Vibration-assisted Polishing Research Articles

Kinetostatic and dynamic analysis for a new 2-DOF compliant mechanism for potential application in vibration-assisted polishing

Kinetostatic and dynamic analysis for a new 2-DOF compliant mechanism for potential application in vibration-assisted polishing

Design, Testing, and Experimental Validation of a Rotary Vibration-Assisted Polishing Device (RVAPD) for Enhanced Machining and Surface Quality.

A rotary vibration-assisted polishing device (RVAPD) is designed to enhance polishing force by converting PZT's linear motion into the rotary motion of a central platform via a flexible mechanism, improving material surface quality. The RVAPD is optimized, simulated, and tested to meet high-frequency and large-amplitude non-resonant vibration polishing requirements. Its structure, designed using theoretical models and finite element software, offers a wide range of polishing parameters. Performance parameters are validated through open-loop tests, confirming effectiveness in polishing experiments. The lever mechanism and Hoeckens connection enhance vibration parameters and motion efficiency, reducing surface flaws in SiC and improving uniformity. Adjusting the RVAPD structure and using the proposed method significantly improve SiC surface quality.

Atomic-scale simulation of ultrasonic vibration-assisted polishing process for graphene/GaN-layered composites

In the realm of semiconductor materials, the integration of graphene (Gr) and gallium nitride (GaN) has emerged as a promising avenue for enhancing device performance. In this study, a Gr/GaN layered nanocomposite was constructed using molecular dynamics simulation and the LAMMPS code. Diamond abrasive was pressed into the composite at a speed of 50 m/s at 300 K, followed by ultrasonic vibration-assisted polishing on the (0001) plane along the [01‾10] direction. By rigorously exploring various factors such as number of Gr layers, vibration amplitudes, vibration frequencies and grinding speeds, the study elucidates the intricate mechanisms governing material removal and subsurface damage. Key findings reveal optimal processing conditions, including three layers of Gr, an amplitude of 5 Å, a vibration frequency of 80 GHz and a grinding speed of 100 m/s, which result in enhanced material removal rates and improved surface quality. Additionally, the insertion of Gr layers within the GaN matrix demonstrates a remarkable reduction in friction and wear rates, highlighting the potential for enhancing device reliability and performance. This comprehensive investigation not only advances our understanding of ultrasonic vibration-assisted grinding processes but also underscores the transformative impact of Gr/GaN composites in semiconductor device fabrication.

Study on optimization of energy consumption and surface quality of ultrasonic vibration-assisted polishing process based on entropy weight method

As a typical hard and brittle material, optical glass is an important part of various optical systems and is widely used in space probes, aerospace technology, and other fields. Due to the unique material properties, the optical glass is prone to form defects such as micro-cracks and sub-surface damage during processing, which adversely affect the surface quality and performance of the workpiece. Ultrasonic vibration-assisted polishing (UVAP) technology is one of the methods to achieve high-quality processing of hard and brittle materials such as optical glass. However, UVAP technology usually suffers from long processing cycles and high energy consumption, which is not consistent with the development concept of the low-carbon economy. In this study, a unified evaluating mechanism for the experimental results was established using the entropy weight method (EWM) from the perspective of green polishing. The UVAP process parameters were optimized for obtaining excellent polishing quality and satisfactory processing energy consumption. The experimental results showed that the maximum reduction rate of energy consumption was 80%. Meanwhile, the improvement rates of surface roughness Sa and Sq were more than 40%.

Design, analysis, and testing of a new asymmetric vibration-assisted stage for roll-type polishing.

Based on the technological characteristics of roll-type polishing, a new asymmetric vibration-assisted stage is proposed in this paper. This stage is characterized by asymmetric displacement and asymmetric stiffness. With the average particle spacing of roll-type polishing as the constraint, the comprehensive characteristics of structural stiffness, kinematic range, and natural frequency are realized. Thus, to reduce the surface roughness, the removal of simple-directional surface textures generated by roll-type polishing can be achieved. First, the asymmetric structure is designed, modeled, and optimized according to working performance design goals of roll-type polishing. Then, the finite element analysis and actual performance test of the stage are carried out to verify the accuracy of the established model and the effectiveness of the optimization design. The results indicate that the stage can meet the design index. Finally, the asymmetric vibration-assisted polishing experiment is carried out. The results show that the single-directional surface textures of the SiC surface are interrupted and the surface roughness is decreased.

