Coordinate Measuring Machine Research Articles

Development of A Computerized Multi-Measurement System for Fine Measurements.(Dept.M)

Microscopic instruments have been widely used in many applications for the purpose of inspection and measurement. Measurescopes are one of these microscopic instruments, which are used in micro measurements. Old 2-D measurescopes are limited to producing X and Y coordinates for individual points according to the movement of attached IWO micrometers. In has been developed using a this paper, a computerized 2-D measurement system Measurescope, personal computer and developed software. The software, named MScope, is 6.0 and is ready to run on any Windows fully written in lab using Microsoft Visual C++ 6.0 environment. The system is capable of performing various types of measurements such as linear, angular, circular and radial measurements. In addition, the system is capable of tracing contours and freeform shapes in a manner, which could simulate a 2-D Coordinate Measuring Machine (CMM). This facility may help in the field of reverse engineering to measure small and complex products. The information of both the traced contours and the freeform shapes are calculated automatically and could be exported to AutoCAD as drawing files for further editing and modifications.

Unknown Surface Modeling Method Based on High-precision CMM

Reverse engineering is typically applied to solve the CAD model of unknown parts. As modern industry requirements on the accuracy of complex surfaces increase, setting up the high-precision CAD modeling of unknown complex surface parts through reverse engineering becomes an interesting research topic. Here, we present a method that combines manual measurement and automatic measurement with a high-precision coordinate measuring machine (CMM) to measure unknown complex-surface to obtain CAD model. In this study, the unknown complex-surface was fixed on the CMM worktable, and cancelling the probe compensation function of PC-DMIS before measurement. Then, 490 measuring points were obtained by manually moving the probe with a diameter of 5mm to measure surface. The measured points generated the CAD model, the CAD model was offset a probe radius, and determined the rough contours of the surface. This CAD model was automatically measured in a CMM, and the function of the “automatic measurement model” was iterated to obtain a high-accuracy CAD model. Each measurement was arranged with 20×20 measuring points. The accuracy of the CAD model obtained by each iterative measurement would be improved, and finally a high-precision CAD model was obtained. After 7 iterations, the final accuracy of the unknown surface CAD model was as high as 0.004 mm as compared to that of the actual part.

Complex Surface Reconstruction Based on Fusion of Surface Normals and Sparse Depth Measurement

Precision measurement and reconstruction of detailed surfaces topography is a challenging task for non-diffuse complex parts. Although coordinate measurement machines (CMM) with the touch-trigger probe are widely used in current industry, the measurement efficiency limits their application in the measurement of complex surfaces. This article proposes a multisensor data fusion strategy by integrating the technical merits of CMM and photometric stereo (PS) to achieve multiscale reconstruction of a complex surface with high efficiency. Considering the complementary measurement characteristics of the two approaches, the sparse points from CMM are used to provide global shape information, and the high-resolution surface normal map from PS is used to provide local detailed structure. A multistage neural network is then proposed to fuse these two kinds of modality information such that the global features from the sparse points and the local features from the surface normal map are fused in a coarse-to-fine multistage process so as to make the training process more stable and the reconstruction more accurate. To enhance the generality of the fusion neural network, a synthetic training data set is also designed to include a large variety of multiscale features enriched surfaces. Experiments are conducted to verify the effectiveness of the proposed multisensor fusion strategy in accurate reconstruction of complex surfaces with high efficiency.

Assessing laser powder bed fusion system geometric errors through artifact-based methods

Additive manufacturing (AM) machines have developed more rapidly than standardized frameworks needed for the qualification of their geometric capabilities. While some manufacturer-specific methods exist to test capabilities and perform some calibration tasks, standardization efforts have only recently been undertaken in the form of ISO/ASTM 52902. In this study, the recommended methodology prescribed by the standard was implemented by building geometric artifacts with a laser powder bed fusion (LPBF) system and performing dimensional inspection with a coordinate measurement machine (CMM), amongst other methods. Typical dimensional capabilities of the LPBF system are identified and commentary is made on applying metrology methods, detecting geometric error, and diagnosing base causes in the LPBF system. In doing so, favored metrology practices and measurement analysis methods auxiliary to the standard are proposed. Artifact measurements were used to characterize beam positioning error and beam offset error. Methods for decoupling the effects of error sources are proposed. Difficulties in the inspection of AM components are identified, and the effects of various CMM measurement strategies are evaluated. Insights on the application of the new standard are presented, along with commentary as to its fitness for the LPBF process.

