Assisted Polishing Research Articles

Prediction of quadratic cylinder surface morphology for ultrasonic assisted polishing

Aluminum alloys with light weight and excellent performance in processing are widely used in different kinds of optical reflector elements. In this paper, An innovative model for predicting the surface morphology of ultrasonic assisted polishing quadratic cylinder surfaces was developed based on the material removal model and calculation of the trajectory methods. Experimental verification was accomplished. By analyzing the simulation and experimental surface roughness analysis and two-dimensional power spectral density, the maximum error between the roughness experiment and the simulation is 9.3%, and the maximum error between the peak two dimensional power spectral density of experimental and simulation results is 9.8%. Surface properties can be enhanced and errors of medium and high frequency in the polished surface region can be diminished with the ultrasonic assisted polishing. This study provides important guidance for ultrasonic assisted polishing of different types of quadratic cylinder surfaces including without limitation cylindrical, elliptic, and parabolic surfaces.

Removal mechanism of NiTi alloy by ultrasonic assisted polishing based on molecular dynamics simulation

NiTi alloy has been widely used in mechanical and electronic, aerospace, energy and transportation, petrochemical industry and various biomedicine fields due to its unique super elasticity and shape memory effect. The traditional polishing method of NiTi alloy has the problems of poor consistency of polishing quality and low efficiency, especially for some NiTi alloy with complex shapes, the traditional mechanical contact method is difficult to polish its inner surface. For some NiTi alloys prepared by additive manufacturing, due to the existence of “step effect” and “spherodizing effect”, there are unmelted powder particles on the surface, and it also needs to be polished. However, it is necessary not to destroy the original structure shape and performance, but also to achieve high efficiency, high quality and consistent polishing, so it is a technical problem. Its polishing process is still unclear, and the polishing effect needs to be improved. Therefore, in this paper, molecular dynamics method was used to study the polishing process of ultrasonic vibration diamond abrasive particles on NiTi alloy. The influences of ultrasonic vibration frequency, ultrasonic amplitude and temperature on polishing force, average friction coefficient, surface morphology, structural evolution and dislocation distribution were studied, and the microscopic material removal mechanism was revealed. The results indicate that as the ultrasonic frequency increases, the number of normal force fluctuations increases, and the elastic and plastic deformation during the scratching process also increases. With the increase of ultrasonic amplitude, the average friction coefficient decreases, and the adoption of larger vibration amplitude is conducive to the scratching process, and the average friction coefficient will increase when the temperature increases, which is not conducive to the polishing process.

Profile prediction for ultrasonic vibration polishing of alumina ceramics

Ultrasonic-assisted polishing methods are widely used for the precision processing of hard and brittle materials such as glass and ceramics due to their excellent polishing performance. Most research has been focused on basic removal mechanisms of ultrasonic-assisted polished materials. Some investigators have studied the profile of surfaces after conventional mechanical polishing, but less research has been done on the profile of faces after axial ultrasonically assisted polishing. This paper has established a novel force prediction model for the ultrasonically assisted polishing, which is critical for geometrical accuracy and surface finish. Also a material removal model has been developed for this process using a spherical polishing head at different tilt angles. Pressure and velocity distributions have been calculated for multi-position contact areas. The experimental study of multiple trajectory polishing of alumina ceramics showed a good correlation between the experimental and simulated surface profiles. The ultrasonic polishing process parameters were optimized by applying the gray correlation analysis. The obtained results can be used not only select ultrasonic assisted polishing process parameters but also provide theoretical underpinning for surface polishing trajectory planning.

Polishing mechanism analysis of silicon carbide ceramics combined ultrasonic vibration and hydroxyl

Silicon carbide (SiC) ceramic is widely used in optical aerospace components due to high-temperature stability and specific stiffness. Considering low polishing efficiency and quality from its extreme hardness, an ultrasonic-chemical assisted polishing (UCAP) approach was developed for SiC using hydroxyl/diamond hybrid slurries to investigate its polishing characteristics and mechanisms. The removal rate increased significantly with the increase of hydroxyl content, abrasive content and size, but with more severe surface deterioration. The softened oxidation of hydroxyl, homogenized distribution, stronger impact and intrusion of abrasives induced by ultrasonic synergistically achieved a 16.8% improvement in removal rate and a 28.1% enhancement of surface roughness relative to conventional diamond slurry, indicating that UCAP provides guidance for multi-field assisted polishing of ceramics.

