Stylus Instrument Research Articles

Influence of Structural Defects on the Polishing of Silicon Carbide Single Crystal Wafers

This study attempts to reveal the influence of major defects such as micropipes and planars on the polishing characteristics of silicon carbide (SiC) wafers. SiC wafers were lapped and finish-polished using chemical-mechanical polishing. The surface finish examinations were performed using atomic force microscopy along with a stylus instrument and revealed that for SiC wafers with a low defect density the average surface roughness is less than 5 A. It was found that scratches are generated due to chipping of the walls of micropipes and planars. Moreover, depending on the micropipe density (MPD), wavy features or so-called “orange peels” are created. The quantitative dependence of roughness parameters and the uniformity of surface finish on the micropipe density were evaluated and the occurrence of orange peel was found to increase when the MPD exceeds 100 cm-2.

English

An experimental study of the drag and roughness characteristics of a Tin-free Self-Polishing Co-polymer ((SPC))and a non-toxic Foul Release system has been carried out. The drag characteristics were measured in towing tank and water tunnel experiments using different friction planes and in a rotor apparatus using coated cylinders. The measurements show that a typical new application of the Foul Release scheme exhibits less drag than a Tin-free SPC scheme.The roughness characteristics of the two coatings were measured both with a stylus instrument and with an opticalmeasurement system. The measurements show that the texture of the Foul Release coatings is significantlydifferent from SPC coatings.The correlation of drag with roughness is reviewed and the two coatings have been compared with a published database of different antifoulings. Contrary to the other types of coatings, the findings show that the roughness of a newly applied Foul Release scheme will not correlate with its drag when characterised solely by a height parameter, but that it is necessary to take the texture into account.

Friction Factor Directly From Roughness Measurements

Pressure drop experiments on natural gas flow in 150 mm pipes at 80 to 120 bar pressure and high Reynolds number were carried out for pipes smooth to rough surfaces. The roughness was measured with an accurate stylus instrument and analyzed using fractal methods. Using a similar approach to that of Nikuradse the measured friction factor was related to the measured roughness values. Taking the value of the relative roughness and dividing it by the slope of the power spectrum of the measured roughness, a greatly improved fit with the measured friction factor was obtained. Indeed, a new friction factor correlation was obtained, but now formulated in terms of direct measurement of roughness.

Comparative analysis of injection systems for manufacturing parts

The present study focuses on aspects of the surface qualities of prototypes obtained by injection techniques. The surface finish and dimensional precision of parts obtained through these manufacturing processes is often highly important. Moreover, it is important to have an estimation of the average surface roughness in order to select the operation parameters adequately. Although there are a lot of different techniques for evaluating the surface roughness, one of the most commonly employed methods for characterising roughness involves assessment of surface roughness average by means of stylus instruments. Prototype manufacturing using two different systems of multijet injection technology was carried out, modifying the manufacturing conditions for obtaining the prototypes. After parts were obtained, an experimental study of effective roughness was done. Also, a comparative study using two injection systems with different accuracy was performed in order to evaluate the capability of these rapid prototyping techniques for manufacturing parts.

Comparison on Nanometrology: Nano 2—Step height

The ability to measure step height and to calibrate step height artefacts is of vital interest in nanometrology. On that score the WGDM7 decided in 1998 to include measurements of step heights in a series of comparisons on the field of nanometrology.The comparison about step height (NANO2) started in September 2000 with the Physikalisch-Technische Bundesanstalt (PTB) as pilot laboratory. Fourteen national metrology institutes worldwide participated in this comparison. A set of five step height standards in the range from 7 nm to 800 nm was used for the comparison. The lateral size of the structures of the step height standards was chosen so that the height could be measured by different types of instruments, for example, interference microscopes, stylus instruments and scanning probe microscopes (SPM). The reference values were calculated as the weighted mean of all measurements that fulfilled the En < 1 criteria.Most of the results were in good agreement with the reference values. It is noticeable that the results obtained by different types of instruments are quite compatible. Also this comparison is the first comprehensive test of the reliability of SPM and their suitability for traceable measurements of step heights. Further it was shown that today step heights on samples can be measured with uncertainties in the sub-nanometre range. Differences in the calculation of the uncertainty depend on the types of instruments and on the users. For each class of instrument, e.g. SPM, it would be meaningful to homogenise these models. Hence the results of this comparison are of great importance in many respects.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCL, according to theprovisions of the Mutual Recognition Arrangement (MRA).

