Workpiece Rotational Speed Research Articles

Design of Freeform Surface Finish Using Synchronous Processes of Electrochemical Finishing and Burnishing

A most effective design system and an advantage of low cost equipment using synchronous processes of electrochemical finishing and burnishing for a freeform surface following turning machining is investigated. The proposed design process uses a feeding finish-tool instead of the mate electrode as in conventional ECM. Hence higher electrical current is not required when the effective design electrode is used to reduce the response area. Through simple equipment attachment, electrochemical finishing can follow the traditional turning on the same machine. The controlled factors include the chemical composition and concentration of the electrolyte, die material, and rotational speed of workpiece. The design finish-tool is primarily discussed among the factors affecting the synchronous processes of electrochemical finishing and burnishing. The experimental parameters are initial gap width, flow rate of electrolyte, current rating, feed rate of finish tool, pulsed period, and the evaluation of different process features. The use of large electrolytic flow rate is advantageous to the finish effect. High rotational speed of the finish tool produces better finish. The finish effect is better with longer off-time because discharge of finish dregs becomes easier. Higher current rating with quicker feed rate of finish tool effectively reaches the fast improvement of the surface roughness of the workpiece is recommend in current study. The effective design finish-tool with an electrode of a globe-form and a burnishing tool of a pin-form have an optimal value for higher current density and provides larger discharge space, which produces a smoother surface. The synchronous processes of electrochemical finishing and burnishing just needs only a short time to make the workpiece smooth and bright and saves the need for the precise process of traditional machining is recommended for the finish process of the freeform surface.

Performance Assessment of Design Electrode in Ultrasonic-Aided of Freeform Surface Finishing

The most effective geometry for design electrode and the advantage of low cost equipment in ultrasonic-aided electrochemical finishing for a freeform surface following turning machining was investigated. The proposed design process used an effective electrode instead of the mate electrode as in conventional ECM. Hence higher electrical current is not required when the effective design electrode is used to reduce the response area. Through simple equipment attachment, electrochemical finishing can follow the traditional cutting on the same machine. The controlled factors included the chemical composition and concentration of the electrolyte, the initial gap width, the flow rate of electrolyte, workpiece rotational speed, and die material. The design electrode is primarily discussed among the factors affecting the electrochemical finishing. The experimental parameters were current rating, electrode feed rate, frequency , power level of ultrasonics, and electrode geometry. The effective design electrode with small wedge angle and small edge rounding radius had an optimal value for higher current density and provided larger discharge space, which produce a smoother surface. The electrode of globe-shape with small radius performed best in the finishing process. The electrochemical finishing needed only a short time to make the workpiece smooth and bright and save the need for the precise process of traditional machining. The ultrasonic-aided electrochemical finishing is recommended for the finishing process of the freeform surface.

Research and Simulation on the Wear Uniformity of Lapping Plate

Lapping plate wear is of great influence on shape precision of workpiece. Investigation on the wear uniformity of uncertain eccentricity plane lapping was carried out in this research. The relative velocity function of the plate to the workpiece is obtained through kinematic analyses in the mode of uncertain eccentricity plane lapping, and material removal rate (MRR) function and wear uniformity function were deduced based on Preston equation. Effects of the ratio and eccentricities on the wear uniformity are discussed in detail through MATLAB simulation. Theoretical analysis and simulation results show that the ratio k1 of workpiece revolution speed to lapping plate is the key to decide whether the lapping plate is lapped uniformly. Theoretically, when k1<0, the greater |k1| is, the better the lapped uniformly of lapping plate can be. The ratio k2 of workpiece rotation speed to lapping plate has great influence on the lapped uniformly when k1 approximate 1, and k2 has little influence on the lapped uniformly when k1<0 or k1>1, Besides, a bit bigger eccentricity e1 is propitious to the lapping uniformly of the lapping plate, and bigger eccentricity e2 are also helpful to lapping uniformly of the lapping plate. And the conclusion could be extended to single-side plane lapping and double-side plane lapping process.

Experimental analysis on evolution of superfinished surface texture

A systematic investigation of the effect of process parameters on evolution of superfinished surface texture is described. For a given stone, the surface roughness reaches a steady state value as the process proceeds, regardless of test conditions, in the rough finishing regime. An analysis of experimental surface roughness data indicates that this process characteristic can be well described by an exponential form of time dependence and the contact pressure has no effect on this time dependence. Optimal performance associated with higher material removal rate, fairly fine surface finish and less production time in rough superfinishing can be achieved using higher workpiece rotational speed and contact pressure.