Numerical Versus Analytical Direct Kinematics in a Novel 4-DOF Parallel Robot Designed for Digital Metrology

Abstract Direct (forward) kinematic solution of the parallel robots is a challenging task for pure pose determination of the movable platform, which is crucial either in designing of the robot or its controlling. The availability of this solution is more critical especially in the case of using robot as a coordinate measuring machine (CMM). Solving direct kinematics (DK) problem of parallel robots is complicated as it is engaged with highly coupled nonlinear equations that are difficult to solve analytically to obtain exact answer. Hence in order to solve the mentioned problem, various approaches including empirical solutions e.g. using auxiliary sensors on the robot, neural network, and numerical methods are utilized. Meanwhile, numerical methods as the most cost-effective approach can acquire one unique accurate answer in a reasonable time. The aim of this article is to solve DK of a novel CMM parallel robot, which has three translational motions and a rotational around horizontal axis, using both analytical and numerical (Newton-Raphson scheme) approach along with comparing the results. After explaining the implementation procedure of methods according to the configuration of this robot, the results of simulations for both methods are presented and compared to each other. Moreover, inverse kinematics and direct kinematics are analyzed for the mentioned mechanism thoroughly. Results show that although analytical method gives more accurate answer especially for horizontal positions, numerical method solves the problem faster and also with acceptable accuracy.

Use of measuring gauges for in vivo accuracy analysis of intraoral scanners: a pilot study.

PURPOSEThe purpose of this study is to present a methodology to evaluate the accuracy of intraoral scanners (IOS) used in vivo.MATERIALS AND METHODSA specific feature-based gauge was designed, manufactured, and measured in a coordinate measuring machine (CMM), obtaining reference distances and angles. Then, 10 scans were taken by an IOS with the gauge in the patient's mouth and from the obtained stereolithography (STL) files, a total of 40 distances and 150 angles were measured and compared with the gauge's reference values. In order to provide a comparison, there were defined distance and angle groups in accordance with the increasing scanning area: from a short span area to a complete-arch scanning extension. Data was analyzed using software for statistical analysis.RESULTSDeviations in measured distances showed that accuracy worsened as the scanning area increased: trueness varied from 0.018 ± 0.021 mm in a distance equivalent to the space spanning a four-unit bridge to 0.106 ± 0.08 mm in a space equivalent to a complete arch. Precision ranged from 0.015 ± 0.03 mm to 0.077 ± 0.073 mm in the same two areas. When analyzing angles, deviations did not show such a worsening pattern. In addition, deviations in angle measurement values were low and there were no calculated significant differences among angle groups.CONCLUSIONCurrently, there is no standardized procedure to assess the accuracy of IOS in vivo, and the results show that the proposed methodology can contribute to this purpose. The deviations measured in the study show a worsening accuracy when increasing the length of the scanning area.

3D modeling and experimental investigation for tool deflection in end mill cutting of AISI 1045

The present paper investigates the tool deflection in three dimensions for two different tool diameters during end milling operation and validates the experimental findings with the finite element results. Cutting forces (i.e., radial cutting force, tangential cutting force, axial cutting force) exerted by the tool on AISI 1045 steel substrate under different combinations of cutting parameters (viz. feed rate, cutting speed and depth of cut) were measured using a dynamometer. For more accurate prediction of tool deflection using finite element analysis (FEA), the tool-workpiece contact region was sliced into small segments for the equal distribution of cutting forces. In order to verify the experimentally measured inaccuracy in the cut profile using a coordinate measuring machine (CMM) under different sets of parameters, the experimental results were compared with the predicted values of FEA. From the results, it was observed that the cutting forces were comparatively larger in magnitude for the larger tool diameter. Also, the depth of cut was found to be the most influential parameter among all, whereas the effect of feed rate and cutting speed on profile error was found to be insignificant. Further, the results show good agreement between the predicted FEA simulated tool defection and experimental values.

Development and Metrological Evaluation of a Force Transducer for Industrial Application

The present investigation reports the development of a force transducer for industrial applications with facile design and manufacturing objectives. The design of the force transducer is based on the analytical and computational approaches, followed by the experimental verification. Factors such as stress, strain and deflection of the force transducer were evaluated while conducting a rigorous assessment of the proposed force transducer. Al 7075 (T6) grade of aluminum alloy has been used as the material for fabrication of the force transducer with a nominal capacity of 2 kN. The fabricated force transducer as per the proposed design has also been investigated for geometrical and dimensional accuracy using precision coordinate measuring machine (CMM). Metrological characterization as per ISO 376: 2011 revealed that uncertainty of measurements is within 0.05 %, which includes relative uncertainty of the force transducer the factors such as repeatability, reproducibility, reversibility, interpolation, resolution, zero offset. Based on the above investigations, it has been found that the designed force transducer is of low cost ($ 200–$ 300), ease to manufacturing, and precise enough (0.05 % uncertainty of measurement) force transducer for force measurement up to 2 kN. The developed force transducer offers sensitivity up to of 0.2 N or better.

Towards the implementation of the Digital Twin in CMM inspection process: opportunities, challenges and proposals

The use of Digital Twin (DT) is adopted by manufacturers and have positive effects on the product manufacturing process. The aim of this paper is to define a Coordinate Measuring Machine (CMM) inspection DT model, based on inspection process digitalized functionalities, from one side, and Industry 4.0 opportunities (Digital thread, Big data, etc.), from the other side. A review about DT definition, is firstly presented. Secondly, we review related studies based on existing DT orientations and usages for CMM inspection. Thirdly, challenges related to the variation management are presented. Finally, a discussion about possible DT functionalities and opportunities is conducted then a CMM inspection DT model is presented.