Process parameter analysis of ultrasonic vibration-assisted polishing of SiCp/Al ceramics based on optimized Hilbert trajectories

As an important ceramic matrix composite material, SiCp/Al ceramics have found extensive applications across several domains. However, the intricate nature of their material properties has resulted in a scarcity of scholarly investigations pertaining to the topic of ultrasonic vibration-assisted polishing (UVAP) of SiCp/Al ceramics. To solve this problem, a theoretical derivation of the material removal model (MRM) for UVAP SiCp/Al ceramics is presented in this paper. The selection of UVAP feeding speed is analyzed and discussed. The process parameters of UVAP of SiCp/Al ceramics are optimized based on the improved Hilbert's trajectory characteristics. According to the experimental results, high-quality machined surfaces can be obtained and the “fish scale” phenomenon can be avoided when the feeding speed is 0.015 m/s. Compared with the traditional trajectory, the improved Hilbert trajectory is easier to achieve uniform surface polishing. The introduction of ultrasonic amplitude (UA) can increase the material removal rate (MRR) by more than 21.6 % compared with the conventional polishing method. The maximum removal depth (MRD) increased by more than 27.76 % and the surface roughness (SR) is reduced by more than 76.45 %. The research results have an important application value for realizing efficient and high-quality polishing of SiCp/Al ceramics.

Surface integrity study of ZrO2 ceramic for ultrasonic vibration-assisted polishing processing

Due to the unique physical property, the surface integrity is a critical indicator to characterize the processing quality for hard and brittle materials. In this study, the ZrO2 ceramic is taken as a representative to investigate the surface integrity during ultrasonic vibration-assisted polishing (UVAP) processing. The effects of processing parameters on surface micro-morphology, surface hardness, scratch property and residual stress are analyzed by UVAP orthogonal experiments. The experiment results indicate that the UVAP processing can effectively improve the surface integrity of the ZrO2 ceramic. The research results are of great significance in guiding the UVAP controlled processing of hard and brittle materials.

Ultrasonic-Assisted Surface Finishing of STAVAX Mold Steel Using Lab-Made Polishing Balls on a 5-Axis CNC Machining Center.

The inconvenience of conventional wool ball polishing is that the surface finishing process should be equipped with a slurry container. The main objective of this research is to develop an ultrasonic-assisted surface finishing process for STAVAX mold steel on a 5-axis CNC machining center, by using new lab-made rubber polishing balls containing the abrasive aluminum oxide instead of the traditional wool ball polishing. In total, five types (type A to type E) of new rubber-matrixed polishing balls with a composite of nitrile butadiene rubber (NBR), an abrasive of aluminum oxide, and an additive of silicon dioxide have been developed. The performance of the composites with different grain sizes (0.05 μm to 3 μm) and concentrations of the abrasive of aluminum oxide have been investigated. The effects of multiple polishing passes on the surface roughness improvement for the lab-made polishing balls have also been investigated in this study. A surface roughness of Ra 0.027 μm on average was achieved by using the multiple polishing process of E-C-B-A. The volumetric wear of the lab-made polishing balls, using ultrasonic vibration-assisted polishing, can be improved from about 12.64% (type A) to 65.48% (type E) compared with the non-vibration-assisted polishing. The suitable combination of the ultrasonic vibration-assisted polishing parameters were an amplitude of 10 μm, a frequency of 23 kHz, a spindle speed of 5000 rpm, a feed rate of 60 mm/min, a stepover of 20 μm, a penetration depth of 180 μm, and a polishing pass of E-C-B-A, based on the experimental results. The surface roughness improvement on a test carrier with a saddle surface has also been presented by using the ultrasonic vibration-assisted polishing with the lab-made polishing balls.

Surface profile prediction modeling of spiral toolpath for axial ultrasonic vibration-assisted polishing

Hard and brittle materials are widely used in many frontier fields because of their better properties, and their efficient precision polishing methods are attracting much attention. The research on surface quality of optical lenses with surface finishing requirement not only involves surface roughness, but also surface form accuracy. The generated surface profile is a key factor affecting the surface form accuracy and overall smoothness. From experience, both processing mechanism of adopted method and toolpath have effects on the generated surface profile. For this, the paper presents a theoretical and experimental study of the generated surface profile of spiral toolpath in axial ultrasonic vibration-assisted polishing (UVAP). Based on classical Preston equation, Hertzian contact theory and the axial vibration-assisted processing principle, a prediction calculation model for generated surface profile of spiral toolpath is proposed. The model can specifically analyze the dwell-time distribution characteristics of periodically varying contact pressure and sliding velocity in the areas near/far-from the curvature center of curve toolpath, accurately predict the surface profile shape and material removal rate (MRR), and scientifically reveal the assisted processing principle. Accordingly, a series of experiments are conducted to verify the rationality of the proposed model and the polishing performance of axial UVAP. Compared to conventional methods, the predictions can more reasonably and accurately present the real surface profile characteristics, both high MRR and superior surface quality are obtained. This study would aid in achieving a deterministic processing technology of higher efficiency and better surface quality, laying a crucial theoretical basis for the global polishing of optical lens.