Effective form design of electrode in electrochemical smoothing of end turning surface finishing

Abstract In the current study, the most effective geometry for the design electrode and the advantage of the low cost equipment in electrochemical smoothing following end turning is investigated. Through simple equipment attachment, electrochemical smoothing can follow the cutting on the same machine. An adequate workpiece rotational speed associated with higher electrode rotation produces better polishing. The effective design electrode with a small wedge angle and a small edge rounding radius have an optimal value for higher current density and provides a larger discharge space, which produces a smoother surface. The electrode of the partial curve with a small line diameter performs the best for the electropolishing. Electrochemical smoothing saves the need for precise turning, making the total process time less than the electrobrightening. But the electrobrightening after precise turning only requires quite a short time to make the workpiece bright. The use of ultrasonics in the electrochemical smoothing and the electrobrightening is more evident than the pulsed current, since the ultrasonics-aided process exempts off time and obtains a better polishing result.

Modelling and analysis of hybrid electrochemical turning-magnetic abrasive finishing of 6061 Al/Al2O3 composite

This paper integrates the electrochemical turning (ECT) process and magnetic abrasive finishing (MAF) to produce a combined process that improves the material removal rate (MRR) and reduces surface roughness (SR). The present study emphasizes the features of the development of comprehensive mathematical models based on response surface methodology (RSM) for correlating the interactive and higher-order influences of major machining parameters, i.e. magnetic flux density, applied voltage, tool feed rate and workpiece rotational speed on MRR and SR of 6061 Al/Al2O3 (10% wt) composite. The paper also highlights the various test results that also confirm the validity and correctness of the established mathematical models for in-depth analysis of the effects of hybrid ECT- MAF process parameters on metal removal rate and surface roughness. Further, optimal combination of these parameters has been evaluated and it can be used in order to maximize MRR and minimize SR. The results demonstrate that assisting ECT with MAF leads to an increase machining efficiency and resultant surface quality significantly, as compared to that achieved with the traditional ECT of some 147.6% and 33%, respectively.

Design and performance assessment for use in ultrasonic-aided cylindrical surface polishing

This paper studies the performance assessment of ultrasonic-aided electropolishing and ultrasonic-aided pulse-electropolishing of external cylindrical surfaces by three groups of design electrode recommended in a previous publication by the author. Six types of feeding electrode are connected with continuous direct current in an electropolishing experiment. It requires no expensive special-purpose equipment nor high material removal as does conventional electrochemical machining, it offers fast improvement of the surface roughness and reduces the residual stress on the workpiece in a new area in electropolishing. The control factors include die material, chemical composition and concentration of the electrolyte, electrolyte temperature, flowrate of the electrolyte, initial gap width, electrical current rating, workpiece and electrode rotational speed, and electrode feed rate. The experimental parameters are the frequency and power level of ultrasonics, the pulse period, and the electrode design. The design change from inner taper to inside pins for full-ring electrodes performs well. The designed flat arrowhead electrode with flute back rake angle and side rake angle comes out better than that of the double-flute arrowhead electrode. The disc electrode with pins attached on edge performs better than the disc with a discharge flute; and the polishing effect of disc-form electrodes is the best, followed by arrowhead electrodes, and ring-form electrodes. Using adequate electrode geometry as well as the ultrasonic aid, an effective and low-cost electropolishing of external cylindrical surface is presented.

Design of thread surface finish using ultrasonic-aid in electrochemical leveling

An effective manufacturing process using ultrasonic energy transmitted into the electrolyte to assist electrochemical leveling as a finishing operation of thread surface following thread cutting is developed. In the current experiment, four types of mating electrode are completely inserted and put through both continuous and pulsed direct current while another four types of feeding electrode are used with continuous direct current with axial electrode feed applied. The controlled factors include the chemical composition and concentration of the electrolyte, electrolyte temperature, flow rate of electrolyte, and initial gap width. The experimental parameters are die material, current density, current rating, rotational speed of workpiece and tool electrode, electrode feed rate, on/off period of pulsed current, frequency and power level of ultrasonics, and electrode geometry. For the mating electrodes, an electrode with a thin plate form provides more sufficient discharge space, which is advantageous for finishing. The electrode with a thin plate on one side has the best finishing effect. For the feeding electrodes, a thin plate form electrode of one side of the borer tip has the best finishing performance in the current investigation. Pulsed direct current can slightly improve the finish effect, at the expense of increased machining time and cost. The electrochemical leveling after thread cutting requires a shorter time than manual or machine polishing to make the thread surface smooth and bright. The average effect of the ultrasonics is better than the pulsed current while the machining time need not be prolonged by the off time.

