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Investigation into Electrorheological Fluid-assisted Polishing with Circular-type Integrated Electrode Tool

Author: ZhangYing
Tutor: ZhangLei
School: Jilin University
Course: Mechanical Manufacturing and Automation
Keywords: ER polishing Integrated electrode tool Surface roughness Continuous polishing
CLC: TG580.692
Type: Master's thesis
Year: 2011
Downloads: 26
Quote: 1
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Abstract

Electrorheological fluids (ERF) consists of a suspension of high dielectric particles in a liquid of low dielectric constant. Solid dielectric particles are polarized in ERF when the electric field is applied. Particles are aligned with the electric field lines. The apparent viscosity of the ER fluid increases in proportion to the strength of the applied electric field and returns to its original viscosity when the electric field is removed. The process of particles from disorder to chain and bunch makes Electrorheological effect.In traditional, the ER fluid-assisted polishing of conductive material such as tungsten carbide, the needle-like tool and the conductive workpiece are directly used as the electrodes. And in the ER fluid-assisted polishing of non-conductive material such as optical glass, an auxiliary electrode in circular shape is needed to surround the glass surface to be polished.The existence of auxiliary electrode limits the application of ER fluid-assisted polishing to the curved surfaces of non-conductive material. This paper develops a newly-designed circular-type integrated electrode. It is suitable to polish not only the conductive material but also the non-conductive material without auxiliary electrode. This paper calculates the electric field strength of circular-type integrated electrode tool. The results show that the center part of the integrated electrode tool has the maximum electric field strength. The electric field strength decreases with the increasing of the radius, the end of integrated electrode tool also has the maximum electric field strength. Uniform electric field formed approximately between electrodes. The electric field strength rapid decreases with the increasing of the distance under the end of tool. The simulation results coincide with the theoretical calculation.Based on the Preston equation, this paper establishes material removal model of ER fluid-assisted polishing. The experiment results show that the material removal model is correct.A series of experiments are conducted on a five-axis electrorheological fluid-assisted polishing equipment. Experimental results show that the various factors affect the surface roughness is as follows:the gap between tool and workpiece surface c>the polishing time T>the spindle rotational speed n>the applied electric voltage U>the mixing ratio for abrasives in ER fluidη> the particle size d. Optimal level of their own is as follows:0.2mm,10/min,4000 r/min,2500V,10%,10μm.The surface roughness increases with the increasing of the gap between tool and workpiece, but decreases with the increasing of spindle rotational speed. An optimal value exists for the polishing time, the applied electric voltage, the mixing ratio for abrasives in ER fluid and the particle size, i.e. T=10min,U=3000 V,η=10 wt%and d=10μm. The abrasive particles mixed into the ER fluid are diamond for polishing of the optical glass in order to get high removal rate. The abrasive particles mixed into the ER fluid are Al2O3 or SIC in order to get smooth surface. Those experiments show ER polishing is a very promising processing method.According to the processing characteristics of ER polishing, linear error and non-linear error are calculated. This paper presents two path planning methods, basing on the workpiece model and the surface equations respectively to obtain the data of cutter location. The data points of workpiece surface are collected. Insert new point if the error of two cutter location point is more than the processing error. Each axis’s displacement of machine tool can be calculated by kinematics equations. The surface roughness decrease after insert new point, mould surface is closer to the ideal surface as well. The other method is basing on the known surface equation, appropriate step size and line spacing are selected after path planning, then the point coordinates and normal vector are calculated. At last, each axis displacement of machine tool can be calculated by kinematics equations. Experimental results show that these methods improve machining efficiency and precision.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal cutting and machine tools > Grinding and grinding machine > General issues > Grinding process > Polishing
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