Search Results (22)

In modern freeform surfaced optics manufacturing, ultraprecision machining through single-point diamond turning (SPDT) plays a crucial role due to its ability to meet the high accuracy demands of optical design and stringent surface quality requirements of the final optic. The process involves meticulous steps, including optic surface modeling and analysis, optic design, machining toolpath generation, and manufacturing. This paper presents an integrated approach to customized precision design and the manufacturing of freeform surfaced varifocal lenses through a web-based e-portal. The approach implements an e-portal-driven manufacturing system that seamlessly integrates lens design, modeling and analysis, toolpath generation for ultraprecision machining, mass personalized customization, and service delivery. The e-portal is specifically designed to meet the stringent demands of personalized mass customization, and to offer a highly interactive and transparent experience for the lens users. By using Shiny and R-script programming for platform development and combining COMSOL Multiphysics for the ray tracing simulation, the e-portal leverages open-source technologies to provide manufacturing service agility, responsiveness, and accessibility. Furthermore, the integration of R-script and Shiny programming allows for advanced interactive information processing, which also enables the e-portal-driven manufacturing system to be well suited for personalized complex products such as freeform surfaced lenses. Full article

Poly(methyl methacrylate) (PMMA), with a glass transition temperature (Tg) over 100 °C, shows good mechanical and optical properties and has broad applications after being machined with single-point diamond turning (SPDT) at room temperature. Because of the high Tg, current efforts mostly focus on optimizing machining parameters to improve workpiece precision without considering the modification of material properties. Cryogenic cooling has been proven to be an effective method in assisting ultra-precision machining for certain types of metals, alloys, and polymers, but has never been used for PMMA before. In this work, cryogenic cooling was attempted during the SPDT of PMMA workpieces to improve surface quality. The machinability and surface properties of cryogenically cooled PMMA were investigated based on the mechanical properties at corresponding temperatures. Nanoindentation tests show that, when temperature is changed from 25 °C to 0 °C, the hardness and Young’s modulus are increased by 37% and 22%, respectively. At these two temperature points, optimal parameters including spindle speed, feed rate and cut depth were obtained using Taguchi methods to obtain workpieces with high surface quality. The surface quality was evaluated based on the total height of the profile (Pt) and the arithmetic mean deviation (Ra). The measurement results show that the values of Pt and Ra of the workpiece machined at 0 °C are 124 nm and 6 nm, respectively, while the corresponding values of that machined at 25 °C are 291 nm and 11 nm. The test data show that cryogenic machining is useful for improving the form accuracy and reducing the surface roughness of PMMA. Moreover, the relationship between temperature, material properties and machinability weas established with dynamic mechanical analysis (DMA) data and a theoretical model. This can explain the origin of the better surface quality of the cryogenic material. The basis of this is that temperature affects the viscoelasticity of the polymer and the corresponding mechanical properties due to relaxation. Then, the material property changes will affect surface profile formation during machining. The experimental results and theoretical analysis show that cryogenically cooled PMMA has good machinability and improved surface quality when using SPDT compared to that at ambient temperature. Full article

Ultra-high-precision single-point diamond turning (SPDT) is the state-of-the-art machining technology for the advanced manufacturing of critical components with an optical surface finish and surface roughness down to one nanometer. One of the critical factors that directly affects the quality of the diamond-cutting process is the cutting force. Increasing the cutting force can induce tool wear, increase the cutting temperature, and amplify the positioning errors of the diamond tool caused by the applied cutting force. It is important to measure the cutting force during the SPDT process to monitor the tool wear and surface defects in real time. By measuring the cutting force in different cutting conditions, the optimum cutting parameters can be determined and the best surface accuracies with minimum surface roughness can be achieved. In this study a smart cutting tool for in-process force measurement and nanopositioning of the cutting tool for compensating the displacements of the diamond tool during the cutting process is designed and analyzed. The proposed smart cutting tool can measure applied forces to the diamond tool and correct the nanometric positioning displacements of the diamond tool in three dimensions. The proposed cutting tool is wireless and can be used in hybrid and intelligent SPDT platforms to achieve the best results in terms of optical surface finish. The simulation results are shown to be almost consistent with the results of the derived analytical model. The preliminary results pave the way for promising applications of the proposed smart cutting tool in SPDT applications in the future. Full article

