results were validated against actual workpiece profile measurements. The relative shift of the wave formed on the surface of the part was expressed using the wheel-workpiece frequency ratio. A comparative study showed that the workpiece roundness profile could be monitored in the frequency domain using the AE signal during grinding.

Roundness and Cylindricity Verification of Cylindrical Workpieces of Magnesium Alloys Obtained by Intermittent Dry Machining

Magnesium is the lightest metal used in industry, above all for aerospace and automotive applications where weight reduction allows an improvement in the fuel efficiency and reducing CO2 emission. In this work, an experimental study was carried out in order to determine with which machining process, turning or milling, are obtained cylindrical bars of magnesium alloy UNS M11917 by intermittent dry cut with improved roundness and cylindricity finish.

Effect of Turning Parameters on Roundness and Hardness of Stainless Steel: SUS 303

Stainless steel JIS:SUS 303 is widely used for automotive part. This part is mostly manufactured by turning operation. However, turning parameters could be affected to roundness and hardness of workpieces. The purpose of this research was to study factors, which were affecting to roundness and hardness of stainless steel turning. Cutting tool was inserted carbide coated TiCN+Al2O3+TiN with polycrystalline vapor deposited (PVD) cutting tools. Experimental design was conducted as two factors and three levels. The parameters were consisted of cutting speed at 100, 150 and 200 m/min. Feed rate was setting at 0.08, 0.12 and 0.16mm./rev. Furthermore, the experiment was done by turning with cooling and non-cooling. The results showed that only one factor affected to roundness was cooling condition. It means that cooling would cause on better roundness than non-cooling. On the other hand, cutting speed and feed rate was not affected to roundness. Moreover, the hardness of specimens was not increasing after turning. The studied parameters were not affected to hardness after turning significantly.

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.

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

This paper deals with the development of an alternative centerless grinding technique, i.e., in-feed centerless grinding based on a surface grinder. In this new method, a compact centerless grinding unit, composed of an ultrasonic elliptic-vibration shoe, a blade and their respective holders, is installed onto the worktable of a surface grinder, and the in-feed centerless grinding operation is performed as a rotating grinding wheel is fed in downward to the cylindrical workpiece held on the shoe and the blade. During grinding, the rotational speed of the workpiece is controlled by the ultrasonic elliptic-vibration of the shoe that is produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body (stainless steel, SUS304). A simulation method is proposed for clarifying the workpiece rounding process and predicting the workpiece roundness in this new centerless grinding, and the effects of process parameters such as the eccentric angle, the wheel feed rate, the stock removal and the workpiece rotational speed on the workpiece roundness were investigated by simulation followed by experimental confirmation. The obtained results indicate that: (1) the optimum eccentric angle is around 6°; (2) higher machining accuracy can be obtained under a lower grinding wheel feed rate, larger stock removal and faster workpiece rotational speed; (3) the workpiece roundness was improved from an initial value of 19.90 μm to a final one of 0.90 μm after grinding under the optimal grinding conditions.

Optimum Geometrical Arrangement of Workpiece in the Ultrasonic Vibration Shoe Centerless Grinding

This paper clarifies the influence of the geometrical arrangement of the workpiece on workpiece roundness in the ultrasonic elliptic-vibration shoe centerless grinding, and determines an optimum geometrical arrangement for minimizing the roundness error of the workpiece. The influences of the geometrical arrangements of the workpiece on workpiece roundness were investigated by computer simulation and practical grinding operations involving pin shaped workpieces. The experimental results agreed closely with those obtained by the simulation, the results of simulation and grinding tests indicated that the final roundness error of the workpiece after grinding reaches a minimum at a particular angle number (= + =7) for various values of the blade angle.

Research on Precision Grinding System and Key Technology Based on PMAC-PC

A high speed experimental numerical control grinding system based on PMAC-PC was designed, realized machining and measurement integration. High speed motorized spindle finite elements dynamics and thermal characteristics, force analysis of linear motor feed element and parameters setting method based on PMAC, work piece roundness error measurement technology were researched. The grinding experiment and dynamic measurement indicated that the system possessed good following performance and stability; grind the elliptic work piece in the system.

Effects of process parameters on workpiece roundness in tangential-feed centerless grinding using a surface grinder

The present authors proposed a new centerless grinding method using a surface grinder in their previous study [Wu, Y., Kondo, T., Kato, M., 2005. A new centerless grinding technique using a surface grinder. J. Mater. Process. Technol. 162–163, 709–717]. In this method, a compact centerless grinding unit composed mainly of an ultrasonic elliptic-vibration shoe is installed onto the worktable of a multipurpose surface grinder to perform tangential-feed centerless grinding operations. However, for the complete establishment of the new method it is crucial to clarify the workpiece rounding process and the effects of process parameters such as the worktable feed rate, the stock removal and the workpiece rotational speed on the machining accuracy, i.e., workpiece roundness, so that the optimum grinding conditions can be determined. In this paper, the effects of the process parameters on workpiece roundness are investigated by simulation and experiments. For the simulation analysis, a grinding model taking into account the elastic deformation of the machine is created. Then, a practical way to determine the machining-elasticity parameter is developed. Further, simulation analysis is carried out to predict the variation of workpiece roundness during grinding and to discover how the process parameters affect the roundness. Finally, actual grinding operations are performed by installing the previously constructed unit onto a CNC surface grinder to confirm the simulation results. The obtained results indicate that: (1) a slower worktable feed rate and higher workpiece rotational speed give better roundness; (2) better roundness can be also obtained when the stock removal is set at a larger value; (3) the workpiece roundness was improved from an initial value of 23.9 μm to a final value of 0.84 μm after grinding.