Analysis of Pin Grinding Mechanism in Twin Axes Synchronous Controlled Cranshaft Pin Grinder

Twin axes synchronous controlled type CNC crankshaft pin grinder has been widely used, but grinding mechanism with this type of pin grinder is not cleared well. In this study, the grinding mechanism is analyzed, and it is found that the cylindrical plunge grinding process carries on. From the investigation of substantial surface speed of both the wheel and the workpiece, grinding speed ratio is formulated. Furthermore, a simulation method, which predicts the grinding results, is developed. In order to realize high precision pin grinding, two methods, which control workpiece rotation speed adequately, are proposed, such as the controlled grinding speed ratio method and the controlled residual stock method. From the analysis, it is made clear that stable grinding force and surface roughness are generated by the controlled grinding speed ratio method, and also high dimensional accracy will be realized by the controlled residual stock method.

An investigation of lapping characteristics for improving the form error of an aspheric lens

In the generation of an aspheric lens process, the angle of inclination between the cup wheel and the lens surface, and also the rotational speed of workpiece all have an impact on the end result. The abrasive grain size, lapping pads and the uniformity of the lapping pressure distribution were selected as the major factors that affect the lapping process. This study also compares the machining effects including grinding, lapping and polishing on an aspheric lens. A form accuracy of 0.6929 μm P-V and a surface roughness of 124 nm Ra were obtained. The conclusions show that the methods proposed are effective for improving the form accuracy and for reducing surface roughness with proper lapping parameters.

Microscale fabrication of pin-shaped machine parts by a new centreless grinding technique

This paper proposes a new centreless grinding technique for the fabrication of microscale pin-shaped machine parts with large aspect ratio, and describes the design, construction and performance confirmation of the experimental apparatus which is composed mainly of an ultrasonic regulator used for controlling the rotation speed of the microscale workpiece. The regulator was constructed by bonding a plate-shaped piezoceramic device on an I-shaped metal body, on the end-face of which microscale ultrasonic elliptical vibration is generated. The structure and dimensions of a regulator were determined in detail by FEM analysis. Following workpiece rotation control tests using a special apparatus under a grinding-like configuration, a regulator was installed on an existing centreless grinder to perform actual microscale centreless grinding operations involving a tungsten carbide pin-shaped workpiece 0.6 mm in diameter and 15 mm in length. The experimental result gave a microscale workpiece 75 µm in diameter and 15 mm in length.

Effect of Ultrasonic Elliptic Vibration on Friction between Shoe and Workpiece in Ultrasonic Elliptic-Vibration Shoe Centerless Grinding

This paper describes an experimental investigation of the effect of ultrasonic elliptic vibration of the shoe on the friction between the shoe and the workpiece in ultrasonic elliptic-vibration shoe centerless grinding, a new centerless grinding technique proposed previously by the present authors. In the new technique, an ultrasonic elliptic-vibration shoe is employed to control the workpiece rotational speed as a regulating wheel does in conventional centerless grinding. The grinding accuracy is affected significantly by the workpiece rotation stability, which is dependent on the frictional force between the workpiece and the ultrasonic elliptic-vibration shoe. The issue relating to the friction between the workpiece and the shoe is therefore very important in the complete establishment of the new centerless grinding technique. In the present work, in order to clarify the effect of ultrasonic elliptic vibration of the shoe on the frictional coefficient and to determine the appropriate ultrasonic elliptic vibration conditions, a measurement apparatus was built up in-house and used to measure the frictional coefficient under the presence and absence of the ultrasonic elliptic vibration. The measurement results indicated that the frictional coefficient decreases with increase in the size of the ultrasonic elliptic motion, and a shape of the elliptic motion, in which the frictional coefficient reaches maximum, exists.

