Aspheric Polishing Research Articles

Introducing Full-Aperture FJP (faFJP), a Technique for Manufacturing Sub-Millimetre Aspheres

We propose a novel approach, "faFJP", to the computer controlled polishing (CCP) of mini aspheres down to 0:2 mm. The generation of locallytunable, full-aperture footprints is accomplished by applying a Fluid Jet Polishing (FJP) beam larger than the full aperture being polished and varying the incident angle.

Fundamental Investigation on the Polishing Aspheric Elements with Doughnut-Shaped MCF Slurry

Previous researches have confirmed that MCF (magnetic compound fluid) slurry shows outstanding performance in the nanoprecision polishing of flat surfaces and V-grooves. However, no investigations have been conducted on the polishing of aspheric surfaces using MCF slurry. In this work, a novel method employing a doughnut-shaped MCF polishing tool and a 6-DOF manipulator has been proposed for the aspheric surface polishing. The time consumption for forming stable polishing tool and its final appearance are investigated. Flat aluminum alloy workpieces that can be considered as a kind of aspheric elements with infinite curve radius were adopted in the investigation of the polished forces under variable parameters. As a typical experimental result, with MCF3 slurry, 2.5ml volume of supplied slurry and work gap 3.5 mm, the surface roughness Ra decreases from 125nm to almost 10nm after 90 min polishing, confirming that the proposed method has the potential to polish aspheric surfaces.

Study on the influence of the rotational speed of polishing disk on material removal in aspheric surface compliant polishing

When a soft polishing tool is compressed on a stiff workpiece of curved surface, the contact area is a piece of the curved surface. In the process of aspheric surface polishing, the machining speed is always provided by the rotational speed of the spindle of a computer numerical control lathe. Yet, the polishing tool is usually made rotating to remove cutting scraps and broken abrasives from the contact area. The rotational speed of the polishing tool would change the distribution state of the relative speed in the whole contact area, and it would definitely change the volume of material removal in the surface of the workpiece. This article studies how the rotational speed of the polishing tool changes the distribution state of the relative speed in the whole contact area and material removal in the volume of the surface of the workpiece. The computing results show that the volume of material removal increases with the increase in both the rotational speed of polishing disk and the rotational speed of lathe spindle, but the polishing quality is totally not in this case.

Study on the orthomogonalization for hybrid motion/force control and its application in aspheric surface polishing

In the process of curved surface polishing and buffing, the tools have to be compressed on the workpiece and moved to wear the surface, so the normal force and tangential feed movements should be provided and controlled synchronously. It is a typical kind of compliant control, which would most likely be done under the hybrid motion/force control policy. Although its related theory is already almost perfect, this method could seldom be used in the process of curved surface polishing and buffing, if ever, for it is always not easy to orthogonalize force control space from movement control space. In this paper, a force control subsystem is developed and fixed on a computer numerical control (CNC) lathe to control the normal force independently, and the normal force control space is orthogonalized from the feed movement control space by geometry defining for aspheric surface polishing. Furthermore, the orthogonalization in the domain of time is taken to make the force control not to interpolate with the displacement control of the feed movements. Experiments in controlling and polishing the normal force show that the hybrid motion/force control policy could be used in the process of aspheric surface polishing and buffing by keeping the normal force control and feed movement control independently in both domains of space and time.

A novel method for aspheric polishing based on abrasive trajectories analysis on contact region

In order to achieve good functional performance on surface texture with high processing efficiency, this article proposes a vertical continuous precession polishing method for aspheric lenses based on the analysis of abrasive trajectories on contact region. First of all, by analyzing the relative motion between bonnet tool and workpiece, the motion model of particle trajectories on contact region was established. Then, comparison and analysis of abrasive trajectories with various polishing methods were carried out. Moreover, a vertical continuous precession polishing method for aspheric lenses and related experiments were presented. The results revealed that the texture on contact zone of aspheric lens polished by vertical continuous precession was approximately random and uniform, which is appropriate for polishing curved surfaces continuously. In addition, the contact zone on different polishing spots with various curvatures can be controlled by adaptive algorithm, and the simulated results validated the feasibility of the proposed polishing method for aspheric lenses.

Research on Mid-Large-Aperture Aspherical Optical Components Rapid Powerful NC Polishing Technology

This paper introduces a new devices and technology of large-aperture quadratic optical components rapid powerful NC polishing, it has greatly improved the efficiency and precision of aspheric polishing. Through self-designed five-axis CNC polishing machine, to achieve the controlling of rotation, revolution integral rapid powerful polishing head. By optimizing the process parameters, determine a reasonable polishing path and polishing mode structure, to obtain good experimental results. Size 340mm × 340mm aspheric optical glass, surface shape accuracy PV λ / 5, surface roughness Rq 1.2nm, processing efficiency has been effectively improved, surface shape convergence stable.

