3D Coordinate Measurement Machine Research Articles

Automated optical distance measurements for counting at a defined solid angle

Two optical distance measurement devices have been compared for accurately defining the source-detector geometry of alpha-particle counters. The first consists of a travelling microscope with unifocal lens, to which a linear distance gauge is attached. The focusing is done by human eye. The second is a modern 3D coordinate measurement machine, equipped with a CMOS colour camera as the sensor. Focusing is performed automatically by software. With both devices, distance measurements of various drop-deposited sources on glass and stainless steel disks have been performed. There is a good mutual agreement of results. Even though the new device can sample more reference points, the accuracy of the measurements has not improved drastically due to the imperfect flatness of the sources. The main advantages of the new system are its ease of use and the lower health risk involved due to the larger distance between the performer and the source.

Dimensional accuracy and repeatability of the NextEngine laser scanner for use in osteology and forensic anthropology

The increasing accessibility of low-cost, desktop scanners has provided researchers with the means to acquire 3D geometric data that can be used to create digital archives of archaeological artifacts, such as bones, for geometric morphometric study in the fields of osteology and forensic anthropology. However, the process of digitizing and assessing in silico models is not straight forward. In this two-part study, we first compared the performance of the 2010 NextEngine model 2020i laser scanner (NE) and Hewlett-Packard Pro S3 structured light scanner (HP) to that of the Keyence VHX 6000 digital microscope (VHX), using a fabricated test block containing bas-relief features with offsets ranging from 3 mm down to 0.1 mm. The xyz coordinate data from the in silico models were also compared to xyz coordinate data obtained using a Microscribe MX 3D coordinate measurement machine (CMM), which showed no evidence of geometric distortion in the in silico models. We applied Bland-Altman analysis to quantify the coefficient of repeatability (CoR) for each instrument used in the study, and to determine agreement between the scanners and the VHX. Dimensional accuracy was assessed by comparing bas-relief offset dimensions on the in silico models derived from the scanners to the VHX measurements of the same features. Second, as an application to osteology we examined intra-observer scanning protocol variability, using the coefficient of variation (CV) to quantify surface area and volume variance between repeated scans of eight porcine capital femoral epiphyses with undulating mammillary processes on one surface with amplitudes covering the range of the test block bas-relief offset values. The CoR showed each test-retest measurement from each instrument differed by no more than their CoR: 0.010 mm, 0.137 mm, 0.068 mm, 0.193 mm for the VHX, NE, HP and CMM, respectively. There was agreement between the instruments, but each instrument (NE, HP and CMM) overestimated bas-relief features as reported by the VHX, on average (bias) by 0.046 ± 0.038 mm, 0.025 ± 0.033 mm, 0.026 ± 0.033 mm for the NE, HP and CMM, respectively. Both scanners captured surface features as small as 0.1 mm. For the intra-observer scanning protocol of the epiphyseal bones using the NE, the coefficient of variation (mean CV ± SD) was 0.69 ± 0.25% for the bone surface area and 0.77 ± 0.26% for bone volume. The scanner appears suitable for capturing bas-relief features in the range of 3 to 0.1 mm, while preserving the ratios of distances between measured points within the spatial volume surveyed. Examples of potential applications include scanning bone or pottery fragments for virtual reconstruction, where capturing dimensional detail and areas is important, reproducing the fine surface features of pottery, figurines, etc. for cultural preservation and for examination by scientists who cannot study the objects directly, as well as to provide access to the public by electronic means. The lower cost of these scanners may provide museums with small budgets with a means to begin to archive some items in their collection.

A developed algorithm for simulation of blades to reduce the measurement points and time on coordinate measuring machine (CMM)

A 3D Coordinate Measurement Machine Facility (CMM) of the latest technology enables both researchers and industrial manufacturers to evaluate the precision of the different manufacturing techniques that are usually applied for the production of the mechanical component. Especially when the examined component is a blade, due to the geometrical complexity, larger errors can occur during the manufacturing procedure. These errors have a strong impact on the final performance. The high precision measurement with a CMM requires scanning with small steps, which means measuring several points that need long-time measurement.The aim of this paper is to develop a method for simulating objects by three-dimensional scanning, with a small number of points, while achieving the goal of a certain allowable deviation. The curves used are of a 3rd degree polynomial form.