Surface improvement through hybridization of electrochemical turning and roller burnishing based on the Taguchi technique

The present work investigates the feasibility of improving surface quality via a novel combined process of electrochemical turning (ECT) with roller burnishing (RB) using the Taguchi fractional factorial experimental design technique. To provide burnishing immediately after the ECT process, non-conductive ZrO2 rollers are attached to the tool electrode during the experiments. The Taguchi technique is employed to identify the effect of ECT working parameters such as applied voltage, electrolyte pressure, workpiece rotational speed, minimum gap, and burnishing force on the output parameters, namely, material removal rate, surface roughness, and the improvement ratio in surface roughness. From the analysis of variance (ANOVA) and signal-to-noise (S/N) ratio response graph, the significant parameters and the optimal combination level of machining parameters are obtained. Experimental results indicate that the combined process effectively improves the surface roughness and eliminates the pitting caused by ECT. Therefore, the combination of ECT and RB is a feasible process by which to obtain a refined finished surface and achieve further surface modifications.

A new centerless grinding technique using a surface grinder

This paper proposes a new centerless grinding technique using a surface grinder. By this technique centerless grinding operations can be performed at low cost by installing a compact centerless grinding unit on the worktable of a multipurpose surface grinder and without the employment of a costly centerless grinder. The unit consists mainly of an ultrasonic elliptic-vibration shoe, a blade, and their respective holders. The shoe is produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body (stainless steel, SUS304), and an elliptic motion occurs on its end-face when two phases of AC voltage are applied to the PZT. The function of the shoe is to hold the cylindrical workpiece in conjunction with the blade, and to control the workpiece rotational speed with the elliptic motion on its end-face during grinding. The detailed structure of the unit was designed by Finite Element Method (FEM) analysis, and an actually constructed unit was installed on the worktable of a CNC surface grinder to perform tangential centerless grinding operations after its fundamental performance such as elliptic motion generation and capacity to control workpiece rotational speed had been investigated. As a result, it was clarified that the workpiece rotational speed changes linearly with variation in the applied voltage. This indicates that the workpiece rotational motion can be precisely controlled by the elliptic motion of the shoe. In addition, the workpiece roundness was clearly improved from an initial value of 23 μm to a final value of 2.6 μm after grinding, indicating that the constructed unit performed well in actual grinding operations.

Controlling the Workpiece Rotation Speed with an Ultrasonic Regulator in Microscale Centerless Grinding(M^4 processes and micro-manufacturing for science (continued))

This paper describes the design, construction, and performance confirmation of an ultrasonic regulator used for controlling the workpiece rotation speed in microscale centerless grinding. The ultrasonic regulator is constructed by bonding a plate-shaped piezoceramic device on an I-shaped metal body (SUS304), on the end face of which microscale elliptic vibration is generated. The structure and dimensions of an ultrasonic regulator capable of controlling the workpiece rotation speed in microscale centerless grinding was designed by FEM analysis. Following workpiece rotation control tests under grinding-like configuration, an ultrasonic regulator produced was installed on an existing centerless grinder to perform actual microscale centerless grinding operations involving a tungsten carbide pin-shaped workpiece 0.6mm in diameter and 15mm in length. The experimental result gave a microscale workpiece 60μm in diameter and 15mm in length.

Tool wear prediction in turning

The aim of the present work is to develop a reliable method to predict flank wear precisely in a turning process by developing a mathematical model and comparing it with the experimental results. Some important factors like the index of diffusion, wear coefficient, rate of increase of normal load with respect to flank wear and the hardness of tool, influencing the flank wear have been used as input parameters to develop the mathematical model. The developed mathematical model was used to relate the wear to the input parameters for a turning operation. The input parameters were established based on the design of experiment technique. The model was then used to predict the tool wear. These tool wear values were compared with the experimental flank wear values to determine the correlation coefficient between them. The correlation coefficient was found to be 0.988 showing the validity of the model. The effect of individual process parameters such as workpiece rotational speed, feed and depth of cut on the flank wear was also studied. Results showed that this flank wear model is reliable and could be used effectively for tool wear prediction.