New developments in fast 3D-surface quality control

Inspection is the process of determining if a product deviates from a given set of specifications. Fast inspection usually involves measurement of specific part features such as assembly integrity, geometric dimensions and surface finish. It is a quality control task, but is distinguished from testing tasks. The visual inspection of 3D parts (car body parts) is a special task within manufacturing that has been automated at a comparatively slow pace up to this time. Different optical methods, applied for 3D measuring at microscopic and macroscopic levels of sheet metal parts, based on the projected fringes method (PFM), electronic speckle interferometry (ESPI), the structured-lighting reflection technique (SLRT), white-light interferometry (WLI) and also SEM-, AFM- and laser scanning methods (LSM) will be discussed. In addition, stylus instruments and also colorimeter measurements are included. The presentation closes with the advantages and disadvantages of different contemporary intelligent methods for car body inspections: neural net based classification, fractal analysis and wavelet transformation.

The characterisation of grinding wheels using 3D surface measurement techniques

Surface measurement using 3D stylus instruments is a relatively new technique which offers numerous advantages over the more common profilometry methods. The information generated is, unlike profile measurements, less subjective and more statistically relevant providing additional insight regarding the surface structure. One application of surface measurement which has encountered problems when using the profilometry method is that of grinding wheel characterisation. The wheel surface texture (topography) and the conditions under which it is generated have a profound effect upon the grinding performance as characterised by the grinding forces, power consumption, temperature, and surface integrity of components. A detailed knowledge of the nature of the topography of the grinding wheel would provide further insight into the surface interaction of the grinding wheel as well as enabling improved control of the grinding process in general. Through the employment of novel 3D surface descriptors, this paper will investigate the topographic change which occurs on both the wheel and workpiece and attempt to relate this to force data and scanning electron microscopy. The results will demonstrate that this topographic characterisation technique correlates well with more accepted methods.

Uncertainty analysis of multijet modelling processes for rapid prototyping of parts

The present study focuses on aspects of the surface qualities of prototypes obtained by multijet modelling (MJM) techniques. The surface finish and dimensional precision of parts obtained through these manufacturing processes are often highly important, especially in those cases where the manufactured prototypes are used as functional parts, as in the case of lost wax casting. Moreover, it is important to obtain an estimate of the average surface roughness in order to select the appropriate manufacturing parameters. Although there are many different techniques for evaluating surface roughness, one of the most commonly employed methods involves the assessment of the average surface roughness by means of stylus instruments. Prototypes were manufactured using two different MJM systems under different conditions for each prototype. After the parts were obtained, an experimental study of effective roughness was carried out. A comparative study using the same MJM systems with different accuracies was also performed in order to evaluate the capability of these rapid prototyping techniques to manufacture parts.