Reduction in the Volumetric Wear of a Ball Polishing Tool Using Ultrasonic-Vibration-Assisted Polishing Process

Ultraprecision freeform polishing using a bonnet or a felt ball mounted on a polishing head plays an important role in the mold and lens production industries. The volumetric wear of a bonnet or a felt polishing ball is still a problem to be solved. The objective of this study was to develop an ultrasonic-vibration-assisted ball polishing process on a CNC machining center to improve the surface roughness of a STAVAX mold steel and to reduce the volumetric wear of the polishing ball. The optimal combination of the ultrasonic-vibration-assisted ball polishing parameters for a plane surface was determined by conducting the Taguchi L18 matrix experiments, ANOVA analysis, and verification experiments. The surface roughness of the polished specimens was improved from the burnished surface roughness of Ra 0.122 μm to Ra 0.022 μm. In applying the optimal plane surface ball burnishing and vibration-assisted spherical polishing parameters sequentially to a fine-milled and burnished aspherical lens surface carrier on a five-axis machining center, the surface roughness of Ra 0.014 μm was obtainable. The improvement in the volumetric wear of the polishing ball was about 62% using the vibration-assisted polishing process compared with the nonvibrated polishing process.

Oblique ultrasonic vibration-assisted polishing for grating structures of BK7 optical glass

As a classical optical structure, grating is widely applied in semiconductor, biomedicine, and optical communication fields. However, the existing machining methods are difficult to accommodate the increasing requirements. A novel polishing method of optical glass BK7 was proposed based on ultrasonic vibration-assisted polishing with polishing oblique angle θ. It has better machining accuracy compared to common polishing. Finite element static analysis was performed to investigate the effect of polishing oblique angle on the processing of grating structures, and the feasibility and advantages of this method were illustrated theoretically. Meanwhile, the path corner profile, material removal rate, material removal depth, and surface roughness were analyzed. A series of single-factor experiments were performed to verify the feasibility of the proposed method. The experimental results indicate that a better grating corner profile and a higher material removal rate can be obtained with ultrasonic vibration. The introduction of polishing oblique angle can significantly improve the accuracy of grating corner profile and material removal rate calculation. This paper can provide useful insight and guidance to facilitate high-efficiency and high-precision machining of grating structures.

Study on the effect of ultrasonic vibration-assisted polishing on the surface properties of alumina ceramic

Due to the excellent biocompatibility and chemical durability, alumina ceramics are widely used in biomedical fields such as dentistry. Meanwhile, the high hardness and brittleness of the alumina ceramic causes difficulties in ensuring the processing quality of conventional machining methods. Ultrasonic vibration-assisted polishing (UVAP) can effectively improve the surface quality of hard and brittle materials as a novel machining method. The surface properties of the alumina ceramic for different ultrasonic amplitudes are obtained in this study. The evaluation of the surface properties includes microscopic topography, frictional property, surface hardness, microscopic strain, and surface roughness. In addition, a surface roughness model of the alumina ceramic is built based on the UVAP machining mechanism. The model considers the effect of different types of abrasive particles (free and fixed abrasive particles) on the material removal mechanism. The experimental results show that the errors of the predicted model are less than 20%. This work will provide some ideas for the subsequent UVAP processing.