우주망원경용 비구면 반사경 표면조도 향상을 위한 진화형 수치제어 연삭공정 모델

우주망원경용 비구면 반사경 가공 공정은 고정입자 연삭, 자유입자 래핑, 연마의 순서를 따른다. 숙련공에 의한 경험적 공정조절에 의해 목표 비구면을 가공하는 전통적 연삭 공정에서는 수 <TEX>${mu}m$</TEX> 높이의 표면 밑 손상을 남기며 뒤이은 자유입자 래핑 및 연마 공정에서 이를 제거하며 가공한다. 본 연구는 컴퓨터 수치 제어 연삭 공정진화 모델을 개발하여, 연삭가공을 통해 반사경 표면조도 최소 40nm이하, 가공 예측정확도 20nm급을 이루었다. 구체적인 방법론으로 초정밀가공기의 연삭모듈을 이용하여 연삭 휠 입자의 크기, 이송속도, 공작물 회전선속도 등 연삭 변수를 변화시키며 직경 20, 100mm Zerodur 소재를 초기 연삭하였다. 초기 연삭 변수와 측정된 표면조도와의 관계를 경험적 해석과 다 변수 회귀분석 해석 방법을 통하여 공정조절용 수치 연삭 모델을 구성하였다. 정량적 공정제어는 입력된 연삭변수들로부터 가공 후 표면조도를 예측하고, 측정된 표면조도를 이용하여 수치연삭 모델을 개량한 후 다음 가공에서 측정될 표면조도를 예측하는 순으로 만복 진행되었다. 본 연구에서는 CNC 연삭공정조절로부터 최소 평균 표면조도 36nm, 예측정확도 <TEX>${pm}20nm$</TEX>를 얻었다. 이 연구결과는 정량적 연삭공정제어 모델을 사용하여 자유입자 래핑 공정을 수행할 필요 없이 연삭에서 직접 연마 공정으로 진행할 수 있는 획기적인 공정 효율 향상을 의미한다. Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about <TEX>$20{mu}m$</TEX> rms in height and the subsurface damage of about 1 <TEX>${mu}m$</TEX> rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to <TEX>${pm}20$</TEX> nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

Design of arrow-head electrode in electropolishing of cylindrical part

The current work investigates the improvement of surface finish of external cylindrical surface finish on several die materials beyond traditional rough turning or drawing by electropolishing using arrowhead electrodes. The electrode is designed effective and low-cost. The controlled factors in electropolishing test include the chemical composition and concentration of the electrolyte, the electrolyte temperature, the flow rate of electrolyte, and the initial gap width. The experimental parameters are die material, rotational speed of workpiece and tool electrode, current rating, the electrode design parameters, and electrode feed rate. The electrode travels across the surface with continuous direct current. Both cone and flat arrow-head features are studied. Small end radius and high rotational speed of electrode produce good polishing. Small end radius also leads to high current density and feed rate. Small taper angle and large flute rake angle provide sufficient discharge space, which is advantageous for electropolishing. The electrode with double discharge flutes is superior to the electrode with single flute. Thin electrode with large flute rake angle and deep flute performs well.

Design of an Ultrasonic Elliptic-Vibration Shoe and Its Performance in Ultrasonic Elliptic-Vibration-Shoe Centerless Grinding

We describe the design of an ultrasonic elliptic-vibration shoe and its performance in ultrasonic elliptic-vibration-shoe centerless grinding. First, the vibration modes of the shoe for the bending and longitudinal directions are discussed and determined from the point of view of fixing the support of the shoe. Then the structure and dimensions of the shoe are determined by FEM (Finite Element Method) analysis. In order to clarify the performance of the produced shoe, an evaluation apparatus is built. The elliptic motions under different applied voltages are investigated using laser vibrometers. Finally, workpiece rotational motion control tests and actual grinding operations are carried out. As a result, it is clarified that the workpiece rotational speed changes linearly with variation of the applied voltage. This indicates that the workpiece rotational motion can be precisely controlled by the elliptic motion of the shoe. In addition, the workpiece roundness was clearly improved from an initial value of 25µm to a final value of 0.64µm after grinding, indicating that the produced shoe performed well in actual grinding operations.

Investigation for Estimating Form Accuracy Ground by a Generating Mechanism (Guide Lines based on Simulation for Design and Grinding Condition)

A rotor housing is one of main parts that compose combustion chambers of Wankel engine. The inside of it is peri-trochoidal form is shape. It is ground with a grinding wheel at a fixed point on the locus of workpiece moved by a generating mechanism. Workpiece radius and speed at the grinding point vary considerably. Inertia force, torque and grinding force that are caused in the grinding process, elastically deform this mechanism and wheel axis system in proportion to the square of workpiece rotational speed. Therefore, the positional errors arise between a workpiece and a grinding wheel and those affect grinding form. To grind it efficiently and accurately, it is extremely important in the design process of grinding machine and in the processing of peri-trochoidal form to forecast quantitatively the ground form accuracy under such grinding condition. In this report, the form accuracy has been analyzed by grinding simulation system when the conditions variously change. Useful and effective guidelines are obtained for designing the machine and grinding the form.