K9 Optical Glass Research Articles

Simulation and experimental investigation of material removal profile based on ultrasonic vibration polishing of K9 optical glass

Ultrasonic vibration polishing (UVP) is an important method for the precision processing of optical glass, which is good for improving surface quality and processing efficiency. So far, the material removal mechanism in UVP is not well understood and the various process parameters involved are not considered. To achieve ultra-precision polishing under optical glass, this paper carries out the axial UVP method. The material removal profile (MRP) is critical to affect the surface accuracy. A new MRP is developed for UVP based on the Urick attenuation model and the proposed material removal coefficient distribution function, considering the dynamic pressure changes under ultrasonic vibration, the attenuation effect of the acoustic pressure propagation process and the inhomogeneous distribution of the abrasive particles in the contact area during the ultrasonic electro-spindle rotation. Through a series of polishing experiments and simulations, the results show that the maximum errors of the actual material removal depth (MRD) and the actual material removal rate (MRR) from the model simulation results are 8.54% and 9.92%, respectively. The accuracy of the model is further demonstrated by the Pearson correlation coefficient. When the amplitude of UVP is 9 µm, Sa and Ra are 60 nm and 68 nm, which are reduced by 37.50% and 22.73%, respectively, compared with conventional polishing. This research can contribute to the deterministic processing of UVP, and provide a theoretical basis for the application of optical glass.

Experimental Study on Dispersion Stability and Polishing Performance of Polishing Solution Based on Micro-Abrasive Water Jet Polishing

In micro-abrasive water jet polishing (MAWJP) technology, where abrasive particles serve as polishing tools, particles tend to form large clusters, leading to increased nozzle wear and diminished material polishing quality. Achieving a polishing solution with good dispersion stability is crucial for enhancing polishing accuracy and minimizing nozzle wear. Therefore, this study employed three dispersants with distinct dispersion mechanisms to examine the impact of each dispersant’s concentration on the dispersion stability of the polishing solution across various abrasive concentrations. Through experimentation, the optimal dispersant type and concentration ratio of abrasive to dispersant were determined, and the effect of the selected dispersant on jet polishing performance was validated. The results of the dispersion stability experiment indicated that, in comparison to Na(PO3)6 and polyethylene glycol (PEG), the polishing solution containing 1.0–2.0 wt% phosphoric ester compounds exhibited a more stable dispersion effect (zeta potential < −50 mV) and superior dispersibility, characterized by a smaller average particle size. Furthermore, K9 optical glass was subjected to fixed-point and local polishing using phosphoric ester compounds as the dispersant. The fixed-point polishing experiment revealed that, at a dispersant concentration of 1.0 wt% and an abrasive concentration of 20 wt%, a smooth and symmetrical material removal profile could be achieved. In the local polishing experiment, the reduction rate of the root mean square of the surface roughness (RMS) increased from 54.33% to 82.24%, and the reduction rate of peak-to-valley height difference in surface (PV) increased from 38.84% to 68.97%. In conclusion, the incorporation of a dispersant proves effective in enhancing the dispersion stability of the polishing solution and dispersibility of the abrasive particles, thereby improving the surface quality of the materials in MAWJP.

Research on picosecond laser-assisted polishing of K9 optical glass: investigation of processing parameters and physical mechanism

Research on picosecond laser-assisted polishing of K9 optical glass: investigation of processing parameters and physical mechanism

A Study on the Influence of Process Parameters on the Workpiece Surface Quality in the Cutting of Hard and Brittle Materials with Trepanning Drill.

Hard and brittle materials have excellent physical and mechanical properties and are widely used in the fields of microelectronics and optoelectronics. However, due to their high hardness and brittleness, the machining quality of a workpiece struggles to meet the requirements of practical applications. In order to improve the surface quality of deep-hole machining of hard and brittle materials, this article analyzes the formation mechanism of surface roughness and the exit-chipping width during the drilling machining of hard and brittle materials and establishes a mathematical prediction model for the surface roughness and the exit-chipping width of hard and brittle materials using a trepanning cutter. The experimental study on K9 optical glass machining shows that the surface roughness of the workpiece and the exit-chipping width increase with the increase in feed rate, and decrease with the increase in rotational speed. Through comparison and verification between theoretical and experimental values, the average errors of workpiece surface roughness and the exit-chipping width are 13.15% and 6.73%, respectively. This article analyzes the reasons for the errors. The results indicate that the theoretical model proposed in this article can be used to predict the surface roughness and the exit-chipping width of hard and brittle materials processed under the same conditions, providing a theoretical basis to optimize process parameters to improve the surface quality of the workpiece.