Research on S-gear design, manufacturing and measuring based on NC machining center

This article presents a method of design, manufacturing, and measuring S-gear. S-gear is a kind of gear whose tooth profile is an S-shaped curve. The sine (cosine) gear, cycloid gear, polynomial gear, and circular arc gear are all S-gears in essence. In the S-gear transmission, the concave surface of one gear and the convex surface of the other gear contact each other. Therefore, the power transmitted by S-gear is much larger than that of the convex-convex-contact involute gear. Some scholars have studied the characteristics of S-gear, but few have explored its manufacturing. In this article, the Numerical Control (NC) machining technology of S-gear is studied in detail for its industrial application. The polynomial curve is used to construct the tooth profile of the S-gear based on the Gear Meshing Theory. The mathematical model of polynomial S-gear is established, by which involute gear can be represented as a special S-gear. The steps of generating NC codes are described. Then, the S-gear sample is processed with an NC machining center. Finally, the sample is measured with a Coordinate Measuring Machine (CMM), and the measurement results show that the accuracy of the S-gear processed by the NC machining center reaches ISO6. This research provides a feasible approach for the design, manufacturing, and measuring of S-gear.

On-machine measurement of geometrical deviations on a five-axis CNC machining centre

ABSTRACT Measurement of high precision components can be performed on-machine using a suitable measuring system or offline using a Coordinate Measuring Machine (CMM). The former approach is desirable, provided it yields reliable results. This paper presents the on-machine measurement of a high precision cylinder used in unmanned aerial vehicles (UAVs) with a contact-type CMM probe. The same component was measured offline on a CMM. The CMM data were used to verify the geometry fitting algorithms identified for the present work. The fitting algorithms were used for evaluating the required geometric deviations on the component based on on-machine measurement data. These values were compared with their corresponding values obtained from CMM software. The difference in geometric deviations obtained by the two approaches was found to be well under 5%. Hence, the proposed approach can be used for practical purposes.

Uncertainty assessment for measurement and simulation in selective laser melting: a case study of an aerospace part

<p class="Abstract"><span lang="EN-US">In this work, the additive manufacturing process selective laser melting is analysed with the aim of realising a complex piece for aerospace applications. In particular, the effect of the manufacturing process and of the following thermal treatments on the dimensions of the workpiece is evaluated. The study is based on a hybrid approach including a simulation of the whole manufacturing process by advanced software packages and the dimensional measurements of the realised pieces taken by a coordinate measuring machine (CMM). The integrated use of simulation and measurements is carried out with the aim of validating the simulation results and of identifying the operational limits of both approaches; this analysis is based on metrological evaluation of the results of both the simulation and the tests, taking into account the uncertainty of the data. In addition, the main causes of uncertainty for the simulation activity and the experimental data have been identified, and the effects of some of them have also been experimentally evaluated. Based on the experimental validation, the simulation seems to predict the absolute displacement of the supports of the piece in a satisfactory way, while it is unable, in the actual configuration, to assess the conformity of the surface to its very tight shape tolerances. Conformity assessment of the surface should be carried out by CMM measurement. Integrated use of simulation and experimental results is expected to strongly improve the accuracy of simulation results for the effective and accurate design and control of the additive manufacturing process, including dimensional control and thermal treatments to mitigate induced thermal stresses.</span></p>

Coordinate stitching measurement of highly steep freeform surfaces

A coordinate measuring machine (CMM) is widely used for surface measurement during milling and grinding of workpieces. However, the measurement uncertainty increases with the surface slope for highly steep freeform surfaces. In addition, local features sometimes exist on the surface out of the accessible space of the CMM. This study presents a coordinate measurement method based on stitching multiple subpatches. The complex freeform surface of a large slope is first divided into subpatches which are individually tilted and measured with smaller uncertainty due to reduced slopes. A global stitching algorithm is then proposed to compensate the motion error and stitch all the subpatches together simultaneously, based on configuration optimization to minimize the overlap inconsistency. The coordinate stitching measurement method is first validated through simulation, which shows that the motion error of the order of 0.05°/0.5 mm is tolerable for a highly steep surface. It is then experimentally verified using the stitching measurement of an optical spherical surface and a steep freeform surface. An ordinary multi-axis adjustment stage is suitable for subpatch repositioning because the stitching algorithm compensates the motion error to a level lower than the CMM uncertainty.

Deformation and Microstructural Analysis of Fiber Laser and TIG Welding of Thin Ti6Al4V Sheet by Coordinate Measurement Machine (CMM)

This paper reports on a study to compare the mechanical and deformation properties of Ti6Al4V titanium alloy joints between a pulsed fiber laser source and a tungsten inert gas (TIG) welding. Ti6Al4V alloy sheets - 0.8 mm thick-deformation modifications were investigated via a 3D laser scanner integrated to a portable-arm Coordinate Measurement Machine (CMM) and PC-DMIS software. Deformation pattern, residual distortions, weld geometry, microstructure and microhardnes properties of the joints produced with fiber laser source and tungsten inert gas welding were compared. