Efficiency Of Polishing Research Articles

Density adaptive path based on stacked rotation convolution model in ultra-precision robotic optical polishing

Deterministic optics fabrication using sub-aperture tools has been vital for manufacturing precision optical surfaces, industrial robotic polishing, which is a more economical and intelligent method is required in modern fabrication process. However, the challenge of robotic polishing lies in the widely used spiral and raster paths, which may leave excess waviness from the tool path, and the unavoidable constant removal layer is added to obtain positive dwell time which cause low polishing accuracy. The waviness can be removed by either using smoothing tools sequentially or randomizing the tool path. However, process efficiency and accuracy are not well considered in the existing tool-path planning. A density adaptive path based on a stacked rotation convolution model to ensure polishing accuracy and efficiency while avoiding waviness generation is proposed in this study, and then the dwell time is calculated by anti-aliasing space-variant deconvolution. The robotic polisher experimental results confirm that the root mean square (RMS) of the final surface figure has been successfully reduced and stabilized at 7.355 nm, and the convergence effect at unit wavelength has been significantly augmented with an improvement of 367%, reducing the measurement from 28% to 131%; in addition, no obvious mid-spatial frequency (MSF) peak was generated in the PSD analysis of density adaptive path polishing results. Henceforth, the polishing accuracy, efficiency, and MSF error of robotic polishing can be greatly enhanced.

Vibration modal analysis of adaptive grinding and polishing tools

Abstract Adaptive grinding and polishing tools have a compact structure, fast response, and stable performance, and they can improve the efficiency of polishing and grinding large welded parts. The vibration frequency of the AGP600 adaptive grinding and polishing tool is abnormal after switching from the blade grinding head to the nylon grinding head, and the vibration is noticeable when the rotational speed is more significant than 4, 000 r/min, which seriously affects the quality of grinding. To analyze the cause of its vibration, this paper adopts HyperWorks to analyze the modal frequency of AGP600, carries out the vibration modal test, and analyses the reasons for the different vibration harmonic frequencies of AGP600. Finally, improvement measures for AGP600 are proposed, through which the vibration of AGP600 grinding tools can be reduced.

Ultra-precision diamond finishing of reaction-sintered silicon carbide enhanced by vibration-assisted photocatalytic oxidation

RS-SiC faces limitations in surface accuracy with conventional finishing processes due to its high mechanical hardness and multiphase nature. In this study, vibration-assisted photocatalytic oxidation is introduced to enhance the efficiency and precision of RS-SiC diamond polishing. By utilizing the photocatalytic reaction, the hard heterogeneous SiC phase and Si phase on the RS-SiC surface are transformed into a "softer" homogeneous oxide layer that can be removed easily. The introduction of vibration increases the relative velocity between the workpiece and the abrasive and prevents the aggregation of the photocatalyst, thus improving polishing efficiency. By reducing the abrasive size to the nanometer scale, the boundary between the Si phase and SiC phase can be smoothed out to further improve the workpiece surface finish. Using TiO2 as the photocatalyst, H2O2 as the oxidant, 25 nm diamond as the abrasive, and introducing vibration, an ultra-smooth surface with a surface roughness of 0.195 nm in Ra is obtained by the finishing method proposed in this paper. The proposed photocatalysis/vibration-assisted finishing approach offers a novel method for ultra-smooth polishing reaction-sintered silicon carbide.

Observing and Modeling the Wear Process of Heterogeneous Interface.

Understanding and controlling the wear process of heterogeneous interfaces between soft and hard phases is crucial for designing and fabricating materials, such as improving the wear resistance of particle reinforced metal matrix composites and the accuracy and efficiency of chemical mechanical polishing. However, the wear process can be hardly observed, as interfaces are buried under the surface. Here, we proposed a nanowear test method by combining focused ion beam cutting to expose interfaces, atomic force microscopy to rub against interfaces, and scanning electron microscope to characterize the interface damage. Using this method, three typical wear forms had been observed in Al/SiC composite, i.e., merely matrix wear, particle fracture, and particle pullout. A theoretical model was proposed that revealed that the increasing interfacial friction would induce particle fracture or pullout, depending on the particle edge angle and tip edge angle. This work sheds light on wear control in composites and nanofabrication.