The accuracy of fast 3D topography measurements

One important factor in surface engineering is the evaluation of the surface topography, i.e. measurement and analysis. These measurements of the surface roughness are normally done by stylus instruments and 2D profiles due to available standards. 3D surface topography evaluation is, however, in some cases necessary and frequently used, a standard is under development, and newly developed measurement instruments are used. Specially interferometric instruments are of interest here since measuring time is critical and their accuracy and comparability to stylus instruments must be evaluated. Therefore, in this study a number of engineering surfaces have been measured and evaluated: plateau-hones cylinder liners for engines, polished steel roller for bearings, grounded and honed gear surfaces from gear boxes, and steel sheet surfaces used in car bodies. By the use of a precise relocation technique, an exact comparison was possible between an interferometric instrument (Wyko RST Plus) and a 3D stylus instrument (Somicronic 3D). To be able to judge and analyze differences between the instruments an Atomic Force Microscope (AFM) was used. The AFM is extremely accurate for this type of surfaces, but limited in its measuring range. The result shows a very good agreement between the instruments with deviations of approximately 5–20% depending on the parameter evaluated. The stylus in general gives lower values. The results from the AFM are generally found between the parameters of these instruments, and for soft surfaces, such as sheets or smooth surfaces, the interference instrument has a slightly better agreement to the AFM. This is due to the stylus tip geometry and the relatively high contact pressure having difficulties measuring small features and also damaging softer surfaces. The result from an interferometric measurement occasionally shows optically introduced artifacts caused by local surface slopes which exaggerate the topography. By knowing the degree of influence from these peculiarities it is still possible to use fast interferometric instruments and to estimate its deviation from what would have been the result with a stylus instrument.

Developments in Australia's surface roughness measurement system

Roughness standards in Australia are established, maintained and disseminated by the Melbourne Branch of the National Measurement Laboratory (NML), Commonwealth Scientific and Industrial Research Organisation (CSIRO). A Taylor Hobson Talysurf 3 stylus instrument has been upgraded by replacement of the original valve amplification with solid-state electronics and the implementation of Windows 95 based software for profile analysis. The amplification is calibrated using gauge blocks wrung onto an optical flat or with master groove standards, calibrated using an interference microscope with a helium–neon laser light source. Measurements of step height or peak-to-valley roughness height in the range 0.1–50 μm are possible. The stylus instrument interfaces directly with a PC via a high speed analogue-to-digital card. Software has been developed to analyse grooves and steps and to characterise surfaces by calculation of various parameters such as arithmetic mean deviation ( R a). Typical uncertainties are better than 4% at a confidence level of 95% and are calculated automatically by the software according to the ISO “ Guide to the Expression of Uncertainty in Measurement”. Technical and administrative procedures are discussed in the context of accreditation within the National Association of Testing Authorities, the Australian laboratory accreditation organisation. The facility has participated informally in a regional Asia–Pacific Metrology Programme intercomparison in which three surface roughness and two groove standards were circulated and the results are discussed. Using historical data, alternate traceability routes, and various artefact chains, the integrity of surface texture measurement at the new facility has been evaluated and verified.

Steel sheet surface topography and its influence on friction in a bending under tension friction test

In order to investigate the frictional response of different surface topographies for steel sheet materials, a Bending-Under-Tension friction test was used. The test included six different surface topographies, of which two were shotblasted (SB), three were electron beam-textured (EBT), and one had electro–chromium deposition (ECD). The testing was performed in mixed lubrication under equal conditions for all materials used. For measurement of the sheet surface-topography, a 3D stylus instrument was used and the ball-filtering technique was applied. The surface topography was measured in the contact zone on the test samples. The ECD material showed the lowest friction coefficient, and an SB material the highest. In order to describe the frictional behaviour caused by the two main lubrication mechanisms, MPHDL and MPHSL, a so-called Wihlborg–Crafoord index (WC index) was determined. The WC index is the number of isolated oil pockets ( NIOP t ) multiplied by the border length of the lubricant area at the area fraction of contact ( BL alfa) divided by the area fraction of contact ( α). This WC index describes how effective the supply of lubrication is at the contact zones and correlates well with the friction coefficient.