This paper addresses the issue of reduced image quality due to annular turning marks formed by single-point diamond turning (SPDT) during the processing of metal-based mirrors and infrared lenses. An ideal single-point diamond turning marks diffraction action model to quantitatively analyze the impact of turning marks diffraction on imaging quality degradation is proposed. Based on this model, a fast estimation algorithm for the optical modulation transfer function of the system under turning marks diffraction (TMTF) is proposed. The results show that the TMTF algorithm achieves high computational accuracy, with a relative error of only 3% in diffraction efficiency, while being hundreds of times faster than rigorous coupled wave analysis (RCWA). This method is significant for reducing manufacturing costs and improving production efficiency, as it avoids the problem of being unable to compute large-size optical systems due to computational resource and time constraints. Full article

NiP coating has excellent physicochemical properties and is one of the best materials for coating optical components. When processing NiP coatings on optical components, single-point diamond turning (SPDT) is generally adopted as the first process. However, SPDT turning produces periodic turning patterns on the workpiece, which impacts the optical performance of the component. Magnetorheological finishing (MRF) is a deterministic sub-aperture polishing process based on computer-controlled optical surface forming that can correct surface shape errors and improve the surface quality of workpieces. This paper analyzes the characteristics of NiP coating and develops a magnetorheological fluid specifically for the processing of NiP coating. Based on the basic Preston principle, a material removal model for the MRF polishing of NiP coating was established, and the MRF manufacturing process was optimized by orthogonal tests. The optimized MRF polishing process quickly removes the SPDT turning tool pattern from the NiP coating surface and corrects surface profile errors. At the same time, the surface quality of the NiP coating has also been improved, with the surface roughness increasing from Ra 2.054 nm for SPDT turning to Ra 0.705 nm. Full article

A freeform imaging telescope (FIT) can achieve a large field of view, high resolution, light weight, and small volume at the same time. Single-point diamond turning (SPDT) is usually used to fabricate FITs, which is made entirely of aluminum alloy. Compared with a traditional telescope, whose reflector is made of glass and whose structure is aluminum, the coefficient of thermal expansion (CTE) of the structure and reflector of which is non-conforming, the CTE of the structure and reflector in an all-aluminum FIT is identical. Therefore, it was expected to theoretically have athermalization properties. In this paper, an all-aluminum off-axis three-mirror FIT was verified. The opto-mechanical–thermal coupling analysis of the FIT at −20 °C was carried out, including data processing and coordinate transformation. The reflector node deformation data of the global coordinates obtained from the finite-element analysis were converted into XY polynomial coefficients of the local coordinate system in ZEMAX. The results showed that the modulation transfer function (MTF) of the FIT at −20 °C~+40 °C still reached the diffraction limit. Moreover, the MTF of the FIT at −20 °C was 0.291 through a thermal environmental test, which was almost the same as the MTF at 22 °C. These results showed that the all-aluminum FIT could achieve athermalization properties. Full article

Microsatellites have a great attraction to researchers due to their high reliability, resource utilization, low cost, and compact size. As the core component of the optical payload, the mirror directly affects the system package size. Therefore, the structural design of mirrors is critical in the compact internal space of microsatellites. This study proposes a closed-back mirror with composite surfaces based on additive manufacturing (AM). Compared with the open-back mirror, it provides excellent optomechanical performance. In addition, AM significantly reduces the intricate mechanical parts’ manufacturing difficulty. Finally, the roughness was better than 2 nm. The surface shape of the AM aluminum mirror reached RMS 1/10λ (λ = 632.8 nm) with the aid of ultra-precision machining technologies such as single-point diamond turning (SPDT), surface modification, and polishing, and the maximum deviation of the surface shape was about RMS 1/42λ (λ = 632.8 nm) after the thermal cycle test, which verified the optical grade application of AM. Full article