Predictive modeling and experimental study of polishing force for ultrasonic vibration-assisted polishing of K9 optical glass

Predictive modeling and experimental study of polishing force for ultrasonic vibration-assisted polishing of K9 optical glass

Predictive and experimental research on the polishing slurry consumption model for ultrasonic vibration-assisted polishing of optical glass BK7

In the actual production process, people usually focus on the machining accuracy and machining efficiency, ignoring the production costs and environmental problems caused by the excessive amount of polishing slurry. Polishing slurry plays an important role during the ultra-precision polishing process, which is often overused so that better surface quality being obtained. However, when the amount of polishing slurry exceeds a threshold, the surface quality would not be significantly improved. Meanwhile, excess polishing slurry can cause environmental pollution and unnecessary waste. In this paper, a new calculation method was proposed, and a novel predictive model of polishing slurry consumption was established to calculate the consumption of polishing slurry in the deterministic polishing. Ultrasonic atomization (UA) was introduced into ultrasonic vibration-assisted polishing (UVAP), and the effects of UA on material removal mechanism (MRM) have taken into consideration. The effect of different machining parameters on the amount of polishing slurry was analyzed. Subsequently, a series of experiments were carried out under three different the flow rate of the polishing slurry (small, appropriate, and excessive) with various ultrasonic amplitudes. The experimental results indicate that the amount of polishing slurry in the deterministic polishing can be accurately calculated by the proposed model, and the maximum consumption of polishing slurry can be reduced by 22.17%. The predictive model of the flow rate of polishing slurry fills the gap and it contributes to the realization of green production, which is an important guidance for the actual production.

Study on machining BK7 optical glass by ultrasonic vibration-assisted polishing considering the micro-contact state of the abrasive particles with the workpiece

Brittle materials such as glass and ceramics have fragile physical properties that result in poor stability in the machining process. Ultrasonic vibration-assisted polishing (UVAP) can improve the surface quality and machining efficiency of the workpiece, which is beneficial to solve the machining problems of brittle materials. In this paper, a theoretical model is established to predict the material removal rate (MRR), surface roughness, maximum contact radius, and maximum material removal depth of BK7 optical glass for different machining parameters. The new model mainly considers the following aspects: (1) Considering the randomness of the shape, the abrasive particle is modeled as a truncated polyhedron. (2) Due to the randomness of distribution, the abrasive particles are considered to be randomly distributed in the contact area between the polishing tool and the workpiece. (3) Based on the Preston equation, a material removal model is established which considers the micro-contact state of the abrasive particles with the workpiece. Compared with the experimental results of BK7 optical glass, the new model has high accuracy in predicting machining performance. It is meaningful to understand the mechanism of UVAP and improve the machining efficiency.

Material removal profile prediction and experimental validation for obliquely axial ultrasonic vibration-assisted polishing of K9 optical glass

K9 optical glass is one of the typical components in optical systems. However, because of its poor fracture resistance, it is difficult to polish it with ultra-precision and high-efficiency and without any surface damage simultaneously. The emergence of the obliquely axial ultrasonic vibration-assisted polishing (UVAP) method can solve this problem which encounters in polishing efficiency and shape accuracy. However, due to the unclear material removal profile (MRP) mechanism, obliquely axial UVAP is not widely used in the processing field. This paper introduces the obliquely axial UVAP method in research processes, mainly focusing on the fixed point MRP analysis of the obliquely axial UVAP. Based on Hertz's contact theory, polishing pressure, the length of the semi-long axis (LLA) and the length of the semi-short axis (LSA) of the contact area are calculated under ultrasonic vibration conditions. Meanwhile, the relative linear velocity distribution of the oblique polishing tool in the instantaneous contact area is modeled by mathematical geometry method. A novel model of the MRP distribution for obliquely axial UVAP is proposed following the Preston equation. Subsequently, a series of polishing experiments were carried out to verify this model. The results show that the numerical model has good agreement with the experimental results on MRP, LLA, LSA, material removal depth and material removal rate (MRR). In addition, the material removal capability can be significantly improved by larger ultrasonic amplitude and larger oblique angle. This model not only more clearly elucidates the processing mechanism of obliquely axial UVAP, but also provides theoretical support for the polishing of free-form optical lenses.

Predictive modeling and experimental study of generated surface-profile for ultrasonic vibration-assisted polishing of optical glass BK7 in straight feeding process

Optical glass BK7 is widely used in optical lenses. It is a kind of hard and brittle material and thus difficult to machine. To solve the problems it has encountered in terms of polishing efficiency and quality, the axial ultrasonic vibration assisted polishing (UVAP) method is adopted in this study. A mathematical-prediction-model, firstly considering the effects of periodically changing pressure caused by ultrasonic vibration, is developed to predict the generated surface-profile. And for the first time, the concept of “Preston-coefficient distribution-function” is proposed to describe the effect of the abrasive-particle distribution on material-removal distribution-function. A series UVAP experiments on optical glass BK7 at different polishing parameters are conducted to validate the polishing efficiency and feasibility of the developed prediction model and proposed concept. The results confirm that UVAP method can realize a higher material removal rate (MRR) and a better surface quality. Compared to conventional method, the predictions are in good agreement with the experiments. The comparison of the obtained surface profiles proves the benefits of ultrasonic vibration as well. Moreover, the research results can be used to guide the adjustment of polishing parameters for deterministic material removal in straight feeding process of UVAP, and provide a valuable basis for trajectory planning of the global polishing of workpiece surfaces.