The processing properties of photocatalysis assisted magnetorheological polishing based on TiO2–CI composite particles

With the development of optoelectronic wafers tend to be high brittleness, high hardness and high chemical stability, a single magnetorheological polishing is difficult to meet the application requirements of optoelectronic wafers. The quality and efficiency of magnetorheological polishing (MRP) of photoelectric wafer can be further improved by electric field assisted polishing or photocatalysis assisted polishing. In this paper, TiO2–CI functional composite particles were synthesized by sol-gel method, and a variety of polishing fluid with magnetic, electric and optical multi field effects were prepared. Silicon wafer and fused silica glass were polished by fixed-point centering polishing method, and the mechanism of photocatalytic assisted magnetorheological polishing (PMRP) was studied by comparing the polishing performance of the polishing fluid under different applied fields. The results show that when the polishing fluids prepared by oil-based liquid, the material removal rate is high under the action of a single magnetic field, but the polishing quality is poor. After polishing for 60 min, the height difference in surface profile ΔRz of fused silica glass is 0.67 μm. When the 2.5 kV/mm electric field is applied, the abrasive distribution can be controlled by electromagnetic composite field, and the stiffness distribution of polishing pad is more uniform, but it will reduce the material removal rate (MRR). Compared with the single magnetic field, the height difference in surface profile ΔRz is reduced by 73.1 % to 0.18 μm under the magnetoelectric compound field, which can obtain a more flattened surface quality. When light field and magnetic field are applied, water-based polishing fluid is used for polishing. Because UV light can induce photocatalytic reaction, the strong oxidation group ·OH generated in the photocatalytic reaction can oxidize the materials of workpiece surface into the lower hardness materials. Therefore, the material removal rate is increased by 249 % to 13.4 mg/h compared with that without light field, and the surface roughness was reduced by 69.32 % to 1.05 nm.

Simulation of Auto Parts Polishing Control Strategy Based on PID Control

With the large increase in automobile production, the demand for automobile parts is also increasing day by day. Aluminum alloy is the most widely used material in automobile parts. The production process of aluminum alloy parts has been automated, but the polishing process is still mainly manual. The high cost and low efficiency of manual polishing restrict the development of parts production technology. Therefore, it is imperative to develop a set of automatic polishing systems for aluminum alloy parts. Robot application in the polishing field has become a trend, but the force/bit coupling relationship in the polishing process of a robot is complicated, which brings great difficulty to the control of the polishing force. To solve the above problems, the key to obtaining stable polishing quality is to realize the force/bit decoupling of robot polishing and control the output constant polishing force. In this paper, an end-effector is used to realize the decoupling of force and position, and a new constant-force polishing control strategy is proposed to improve the automatic control level of robot polishing aluminum alloy auto parts. According to the nonlinear characteristics of the end-effector mathematical model and the feedback linearization characteristics of the backstepping method, a new type of backstepping PID constant force controller is designed, and the control flow is set up for simulation analysis. Simulink was used to build the simulation process and set up a reasonable controller gain for simulation verification. The simulation results of end-effector output polishing force under different strategies show that the reverse PID control has better response speed and anti-interference ability than the simple reverse control.

Parameter Optimization of RB-SiC Polishing by Femtosecond Laser

Reaction-boned silicon carbide (RB-SiC) is considered a new material for large lightweight ground-based space telescopes due to its high specific stiffness, low thermal deformation, and excellent optical quality. The excellent mechanical properties of RB-SiC result in the low efficiency of traditional polishing and mechanical polishing. In this paper, a polishing method for RB-SiC based on a femtosecond laser is proposed to improve surface quality. A theoretical heat conduction model was established in the process of femtosecond laser irradiation of SiC. We analyzed the ablation type and calculated the single-pulse ablation threshold of SiC, which verified the feasibility of femtosecond laser polishing. Further, the effects of polishing parameters on the polished surface quality were analyzed by a series of experiments, and the optimal parameters were selected. It was observed to improve polishing efficiency and can replace the intermediate steps of traditional mechanical polishing.

Ultrasonic coupled abrasive jet polishing (UC-AJP) of glass-based micro-channel for micro-fluidic chip

The efficiency of abrasive jet polishing (AJP) is relatively low for glass-based micro-channels, and an ultrasonic coupled AJP (UC-AJP) approach was thus proposed. The fluid mechanic model of the UC-AJP was established to reveal the ultrasonic enhancement law and the optimal design parameters. The calculation results indicated that ultrasonic vibration could help significantly improve the turbulent kinetic energy and impact erosion that had an important role in jet stability and polishing efficiency. High-speed photograph and polishing experiments with different amplitudes were then performed to explore the performance of the proposed UC-AJP method. It was found that for glass-based micro-channel UC-AJP produced a smoother surface and higher polishing efficiency than AJP. There is an optimal amplitude range in the UC-AJP process, which can maximize the polishing efficiency for the micro-channel. Such improvements were ascribed to the synergistic effect of the pulse and cavitation as a result of the formation of pulsed abrasive jet.

