Ball End Magnetorheological Finishing Process Research Articles

Modeling and experimental study of surface roughness in smart MR fluid-based finishing process

Ball-end magnetorheological finishing (BEMRF) is a high-efficiency nano-finishing technology based on smart magnetorheological fluid to polish complex materials precisely. The surface roughness can be linked with the experimental data to understand the finishing mechanism based on advancements in manufacturing automation and the prediction of material removal. This study proposes a mathematical model to predict surface roughness, helping to understand the effects of various process parameters on surface quality during the BEMRF process. This study adds value to practitioners by providing a mathematical model to predict the optimum parameters for attaining the desired surface finish in BEMRF polishing.

Surface topography assessment using chemical assisted ball end magnetorheological finishing

The generation of residual stresses by grinding process on the surface for a soft material result in poor performance and diminished life. Ball end magnetorheological finishing (BEMRF) process is a recently developed process that is effectively used for fine figuring and polishing of a variety of magnetic and non-magnetic materials. In this paper, grinding-induced residual stresses are addressed, and an attempt is made to relieve these residual stresses while achieving high surface finish using chemical assisted ball end magnetorheological finishing (CA-BEMRF) process. The chemical used in the present work is applied first time in BEMRF process and aluminium 7075 alloy workpiece has not been finished with this novel finishing process. The impact of various CA-BEMRF variables on percentage surface roughness reduction and percentage reduction in residual stresses are discussed statistically and graphically. Residual stresses of workpiece surfaces have been measured by using portable x-ray residual stress analyzer. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the finished workpiece before and after CA-BEMRF process is carried out to assess the effects of magnetizing current, tool rotation and working gap on surface topography of machined surface. It has been observed that reduction in residual stress is achieved along with high surface finish on aluminium workpiece surface using CA-BEMRF technique. Significant process parameters affecting the residual stresses and surface roughness during polishing of workpiece are obtained using Analysis of variance (ANOVA) and F-test. The optimization problem for maximum percentage reduction in surface roughness and maximum percentage reduction in residual stress is formulated as multi objective, multi variable, nonlinear optimization problem. Maximum percentage surface roughness reduction and minimum residual stress has been found at magnetizing current 2.3 A, rotational speed of tool 550 rpm and working gap of 0.5 mm. Confirmatory experimental tests have been conducted and results obtained were found very close to the predicted outcome.

Improved CNC ball-end magnetorheological finishing process for borosilicate glass polishing

ABSTRACT This research aims to present an improved design of the Ball-End Magnetorheological Finishing (BEMRF) tool with the capability of being mounted on a CNC milling machine for polishing borosilicate glass (Bk7) lenses. Subsequently, the new BEMRF tool was designed, researched, and adjusted with magnetostatic simulation in Ansys Maxwell software. A response surface method experimental investigation was conducted to discover the optimized constitution of the magnetorheological fluid’s abrasive and carbonyl iron particles used for finishing operation on flat Bk7 glass. The simulation results and afterward measurements with a Gauss meter showed that changes in the BEMRF tool improved the variation in the density of magnetic flux in the polishing gap. At the optimum fluid constituents of 16 vol% abrasives and 29 vol% carbonyl iron particles, a 59% improvement in surface roughness was achieved. The proposed CNC tool found an appropriate way to finish Bk7 glass.

Chemical assisted ball end magnetorheological finishing of aluminium 7075 alloy

Areas like aerospace, solar, medical, electronics, optics widely use nano-finished or high precision aluminium alloys. These nano-finished aluminium alloys are being used as metal mirrors, micro-electronics devices, diaphragm in optical sensors etc. In general, aluminium alloys are finished by conventional processes such as grinding, lapping. However, to achieve nano-level finish on soft material like aluminium alloys which possess high malleability and ductility is difficult for traditional processes without producing high residual stresses, subsurface damage etc. In this work, the surface finish of aluminium 7075 alloy workpiece was improved using a novel finishing technique viz. chemical assisted ball end magnetorheological finishing (CA-BEMRF). To validate the results a comparison of % decrease in surface roughness obtained after ball end magnetorheological finishing (BEMRF) as well as achieved after CA-BEMRF process is carried out. Results showed a 1.84 % improvement in % decrease in surface roughness after CA-BEMRF process as compared to BEMRF without chemical assistance. The statistical and graphical effects of various changing process parameters on % decrease in surface roughness are addressed. Using analysis of variance (ANOVA) and the F-test, significant process factors impacting surface roughness during workpiece finishing are identified. Optimum value of % decrease in surface roughness has been found as 55.316 at magnetizing current 3.43amp, tool rotational speed 326.97 rpm and working gap of 0.74 mm. Confirmatory experimental tests have been conducted and results obtained were found very close to the predicted outcome. Scanning electron microscopy (SEM) of the workpiece finished using BEMRF process and CA-BEMRF technique are compared to assess the effects of magnetizing current, tool rotation and working gap on surface topography of machined surface.

Experimental Investigation into Residual Stress in Ball End Magne-Torheological Finishing

Ball end magnetorheological finishing (BEMRF) is a novel finishing process used to finish variety of surfaces ranging from flat, curved, complex, two dimensional, three di-mensional and non linear. The residual stress and surface finish play an important role in overall efficiency and durability of the components. The present work is aimed to relieve the residual stress of work-piece surface with the improvement in surface finish using pulse DC power supply (PDCPS) in BEMRF process. The preliminary experiments have been conducted on flat EN-31 steel with and without pulse DC power supply (WPDCPS). The process parameters during experiments were considered as magnetiz-ing current (MC) of 2.5A, tool rotational speed (TRS) 500 rpm, and working gap (WG) 1.5 mm with finishing time 35 minutes and 55 mm/minute feed rate given to the work-piece. The responses such as residual stress and surface roughness have been measured before and after experimentation. Residual stress of EN-31 surface was measured with X-ray residual stress analyzer using Cosα method. It has been observed that the residual stress was found reduced from 130 to 66 MPa and surface roughness was reduced drastically wit h the use of pulse DC power supply in BEMRF process. After preliminary experi-mentation, the statistical analysis with design of experiment has been conducted with pulse DC power supply on EN-31 steel to visualize the effect of various process parame-ters on residual stress using RSM technique.

Experimental and theoretical investigation into surface roughness and residual stress using ball end magnetorheological finishing

The generation of residual stresses by grinding process on the surface for a soft material results in poor performance and diminished life. In this paper, grinding-induced residual stresses is addressed and an attempt is made to relieve these residual stresses while achieving nano level surface finish using ball end magnetorheological finishing (BEMRF) process. BEMRF is a recently developed process that is effectively used to for fine figuring and polishing of a variety of magnetic and non-magnetic materials. In our present work we will demonstrate the relieving of residual stresses and reduction in surface roughness generated after surface grinding of Aluminium 7075 workpiece using BEMRF process. The impact of various BEMRF variables on reduction in surface roughness and residual stresses are discussed statistically and graphically. Residual stresses of workpiece surfaces have been measured by using portable X-ray residual stress analyzer. Significant process parameters affecting the residual stresses during polishing of workpiece are obtained using Analysis of variance (ANOVA) and F-test. It has been observed that reduction in residual stress is achieved along with nano level surface finish on aluminium workpiece surface using BEMRF technique.

Automated insular surface finishing by ball end magnetorheological finishing process

ABSTRACT Ball end magnetorheological finishing (BEMRF) is a process employed for precision finishing of flattened, intricate form complex 3D surfaces up to the nano level. Roughness of a surface determines the quality of results produced, which is usually measured by stylus-based instruments, with some optical methodologies also being adopted. These conventional methods when used for BEMRF tend to introduce errors in the part, which have to be removed from its fixture for measurement, and it is not feasible to remount it in the exactly same orientation again. Applications such as insular finishing (i.e., confined to a narrow region on the workpiece) demand the workpiece to be kept in the same orientation throughout, leading to requirement of measuring roughness in situ during the BEMRF process. A confocal sensor fits the requirement because of its confined design and lightweight capabilities. This work presents integration of a confocal sensor into the BEMRF setup for in situ roughness measurement. An initial Ra value of 352 nm was reduced to 289 nm just by insular finishing before finishing the full surface down to 78 nm in the case of a grinding error, from 420 nm to 342 nm by insular finishing, and finally down to 142 nm in the case of lapping error.

Detailed Review of Ball End Magnetorheological Fluid Finishing Process

For precision finishing of various newly and difficult of finish materials like optical glasses, metals, 3D-printed workpieces etc. Ball End Magnetorheological Finishing (BEMRF) finishing processes has been recently developed. This method utilizes a paste like fluid consisting of a base fluid which can be either water or oil, both magnetic and non-magnetic particles and stabilizing agents if necessary. Rheological behavior of this mixture of magnetorheological (MR) fluid with abrasives changes under the influence of magnetic field which in turn regulates the finishing forces during finishing processes. Present study critically reviews the BEMRF process used for achieving nano-level finishing variety of materials like mild steel, EN-31, copper etc. and the factors influenced this process so far which led to further advancements in this method.