The NiP coating has excellent wear and corrosion resistance, and electroless nickel-phosphorus coating is one of the best measures for surface modification of metal optical devices. The NiP layer could be processed by single-point diamond turning (SPDT). However, the periodic marks on the surface of the NiP coating processed by SPDT will lead to diffraction and stray light, which will reduce the reflectivity and image quality of the mirror. This paper studied smoothing polishing based on chemical mechanical polishing to remove turning periodic marks efficiently. Firstly, we studied the chemical corrosion and mechanical removal mechanism of smoothing polishing of the NiP coating through theoretical analysis. Then, the influencing factors of processing the quality of smoothing polishing are analyzed, and the optimal machining parameters and polishing slurry formula are formulated. Finally, through the developed process, the surface roughness of Root Mean Square (RMS) 0.223 nm is realized on the NiP coating, and an ultra-smooth surface that can meet the service accuracy of a hard X-ray mirror is obtained. Our research simplifies the high-precision machining process of the NiP coating and improves the machining efficiency. Therefore, it can be used as a new high-precision manufacturing NiP coating method. Full article

As one of the most-critical components in space optical cameras, the performance of space mirrors directly affects the imaging quality of space optical cameras, and the lightweight form of mirror blanks is a key factor affecting the structural quality and the surface-shape accuracy of mirrors. For the design requirements of lightweight and high surface-shape accuracy with space mirrors, this study proposes a design and manufacturing method that integrates topology-optimization with additive-manufacturing technology. This article firstly introduced the basic process and key technologies of space-mirror design and analyzed the superiority of combining a topology-optimized configuration design and additive-manufacturing technology; secondly, the topology-optimized design method of a back-open-structure mirror was used to complete the scheme design of a $\Phi$260 mm aperture mirror; finally, the laser selective-melting manufacturing technology was used to complete the $\Phi$260 mm aperture mirror blank. The mirror and its support structure were assembled and tested in a modal mode; the resonant frequencies of the mirror assembly were all over 600 Hz; and the deviation from the analytical results was within 2%. The optical surface of the mirror was turned by the single-point diamond-turning (SPDT) technique. The accuracy of the optical surface was checked by a Zygo interferometer. The RMS accuracy of the mirror surface was 0.041$\lambda$ ($\lambda$ is the wavelength; $\lambda$ = 632 nm). In the test of the influence of gravity on the surface-shape accuracy, the mirror was turned over, which was equivalent to twice the gravity, and the RMS of the mirror surface-shape accuracy was 0.043$\lambda$, which met the requirement. The verification results show that the mirror designed and fabricated by the additive-manufacturing-based mirror-topology-optimization method can be prepared by the existing process, and the machinability and mechanical properties can meet the requirements, which provides an effective development method for improving the structural design and optimizing the manufacturing of space reflectors. Full article

Aluminum alloy (Al6061) is a common material used in the ultraprecision area. It can be machined with a good surface finish by single-point diamond turning (SPDT). Due to the material being relatively soft, it is difficult to apply post-processing techniques such as ultraprecision lapping and ultraprecision polishing, as they may scratch the diamond-turned surface. As a result, a novel low-pressure lapping method was developed by our team to reduce the surface roughness. In this study, a finite element model was developed to simulate the mechanism of this novel lapping technology. The simulation results were compared with the experimental results so as to gain a better understanding of the lapping mechanism. Full article

In the field of single-point diamond turning (SPDT), machining ferrous metal is an important research topic with promising application. For SPDT of ferrous metal, the influence of lubricant on the workpiece surface morphology remains to be studied. In this study, three lubricant machining environments were selected to carry out specific control experiments. The machined surface morphology and cutting force in different lubricant machining environments were analyzed. The experiment results showed that the lubricant environment will have significant impacts on the quality of the machined surface morphology of ferrous metal. In the environment of minimum quantity lubrication machining (MQLM-oil), better machined surface quality can be obtained than that in ordinary dry machining (ODM) and high-pressure gas machining (HGM). Furthermore, the cutting force captured in the ODM and HGM environment increased with the increase of the cutting depth, while the cutting force in the MQLM-oil environment remained almost unchanged. That indicates MQLM-oil can suppress the formation of hard particles to improve the machining quality. Full article

