Optimization study on magnetorheological fluid components and process parameters of cluster magnetorheological finishing with dynamic magnetic field for sapphire substrates

Abstract

Sapphire is used as the base material of high-brightness LED devices, high-speed and high-frequency wireless communication devices, and solar photovoltaic conversion chips. Its surface quality determines the performance of the device. Magnetorheological (MR) finishing can avoid scratches and surface/subsurface damage caused by uneven abrasive particles due to the viscoelasticity of the polishing pad. When MR polishing was used to polish sapphire substrates, the adaptability of the MR fluid components and the rationality of polishing process was the key to quickly obtain high-quality workpiece surface. In this study, sapphire substrates were polished using cluster MR finishing with dynamic magnetic fields formed by multiple synchronous rotation magnetic poles. The components of the MR fluid were optimized by single-factor experiments, and the polishing process parameters were optimized through orthogonal experiment. The results showed that an ultra-smooth surface of Ra 0.27 nm could be obtained when sapphire substrate was polished 8 h by using the optimized MR fluid, which contained 120 nm silica sol with a mass fraction of 8 wt% and W3 carbonyl iron powders with a mass fraction of 16 wt%, also with the optimized process parameters as the machining gap, the workpiece speed, the magnetic pole speed and the rotation speed of the polishing disc were 1 mm, 350 r min−1, 45 r min−1 and 40 r min−1, respectively.

Investigations on Process Parameters of Cluster Magnetorheological Polishing in a planet motion model

“…In the polishing test, the specific processing parameters are shown in Table 4. In order to ensure the accuracy of the experiment, L26(6 5 ) orthogonal experiment was designed [20][21]. And the test scheme is shown in Table 5.…”

Improvement of roughness in ultrasonic assisted magnetorheological finishing of small titanium alloy nuts by orthogonal test method

“…The MR finishing method based on the point-contact type is often used for polishing complex shape workpieces due to its small polishing tool. The polishing films can be formed on the polishing disc by the MR polishing fluid having a or a few area contacts with the workpiece surface (many small magnetic poles clustered) 15 , 28 , 29 , which is called area-contact type. This method based on the area-contact type is often used for polishing large-size workpieces due to the large polishing tool.…”

Mid-spatial frequency error restraint based on variable optimal angle-step trajectory strategy for the removal attenuation effect of magnetorheological finishing

“…Current MSF error suppression methods are based on the assumption of time-invariant TIF, and the removal attenuation effect of MRF on MSF error is not studied yet. The removal attenuation effect of MRF is that during the long continuous polishing process, the TIF is constantly attenuating due to the change of various parameters and environmental conditions [17][18][19], such as water evaporation and abrasive loss. This removal attenuation effect leads to deviations between the initial processing parameters and the actual needed processing parameters, thereby the residual errors, including MSF error, are generated on the surface of the polished component.…”