Preliminary study: Polishing force measurement by viscosity - the return of ketchup polishing

Due to the advantages over conventional polishing strategies, polishing with non-Newtonian fluids are state of the art in precision shape correction of precision optical glass surfaces. The viscosity of such fluids is not constant since it changes as a function of shear rate and time. An example is during the shape correction by polishing with pitch or ice, where pitch flows slowly under its own weight and acts like a solid body during short periods of stress as its viscosity increases. The effect can be measured in the polishing gap with a viscometer. If there is a change in force or a process variation of the polishing pressure in the polishing gap, the viscosity also changes. Conversely, the viscosity value could be used to determine the process variation of the polishing force, at least quantitatively. It is to be expected that the distance of the sensor to the polishing gap (effective zone of the polishing force) and the associated change in the viscosity value has a decisive influence on the accuracy of the measurement resolution. First polishing results will be presented and a bowl feed polishing like approach will be presented

Achieving Highly Stable Removal Rate in Small Tool Polishing of Glass Lenses

The demand for improving the image quality of cameras has increased significantly, especially in industrial applications, such as broadcasting, on-vehicle, security, factory automation, and medicine. Surface of glass lenses, which is a key component of cameras, is formed and finished by polishing using small tools. However, the existing small tool polishing technologies exhibit serious problems including an unstable removal rate with the accumulated polishing time. In concrete, low removal rate at the beginning of the polishing process and sudden decrease in the removal rate during the polishing process significantly deteriorate stability of the removal rate. To improve the stability of the removal rate, we proposed a vibration-assisted polishing method using newly developed polishing pads with titanium dioxide particles in the previous work. Polishing experiments on glass lenses confirmed that the variation in the removal rate was suppressed by the developed polishing method; however, the reason for the improvement, in concrete, the relation between the vibration of polishing pressure and the stability of the removal rate remains unknown. In this study, we investigated and clarified the effect of the vibration of polishing pressure on the surface conditions of polishing pads, which strongly affected removal rate.

Best Practice for Metallurgical Quality Evaluation of Nitrided Components

Surface hardening by nitriding is a commonly used heat treatment to enhance tribological characteristics, fatigue, and corrosion resistance of ferrous components. Nitrided white layer is known for its high hardness but also for its brittle nature. It is not uncommon to see white layer chipping or breakaway during metallurgical sample preparation that may complicate the analysis of the ‘true’ white layer characteristics in the microstructure of the nitrided load. This paper discusses the results of the several studies performed to evaluate the effect of cutting and polishing operation, polishing pressure, use of foils, and Ni plating. Best practice procedure has been developed for metallurgical sample preparation to minimize uncertainty in parts quality evaluation.

Study on Polishing Characteristics of Pyramidal Structured Polishing Pad

We conducted a polishing test to clarify the change in polishing characteristics resulting from the wear of a pyramidal-structured polishing tool, and discuss the polishing mechanism unique to the pyramidal-structured polishing pad. When the pyramidal-structured polishing pad is used for polishing, there exists an initial polishing stage in which the removal rate is high but the finished surface is rough; followed by a steady-state polishing stage in which the wear rate is low, removal rate is stable, and a high-quality finish is obtained. The true polishing pressure is constant in the steady-state polishing stage regardless of the nominal polishing pressure, although it differs with workpiece hardness. Polishing was carried out using the pyramidal-structured polishing pad containing 6 μm alumina abrasive grains for 90 min without any scorching or clogging. This resulted in finished surfaces of 0.4 μmRzand 0.07 μmRzfor oxygen-free copper and S45C, respectively.

Lightweight Design of Multi-Objective Topology for a Large-Aperture Space Mirror

For a large-aperture space telescope, one of the key techniques is the method for designing the lightweight primary mirror assembly (PMA). In order to minimize the mirror surface error under axial gravity, lateral gravity, and polishing pressure at the same time, a method for topology optimization with multi-objective function combined with parametric optimization is introduced in this paper. The weighted compliance minimum is selected as the objective function to maximum the mirror structural stiffness. Then sensitivity analysis method and size optimization are used to determine the mirror structure parameters. Compared with two types of commonly used lightweight configurations, the new configuration design shows obvious superiority. In addition, the surface figure root mean square (RMS) of the mirror mounted by given bipod flexure (BF) under 1 g lateral gravity is minimized only with a value of 3.58 nm, which proves the effectiveness of the design method proposed in this paper.

Effects of Process Parameters on Material Removal in Vibration-Assisted Polishing of Micro-Optic Mold

Process parameter conditions such as vibrating motion, abrasives, pressure and tool wear play an important role in vibration-assisted polishing of micro-optic molds as they strongly affect material removal efficiency and stability. This paper presents an analytical and experimental investigation on the effects of process parameters, aimed at clarifying interrelations between material removal and process parameters which affect polishing quantitatively. The material removal rate (MRR) and surface roughness which represent the polishing characteristics were examined under different vibrating motions, grain sizes of abrasives and polishing pressure. The effects of pressure and tool wear conditions on tool influence function were analyzed. The results showed that 2D vibrating motion generated better surface roughness with higher material removal efficiency while a smaller grain size of abrasives created better surface roughness but lower material removal efficiency. MRR gradually decreases with the increase of polishing pressure when it exceeds 345 kPa, and it was greatly affected by the wear of polisher when wear diameter on the polisher’s head exceeds 300 μm.

Surface Removal of Copper Thin Film under the Ultrathin Water Environment for Nanoscale Process

The surface planarity and asperity removal behaviors of atomic scale under the ultrathin water environment was studied for the nanoscale process by molecular dynamics simulation. The monolayer atomic removal was achieved under the noncontact and monoatomic layer contact conditions with different water film thickness, and the newly formed surface is relatively smooth and no deformed layer and plastic defects exist. The nanoscale processing is governed by the interatomic adhering action during which the water film transmits the loading forces to Cu surface and thereby result in the migration and removal of surface atoms. With scratching depth ≥ 0.5 nm, the abrasive particle squeezed out the water film from scratching region and scratched Cu surface directly, leading to the surface quality deterioration mainly governed by the plowing action. This study brings the goals of “0 nm planarity, 0 residual defects and 0 polishing pressure” closer to us in the nanoscale process for the development of ultra-precision manufacture technology.