In this paper, synthetically using refraction, diffraction, and interference effects to achieve free manipulation of the focused optical field, we firstly present a photonic nanojet (PNJ) generated by a micropyramid, which is combined with multilayer thin films. The theory of total internal reflection (TIR) was creatively used to design the base angle of the micropyramid, and the size parameters and material properties of the microstructure were deduced via the expected optical field distribution. The as-designed bilayer micropyramid array was fabricated by using the single-point diamond turning (SPDT) technique, nanoimprint lithography (NIL), and proportional inductively coupled plasma (ICP) etching. After the investigation, the results of optical field measurement were highly consistent with those of the numerical simulation, and they were both within the theoretical calculation range. The bilayer micropyramid array PNJ enhanced the interference effect of incident and scattered fields; thus, the intensity of the focused light field reached 33.8-times that of the initial light, and the range of the focused light field was extended to 10.08$\lambda$. Moreover, the full width at half maximum (FWHM) of the focal spot achieved was 0.6$\lambda$, which was close to the diffraction limit. Full article

Pd₄₀Ni₁₀Cu₃₀P₂₀ bulk metallic glass (BMG) is widely used in industrial fields due to its excellent oxidation resistance, corrosion resistance, and thermal stability. However, the lack of research on the machinability and cutting performance of BMG using single-point diamond turning (SPDT) limits its application for engineering manufacturing. In the present research, a series of turning experiments were carried out under different cutting parameters, and the machinability reflected by the quality of machined surface, chip morphology, and tool wear were analyzed. Based on the oxidation phenomenon of the machined surface, a molecular dynamics (MD) simulation was conducted to study the mechanism and suppression of the machined surface oxidation during the cutting. The results show that: (1) The Pd-based BMG had good machinability, where the machined surface roughness could go down to 3 nm; (2) irregular micro/nanostructures were found along the tool path on the outer circular region of the machined surface, which greatly affected the surface roughness; and (3) the cutting heat softened the workpiece material and flattened the tool marks under surface tension, which improved the surface quality. This research provides important theoretical and technical support for the application of BMG in optical mold manufacturing. Full article

The material swelling effect in single point diamond turning (SPDT) causes ragged materials on a machined surface which slows down the movements of tool tip vibration, and acts as a simple impacted pendulum system with a damping effect and displays a single twin peak in fast Fourier transform (FFT). Due to the low elastic modulus and low thermal conductivity of titanium alloys, the material swelling effect of titanium alloys in SPDT is much more serious than that of traditional metals. For this reason, the tool tip vibration in SPDT of titanium alloys is expected to be different from previous reports. In this study, apart from the demonstration of the original single twin peak induced from the material swelling effect by the main cutting motion, we reported recently that there exists another twin peak induced by secondary material swelling arising from the movement of tool tip vibration in the SPDT of titanium alloys. The additional twin peak was located at the right side of the original twin peak in FFT, displaying two twin peaks in the frequency domain of cutting force and suggesting the existence of another tool tip vibration system with a new damping factor in the SPDT of titanium alloys. Combining the effects of primary and secondary material swelling, the new dynamic model with the modified damping factor of tool tip vibration system are developed, which surface roughness of the machined titanium alloys in SPDT was predicted in higher accuracy by using the new model. The FFT of cutting force, surface roughness, and surface profile were provided in this article for the experimental validations. Full article

Chalcogenide glass (ChG) is increasingly demanded in infrared optical systems owing to its excellent infrared optical properties. ChG infrared optics including ChG aspherical and freeform optics are mainly fabricated using the single point diamond turning (SPDT) technique, which is characterized by high cost and low efficiency. This paper presents an overview of the ChG infrared optics fabrication technique through precision glass molding (PGM). It introduces the thermo-mechanical properties of ChG and models the elastic-viscoplasticity constitutive of ChG. The forming accuracy and surface defects of the formed ChG are discussed, and the countermeasures to improve the optics quality are also reviewed. Moreover, the latest advancements in ChG precision molding are detailed, including the aspherical lens molding process, the ChG freeform optics molding process, and some new improvements in PGM. Full article