Modelling of transient behaviour of roughness reduction in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) process provides nano level of surface finish for materials which are magnetic as well as non-magnetic in nature. The available literature on this process has been vastly limited to establishing its finishing capabilities on materials of different nature. This research work deals with theoretical investigations into surface roughness reduction in BEMRF process, performance of machining parameters during long time periods and providing their representation in mathematical terms. Starting with the mechanism of abrasive wear in BEMRF process, this work advances to find out prolonged effect of abrasive rubbing on a ferromagnetic workpiece surface. The study finds out a phenomenon termed as transient roughness reduction in which the material removal by abrasive wear in BEMRF process is diminished with time and a particular combination of machining parameters and fluid composition reduce roughness only up to a critical value, beyond which no further reduction is achieved. A mathematical model is developed to depict this transient roughness reduction phenomenon, the model is then experimentally verified and the close proximity of the experimental results with the theoretical ones validates the model and the transient roughness reduction phenomenon in BEMRF process.

Modelling of transient behaviour of roughness reduction in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) process provides nano level of surface finish for materials which are magnetic as well as non-magnetic in nature. The available literature on this process has been vastly limited to establishing its finishing capabilities on materials of different nature. This research work deals with theoretical investigations into surface roughness reduction in BEMRF process, performance of machining parameters during long time periods and providing their representation in mathematical terms. Starting with the mechanism of abrasive wear in BEMRF process, this work advances to find out prolonged effect of abrasive rubbing on a ferromagnetic workpiece surface. The study finds out a phenomenon termed as transient roughness reduction in which the material removal by abrasive wear in BEMRF process is diminished with time and a particular combination of machining parameters and fluid composition reduce roughness only up to a critical value, beyond which no further reduction is achieved. A mathematical model is developed to depict this transient roughness reduction phenomenon, the model is then experimentally verified and the close proximity of the experimental results with the theoretical ones validates the model and the transient roughness reduction phenomenon in BEMRF process.

Constant work gap perpetuation in ball end magnetorheological finishing process

Ball end magnetorheological finishing (BEMRF) is an advanced finishing method employed for super finishing of flat, curved, intricate and complex surfaces. The surface finish achieved in BEMRF process is governed by machining parameters and fluid parameters. A main contributor towards super finishing by BEMRF process is the work gap. A constant work gap ensures a uniform finishing operation throughout the entire surface; however, there are many cases wherein the work gap between tool tip and workpiece varies over the surface due to geometric form deviations induced by preceding manufacturing process or linear positioner having a tilt error. This paper describes a method to keep a constant work gap for finishing in BEMRF process. A confocal sensor is used to scan the surface in order to detect any height deviations that prevent a constant work gap. Experimental results show a considerable improvement in the surface quality while finishing with perpetuated work gap.

Effect of polishing fluid composition on forces in ball end magnetorheological finishing process

Ball end magnetorheological finishing is a nanofinishing process that uses magnetorheological polishing (MRP) fluid containing carbonyl iron particles (CIPs) and polishing grade abrasives to remove materials from the workpiece surface. The composition of the MRP fluid greatly influences the finishing forces. Using a dynamometer both normal and shear forces applied by the MRP are recorded on-line. A central composite design of experiments is used to plan the experiments and ANOVA to correlate these forces and process parameters. The process parameters selected here are vol.% of CIPs and vol.% of abrasives which are varied from 5% to 25% and 5% to 20% respectively to measure the forces during experimentation. Both normal and shear forces increase with increase in the CIPs content in the fluid. In case of abrasive concentration, it is observed that the forces initially increase with increase in abrasive content but begins to decline after a certain point.