Effect of the Binder during Ultra-Precision Polishing of Tungsten Carbide Using a Semirigid Bonnet Tool.

Tungsten carbide (WC) has the characteristics of high hardness, high strength, corrosion resistance, wear resistance and excellent fracture toughness. Accordingly, it has been commonly used as the material for cutting tools and molds in glass-forming techniques. To obtain ultra-smooth surfaces, fine polishing of WC is indispensable. However, the efficiency of WC polishing is low using the existing polishing methods, and the mechanism behind the polishing process requires further investigation. Specifically, the effect of the binder in WC polishing is not clear since there are different kinds of WC with various weight percentages of the binder. In this paper, we present the findings of a study on the polishing performance of two kinds of WC material, with and without the binder, using a semi-rigid (SR) bonnet polishing tool. A series of experiments were performed on a 6-DOF robotic polishing instrument to investigate the material-removal characteristics, surface integrity and sub-surface damage after polishing. The results demonstrate that the SR bonnet polishing tool successfully reduced the surface roughness of WC with and without the binder to the nanometric level, though the lowest surface roughness was obtained on binder-less WC. No obvious sub-surface damage was observed under SEM inspection, while the processing efficiency was greatly improved owing to the high material removal rate of the tool. Based on our analysis of key polishing parameters and corresponding surface integrities, the effect of the binder on the polishing performance is explained, which offers excellent guidance for WC polishing.

Study on mechanism of improving efficiency of permanent-magnet small ball-end magnetorheological polishing by increasing magnetorheological fluid temperature

Permanent-magnet small ball-end magnetorheological polishing method can be used to polish the small part with complex structure. However, the material removal rate of this method is low, which is difficult to improve the output and reduce the cost. In this research, the effect of magnetorheological fluid temperature on the material removal rate is theoretically analyzed by measuring the effect of temperature on the flow properties of magnetorheological fluid, establishing the hydrodynamic model of polishing zone and solving the material removal parameters. It is found that with the increase of the magnetorheological fluid temperature, the polishing relative velocity increases accordingly, which can promote the improvement of material removal rate. But the shear stress decreases accordingly, which inhibits the improvement of material removal rate. The verification experiment results show that the promoting effect can exceeds the inhibitory effect, so that the material removal rate increases with the increase of magnetorheological fluid temperature. When the magnetorheological fluid temperature increases to 60 °C, the material removal rate is improved by 108.4% and the polished surface roughness Sa can reach 14.9 nm. Therefore, increasing the magnetorheological fluid temperature can significantly improve the efficiency of permanent-magnet small ball-end magnetorheological polishing and obtain high quality polished surface.

The effectiveness of scaling and root planing with combined application of air polishing and Nd:YAG laser in periodontal pockets of stage III grade C periodontitis patients: a single-blinded randomized clinical trial.

Evaluating the efficiency of combined air polishing and Nd:YAG laser application in addition to scaling and root planning (SRP) in treatment of periodontal pockets of stage III grade C periodontitis patients was the aim of this clinical trial. Twenty-four systemically healthy, stage III grade C periodontitis patients were recruited for this clinical trial. In this split-mouth study, the quadrants were randomly allocated to either SRP with combined air polishing (erythritol/chlorhexidine powder) and Nd:YAG laser (2W, 200mJ/pulse, 10Hz) therapy (test group) or SRP alone (control group). A masked examiner recorded clinical parameters such as plaque index (PI), gingival index (GI), bleeding on probing (%) (BOP %), probing depth (PD), and clinical attachment level (CAL) on periodontal charts at baseline, 1month and 3months after treatment. The clinical parameters had significantly reduced 1 and 3months after treatment compared to baseline for both study groups (p < 0.05). Considering PI, GI, and BOP (%) parameters, there were no significant differences between the study groups at any time points (p > 0.05). While PD and CAL reductions were similar in study groups for moderately deep pockets (5 to 6mm) (p > 0.05), PD and CAL reductions were significantly greater in test group compared to control group for deep pockets (PD ≥ 7mm) (p < 0.05). The present clinical trial demonstrated that SRP with combined application of air polishing and Nd:YAG laser may be advantageous in sites where mechanical debridement alone cannot access, such as deep pockets in the short term. Long-term, well-designed future studies including clinical, biochemical, and microbiological analyses are needed to determine the effectiveness of this procedure. SRP with combined application of air polishing and Nd:YAG laser provided more reductions in probing depth and clinical attachment level parameters in deep pockets compared to SRP alone.

