Ultrasonic Vibration-assisted Polishing Research Articles

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.

The ultrasonic vibration–assisted polishing material removal model of tilted cylindrical polishing tool based on BK7 glass

BK7 glass is widely used in various optical instruments as a common ceramic material. However, there are still several difficulties in the polishing process due to its material properties. Ultrasonic vibration–assisted polishing (UVAP) is used widely for its excellent material removal properties. However, there are few researches on the model of UVAP material removal for tilted. Therefore, this paper investigates this problem. A model of UVAP material removal was established for titled column polishing; The pressure distribution and velocity distribution in the contact zone were modeled by means of experiments and geometric analysis. A series of orthogonal experiments were conducted, and the experimental results showed that the coefficient of determination was above 0.9 after fitting the actual profile to the predicted profile. The results of the orthogonal experiments were also analyzed by ANOVA. The predict error of maximum removal depth was less than 13.12%. The error of material removal rate (MRR) was less than 9.24%. By power spectral density (PSD) analysis, it was found that the introduction of ultrasonic amplitude has a good effect on suppressing the medium and high-frequency errors on the machined surface. The novel model can be used to optimize machining parameters and provide theoretical support for complex parts polishing.

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 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.

Modeling and analysis of the material removal rate for ultrasonic vibration–assisted polishing of optical glass BK7

The emergence of ultrasonic vibration–assisted polishing technology has effectively improved the machining accuracy and efficiency of hard and brittle materials in the modern optical industry; however, the material removal mechanism of ultrasonic vibration–assisted polishing (UVAP) still needs to be further revealed. This paper focuses on the material removal mechanism of ultrasonic vibration–assisted polishing of optical glass (BK7), the application of ultrasonic to axial vibration, and the atomization of the polishing slurry; the material removal model was established. Based on the analysis of the relationship between the nominal distance d of the polishing pad and the actual contact area distribution, the prediction of the material removal profile is realized. In addition, the effects of different parameters on the material removal rate (MRR) were analyzed, including polishing force, spindle speed, abrasive particle size, ultrasonic amplitude, feed rate, and flow rate of polishing slurry. Based on the motion equation of abrasive particles, the trajectory of abrasive particles in the polishing slurry was simulated, and the simulation results show that the introduction of the ultrasonic vibration field changes the motion state and trajectory of embedded and free abrasive particles. The new model cannot only qualitatively analyze the influence of different process parameters on MRR, but also predict the material removal depth and MRR, providing a possibility for deterministic material removal and a theoretical basis for subsequent polishing of complex curved surfaces of optical glass.

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.

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.

Effect of ultrasonic vibration on polishing monocrystalline silicon: surface quality and material removal rate

Monocrystalline silicon is difficult to achieve high material removal rate (MRR) and good surface quality for conventional mechanical polishing (MP). Therefore, ultrasonic vibration assisted polishing (UVP), combined with the functions of conventional mechanical polishing and ultrasonic vibration machining, is employed to polish single crystal silicon in our research. The results show that ultrasonic vibration can effectively increase the MRR and quickly obtain a better surface quality. The effects of ultrasonic vibration on the surface quality and the MRR of single abrasive were analyzed by molecular dynamics simulation (MDS) in the atomic point of view. A material removal model of single abrasive is set up to verify the results of molecular dynamic simulation. Experiments are conducted for model verification, which results show that the MRR model can predict the effect of the amplitude on the material removal rate well.

Study on optimization of ultrasonic-vibration-assisted polishing process parameters

Rapid developments in the field of optics has generated much demand for high performance optical components. In order to improve the polishing efficiency and obtain a high surface quality, an increasing number of ultrasonic-vibration-assisted processing methods have been employed to polish optical components, and the ultrasonic process parameters that play a critical role in effecting this improvement are identified. In this study, axial ultrasonic vibration assisted polishing method was employed to realize this improvement, an orthogonal experiment method was adopted to research the effects of five key process parameters – the spindle speed, gap size between polishing tool and workpiece, abrasive diameter of polishing liquid, ultrasonic amplitude, and working time–on the material removal rate and surface roughness, respectively, and an effect rule was obtained. As the parameter optimization schemes used differ, the optimization of process parameters becomes complex when the polishing efficiency and surface quality are taken into account at the same time. Hence, the main objective of this study is a process-parameter scheme that optimizes both the polishing efficiency and resulting surface quality of a self-built ultrasonic-vibration-assisted polishing (UVAP) device using the gray relational analysis method. We have realized and verified the optimization of UVAP process parameters under multi-objective optimization indices, using a simple optimization procedure.

Material removal mechanism in ultrasonic vibration assisted polishing of micro cylindrical surface on SiC

In consideration of the high hardness of the mold insert material SiC, ultrasonic vibration was introduced in the abrasive polishing (AP) of the linear micro cylindrical surface aiming to enhance the surface quality while improving the machining efficiency. However, the interaction behavior in between the material and polishing tool under ultrasonic vibration has not been studied so far. In this paper, the material removal mechanism of ultrasonic vibration assisted polishing (UVAP) on micro cylindrical SiC surface was investigated to fulfill a fundamental understanding of this process in comparison to the conventional polishing without employing ultrasonic vibration. The collection method of high frequency friction forces was firstly proposed to analyze the friction behavior on the SiC cylindrical surface. Then the relationship between ultrasonic vibration, friction force and micro cylindrical surface quality was studied respectively. The experimental results indicated that when the ultrasonic vibration was applied, the friction force decreased accordingly corresponding to a better surface quality. In addition, the lubrication condition was discussed in UVAP process based on the establishment of the stribeck curve. Furthermore, the wear coefficients were calculated through measuring the material removal depth, the surface morphologies were measured by a scanning electron microscopy in revealing the different material removal modes under various different polishing parameters. Through computation and analysis, it shows that the lower polishing force and relative lower speed as well as the higher vibration frequency and amplitude could result in a lower surface roughness and less polishing marks of micro cylindrical surface on SiC. Finally, the cylindrical arrays were successfully polished with the optimized parameters on precision diamond ground SiC surfaces.

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.