Study on material removal mechanism in ultrasonic chemical assisted polishing of silicon carbide

An ultrasonic chemical assisted polishing (UCAP) method exploiting the recombination mechanism of ultrasonic vibration, Fenton oxidation and mechanical impact is proposed for efficient finishing of silicon carbide (SiC). Experiments and theoretical analyses were performed to explore the effect of H2O2 content, FeSO4 content and ultrasonic amplitude on removal rate and surface roughness of UCAP and material removal mechanism. The combined interactions of ultrasonic and Fenton oxidation achieved superior polished efficiency and quality with a 19.51 % improvement in MRR and a 18.3 % increase in Ra compared to MP. This originates from the synergistic effect of oxidation of OH generated by chemical polishing slurry and the promotion of mechanical removal of abrasives and oxidation rate of SiC by ultrasonic vibration. Excessive FeSO4 and insufficient H2O2 can induce flocculent precipitates, thus reducing the MRR of SiC UCAP. Moreover, a larger ultrasonic amplitude generated a greater MRR, but with a smaller deterioration of the machined surface. This investigation reveals that UCAP is a progressive precision machining approach for optical ceramic materials polishing. The proposed polishing process will promote hybrid processing technologies research and simplify the existing SiC machining process to achieve extremely efficient polishing of SiC.

Ultrasonic dispersion method used in glass polishing experiment

To solve the problems of low processing efficiency and poor glass surface quality when using rare earth polishing powder to grind super-hard K9 glass. The potential, phase structure, surface morphology, and particle size distribution of the nano-rare earth polishing powder were characterized. Compare the evaluation indexes such as polishing efficiency, surface morphology, and contact angle after the polishing process is changed. The results of the comparative study show that the average surface roughness of the glass after heating ultrasonic polishing process is 0.9064 nm, the polishing rate reaches 0.748 μm/min, the average surface roughness of the glass without heating ultrasonic polishing process is 1.3175 nm, and the polishing rate reaches 0.586 μm/min, the ultrasonic assisted polishing process is superior to the conventional polishing process. The heating ultrasonic method provides experimental basis for precise and rapid processing.

Investigation on Feasibility of Polishing Concave Surfaces Using Magnetic Compound Fluid Slurry

Concave surfaces are widely used in the shells of smart devices, such as smartphones, watches, or molds. The quality of the concave surface is important in enhancing the value of these products. In order to improve the surface quality, the polishing process is crucial for removing defects on the concave surface and for smoothing the surface after machining or grinding. Magnetic assisted polishing is a promising method that can be used to meet the high standard of surface quality required. In this work, as a promising smart material in nano-precision polishing, magnetic compound fluid (MCF) slurry was used for the first time to polish a concave surface with a magnet that is magnetized in the radial direction. A simulation of the magnetic field distribution was performed in advance to clarify the polishing characteristics in theory. Subsequently, a polishing experiment was conducted to investigate the feasibility of this polishing method. Finally, the results demonstrated that both a curved surface and a flat surface could be polished successfully. Furthermore, the nano-precision PV value (the distance from the peak to the valley in the surface profile) and the surface roughness Ra were obtained for both areas, and this method was demonstrated to be capable of polishing concave surfaces and worthy of further research.

Ultra-fine grooving technology with high aspect ratio for cemented carbide by PCD (poly-crystalline diamond) blade

A novel dicing technology with high rigidity and hardness was developed for difficult-to-cut materials such as cemented carbide. The highly precise and ultra-thin dicing blade of 20 μm thick and free of crack was manufactured from a round body of polycrystalline diamond (PCD) by an electrical discharge process and ultra-violet assisted polishing. The blade has continuous cutting edges made of crystal grain boundary of PCD. Therefore, fine grooves can be cut in the cemented carbide with ductile-mode. In addition, the autogenous cutting edge regeneration effect was confirmed by partly maintaining the roughness of cutting edge without blunting the PCD surface state. It is speculated that cemented carbide particles detached from the workpiece caused micro-cracks to regenerate the cutting edges on the PCD blade. Finally, it was demonstrated that ultra-fine grooves with high aspect ratio of 20 μm width and 1 mm depth could be cut in a cemented carbide substrate, which has never been achieved in the past.

The study of ultrasonic vibration assisted polishing optical glass lens with ultrasonic atomizing liquid

In this paper, our study is ultrasonic vibration assisted polishing optical glass lens with ultrasonic atomizing liquid. The ultrasonic vibration is applied to the axial direction of the main shaft, which can make abundant grains to impact the workpiece with the high-frequency reciprocating style. And the ultrasonic atomizing liquid is applied to the nozzle in order to make grains more homogeneous and decrease clustering phenomenon, which can improve the surface quality. The material removal rate model of single and multiple grains in the holes and micro-peaks of the polishing head are established by analyzing the removal mechanism of ultrasonic vibration assisted polishing for optical glass lens with ultrasonic atomizing liquid. Several sets of experiments were designed and the optical glass lenses were polished through contrast experiment. The contrast experiment results show that the material removal rate of ultrasonic assisted polishing of optical glass lens with ultrasonic atomizing liquid is better than that of one-dimensional ultrasonic assisted polishing and common polishing. And the surface roughness of ultrasonic vibration assisted polishing with ultrasonic atomizing liquid can reach 2 nm. And the results of experiments can be seen that the removal rate of the material is related to the abrasive grain diameter, the rotational speed and the feed rate of polishing head, and the ultrasonic amplitude. The experimental results are basically consistent with the prediction model.