Experimental Study of Tangential-Feed Centerless Grinding Process Performed on Surface Grinder

In our previous study, a new centerless grinding method using surface grinder was proposed. In this method, a compact unit consisting mainly of an ultrasonic elliptic-vibration shoe, a blade, and their respective holders is installed on the worktable of a multipurpose surface grinder to conduct tangential-feed centerless grinding operations. For the complete establishment of this new method, firstly in this paper workpiece rotational speed control tests were carried out to make sure that the workpiece rotational speed is exactly controlled by the elliptic vibration of shoe to achieve high-precision centerless grinding. Then, the effects of the process parameters such as the worktable feed rate, the stock removal and the workpiece rotational speed on the workpiece roundness were clarified experimentally. The obtained results showed that (1) The workpiece rotational speed can be controlled exactly by the shoe ultrasonic vibration, (2) The roundness is improved with the increases in the voltage applied and the stock removal, but the decrease in the worktable feed rate; The best roundness obtained was 0.84m.

Simulation Investigation of Tangential-Feed Centerless Grinding Process Performed on Surface Grinder

In our previous study, a new centerless grinding method using surface grinder was proposed. This paper describes a simulation method for investigating the workpiece rounding process in which a model taking the elastic deformation of the machine into consideration is created, and revealing how the process parameters affect the machining accuracy in the new grinding technique. In addition, a practice way to determine the machining-elasticity parameter showing the elastic deformation is developed. The simulation results are compared to show the effect of process parameters on the machining accuracy.

E15 A Method to Increase Material Removal Rate in Tangential-feed Centerless Grinding Performed on Surface Grinder(Grinding technology)

In our previous study, a new centerless grinding method using surface grinder was proposed. However, the material removal rate was very small owing to the low worktable feed rate. This paper describes a practical method for increasing removal rate while workpiece roundness is maintained at a high level. In this method, the worktable feed rate is adapted appropriately so that the wheel depth of cut is kept constant during grinding. The actual grinding experimental results showed that the same level of workpiece roundness can be achieved only with a half of grinding cycle time once the worktable feed rate is adapted appropriately instead of the constant feed rate during grinding.

Continuous workpiece speed variation (CWSV): Model based practical application to avoid chatter in grinding

The continuous variation of rotation speeds provides a means of avoiding chatter instability in different machining processes. This paper presents a time domain dynamic model that simulates chatter vibration during infeed centerless grinding for any continuously variable work rotation speed strategy. As a result of taking machine dynamics and main non-linear effects of the process into account, part roundness error is predicted for the whole grinding cycle. Lastly, experimental results have validated the model and verified that adequate speed variation strategies are capable of avoiding chatter and improving workpiece roundness and roughness, both for infeed and throughfeed centerless grinding.

Applying particle swarm optimization algorithm to roundness measurement

Measuring the roundness of a circular workpiece is a common problem of quality control and inspection. In this area, maximum inscribed circle (MIC) and maximum circumscribing circle (MCC), minimum zone circle (MZC) and least square circle (LSC) are four commonly used methods. In particular, MIC, MCC, and MZC, which are nonlinear constrained optimization problems, have not been thoroughly discussed lately. This study proposes a machine vision-based roundness measuring method that applies the particle swarm optimization algorithm (PSO) to compute MIC, MCC and MZC. To facilitate the PSO process, five different PSO’s were encoded using a radius ( R) and circle center ( x, y) and extensively evaluated using an experimental design, in which the impact of inertia weight, maximum velocity and the number of particles on the performance of the particle swarm optimizer was analyzed. The proposed method was verified with a set of testing images and benchmarked with the GA-based (genetic algorithm) method [Chen, M. C. (2000). Roundness inspection strategies for machine visions using non-linear programs and genetic algorithms. International Journal of Production Research, 38, 2967–2988]. The experimental results reveal that the PSO-based method effectively solved the MIC, MCC, and MZC problems and outperforms GA-based method in both accuracy and the efficiency. As a finals, several industrial applications are presented to explore the effectiveness and efficiency of the proposed method.

The Effect of Workpiece Roundness of the Run-Out of CBN Electroplated Grinding Wheels

Electroplated CBN grinding wheels are not normally trued on a grinding machine and therefore inherently have a degree of run-out. The effect of run-out on workpiece roundness has both been modelled and measured experimentally. As well as affecting roundness, run-out can result in intermittent grinding around the wheel periphery, which can then lead to preferential wear on the most eccentric part of the wheel. This intermittent effect has been investigated by modelling the variation of the normal grinding force around the wheel and by measuring the variation of acoustic emission around the wheel during grinding tests.