Study of manufacturing and measurement reproducibility on a laser textured structured surface

In recent years there has been increasing interest in the use of structured surfaces to provide specific functional performance. Such surfaces often consist of localised micro-scale surface features with predetermined geometries. The performance of the feature manufacturing process affects the functional performance of the surface, and can be assessed by measurement of the resulting surface features. Measurement of the resulting micromanufactured surface features necessitates use of areal optical surface topography instruments. However, conventional characterisation methods, based on areal surface texture parameters, often prove inadequate, and may fail to capture the relevant geometric properties needed for an effective dimensional verification. This paper investigates an alternative route to verification, based on the determination of geometric attributes of the microfabricated features. This approach allows for direct assessment of manufacturing process performance, by comparison of the geometric attributes with their nominal values. An example application is shown in which a micromachining process (laser texturing) is used to fabricate a periodic pattern of dimples, which provide a low friction bearing surface. In this paper, manufacturing process performance is assessed by characterisation of the diameter and out-of-roundness. Sources of uncertainty associated with these geometric parameters are also considered

Structural, optical and electrostatic properties of single and fewlayers MoS2:effect of substrate

We have decoupled the intrinsic electrostatic effects arising in monolayer and few-layer MoS2 from those influenced by the flake-substrate interaction. Using ultrasonic force microscopy nanomechanical mapping, we identify the change from supported to suspended flake regions on a trenched substrate. These regions are correlated with the surface potential as measured by scanning Kelvin probe microscopy. Relative to the supported region, we observe an increase in surface potential contrast due to suppressed charge transfer for the suspended monolayer. Using Raman spectroscopy we observe a red shift of the E12g mode for monolayer MoS2 deposited on Si, consistent with a more strained MoS2 on the Si substrate compared to the Au substrate

Lateral scale calibration for focus variation microscopy

Areal surface texture measuring instruments can be calibrated by determining a set of metrological characteristics currently in the final stages of standardisation. In this paper, amplification, linearity and perpendicularity characteristics have been determined to calibrate the lateral performance of a focus variation microscope. The paper presents a novel and low-cost material measure and procedures that are used to determine the characteristics. The material measure is made of stainless steel with a cross-grating grid of hemispherical grooves. The design, manufacturing and calibration of the material measure are discussed. The (20 × 20) mm grid is measured with and without image stitching. The results show that the proposed material measure and procedures can be used to determine the error of the amplification, linearity and perpendicularity characteristics. In addition, the lateral stage error can be significantly reduced by measurement with image stitching

Fear - A Barrier to Materializing our Desires

Fear, like any other emotion, first manifests in the body. The body is the first one it signalsfear by simply blocking it because fear, in whatever form, would manifest itself, leads to non-action. Inorder to escape the fear, we do not need to oppose them, to fight, to fight we fight in some way. It isenough to make it aware, to accept it and then to act. Action means movement, movement unlocks thebody so we take control and fear does not it influences more. The equation is very simple: fear = nonaction,action= fear disappears

Development of a spatially dispersed short-coherence interferometry sensor using diffraction grating orders

Modern manufacturing processes can achieve good throughput by requiring that manufactured products be screened by better quality control exercised at a quicker rate. This trend in the quality control of manufactured products increases the need for process-oriented precision metrology capable of performing faster inspections and yielding valuable feedback to the manufacturing system. This paper presents a spatially dispersed short-coherence interferometry sensor using diffraction orders of the zeroth and first order for a diffraction grating introduced as a new compact system configuration for surface profile measurement. In this modified design, the diffraction grating acts as the beam splitter/combiner. Diffractions for the zeroth and first orders are represented by the reference and measurement arms, respectively, of a Michelson interferometer, which reduces the optical path length. This innovative design has been proven effective for determining the step-height repeatability in the sensor range from 27 nm to 22 nm for profiles spanning the step heights of the tested specimens

Optimisation of surface measurement for metal additive manufacturing using coherence scanning interferometry

Surface topography measurement for metal additive manufacturing (AM) is a challenging task for contact and non-contact methods. In this paper, we present an experimental investigation of the use of coherence scanning interferometry (CSI) for measurement of AM surfaces. Our approach takes advantage of recent technical enhancements in CSI, including high dynamic range for light level and adjustable data acquisition rates for noise reduction. The investigation covers several typical metal AM surfaces made from different materials and AM processes. Recommendations for measurement optimisation balance three aspects: data coverage, measurement area and measurement time. This study also presents insight into areas of interest for future rigorous examination, such as measurement noise and further development of guidelines for the measurement of metal AM surfaces

Development of a traceability route for areal surface texture measurements

Modern manufacturing industry is beginning to benefit from the ability to control the three dimensional, or areal, structure of a surface. To underpin areal surface manufacturing, a traceable measurement infrastructure is necessary. In this thesis a practical realisation of areal surface traceability is presented, which includes the development of: a primary in-strument, methodologies for using the primary instrument to calibrate material measure-ment standards used as standard transfer artefacts, and the process of transferring this traceability to industrial users of stylus and optical instruments. The design of the primary instrument and its complex measurement uncertainty model are described, including detailed analysis of the input parameters of the uncertainty model and their effect on the co-ordinate measurements of the instrument. The development of the process of transferring the areal traceability to industrial users lead to a set of metrological characteristics applicable to all areal surface topography measuring instruments. The set of metrological characteristics, now included into international stand-ards, comprise of: measurement noise, flatness deviation, amplification, linearity and squareness, and resolution. Despite the differences in operation of the various types of in-strument, the idea behind this set of metrological characteristics is based on the fact that these instruments produce three dimensional data sets of points, which is a new approach in the field. Metrological characteristics are quantities that can be measured directly, gener-ally using calibrated material measures. The development of standard methodologies for calibrating the metrological characteristics, and the explicit relationship between the metro-logical characteristics and the measurement uncertainty associated with the co-ordinate measurements provided by the instrument is presented. Many of the techniques described in this thesis are now being discussed for inclusion into international standards