Study On Machining Mechanism Of Polishing Tool With Grinding Brush Cluster Based On Magnetorheological Effect

With the development of photovoltaic technology, the demand for optical part with super-smooth surface is increasing. The optical components made of optical glass, resin and other hard and brittle materials must have good optical properties, and their surfaces must reach a certain machining accuracy and surface quality, so it requires advanced processing methods to safisty the need. The conventional optics machining method which is inefficient and difficult to control machining quality is hard to satisfy the demand of social development. Therefore, as an advanced optical manufacturing technology, magnetorheological finishing (MRF) has been developed in recent years. It combines electromagnetic theory, fluid dynamic, analytical chemistry and mechanical machining theory with each other, and can effectively control the processing, finally, achieves high material removal rate and low surface roughness with little subsurface damage. In order to improve processing efficiency and improve processing quality, according to the polishing principle based-on cluster magnetorheological effect (MR effect), the machining mechanism of polishing tool with grinding brush cluster based on MR effect is studied. The main research contents are listed as following:1. Design of polishing apparatus based on cluster MR effect.According to the polishing principle based-on cluster MR effect and the need for precision machining, the design scheme of polishing apparatus based on cluster MR effect is presented, and the design of each functional unit is completed, then we focus on the design of polishing tool with grinding brush based on MR effect. The polishing tool with a single grinding brush is formed by using an electromagnetic device to create a magnetic field, then produce a grinding brush based on MR effect at the end of the electromagnetic core. The polishing tool with the cluster grinding brushes is formed by an array of permanent magnets on the base plate, and at each bottom of permanent magnets, the tool generates the cluster grinding brushes based on MR effect.2. Simulation and analysis of polishing tool based on cluster MR effects.Using finite element analysis software (Maxwell3D) to simulate and analyze the magnetic field distribution of polishing tool, and analyze the effect of parameters such as shape, size, spacing, interaction, and array mode of magnetic poles on performance of the grinding brush, and optimize the structure of polishing tool. Using analysis software Matlab to simulate and analyze the motion of grinding brush of polishing tool, and analyze the machining effect of trajectory distribution and velocity distribution of grinding brush, finally offer the advice to the further optimization of the arrangement of magnetic poles.3. Research on semi-bond mechanism of abrasive particle based on MR effect.According to the machining characteristics of abrasive under MR effect is between free abrasive and fixation abrasive, the semi-bond theory of abrasive of grinding brush based on MR effect is proposed. The grinding brush based on MR effect uses the chain structure of magnetic particle in the magnetic field to hold abrasive particles, so that abrasive particles are changed into a semi-solid state. During the process, the semi-bond abrasive particle is flexible to adapt the depth of cut automatically. So it overcomes the disadvantages of the adverse effects of surface morphology and particle size and so on, and helps process steadily to improve the machining effect. The influence of the abrasive particle characteristics under MR effect on the semi-bond performance of abrasive particle is analyzed through modeling. When the non-magnetic abrasive particle is added into magnetic particle chains, the magnetic particle chains deformed. Then, MR effect is weakened and the constraint intensity of abrasive particle by magnetic particle chains is also weakened.4. Research on motion state and machining behavior of abrasive particles under MR effect.To further study the machining mechanism of the cluster grinding brushes based on MR effect, under some hypothetical premise, the force and motion of abrasive particle under MR effect are analyzed through modeling. The cluster grinding brushes based on MR effect carry on two-body polishing of abrasive particle. The abrasive particle under external force shows different motion state and machining behavior. The motion state and machining behavior of abrasive particle is affected mainly by the constraint intensity of magnetic particles under magnetic field. But in order to improve the material removal effect of the grinding brush composed of semi-bond abrasive particle based on MR effect, it is very necessary to prepare MR fluid and select magnetic particle and abrasive particle reasonably. The machining effect of the cluster grinding brushes based on MR effect can be improved by effectively controlling motion state and machining behavior of abrasive particles.5. Experimental study of polishing based-on cluster MR effect.Using self-made experimental apparatus, the polishing experiment of optical glass with single factor has been completed. The experimental results of material removal effect of the grinding brush composed of semi-bond abrasive particles based on MR effect agree with the theoretical analysis. This shows that semi-bond theory of abrasive particle based on MR effect is credible, and the method is feasible to analyze the machining effect influenced by motion state and machining behavior of abrasive particle through modeling. The experimental results of machining effect of polishing tool with cluster grinding brushes based on MR effect are consistent with simulation analysis. This verifies the effect of properties of magnetic pole and process parameters on machining performance of polishing tool.The machining mechanism of polishing tool with grinding brush cluster based on MR effect is researched basically, the theoretical analysis and the experimental results are consistent. The research provides some basic theories, so as to lead to further development of the polishing equipment based on cluster MR effect, and the machining mechanism and technology for hard and brittle materials.