Fundamental investigation of ultrasonic-vibration assisted MCF polishing

Fundamental investigation of ultrasonic-vibration assisted MCF polishing

Surface Finishing on Arc-Shaped Inner Surface by Ultraviolet Assisted Polishing

Recently, diamonds have been utilized gradually for sliding parts and wear-resistant parts because of their excellent properties. The shape of diamond applied to these parts is not only plane but also arc-shaped inner surface. Therefore, development of diamond polishing technology is required. In this study, ultraviolet assisted polishing was thought to develop to polish polycrystalline diamond (PCD) on arc-shaped inner surface. The authors investigated effect of ultraviolet radiation on polishing efficiency and surface roughness. As a result, the surface roughness Ra of PCD showed less than 15 nanometers. In addition, polishing efficiency was improved about 30 percent due to ultraviolet assisted polishing.

Study on Removal Mechanism of Sapphire in Plasma Assisted Polishing

A sapphire substrate is essential for epitaxial growth of GaN, which is used for high brightness light-emitting diodes (LEDs), high-power and high-frequency devices. However, the material removal rate (MRR) of sapphire in conventional polishing is very low because of its high hardness and chemical inertness. We proposed application of plasma assisted polishing using a resin-bonded silica grinding stone for finishing of sapphire surface and investigated basic removal properties. The results of a ball-on-disc type test results showed that irradiation of water vapor containing atmospheric pressure Ar gas plasma promoted the MRR of sapphire by a factor of 7.4. Strong emission from hydroxyl radical was observed by an optical emission spectroscopy measurement of the plasma. XPS measurements revealed that the surface of both sapphire and silica were hydroxylated after the plasma irradiation. From these experimental and measurement results, we proposed the removal model in plasma assisted polishing of sapphire as follows. Firstly, irradiation of water vapor plasma hydroxylates the surfaces of sapphire and silica. Then, Al-O-Si bonding is formed by dehydration reaction between sapphire and silica surfaces. Finally, surface atom of sapphire is removed by the motion of silica abrasive. In this paper, we describe the preliminary experimental results and measurement results which support the proposed removal model in plasma assisted polishing of sapphire.

Study on Removal Mechanism of Sapphire in Plasma Assisted Polishing

A sapphire substrate is essential for epitaxial growth of GaN, which is used for high brightness light-emitting diodes (LEDs), high-power and high-frequency devices. However, the material removal rate (MRR) of sapphire in conventional polishing is very low because of its high hardness and chemical inertness. We proposed application of plasma assisted polishing using a resin-bonded silica grinding stone for finishing of sapphire surface and investigated basic removal properties. The results of a ball-on-disc type test results showed that irradiation of water vapor containing atmospheric pressure Ar gas plasma promoted the MRR of sapphire by a factor of 7.4. Strong emission from hydroxyl radical was observed by an optical emission spectroscopy measurement of the plasma. XPS measurements revealed that the surface of both sapphire and silica were hydroxylated after the plasma irradiation. From these experimental and measurement results, we proposed the removal model in plasma assisted polishing of sapphire as follows. Firstly, irradiation of water vapor plasma hydroxylates the surfaces of sapphire and silica. Then, Al-O-Si bonding is formed by dehydration reaction between sapphire and silica surfaces. Finally, surface atom of sapphire is removed by the motion of silica abrasive. In this paper, we describe the preliminary experimental results and measurement results which support the proposed removal model in plasma assisted polishing of sapphire.

紫外光援用研磨によるダイヤモンドの平坦化 1cm 角サイズの単結晶ダイヤモンド基板の加工

紫外光援用研磨によるダイヤモンドの平坦化 1cm 角サイズの単結晶ダイヤモンド基板の加工

Investigation of Removal Mechanism of Sapphire in Plasma Assisted Polishing

Single crystal sapphire is widely used as the material for precision equipments, due to its high hardness, chemical inertness and light transmission. However, it is difficult to obtain a scratch-free and damage-free sapphire surface with high-efficiency through traditional mechanical polishing or etching. We developed plasma assisted polishing (PAP) for the finishing of difficult-to-machine materials, such as silicon carbide, diamond, and sapphire. In this article, preliminary research results are showed about PAP applied to polishing of single crystal c-plane sapphire substrates. Combination of helium based atmospheric pressure water vapor plasma irradiation and silica abrasive polishing drastically increased removal rate of the sapphire c-plane. XPS measurements of the surfaces with and without irradiation of water vapor plasma revealed that alumina hydrate was formed by plasma irradiation at low temperature of less than 40°C. It is assumed that formation of alumina hydrate promoted the removal rate of sapphire.