Applying a new artificial intelligence algorithm to Optimize technological parameters when polishing K9 optical lens materials by magnetized liquid solution

ABSTRACT In order to achieve a high-quality superfine surface on K9 glass, a novel algorithm was developed for addressing optimisation challenges in high-precision machining using magnetised liquid solution. This algorithm employs a collective global exploration developed based on AI (Artificial Intelligence) inspiration, which effectively coordinates various nonlinear systems encountered during the machining process. By integrating multiple nonlinear systems and utilising straightforward physical techniques, the goal is to create a powerful artificial intelligence algorithm in optimising nonlinear systems (AIONS). This algorithm aims to achieve the same level of versatility and rapid convergence observed in enhancing surface quality during the burnishing of optical material K9. To demonstrate the effectiveness of the AIONS algorithm, benchmark functions were analysed in conjunction with optimising the K9 optical glass polishing process. Polishing experiments were conducted to determine the ideal technical parameters using the new algorithm and a straight permanent magnetic yoke surface finishing approach. The analysis and experimental results revealed that when polishing K9 optical glass materials with a permanent-magnetic yoke field and employing a magnetised liquid solution (MLS) with technological parameters guided by the AIONS algorithm, exceptionally smooth surface finish with an Ra value of 0.480 nm was achieved, leaving no scratches on the polished surface. The objective of this study is to provide valuable insights into optimising the surface polishing of challenging materials like K9 optical glass and other materials used in the optical industry.

Mathematical Modeling and Experimental Study of Cutting Force for Cutting Hard and Brittle Materials in Fixed Abrasive Trepanning Drill.

Hard and brittle materials have excellent physical and mechanical performance, which are widely applied in the fields of microelectronics and optoelectronics. However, deep-hole machining of hard and brittle materials is very difficult and inefficient due to the high hardness and brittleness of these materials. To improve the quality and efficiency of deep-hole machining of hard and brittle materials, according to the brittle crack fracture removal mechanism of hard and brittle materials and the cutting model of the trepanning cutter, an analytical cutting force prediction model of hard and brittle materials processed using a trepanning cutter is established. This experimental study of K9 optical glass machining shows that as the feeding rate increase, the cutting force increase, and as the spindle speed increase, the cutting force decrease. By comparing and verifying the theoretical and experimental values, the average errors of axial force and torque are 5.0% and 6.7%, respectively, and the maximum error is 14.9%. This paper analyzes the reasons for the errors. The results indicate that the cutting force theoretical model can be used to predict the axial force and torque of machining hard and brittle materials under the same conditions, which provides a theory for optimizing machining process parameters.

Study of Gas Film Characteristics in Electrochemical Discharge Machining and Their Effects on Discharge Energy Distribution.

Glass is a hard and brittle insulating material that is widely used in optics, biomedicine, and microelectromechanical systems. The electrochemical discharge process, which involves an effective microfabrication technology for insulating hard and brittle materials, can be used to perform effective microstructural processing on glass. The gas film is the most important medium in this process, and its quality is an important factor in the formation of good surface microstructures. This study focuses on the gas film properties and their influence on the discharge energy distribution. In this study, a complete factorial design of experiments (DOE) was used, with three factors and three levels of voltage, duty cycle, and frequency as the influencing factors and gas film thickness as the response for the experimental study, to obtain the best combination of process parameters that would result in the best gas film quality. In addition, experiments and simulations of microhole processing on two types of glass, quartz glass and K9 optical glass, were conducted for the first time to characterize the discharge energy distribution of the gas film based on the radial overcut, depth-to-diameter ratio, and roundness error, and to analyze the gas film characteristics and their effects on the discharge energy distribution. The experimental results demonstrated the optimal combination of process parameters, at a voltage of 50 V, a frequency of 20 kHz and a duty cycle of 80%, that achieved a better gas film quality and a more uniform discharge energy distribution. A thin and stable gas film with a thickness of 189 μm was obtained with the optimal combination of parameters, which was 149 μm less than the extreme combination of parameters (60 V, 25 kHz, 60%). These studies resulted in an 81 μm reduction in radial overcut, a roundness error reduced by 14, and a 49% increase in the depth-shallow ratio for a microhole machined on quartz glass.