Precision asphere polishing with MRF technology and Subaperture Stitching Interferometry

The paper presents results of aspheric lens manufacturing in Infrared Technology and Thermovision Section in Military University of Technology. Briefly MRF and SSI technologies utilized in the process are described and a case study of three aspherization processes follows. First two elements are silicon lenses designed for a mid-wave infrared (MWIR) lens. The third one is a parabolic mirror substrate. Technical aspects and requirements of each case are discussed. Full Text: PDF References Forbes, G. W., "Shape spcecification for axially symmetric optical surfaces", Optics Express, Vol. 15, Issue 8, pp. 5218-5226 (2007) CrossRef

Study on Polishing Tool Contact Deformation for Large Robotic Aspheric Surface Compliant Polishing

Due to the problem of the mutual interaction between the polishing tool system and the control of poses and positions, it is difficult to hybrid-synchronizationally control the polishing force, the posture of polishing tool head and the polishing trajectory. So the article designed a set of compliant tools that take the pneumatic servo system as the control system, which was used for active polishing aspheric surface of Robot. It was to accomplish the Robots self-adaptive control to the posture of the polishing tool as well as to figure out the correlation of the contact deformation between the polishing tool and the work piece surface, which makes a theoretical analysis on dynamic and steady characteristics of the contact deformation of the tool system. It applied the meek and polishing tools to the polishing processing of the rough machining of large aspheric surface samples to obtain the data. According to the statistics, the polishing tools can effectively solve the problem of the mutual interaction between the polishing tool system and the control of poses and positions. It also owns good adaptive ability and its machining aspheric surface quality can achieve nanoscale.

Aspheric Surface NC Polishing Force-Position Decoupling Control Technology

Based on MTTSD (Magneto-rheological Torque Transmission Servo Devices) and force-position decoupling control technology, an aspheric surface NC polishing project is put forward. The aspheric surface polishing fundamental theory is researched. Under the condition of a constant material removal rate, a new aspheric surface polishing model is brought forward. In addition, under the condition of a constant material removal rate, this paper brought up a polishing force control model and a workpiece rotating speed control model, according to witch, force and rotating speed change with the coordinates of working points, and variation curves are drawn.CLC Number: TH166 Document Identifier: A

Study on the manufacturing process controlling for aspheric surface ballonet polishing

Ballonet polishing tools, soft gasbags filled with compressed gas, have already been one of the most reliable tools in curved surface polishing due to their adaptability to change their shape to fit the worked surfaces with the same contact stress everywhere. When the internal pressure of the gasbag is adjusted on-line, the contact stress could be controlled as you want. But, because of the tensile stress of the gasbag's material, the internal pressure could not identify the real contact condition anymore. In this paper, the contact force is used to identify the real contact condition for workpieces of aspheric surfaces which is indispensable to the polishing process control. Based on the measured internal pressure of the gasbag and the on-line-controlled contact force in the normal direction, this paper studies the arithmetic of the contact area for aspheric surfaces, finds a way to eliminate the great difference of machining speed, and advances an arithmetic of the machining time for material removal controlling in the process of aspheric surface ballonet polishing. A real ballonet polishing system is developed for aspheric surfaces, and experiments show that it is a better way by controlling the contact force rather than by controlling the internal pressure in the process of aspheric surface ballonet polishing.

Using FEM technology for optical surfaces polishing

The aim of this article is optical surfaces polishing on the 6-axis computer-controlled (CCM) machine Optotech MCP 250 CNC using FEM technology, which is suitable for aspheric elements polishing. The main attention is dedicated to the choice and to the precise adjustment of major process parameters. The possibility of usage the multi wave interferometer Luphoscan as a data source for the2D surface correction is solved too.

707 回転工具による非球面金型研磨の特性(OS7 オーガナイズドセッション《精密/微細加工と評価》)

707 回転工具による非球面金型研磨の特性(OS7 オーガナイズドセッション《精密/微細加工と評価》)

Research on the Optimized Tool-Path Planning of Computer Controlled Optical Surfacing

Computer controlled optical surfacing (CCOS) is widely used in aspheric optical lenses fabrication because of their high convergence rate on surface based on deterministic removal processes since 1963. As an important part of CCOS techniques, reasonable tool-path would increase the polishing speed, decrease the processing time and then improve the efficiency of polishing. Optimized policy combined with improved Prim algorithm is presented in this paper based on the study of the characteristic of aspheric polishing and the tool-paths in common use. The simulated results show that the length of tool-path is reduced so as to decrease the processing time and increase the working efficiency.

Modeling of Machining Force Error in Aspheric Surface Polishing by Hybrid Movement/Force Control Policy

By the hybrid movement/force control policy, machining force could be controlled in aspheric surface polishing. However, the controller could not eliminate and restrain the errors of position and pose which would disturb the force controll consequentially in real system. In this paper, an angle is defined to express all the errors of position and pose for aspheric surface polishing, and the errors are modeled for machining force controll. By detecting this angle, the errors of position and pose could be used by the system controller to eliminate the disturbance in hybrid movement/force controll system and compensate feed movement controll in aspheric surface polishing. Simulation shows that the model could effectively express the errors of position and pose .

