Papers by Keyword: Magnetorheological Finishing (MRF)

Abstract: To improve the effect of magnetorheological finishing (MRF), it is necessary to control the behavior of abrasive particle effectively in machining process. This article described the machining principle of semi-bond abrasives under the MR effect, then, analyzed the magnetic field of the polishing tool. Based on the magnetic field theory, the constrained model of abrasive particle was established, consequently, the force and the machining behavior of abrasive particle were analyzed. And an experiment was carried out to analyze the effect of the abrasive behavior on the material removal. The results show that the experimental results are identical with the theoretical analysis. Therefore, the control of the particle behavior in process is proved to be available.

Abstract: Based on the analysis of the machining process of magnetorheological finishing with the tiny-grinding wheel cluster, the motion model of abrasive in the tiny-grinding wheel cluster was proposed to describe the motion trajectory and the dwell time of abrasive relative to the surface of workpiece. Then, the experiment was applied to study the effects of the motion trajectory and the dwell time on surface quality and machining efficiency of the workpiece. According to the analysis, a method to improve surface quality and machining efficiency in MRF with the tiny-grinding wheel cluster was presented.

Abstract: Magnetorheological finishing technology is a new generation of high-precision optical accessory polishing and processing methods. It presents a MRF dwell time algorithm that can quickly calculate the resident time during magnetorheological processing of the rotational optical parts. A magnetorheological forming polishing experiment on a prototype has been carried out on BK9 glass parts of 20mm rotary symmetrical face shape. The algorithm can improve the surface shape precision of the workpiece from 6.5um to 0.61um. Emulational and experimental results show that the surface shape error of a spherical polished workpiece is convergent by this method, which is also, applies to magneto-rheological finishing of non-spherical and planar workpiece.

Abstract: Magnetorheological Finishing(MRF) is an advanced optical manufacturing technology, It is a kind of deterministic process. It conquers the defections such as low-efficiency and low-grade surface quality of the traditional method. Deduced from the hydrodynamic lubrication theory of the Bingham plastic flow, the material removal model of MRF is established. The reliability of the model is verified by the experiment. finally, we get the mean Preston coefficient by the theoretical curve and the actual measured curves, the value will be applied to optical components of the computer-controlled MRF operation. Through the magnetorheological finishing experiments , the results that compared with the experimental results in good agreement prove that our proposed model is reasonable.

Abstract: Optical glass is widely used as the most important basic material in optical field. In this paper, four different shape finishing tools are designed for polishing flat K9 glass by using magneto-rheological finishing process. Influences of the finishing tool’s shape on surface roughness are investigated and analyzed under different related parameters such as finishing time, rotational speed of tool and finishing gap. The result shows that the slotted tool could obtain better surface roughness than the non-slotted tool under the same conditions. Through changing the magnetic field intensity, finishing gap, rotational speed of tool and finishing time, an orthogonal experiment is conducted to obtain the optimal finishing process parameters.

Abstract: Based on the characteristics of magneto-rheological fluid, a new type of transmission device has been developed in this paper, in which output torque can be controlled accurately by adjusting electric current. It can be applied to replace magnetic particle clutch widely used at present to achieve tension control in some small-sized winders. A structure design of prototype has been proposed. By using the Bingham plastic constitutive model, the output torque of the device has been derived. Electromagnetic finite element analysis has been employed to simulate the magnetic circuit of this magneto-rheological fluid tension control device. It is shown that this magneto-rheological fluid tension control transmission has its significant advantages comparing with traditional magnetic particle clutch. The new one can produce higher controllable torques, and may be applied widely in the future.

Abstract: Combining the advantages of rheological behavior of magnetorheological fluid (MRF) and flexibility adjustability of rubber gasbag, a magnetorheological flexible gasbag polishing technique applied to free-form mould is proposed. With the development of robotic gasbag polishing technique, the flexibility of rubber gasbag can be adjusted by three methods of changing its internal pressure controlled through a pressure control unit, its own material property and structural parameter, and the rheological behavior of MRF inside of it in response to the application of an alterable magnetic field. Effect of rheological behavior to the flexibility of rubber gasbag and surface quality of mould is the single most important focus in this paper. The magnetorheological flexible gasbag polishing system is established and rheological behavior of MRF with magnetic field is described. Through polishing experiment focusing on the relationship between the surface roughness and current around electromagnetic coil, it can be obtained that magnetorheological flexible gasbag polishing technique is effective to improve surface quality when increasing current around coil in certain extent.

Abstract: Magnetic compound fluid (MCF), a functional fluid responding to magnetic field, is expected for an application to many engineering fields. In this paper, the effect of magnetic fields on the polishing force and the restoring ability of the MCF are studied followed by the proposal of a new polishing technique using the MCF. Under a fluctuating magnetic field generated by a revolution of permanent magnet, the magnetic particles in the MCF show a higher particle disposition and an accumulating action compared to a static magnetic field. Thus the MCF generates the greater restoring ability but the lower polishing force compared to that under the static magnetic field. When the MCF under the fluctuating magnetic field is applied to the polishing as the flexible tool, it shows the high polishing performance. As a result, a feasibility of a new polishing technique using the MCF for a three-dimensional structure is confirmed.

Abstract: ELID (electrolytic in-process dressing) grinding was proposed by one of the authors for automatic dressing the grinding wheel while performing grinding for a long time. It offers a high effective way and has been widely used for grinding hard and brittle optical materials. However, those surfaces produced by fixed abrasive grinding are characterized by considerable sub-surface damage, micro-crack. Magneto-rheological finishing (MRF) is a novel precision finishing process for deterministic form correction and polishing of optical materials by utilizing magneto-rheological fluid. In this paper, an ultra-precision synergistic finishing process integrated MRF and ELID grinding is proposed for shorten total finishing time and improve finishing quality. A lot of nano-precision experiments have been carried out to grind and finish some optical materials such as silicon, silicon carbide, etc. ELID grinding is employed to obtain high efficiency and high surface quality, and then, MRF is employed to improve further surface roughness and form accuracy. In general, form accuracy of ~ λ/20 nm peak-to-valley (P-V) and surface roughness less than 10 Angstrom are produced in high efficiency.