Extraction of roughness properties from captured images of surfaces

Surfaces of industrial parts need to be specified on the basis of their use and application environment. Hence, surface characterization is vital for design, manufacturing and inspection. Furthermore, the development of new industries has led to a requirement for super-smooth surfaces and for the ability to measure such surfaces accurately; therefore, the measurement of engineering surface roughness is becoming increasingly important. Many methods of measuring surface finish have been developed ranging from the simple touch comparator to sophisticated optical techniques (light scattering). The latest technology for measuring surface roughness is the computer vision systems. Unlike the stylus instruments, the optical techniques and computer vision systems have the advantages of being non-contact and are capable of measuring an area from the surface rather than a single line. This paper introduces a new technique to capture an image for a surface and then to extract the roughness heights from the captured image. A set-up consists of a charge-coupled device (CCD) video colour camera, a frame grabber, IBM-compatible PC and a microscope used to capture the images. The images were stored using the bitmap image file format (BMP). A program was written in Visual C++ to convert the captured colour images into grey scale images and then to extract the grey level for each pixel and to store it into a two-dimensional array sized to the image width and the image length. The program is capable of reading six different image file formats: these are BMP, TIFF, GIF, PCX, JPG and WMF. The grey levels range between 0 and 255. The grey level 0 represents the black colour, which represents the minimum height in the image, and the grey level 255 represents the white colour, which represents the maximum height in the image. The grey levels between 0 and 255 represent different heights according to their grey level values. After extraction of the grey levels from the image, a three-dimensional view is displayed to view the topography of the surface. The three-dimensional view can be displayed, virtually, from any point of view using the same basics as those of three-dimensional computer aided design (CAD) systems. From the three-dimensional surface topography it is easy to assess any scratches or cracks in the surface. The developed software works independently and does not need any other software. The package includes the unique feature of calculating a multitude of surface roughness parameters (59 in all) that have not been included in any other package hitherto.

Wear investigation of spur gear teeth

AbstractAn FZG back‐to‐back gear test machine has been used to investigate the initial wear of spur gears. By making plastic replicas of the tooth surfaces, and measurements of the same using a 3D stylus instrument, the wear pattern has been analysed. The wear tests were run on the machine according to a predefined schedule. During planned stops, negative surface replicas were made. The replicas were measured, and the amount and distribution of wear analysed. SEM pictures were also taken of the tooth surfaces, and several different types of damage were identified. The results were compared with simulated results using identical loading and geometry. It was found that the wear was quite severe at the root of the wheels and also significant at the tip. The wear was also found to form an overloaded wave pattern on the original involute form of the tooth.

Evaluation of polishing damage in alumina

Abstract Grazing incidence X-ray scattering and line focus acoustic microscopy have been applied to the study of grinding, lapping and polishing processes on alumina. Changes as a function of polishing time in the near-surface density, measured from the critical angle for total external reflection of X-rays, were related to changes in the bearing area and surface morphology. No relation was found between the micrometre-scale roughness measured by a stylus instrument and the integrated diffuse scatter, the latter being related to the nanometre-scale roughness on the top of the polished mesas remaining after grain pull-out during the grinding and lapping process. The surface acoustic wave velocity was also found to vary with polishing time. These changes cannot be ascribed to changes in roughness and are believed to measure changes in the residual crack density.

Evaluation of the root-mean-square slope of 3D surface topography

Based on the application of fractal geometry theory, a quantitative evaluation method of root-mean-square (RMS) slope of 3D homogeneous and stochastic surface topography is proposed, by means of the concept of surface spectral moments. Through the FFT of discrete data from the profiles measured by a Talysurf-5 contact stylus instrument, the power spectrum and the fractal dimensions of the profiles are obtained. Furthermore, the second order spectral moments of the profiles and the surfaces are found. These parameters are used to define the evaluation measure of RMS slope of the surface. By the experiments for ground and fine turned specimen, the results confirm the correctness of this method.

