Fine Ground Surface Research Articles

Convergent polishing: a simple, rapid, full aperture polishing process of high quality optical flats & spheres.

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial shape (i.e., surface figure), will converge to final surface figure with excellent surface quality under a fixed, unchanging set of polishing parameters in a single polishing iteration. In contrast, conventional full aperture polishing methods require multiple, often long, iterative cycles involving polishing, metrology and process changes to achieve the desired surface figure. The Convergent Polishing process is based on the concept of workpiece-lap height mismatch resulting in pressure differential that decreases with removal and results in the workpiece converging to the shape of the lap. The successful implementation of the Convergent Polishing process is a result of the combination of a number of technologies to remove all sources of non-uniform spatial material removal (except for workpiece-lap mismatch) for surface figure convergence and to reduce the number of rogue particles in the system for low scratch densities and low roughness. The Convergent Polishing process has been demonstrated for the fabrication of both flats and spheres of various shapes, sizes, and aspect ratios on various glass materials. The practical impact is that high quality optical components can be fabricated more rapidly, more repeatedly, with less metrology, and with less labor, resulting in lower unit costs. In this study, the Convergent Polishing protocol is specifically described for fabricating 26.5 cm square fused silica flats from a fine ground surface to a polished ~λ/2 surface figure after polishing 4 hr per surface on a 81 cm diameter polisher.

A study on the effect of surface topography on rough friction in roller contact

The friction behaviour of gear teeth in the context of tribology can have a strong effect on housing vibration, noise and efficiency. One of the parameters that greatly influences the friction under certain running conditions is surface roughness. In this work, rough friction was studied in lubricated sliding of roller surfaces, which were manufactured to simulate the real gear surfaces. By examining 3D surface topography of two mating bodies, both surface roughness and its effect on friction behaviour can be studied. In a previous study, a rough-friction test rig has been designed, constructed and initially verified. The types of surfaces involved in this study are ground, shot-peened, phosphated and electrochemically deburred. These rollers were subjected to the same friction testing procedures. Roller surfaces were then examined, and correlation between the topography and the frictional behaviour was analysed. Friction behaviour was interpreted in terms of Stribeck curves (friction coefficient as the function of Hersey parameter ( ην/p)). The results showed that electrochemically deburred and certain phosphated surfaces provide lower friction coefficient values which are competitive to fine-ground surfaces in lubricated rolling/sliding contact.

数値制御機能を用いたスラント研削に関する研究―仕上げ面粗さ改善原理の解明―

This study deals with the improving method of ground surface roughness by numerical control function with a machining center. In the present report, we researched effective factors to improve the ground surface roughness after slant grinding by numerical control function. That is, we investigated the relationship between the surface roughness curves and slant grinding conditions. As a result, it is clear that there are two important parameters (hs: height formed by a cutting edge pre revolution and X0/Z0: incline of envelope curve of a cutting edge) to form the fine ground surface in slant grinding. Additionally, it was also confirmed that the wear of wheel was small in appropriate slant grinding conditions

研削面プロフィル創成シミュレーションから考察した砥石面トポグラフィの具備条件

The purpose of this study is to analyze the requisite conditions of grinding wheel topography for improving surface finish. In this report, a wide variety of wheel surface topography is examined with the previously developed simulation in which measured distribution of mounting spring constant, dimensional position and shape of abrasive grains are considered. The simulation makes clear that the necessity of wheel surface topography for the fine ground surface profile are to have the extremely small spring constant of grain mounting in a very top surface and its higher average and variation in the inner position from the wheel surface. In addition, to true up the grain edge position and to make a pointed edge of grains flat are necessary. The knowledge obtained from these analysis may be an important guideline in manufacturing, dressing and truing a grinding wheel.

Surface Structure of Fine Ground Surface

The structure of a surface layer of ground glass consists of relief layer and crack layer. Their dimensional characteristics influence directly the subsequent polishing process. The understanding of the role of both layers in the polishing process is the key factor for optimizing the efficiency of optical surfacing by selecting proper techniques for both grinding and polishing operation. In this paper, the role of the microstructure of the grind surface layer in polishing process will be discussed; methods of its evaluation presented, and several examples of surface structure for some representative grinding methods evaluated.

Improved Oblique-Incidence Interferometer

An oblique-incidence interferometer for testing the flatness of fine-ground surfaces is described. This uses reflecting diffraction gratings to divide and recombine the beams, resulting in a very compact optical system. In addition, the relative amplitudes of the interfering beams can be adjusted, by a suitable choice of the grating orders used, to give fringes of excellent visibility with surfaces having a wide range of refleetances.

Effect of metal surface treatment on the masking power of opaque porcelain.

Spectral reflectance was determined as a function of incremental thickness of opaque porcelain applied to precious metal alloy surfaces treated in three ways. Sandblasted and fine-ground surfaces required comparable thicknesses of porcelain to achieve the same degree of opacity at selected wavelengths, whereas specimens conditioned with a gold flashing agent required 40 to 60% less opaque porcelain to achieve the same result. A logarithmic model for predicting reflectance as a function of porcelain thickness was applicable for gold-flashed surfaces at wavelengths greater than 550 nm.

Application of Wax to Fine Ground Surfaces to Simulate Polish

Application of Wax to Fine Ground Surfaces to Simulate Polish

A comparative method of checking angles on glass samples

An optical method of checking angles on glass samples is described. The method is comparative: the reference is a polished sample, the angle of which has been measured on a precision goniometer. It has the advantage that angles with either polished or fine-ground surfaces can be measured since use is made of reflections off the faces of the angle at close to grazing incidence. Angles with fine-ground surfaces can be checked to 5 seconds of arc and with polished surfaces to 2 seconds of arc.

Testing of Polished or Fine Ground Surfaces for Flatness

The testing of nearly flat surfaces by the astigmatism produced in a light beam reflected from the surface is discussed. The use of the test for ground surfaces is described, and attention is drawn to its use in the working of soft materials such as rock salt.