Analysis of turbine performance degradation effects due to geometry variations between actual components and design Intent

AbstractThis paper presents a computational analysis regarding the effect of the camber line deformation due to structural errors, on the aerodynamic behavior of a high-pressure steam turbine.In several cases, inaccuracies in the blade geometry can lead to undesirable flow phenomena strongly affecting its overall performance when put in service. The effect of the camber line deformation on the performance of an experimental axial steam turbine is investigated hereafter. A high fidelity inspection of the actual geometry of both a stator and a rotor blades randomly chosen among the similar blades of the same row has been carried out, using a 3D co-ordinate measurement machine. The cross sections of the blades obtained by the measurement were compared with those produced by the design process to evaluate the change in blade inlet/exit angles. The actual (measured) model has been used as input into a streamline curvature solver to evaluate its overall performance assuming a uniform distribution of the geometrical error across the blades of the same blade row, the loss generation mechanisms within the flow field have been further investigated and analysed using a high fidelity 3D Navier-Stokes solver.A measurable change of efficiency as well as in the total power delivered by the turbine was found. This suggests that the accumulated error caused during the manufacturing procedure plays a significant role in the overall performance of the machine by making it less efficient by almost 1% due to the intensification of the hub and casing secondary flows, as well as to the thicker boundary layers on the blade surfaces revealed by the numerical prediction of the flow.

Evaluation of moment arm length and fulcrum sensitivity limit in a 10 N·m dead weight torque standard machine

Many torque tools, such as torque wrenches and torque screwdrivers, as well as torque measuring devices (TMDs) with a rated capacity of less than 5 N·m are being widely used in industry. Thus, a small-rated-capacity torque standard has to be established as soon as possible. A 10 N·m dead weight torque standard machine (10 N·m DWTSM) has been under development since 2006 at the National Metrology Institute of Japan (NMIJ), part of the National Institute of Advanced Industrial Science and Technology (AIST). Characteristically, the main parts of the moment arm are made of low thermal-expansion alloy (Super INVAR), and an aerostatic bearing is employed as the fulcrum supporting the moment arm to minimize rotational friction. The moment arm was evaluated with regard to the coefficient of thermal expansion (CTE), the lengths measured by a 3D coordinate measurement machine (CMM), and temperature correction realized by measuring the moment arm temperature. The sensitivity limit of the fulcrum in the 10 N·m DWTSM was also estimated. As a result, the apparent overall CTE of the moment arm was 1.06 × 10 −6 K −1, and the expanded uncertainty was 2.24 × 10 −9 K −1 ( k = 2). The results of the CMM measurement were a right-hand side length of 510.2773 mm and a left-hand side length of 510.2657 mm, with a relative expanded uncertainty of 4.0 × 10 −5 ( k = 2). The moment arm temperature increased by approximately 0.6 K during the ordinary calibration process. The corresponding change in the lengths of the moment arm was estimated to be approximately 0.3 μm, which is considered to be sufficiently small compared with the expanded uncertainty of the lengths of the moment arm. The fulcrum of the 10 N·m DWTSM was found to have sufficient sensitivity under three conditions: without the weight loading components, with the weight loading components, and with loaded weights. In particular, the fulcrum had sufficient sensitivity of at least 0.5 mg when weights of 100 g were loaded on both 5th stages in the weight loading components to generate a radial load equivalent to 1 N·m.

Turbine Blading Performance Evaluation Using Geometry Scanning and Flowfield Prediction Tools

This paper investigates the effect of blade deformation, caused by manufacturing inaccuracies, on the performance of a 2-stage axial steam turbine. A high fidelity 3D coordinate Measurement Machine has been employed to obtain the exact geometrical model of the blades. A Streamline Curvature solver was used to predict the overall performance of the turbine. During the manufacturing process of the casts and of the blades themselves, several types of errors can occur which lead to a different geometry from that envisaged by the designer. The main objective of this study is to investigate the effect of those errors on the performance of a 2-stage experimental axial steam turbine. A high fidelity measurement of the actual geometry of both stator and rotor blades has been carried out, using a 3D Coordinate Measurement Machine. The cross sections of the blades obtained by the measurement were compared with those produced by the design process to evaluate the change in blade inlet/exit angles. In addition, the geometrical deviations from the initial design have been subjected to a statistical study in order to locate the nature of the error. The actual (measured) model has been used as input into a Streamline Curvature solver to evaluate its performance. Finally, a comparison with the performance plots of the original geometry has been carried out. A measurable change of efficiency as well as in the total power delivered by the turbine was found. This suggests that the accumulated error caused during the manufacturing procedure plays a significant role in the overall performance of the machine by making it less efficient by more than 1%. Reverse engineering techniques can be applied to predict and alleviate these errors leading thereby to a final design of each stage with improved performance.