Sub-regional polishing and machining trajectory selection of complex surface based on K9 optical glass

With the rapid progress of science and technology, complex optical surfaces have been widely used in various devices. Due to the complexity of their geometric features, machining with a single trajectory inevitably has an impact on the accuracy of the machined surface. Sub-regional milling has been studied intensively by researchers worldwide. However, few studies have focused on sub-region polishing. Therefore, sub-regional polishing is not widely used in the machining field. This paper investigates the method of sub-regional polishing of complex surfaces and focuses on the selection of polishing trajectories for different processing areas. The method takes into account the curvature characteristics of each point on the surface and combines the Freeman code method to divide the surface into multiple processing regions. The selection of polishing trajectories for each processing area is analyzed from the viewpoint of surface roughness and power spectrum density analysis. The correctness of the trajectory selection is verified by polishing experiments on K9 optical glass. The results show that all three trajectories used in the experiments can reduce the surface roughness of the workpiece by more than 90%. Using the Hilbert trajectory can effectively reduce the medium-frequency and high-frequency errors of the machined surface and improve the optical properties of the surface. This work is expected to provide significant guidance for efficient and high-quality processing of complex optical surfaces compared with traditional machining methods using a single trajectory.

Parameter optimization of ultrasonic vibration polishing K9 optical glass based on ultrasonic atomization

To further improve the surface finish and processing efficiency of optical components, ultrasonic vibration technology is frequently combined with conventional processing and the process parameters that play a critical role in this composite processing are identified. This research proposes an ultrasonic vibration polishing method based on ultrasonic atomization (UA-UVP). The polishing performance of K9 optical glass is increased by ultrasonic atomization (UA) assisted by polishing solvent for ultrasonic vibration polishing (UVP). Orthogonal experiments are used to study the effects and variation laws of the flow rate of ultrasonic atomization (Q), the gap distance between the polishing tool and workpiece (G), ultrasonic electro spindle speed (W), abrasive particle size (D) and ultrasonic amplitude (A) on surface roughness (SR) and material removal rate (MRR), respectively. When these two polishing characteristics are considered together, the optimization of polishing parameters becomes complicated. Therefore, the principal component analysis (PCA) and grey relational analysis (GRA) methods were employed to the optimal experimental combination as Q:18 ml/min, G: 5 μm, W: 4000 r/min, D: 0.5 μm, A: 8 μm. The experimental results showed that Ra and MRR were measured as 10.466 nm and 0.473*10^8 μm3/min, respectively. Compared with the best experimental combination of orthogonal experiments, the improvement rates of SR and MRR were 26.65% and 25.80%, respectively. Overall, the application of ultrasonic vibration technology contributes to enhancing the uniform distribution of polished abrasive particles and improving the polishing characteristics.

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

Experimental investigation of ultrasonic-vibration polishing of K9 optical glass based on ultrasonic atomization