Closed Loop Ball End Magnetorheological Finishing Using In-situ Roughness Metrology

Ball end magneto rheological finishing (BEMRF) is a recently developed advanced finishing process. Over the past decade the analytical and qualitative research has been established on various materials with this process. No work is done to automate the BEMRF process; this research work first establishes a time based reduction in roughness for the surfaces in BEMRF process. Suitable machining parameter sets are found for optimum time based finishing, a parameter selection algorithm is developed to select the next best parameter set to achieve maximum ΔRa in the next finishing cycle. A dedicated NC part program controls the operation of BEMRF process automatically. An in-situ roughness measurement system is used to get the roughness feedback after every finishing cycle to determine the initial Ra for next finishing cycle. Using the NC part program and developed algorithm the closed loop implementation of BEMRF process is carried out. Using closed loop finishing roughness parameter Ra from 800 nm range is brought down to 60 nm range in finishing time of 200 min, the same roughness reduction is achieved in 360 min of finishing time if finishing is carried out using individual parameter set. Thus by implementing closed loop finishing the optimum time for roughness reduction is achieved while conducting the whole process automatically.

Nanofinishing of FDM-fabricated components using ball end magnetorheological finishing process

ABSTRACTFused deposition modeling (FDM) is among the extensively used and the most economical additive manufacturing processes. Currently, the surface finish obtained for FDM additive manufactured parts are not at par with the current industrial application. To overcome the limitation of high surface roughness of 3D printed parts, a novel finishing technique has been proposed which includes primary and secondary finishing processes. While facing and lapping has been used as primary finishing technique, the secondary finishing involves the use of ball end magnetorheological finishing (BEMRF) process. BEMRF process is an unconventional finishing process which utilizes an advanced approach to impart finish on magnetic as well as non-magnetic materials that may be flat or freeform in shape. This article presents the experimental and analytical study to finish a polylactic acid (PLA) workpiece material manufactured by FDM process and finished using the BEMRF technique. The surface roughness of the FDM component has been reduced from initial surface roughness Ra = 20 µm to final value of Ra = 81 nm by combined primary and secondary finishing processes. The effect of magnetorheological polishing (MRP) fluid’s composition and finishing time is discussed and is followed by optimization of MRP fluid for maximum percentage reduction in surface roughness.

Experimental investigations into transient roughness reduction in ball-end magneto-rheological finishing process

ABSTRACTBall-end magneto-rheological finishing (BEMRF) process is a variant of magneto-rheological finishing (MRF) which is capable of finishing magnetic as well as nonmagnetic materials to finish surfaces up to the order of nanometers. The development of this process has been fairly recent and the literature has focused on quantifying and analyzing the effects of finishing on different materials with it. This research work presents a time-based roughness reduction study of BEMRF process to find out the behavior of machining parameters in finishing over lengthy time intervals. EN31 steel has been chosen as the work material for this study. Firstly, a machining parameter optimization is carried out for finishing of EN31 steel with BEMRF process. A detailed time-based experimental study is then carried out to find the effect of time on finishing with BEMRF process. The time-based study revealed a transient roughness reduction phenomenon in which a particular set of machining parameters was capable of reducing the surface roughness only up to a limited roughness value. The study concluded a database for finishing of EN31 steel with BEMRF process which can be used for optimum time-based finishing with BEMRF process.

Nanofinishing of 3D surfaces by automated five-axis CNC ball end magnetorheological finishing machine using customized controller

Ball end magnetorheological finishing (BEMRF) is a novel method for nanofinishing of ferromagnetic as well as nonmagnetic materials. With increasing demands of precision finished products in various markets, the quality of surface finish and production rate are of prime importance. For products having complex geometries, this need intensifies as the manual finishing methods are incapable of producing uniform finish throughout the complex geometry of the surface. This paper describes the finishing of 3D surfaces using five-axis CNC BEMRF process in a fully automated manner such that a uniform finish is obtained throughout the workpiece. This eliminates the labor-intensive efforts and the subjective errors involved in manual finishing operations and increases the production rate of the finished products. A customized five-axis CNC controller is developed that enables the sequential and precise control of motion as well as process parameters in the BEMRF machine. The magnetizing current which governs the forces responsible for finishing in BEMRF process is controlled in-process through CNC part program using a specially defined “E” code for magnetizing current. A dedicated graphical user interface is also developed in Visual C# for the control of BEMRF process, enabling the user to make use of BEMRF machine without going into the complexities of the system. Using the customized five-axis CNC controller, automated finishing of a freeform mild steel workpiece is done. The finishing results obtained by the automated five-axis BEMRF machine shows uniformly finished surface profile (up to order of nanometer) on the mild steel test specimen.