A New Aspheric Surfaces Polishing by Parallel Orthogonality Movement/Force Servomechanism

According to the all-pervading theory, the best strategy for multiaxis compliant control system is the famous hybrid movement/force control. Until now, the typical way to get it inclines to integrate force control with movement control into one numerical control (NC) interpolator. The more axes being taken for the interpolator, the lower calculating and computerizing speed and the greater errors are. Furthermore, the errors of movement control, including the position errors and pose errors, would inevitably disturb the processing of force control for their coupling relationship. In this paper, the orthogonal movement/force servo strategy is brought forward based on the orthogonality relation of force control and movement control. Combining with the processing of aspheric surfaces polishing, the paper develops a new three-axis computer numerical control (CNC) compliant polishing method and system by the hybrid orthogonal movement/force servomechanism, in which the force controlling and movement controlling are taken in its orthogonal complement space, respectively. Experiments show that this new polishing system is of great robustness for the change of slope and curvature of the aspheric surfaces and it can polish aspheric surfaces to get ultrasmooth surfaces at nanoscale.

E28 超音波2軸援用マイクロ非球面研磨法の開発(OS-11 超精密加工(1))

E28 超音波2軸援用マイクロ非球面研磨法の開発(OS-11 超精密加工(1))

Investigation of the material removal model for bonnet tool polishing with precession

Bonnet tool polishing is a novel aspherical polishing method. This paper describes a method to obtain the local removal rate for the polishing process by using bulbous flexible membrane covered with a polishing pad and pressurised by an internal fluid. During the polishing process the precession process, in which the bonnet tool cannot only spines itself but also precesses along the local normal on the specimen surface, was applied. The local removal rate model was established according to the Preston equation. The influence of the precession process on the material removal rate was analysed and also the polishing pressure distribution was obtained according to the experiment data. It is confirmed by the experiments that the dwelling time has a linear relation with the local removal depth. Preston coefficient can be calculated from the experimental data. Finally, the expression of the local removal rate in bonnet tool polishing was acquired experimentally.

Study of Local Material Removal Model of Bonnet Tool Polishing

Bonnet tool polishing is a novel aspherical polishing method. This paper describes a method to obtain the local removal rate for the polishing process using bulbous flexible membrane covered with a polishing pad and pressurized by an internal fluid. According to the principle of bonnet polishing and Preston equation, the local removal rate model was established. It is confirmed by the experiments that the local removal depth has a linear relation with the dwell time. Preston coefficient can be calculated from the experimental data. Finally the expression of the local removal rate in bonnet tool polishing is acquired semi-empirically.

Design Optimisation Of The Head Of A HighprecisionOptical Polishing Machine

A highly deformable polishng tool has been specified for a revolutionary aspheric polishing system. This rubber tool is required to retain a spherical outer surface with minimal change in shape when subjected to internal pressure. It is proposed here that using a variable wall thickness around the tool will reduce deviations from the spherical shape. This paper describes a theoretical study carried out using finite element analysis to determine the optimum wall thickness variation. The component performance was judged against the three criteria of change in radius, center of curvature drift and loss of sphericity. A multi-criteria optimization code llnked to a parametric finite element model was used to analyze the problem and generate a set of Pareto optimal solutions. The characteristics of this Pareto set are described in this paper and used to explain the various deformation modes of the tool. It is concluded that varying the wall hckness will achieve the desired objective.

単結晶Ｓｉレンズの非球面創成研磨に関する研究

Aspherical lenses of single crystal silicon (Si) are used for the scope and the camera of infrared wavelength, because the very large refractive index of the material leads to substantial reflection loss. These aspherical lenses of infrared wavelength materials were manufactured by diamond cutting. But the single crystal silicon is a hard and brittle material, it is difficult to obtain a mirror surface without a micro crack when the lens diameter is large. In this case, aspherical polishing has to be applied after diamond cutting in order to generate an aspherical surface most precisely. In this study, a computer controlled polishing system using a small rotating polisher was developed for precision finishing of a large size of aspherical surface after diamond cutting. The characteristics of this polishing system are, as follows: (1) A disk shape of forming polyurethane pad was used as the polishing tool, and its rotating axis was controlled to be always normal at the machining point of the workpiece surface. (2) The polishing load was applied from the normal direction of the machining point and controlled to be constant. In the aspherical polishing tests, spherical surface of diamond turned single crystal silicon (111) was polished to generate an aspherical shape. As a polishing abrasive, colloidal silica was used. As a result, a form accuracy of about 0.2 μm P-V (±0.1 μm) and a surface roughness of less than 0.02 μm Rmax were obtained.