Experimental Studies on Water Vapor Plasma Oxidation and Thermal Oxidation of 4H-SiC (0001) for Clarification of the Atomic-Scale Flattening Mechanism in Plasma Assisted Polishing

4H-SiC is difficult to be polishing due to its high hardness and chemical inertness. We proposed a novel polishing technique named plasma assisted polishing (PAP), in which oxidation by water plasma and polishing soft abrasive were combined. In order to increase the material removal rate of PAP and clarify the atomic-scale flattening mechanism, experimental studies on water vapor plasma oxidation and thermal oxidation of 4H-SiC (0001) were conducted. Experimental results indicated that the initial oxidation rate of water vapor plasma oxidation (185 nm/h) was much higher than that of thermal oxidation (29nm/h). In the case of water vapor plasma oxidation, the oxide/SiC interface was rough when the oxide layer was thin and it became flatter along with the increase of the thickness of the oxide layer. In contrast, the oxide/SiC interface was atomically flat regardless of the thickness of the oxide layer in the case of thermal oxidation. CeO2 abrasive polishing was conducted on the oxidized SiC surfaces, well-ordered step/terrace structures were obtained in both cases. The step height was about 0.25 nm, which corresponds to a one-bilayer structure of 4H-SiC.

알루미나 세라믹스 ELID연삭면의 자기연마 가공 특성

This study has focused on the application of magnetic assisted polishing for ELID ground surface of aluminum oxide ceramics. Aluminum oxide ceramics has been widely used as advanced materials for electric, optic, mechanic, chemical usage and so on. In this study, ELID grinding and magnetic assisted polishing technology was adopted for high-effective manufacturing and high quality surface of ceramic parts. The characteristic of MAP machining have been evaluated by the value of surface roughness and surface profile before and after magnetic assisted polishing. As the results of experiments, the surface roughness after magnetic assisted polishing has shown a significant improvement and the surface roughness was more improved when the feed rate of tool became slow.

Effects of Magnetic Fluid on Machining Characteristics in Magnetic Field Assisted Polishing Process

Magnetic characteristics of three magnetic polishing fluids such as magnetic fluid (MF), magnetorheological fluid (MRF), and magnetic compound fluid (MCF) under magnetic field are experimentally investigated and analyzed. Their magnetic cluster structures under action of magnet field are observed, and their magnetic cluster models are established. Magnetic flied assisted polishing experiments for tungsten carbide are developed used these three kinds of magnetic fluids, material removal and surface roughness are respectively measured. At last, the machining characteristic of three magnetic fluids are contrasted and discussed according to experimental results.

Atomic-scale flattening mechanism of 4H-SiC (0 0 0 1) in plasma assisted polishing

Plasma assisted polishing (PAP), in which the irradiation of atmospheric pressure water vapor plasma and ceria (CeO2) abrasive polishing are combined, is a novel finishing technique for single-crystal silicon carbide (4H-SiC). An atomically flat 4H-SiC surface (rms about 0.2nm) with a well-ordered step/terrace structure was obtained by PAP. Cross-sectional transmission electron microscopy (XTEM) observation revealed that plasma oxidation atomically flattened the interface of SiO2/SiC. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) measurement results showed the existence of a thin silicon oxycarbide layer, which is corrosion-resistant to hydrofluoric acid, at the interface. The combination of water vapor plasma oxidation and the mechanical removal of silicon oxide as well as silicon oxycarbide layers by a soft abrasive is effective in obtaining an atomically flat surface of 4H-SiC (0001) without introducing crystallographic subsurface damage.

Chemo-mechanical manufacturing of fused silica by combining ultrasonic vibration with fixed-abrasive pellets

Vibration-assisted grinding, in which harder abrasives than materials to be machined are employed, has been a viable and effective approach to increasing material removal rate (MRR) and/or reducing surface roughness of ground surfaces. We transfer this ideology to fused silica polishing by incorporating ultrasonic vibration into recently developed fixed-abrasive pellets in an attempt to enhance MRR and/or to improve manufactured surface quality. A prototype ultrasonic vibrator, the heart of the polishing head, was designed and the related experimental work was performed on an in-house built setup in conjunction with the constructed head. The vibrator is devised for the generation of 2-D tool path despite using only one actuator in lieu of two actuators in conventional 2-D ultrasonic machining systems. We then combined the ultrasonic vibration with fixed abrasive polishing pellets to machine fused silica glass. Machining experiments reveal that MRR is considerably increased up to >50% upon the introduction of ultrasonic vibration (UV) whilst surface roughness is not degraded appreciably. It was also noted that a overwhelmingly greater deal of polishing debris was dispelled during ultrasonic vibration assisted polishing than conventional bound-abrasive polishing, which may account for the greater MRR in UV assisted polishing.