K9 optical glass has an important position in the field of optical material because of its excellent chemical stability and optical projection. The hard and brittle characteristics of K9 optical glass make conventional processing difficult and time-consuming. A non-conventional hybrid polishing system combining ultrasonic atomization (UA) spraying method and axial ultrasonic vibration was developed for processing K9 optical glass. This system utilizes the high-frequency vibration characteristics of ultrasonic vibration technology: On the one hand, the ultrasonic atomization spraying method is used to generate evenly distributed atomized droplets for polishing, on the other hand, the axial ultrasonic vibration of the polishing tool provides impact kinetic energy for the free abrasive particles. Mechanical polishing (MP), ultrasonic-assisted polishing (UVP), mechanical polishing under ultrasonic atomization spraying (UA-MP) and ultrasonic vibration polishing under ultrasonic atomization spraying (UA-UVP) were carried out on K9 optical glass. The material removal rate (MRR), material removal depth (MRD), surface quality and surface micromorphology of the polished workpieces were also analyzed and compared. The experimental results showed that the best surface was obtained at UA-UVP (AⅠ = 9 μm) with MRR of 0.0994 mm3/min, material removal depth of 26.816 μm, the Ra and Sa values were 0.028 μm and 0.033 μm respectively. Meanwhile, no obvious pits and scratches were observed on the micromorphological surface. Ultrasonic atomization contributes to even material removal from the polished surface and axial ultrasonic vibration of the polishing tool has a significant effect in improving the polishing characteristics, which provides the experimental basis for applying ultrasonic vibration technology in polishing.

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.

Study on Material Removal Model by Reciprocating Magnetorheological Polishing.

In this study, a new reciprocating magnetorheological polishing (RMRP) method for a flat workpiece was proposed. Based on the RMRP principle and Preston equation, the material removal rate (MRR) model of the RMRP as well as its normal polishing pressure model was established. On this basis, the effects of different technological parameters including workpiece rotation speed, eccentric wheel rotation speed and eccentricity on the MRR of the workpiece were investigated. The K9 optical flat glass was polished with the RMRP setup to verify the MRR model. The experimental results showed that the effect of workpiece rotation speed on the MRR was much greater than that of eccentric wheel rotation speed and eccentricity, and the MRR increased from 0.0115 ± 0.0012 to 0.0443 ± 0.0015 μm/min as workpiece rotation speed rose. The optimum surface roughness reduced to Ra 50.8 ± 1.2 from initial Ra 330.3 ± 1.6 nm when the technical parameters of the workpiece rotation speed of 300 rpm, the eccentric wheel rotation speed of 20 rpm and the eccentricity of 0.02 m were applied. The average relative errors between the theoretical and experimental values were 16.77%, 10.59% and 7.38%, respectively, according to the effects of workpiece rotation speed, eccentric wheel rotation speed and eccentricity on MRR.

Optical properties of combined dynamic thermal dynamicloading optical window

Aiming at the large aperture optical window working in the complex environment such as pressure difference and temperature gradient, a combination scheme of optical window was proposed, which was composed of optical glass and acrylic plate. Based on the thermal-optical analysis, the overall strength and thermal environment of optical window were analyzed and calculated theoretically, and the minimum thickness of optical window glass was obtained. The pressure field and axial temperature field were mapped to three-dimensional structure model by finite element software. The surface shape change and imaging quality evaluation index of 380 mm diameter optical window under different glass thickness were calculated. The simulation results were verified by corresponding environmental tests. The results show that the thickness of large aperture optical window with K9 optical glass as raw material is not less than 32.5 mm under this working environment; when the thickness of optical window is 35 mm, the thermodynamic effect can be ignored. Therefore, the large aperture combined optical window of 35 mm can not only meet the intensity, but also meet the imaging quality requirements of multi-spectral camera, which provides a basis for the design of this kind of window.

Research on chemical strengthening technology for K9 optical glass

Research on chemical strengthening technology for K9 optical glass

Model for Predicting the Micro-Grinding Force of K9 Glass Based on Material Removal Mechanisms.

K9 optical glass has superb material properties used for various industrial applications. However, the high hardness and low fracture toughness greatly fluctuate the cutting force generated during the grinding process, which are the main factors affecting machining accuracy and surface integrity. With a view to further understand the grinding mechanism of K9 glass and improve the machining quality, a new arithmetical force model and parameter optimization for grinding the K9 glass are introduced in this study. Originally, the grinding force components and the grinding path were analyzed according to the critical depth of plowing, rubbing, and brittle tear. Thereafter, the arithmetical model of grinding force was established based on the geometrical model of a single abrasive grain, taking into account the random distribution of grinding grains, and this fact was considered when establishing the number of active grains participating in cutting Nd-Tot. It should be noted that the tool diameter changed with machining, therefore this change was taking into account when building the arithmetical force model during processing as well as the variable value of the maximum chip thickness amax accordingly. Besides, the force analysis recommends how to control the processing parameters to achieve high surface and subsurface quality. Finally, the force model was evaluated by comparing theoretical results with experimental ones. The experimental values of surface grinding forces are in good conformity with the predicted results with changes in the grinding parameters, which proves that the mathematical model is reliable.