810 種々の塑性変形における多結晶金属の表面あれ形態の三次元的評価

The surface roughening topography on the free surface of polycrystalline metal has important information for understanding the inhomogeneous deformation behavior during plastic deformation. In the present study, the three-dimensional surface shapes of pure aluminum in the deformation patterns with different strain ratio as well as torsion test are characterized. The filtering operation and the newly developed evaluation technique of anisotropy are adapted to the roughened shape measured by the stylus instrument. The differences in the characteristics of surface topography in various plastic deformation is well characterized, thus the influence of macroscopic deformation pattern on the microscopic inhomogeneity of polycrystalline metal is discussed.

Three dimensional measurement of the surface topography of ceramic and metallic orthopaedic joint prostheses.

The comprehensive study of surface topography of the orthopaedic joint prostheses has become very important for analysis of the wear mechanism and the performance life of the joint replacement systems. The aim of the study to investigate "best" methods for the three-dimensional (3D) surface metrology of orthopaedic joint prostheses. Characterization techniques for the identification and evaluation of the functional features of the bearing surface topographies has been provided in previous work. This paper concentrates on addressing issues of measurement and application techniques for assessment of the 3D surface topography of the joint replacement systems by using contacting stylus instruments, atomic force microscopes (AFM), and non-contacting measurement supported by focus detection instruments and phase-shifting interferometers. The techniques are discussed according to different analysis requirements of the orthopaedic joint prostheses. This work also discusses the performances of the instruments in terms of the measurement of femoral heads. Finally, recommendations for acceptable measurement techniques and application for analyzing surface topography of orthopaedic joint prostheses are summarized.

A fibre-optic surface-roughness sensor

A technique applicable to surface-roughness measurement in limited spaces is presented. The measurement principle is light scattering, the surface under test being illuminated using a He–Ne laser, λ = 632.8 nm, with the light being lead to the surface by an optical fibre. The light scattered by the surface is lead by a fibre to a detector. This arrangement makes a very small system possible, a system that can be used to make relative surface-roughness measurements inside a tube or a cylinder. The experimental results presented in this paper show the applicability of this sensor. The surfaces were classified in the same order as when using a stylus instrument. Surfaces in the range of 10 nm < R a < 200 nm were measured, R a being the arithmetical mean deviation of the profile.

Fractal characterisation of the anisotropy of rough surfaces

Existing techniques for measuring and characterising anisotropy are discussed. The advantages are suggested in treating anisotropic surfaces as self-affine fractals, characterised by two parameters, the fractal dimension and the topothesy. These parameters are conveniently determined experimentally by measuring the slope and intercept of a logarithmic plot of the structure function. A 3D version of the structure function is presented, any section for which is equivalent to an ensemble average of profile structure functions. The angular variation of topothesy and fractal dimension obtained from such sections describes the anisotropy of the parent surface. Also, a bifractal structure function, typical of surfaces with stratified textures, may be split into its component straight lines by fitting with a hyperbola. The intersection of the asymptotes then defines the so-called “corner frequency” between the two fractals. The 3D height measurements were made on a grit-blasted, a ground and a plateau-honed surface with a scanning white-light interferometer and a stylus instrument. On the isotropic grit-blasted surface, fractal parameters did not vary with direction. On the strongly anisotropic ground surface, the fractal dimension varied only parallel to the lay, as predicted, but the topothesy varied by some orders of magnitude. On the stratified plateau-honed surface, the only true bifractal, fractal parameters were found to be sensitive to the direction of honing scratches.

Evaluation of the root-mean-square wavelength of machined 3D surface topography

Based on the application of fractal geometry theory, a quantitative evaluation method of root-mean-square wavelength of 3D stochastic surface topography is proposed, by means of the surface spectral moments. Through the FFT of the discrete data of the profile measured by a Talysurf-5 contact stylus instrument, we obtained the power spectrum and the fractal dimension of the profile. Furthermore, the zero and 2nd order spectral moments of the profile and the surface are found. Using these parameters, the evaluation of RMS wavelength may be processed. By the experiments for ground samples, the results confirm the correctness of this method.