Tribochemical action on the tribochemical mechanical lapping (0001) C plane of the SiC single-crystal substrate

The SiC single-crystal substrate with ultrasmooth and damage-free properties has potential applications in the field of optoelectronics and microelectronics. Lapping is one of the important processes for ultraprecision machining of the SiC single-crystal substrate. The lapping quality has an important impact on the surface quality, processing time, processing cost and processing efficiency of the subsequent chemical mechanical polishing (CMP) of the SiC single-crystal substrate. In this paper, four kinds of lapping pastes with different ingredients were prepared. The tribochemical action and mechanism of the oxidant in the lapping paste were studied. The results show that NaOH can be used as an oxidant for the tribochemical mechanical lapping of the SiC single crystal. Under the catalysis of iron oxide and frictional force, the tribochemical reaction between the SiC single-crystal substrate and the oxidant NaOH occurred and the silicon oxides (such as SiO[Formula: see text], gaseous carbon oxides and other reactants were produced. The surface energy of the SiC substrate was reduced and the material removal rate was improved effectively. These results can provide a reference for further research on the mechanism of tribochemical mechanical lapping.

Effects of Chemical-Electrical and Mechanical Parameters on Electrical-induced Chemical Mechanical Polishing of GaN

Overcoming the low fabricating efficiency of traditional chemical mechanical polishing (CMP) for Gallium nitride (GaN) is a challenge owing to its high hardness, high brittleness, and chemical inertness. Here, electrochemical etching is proposed to increase the material removal rate and acquire a high-quality surface on GaN wafers. To reveal the synergistic etching mechanism of oxidizing agent and corrosion inhibitor on the GaN wafers, electrochemical etching experiments were carried out. The optimal etching solution contained 4 wt% H2O2 and 10 mmol l−1 purified terephthalic acid. Experiments with various polishing parameters were comparatively investigated to verify the auxiliary effect of etching and determine the ideal parameters. Cathodoluminescence spectroscopy shows that the electrochemical etching removes the SSDs completely and the CMP process with befitting parameters does not induce supernumerary SSDs.

A novel high efficiency magnetorheological polishing process excited by Halbach array magnetic field

Magnetorheological polishing is a potential process for the low-damage manufacture of optics, semiconductors, and related devices. However, due to magnetic materials’ size and magnetic field strength limitations, a high-efficiency material removal rate can hardly be achieved in practical application. This work presents a novel high-efficiency magnetorheological polishing process, which employs Halbach array as magnetic field excitation to improve the processing efficiency. The Halbach array provides a large-area, high-intensity magnetic field, which is verified by finite element simulation and experiments. The force analysis of carbonyl iron particles in the magnetic field revealed the distribution of polishing pressure and polishing marks. The polishing performance of the process as well as the distribution of polishing pressure and polishing marks were investigated by polishing experiments. The effects of process parameters on the removal rate and surface roughness have also been systematically investigated. The novel magnetorheological polishing process can achieve 3.8 times material removal rate compared with the previous process. In the polishing processes of fused silica, the surface roughness reduced from 1979.154 nm to 0.544 nm in 60 min. To sum up, Halbach array could significantly improve the efficiency of magnetorheological polishing while preserving polishing quality.

Press-On Force Effect on the Efficiency of Composite Restorations Final Polishing—Preliminary In Vitro Study

The surface texture of dental restorations has a major influence on plaque accumulation and aesthetical appearance. The study aimed to evaluate the surface roughness of composite resins depending on the varying polishing sequences and applied forces. A total of 60 samples from two composite resins (Boston and Charisma) were polymerized using a lamp with 1200 mW/cm2 intensity and covering celluloid strip. The polishing sequence consisted of 12.6 mm OptiDisc (Kerr) – with increased disc per each subsequent step. Half of the samples were polished at 1N force, with the other half at 2N. The surface roughness examination was performed using a WYKO NT930 (Veeco) optical profilometer. The selected roughness parameters were compared by ANOVA with the significance level α = 0.05. The more complex polishing sequence affected on the composite smoothness. Higher roughness was identified in Charisma samples as compared to Boston. The specimens polished with 2N force contained a slightly rougher surface than those polished with 1N. However, these differences were not statistically significant. Despite the satisfactory visual effect obtained by polishing the composite samples, the profilometric examination revealed the roughness. Finishing is crucial for providing a smooth composite surface, allowing it to function properly in the oral environment.