A study on the effect of polishing fluid volume in ball end magnetorheological finishing process

ABSTRACTBall end magnetorheological finishing is a unique process that utilizes a magnetically controlled ball of polishing fluid at the tip of the rotating tool to finish workpiece of different materials and shapes. The aim of this research is to study the effect of polishing fluid volume on finishing spot size and the surface finish associated with it. A magnetostatic simulation is done to find the variation of flux density in the working gap and on the workpiece surface. The maximum limit of the polishing fluid volume is selected on the basis of area of threshold magnetic flux density (minimum value required for finishing) region on the workpiece surface. The surface characteristics and the diameter of the finished spot are analyzed by varying the fluid volume. The surface obtained with high fluid volume is poorly finished and has scratch marks as the excess fluid flows out from the working gap and forms a thick ring at the periphery of the tool tip. Contrary to this, if the fluid volume is too less, then it merely rotates over the workpiece surface without causing any finishing action. An optimum range of fluid volume produces a good quality surface finish with constant finished spot size.

Synthesis of polishing fluid and novel approach for nanofinishing of copper using ball-end magnetorheological finishing process

ABSTRACTBall-end magnetorheological (MR) finishing process utilizes the magnetically controlled stiffened ball of an MR fluid for finishing purposes. Copper is a mechanically soft and chemically reactive material, so it is difficult to finish up to the nanometer-order level by traditional and most of the advanced finishing processes. In this research work, the problems associated with ball-end MR finishing of copper have been explored and a fluid composition suitable for the finishing of copper has been developed. A novel approach using two opposite magnetic poles has been used to enhance the magnetic flux density distribution between the tool tip and the copper workpiece surface. The same has been magnetically simulated and verified experimentally. The effect of fluid composition parameters has been analyzed by the statistical model developed by response surface. After 30 minutes of finishing time, a nano-finished surface with very few shallow scratches was achieved.

Reprint of ‘‘Modeling of surface roughness in ball end magnetorheological finishing (BEMRF) process’’

A new precision finishing process called the ball end magnetorheological finishing (BEMRF) process was developed for super finishing of complex 3D surfaces. This process is based on magnetorheological polishing (MRP) fluid whose rheological behaviour varies with the magnitude of the applied magnetic field. The magnetically energized MRP fluid is used at the tip of a rotating tool to finish workpiece of different materials and shapes. The MRP fluid is a mixture of abrasives and magnetizable carbonyl iron particles (CIP) in a carrier medium. To improve the in-depth understanding of the BEMRF process, this work deals with the theoretical investigations into modeling of surface roughness and mechanism of material removal associated with ferromagnetic workpiece. Since it is very difficult to understand the complex structure of the magnetically energized MRP fluid during finishing operation, microstructure of the constituents of the MRP fluid has been proposed. A theoretical model of magnetically induced normal and shear forces acting on the abrasive is also proposed in the present study. Based on these forces, the material removal process and wear behaviour during finishing operation have been analyzed. While the normal force model explains the penetration of abrasives into the workpiece surface, the shear force model aids in the understanding of three body wear mechanism between the abrasives and the workpiece surface. A mathematical model has been developed to evaluate the surface roughness. Using the developed model, the theoretical value of surface roughness is computed. The close agreement of theoretical and experimental results validates the proposed model.

Modeling of surface roughness in ball end magnetorheological finishing (BEMRF) process

A new precision finishing process called the ball end magnetorheological finishing (BEMRF) process was developed for super finishing of complex 3D surfaces. This process is based on magnetorheological polishing (MRP) fluid whose rheological behaviour varies with the magnitude of the applied magnetic field. The magnetically energized MRP fluid is used at the tip of a rotating tool to finish workpiece of different materials and shapes. The MRP fluid is a mixture of abrasives and magnetizable carbonyl iron particles (CIP) in a carrier medium. To improve the in-depth understanding of the BEMRF process, this work deals with the theoretical investigations into modeling of surface roughness and mechanism of material removal associated with ferromagnetic workpiece. Since it is very difficult to understand the complex structure of the magnetically energized MRP fluid during finishing operation, microstructure of the constituents of the MRP fluid has been proposed. A theoretical model of magnetically induced normal and shear forces acting on the abrasive is also proposed in the present study. Based on these forces, the material removal process and wear behaviour during finishing operation have been analyzed. While the normal force model explains the penetration of abrasives into the workpiece surface, the shear force model aids in the understanding of three body wear mechanism between the abrasives and the workpiece surface. A mathematical model has been developed to evaluate the surface roughness. Using the developed model, the theoretical value of surface roughness is computed. The close agreement of theoretical and experimental results validates the proposed model.