Investigation of the optimal parameters for the surface finish of K9 optical glass using a soft abrasive rotary flow polishing process

A workpiece polished by soft abrasive flow polishing has the advantages of low damage and ultrasmoothness. However, due to the need to use a constrained flow path, the fluid dynamic pressure on the near wall surface of the workpiece has a gradient distribution, so achieving uniform polishing of workpieces of large size is difficult. To address this problem, this paper proposes a new method of soft abrasive rotary flow (SARF) polishing to achieve low damage, ultrasmooth, uniform polishing of a large-size K9 optical glass surface. A new SARF polishing system and a 6-outlet rotary polishing tool are designed. The SARF polishing principle is analyzed, and a polishing experiment is conducted on K9 glass. The experiment of surface roughness improvement of the K9 optical glass is designed by Taguchi method. Orthogonal arrays and the signal-to-noise ratio (S/N) are used to determine the optimal parameters for SARF polishing. Analysis of variance (ANOVA) is used to determine the effect of the main polishing parameters on the surface roughness of K9 glass. According to the results of the polishing experiment using a Taguchi L18 orthogonal array and S/N ratio analysis, the optimal parameters for K9 glass SARF polishing are revealed to be as follows: the abrasive material is CeO2, the polishing pressure is 0.35 MPa, the abrasive particle concentration is 5 wt.%, the average size of the abrasive particles is 0.7 μm, the polishing time is 1.5 h and the platform rotation speed is 10 rpm. After polishing the sample for 1.5 h under these parameters, the surface roughness decreases from the original value of Ra = 37.28 nm to Ra = 4.51 nm, and the surface roughness improves by 87.9 %.

Theoretical model of brittle material removal fraction related to surface roughness and subsurface damage depth of optical glass during precision grinding

Brittle material removal fraction (BRF) is defined as the area fraction of brittle material removed on machined surface. In the present study, a novel theoretical model of BRF was proposed based on indentation profile caused by intersecting of lateral cracks. The proposed model is related to surface roughness and the subsurface damage (SSD) depth of optical glass during precision grinding. To investigate the indentation profile, indentation tests of K9 optical glass were conducted using single random-shape diamond grains. The experimental results indicate that the indentation profile is an exponent function. To verify the proposed BRF model, BRF, surface roughness and SSD depth of K9 optical glasses were investigated by a series of grinding experiments with different cutting depths. The experimental results show that BRF is dependent on surface roughness and SSD depth. The relationship between BRF, surface roughness and SSD depth is in good accordance with the proposed theoretical model. The proposed BRF model is a reasonable approach for estimating surface roughness and SSD depth during precision grinding of optical glass.

Estimation of the surface roughness of K9 optical glass in precision grinding using the brittle material removal fraction based on an improved image processing algorithm

Estimation of the surface roughness of K9 optical glass in precision grinding using the brittle material removal fraction based on an improved image processing algorithm

Experimental Study on Effects of Translational Movement on Surface Planarity in Magnetorheological Planarization Process

To improve surface planarity, a translational movement is added into the magnetorheoloigcal planarization process. To explore effects of some process parameters, including trajectory type, stroke and reciprocate velocity, on surface planarity, a set of finishing experiments are carried out. The results show that planarity is well improved when the trough reciprocates perpendicularly to the air gap. Surface planarity decreases as stoke increases but is hardly affected by reciprocate velocity. Using the magnetorheoloigcal planarization process with addition of translational movement, an ultra-smooth surface with planarity of micron order in PV is achieved on a K9 optical glass.