Non-resonant vibration-assisted magnetorheological finishing

Nano-finishing of material surfaces is an important class of technology in precision manufacturing. This paper presents a non-resonant vibration-assisted magnetorheological finishing method for difficult-to-process materials. The aim is to enhance the shearing effects of the magnetorheological finishing. A two-dimensional vibration-assisted polishing device was developed, and the impact forces generated by the vibration could change the contact force during the experiments. A polishing force model that considered the vibration parameters was established, which could analyze the processing principles and explain the reason for the increase in shear force. Then, a set of processing experiments were carried out to study the effects of vibration parameters on the surface roughness and peak-to-valley value of silicon carbide samples. Finally, the relationship between the vibration parameters, surface quality, and polishing forces was studied. Theoretical calculations and experimental analyses show that the vibration could improve the shearing effects of the flexible polishing cluster. Meanwhile, a higher amplitude and frequency could raise the total shear force, which can lead to a better surface quality.

Modeling and prediction of generated local surface profile for ultrasonic vibration-assisted polishing of optical glass BK7

• Preston coefficient is affected by ultrasonic amplitude. • Contact pressure is affected by ultrasonic amplitude. • Large ultrasonic amplitude helps to improve the polishing ability. • Local surface profile can be well predicted by the proposed calculation model. • Prediction of surface profile is a basis for free-form surface polishing of UVAP. With the rapid progress of science and technology, many applications of hard and brittle materials require advanced and suitable machining-techniques. One technique in particular, ultrasonic vibration-assisted polishing (UVAP), has been studied intensively by researchers worldwide. These studies indicate that UVAP has the capability to improve the surface quality as well as the machining efficiency. However, few studies focus on the deterministic material-removal of UVAP. The difference between generated and theoretical surface profiles determines the surface accuracy. Therefore, this paper focuses on predicting the generated local surface profile and providing a theoretical basis to reduce this error by controlling the polishing parameters. In addition to the axial ultrasonic vibration of polishing tool, ultrasonic atomization was adopted to provide uniformly distributed polishing slurry. To ensure sufficient surface-accuracy, it is necessary to predict the generated surface profile for a fixed spot as a basis research. This means, to enable accurate predictions the following improvements are realized: (i) A novel model for the elastic spherical contact-deformation of the polishing tool is used to calculate both the polishing force and contact radius. It takes into account the nonlinear elasticity of the polishing tool and the lateral extension of the contact area, which makes it more consistent with the actual deformation. (ii) A novel model for the material-removal distribution function for UVAP is proposed, based on the Preston equation. It considers the periodic changes of polishing force and contact radius caused by ultrasonic vibration. (iii) A series of fixed-spot polishing experiments on BK7 glass are carried out to verify the proposed models. The results show that the Preston coefficient is affected by axial ultrasonic amplitude, and large ultrasonic amplitude improves the polishing ability. In addition, the generated local surface profile, the maximum contact radius, as well as the material-removal depth and material-removal rate (MRR) can be predicted well. The new models not only provide a possibility to realize deterministic material removal but also enables in-depth-understanding of UVAP. It also represents a basic theoretical foundation for future, flat or free-form surface-polishing.

Design, analysis, and testing of a novel 2-DOF vibration-assisted polishing device driven by the piezoelectric actuators

In order to increase surface quality and material removal efficiency, a 2-DOF vibration-assisted polishing device driven by piezoelectric actuators (PZTs) was developed. The matrix-based compliance modeling (MCM) method was used to calculate stiffness, and Lagrange’s method was used to analyze the natural frequency of the device. To make the 2-DOF vibration-assisted polishing device achieve better performance, the dimensions of the device were optimized by the Whale optimization algorithm (WOA). Meanwhile, FEA was used in simulation and analysis of the device. The open-loop testing results show that the 2-DOF vibration-assisted polishing device has the characteristics of large stroke and high resolution. The polishing experimental results show that vibration-assisted polishing can improve the surface quality and material removal rate.