Influence of robotic structural deformation on bonnet polishing removal function

Precision polishing system for opticals based on bonnet polishing technology and industrial robot can not only meet the requirements of high efficiency and precision of rapid polishing, but also reduce the development cost, thus it is a potential development solution for polishing. Bonnet polishing requires stable and deterministic material removal characteristics, and the stability of polishing spot is usually around 90%. The influence of robot stiffness on the stability of robot bonnet polishing system in the process of multi-step discrete precession polishing was studied. The robot end deformation was analyzed by the stiffness matrix, and the removal function of bonnet polishing with deformation error was established based on Preston theory. Finally, a four-step discrete polishing experiment was designed. According to the results, the polishing spot was Gaussian on the xy section contour line, and the xy section contour line was basically the same, with a good coincidence degree. Comparison of the cross-section profiles at different polishing positions indicates, the relative errors are below 5%. The experiment proves that the robot bonnet polishing system has a good stability in discrete precast polishing.

Picosecond Laser-Assisted Chemical Mechanical Polishing (CMP): Aiming at the Si-Face of Single-Crystal 6H-SiC Wafer

Silicon carbide (SiC) presents huge application potential in semiconductor devices. However, attributed to its high hardness and stability, there always appears an urgent problem about how to improve the efficiency of chemical mechanical polishing (CMP) of the SiC Si-face. In this study, an effective picosecond laser-assisted CMP method is proposed, which first preprocesses the Si-face with picosecond laser and then carries out CMP. Scanning electron microscopy (SEM), nano scratch tester (NST), and X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface alteration of SiC Si-face by picosecond laser pretreatment (PLP). The results demonstrate that the ripples and polycrystalline layer produced by PLP improve the surface machinability, and the C–O, Si–C–O, and Si–O bonds oxidized by PLP lead to easier removal by CMP. Hence compared with the no laser pretreated (NLP) samples, the material removal rate (MRR) of PLP samples is much higher in the first 45 min of CMP and the surface roughness (Rq) is lower after CMP. The proposed method has certain scientific significance and industrial production guidance for SiC semiconductor device manufacture.

Analysis of electric field electrode distribution on dielectrophoresis abrasive flow for polishing internal surface of ceramic workpiece

For the polishing of the internal surfaces of thin-walled ceramic parts, a dielectrophoresis abrasive flow polishing (DAFP) method is proposed. A non-uniform electric field is applied on the outer wall of the ceramic part, and abrasives in polishing fluid are polarized in the region of non-uniform electric field. The polarized abrasives are moved to the internal surface of ceramic parts by dielectrophoretic forces, so that more abrasives will effectively participate in the process of polishing internal surface of the ceramic part. Theoretical analysis of the forces on the abrasive particle is carried out. The flow field and electric field of different electrode ratios are simulated using COMSOL, the optimal dielectrophoretic force coefficient (e1), and thickness of active layer (δ3 = 2.15 mm) can be obtained when ER = 3. The original internal surface roughness of the workpiece is at 208 ± 5 nm. After 10 h of polishing, the roughness values of the inner surface of the workpiece reached 23 nm and 51 nm respectively, with and without dielectrophoresis. The efficiency of dielectrophoresis abrasive flow polishing of the inner surface of ceramic workpieces has been validated.

Kinematics Analysis and Trajectory Planning of Polishing Six-axis Robot

With the development of intelligent manufacturing, due to the low production efficiency and poor production environment of manual polishing, which is gradually replaced by the polishing robot. Take the polishing robot as the research object in this paper, a three-dimensional model of the robot with the end effector is established. The kinematics is modeled, solved and simulated with the D-H method and MATLAB Robotics Toolbox. The trajectory planning of the robot in joint space and cartesian space is analyzed and simulated.

Development of a fluid line-jet polishing process for rotational axisymmetric surfaces

In this paper, a fluid line-jet polishing (FLJP) process was developed for the polishing of rotational axisymmetric surface (RAS). FLJP aims to enhance the polishing efficiency of fluid jet polishing without degrading the polished surface integrity, together with better material removal uniformity than linear-array multi-jet polishing (MJP). The fluid field was analyzed by comparing to the normal fluid jet polishing (FJP) based on computational fluid dynamics (CFD) method so as to test the stability of the fluid line-jet. A series of polishing experiments were conducted to analyze the performance of the FLJP and compared to FJP and MJP in terms of material removal characteristics, the effect of the main factors (i.e. fluid pressure, stand-off distance, etc.), material removal uniformity and surface quality after polishing on cylindrical surfaces. The results indicate that FLJP has much higher material removal rate than FJP under the same polishing conditions together with superior surface quality. The material removal after FLJP is much more uniform than MJP, especially at the region along the length direction of the line orifice. Moreover, it is also found that the relationship between the polishing factors and the material removal rate in FLJP is similar to FJP, resulting in good control of material removal.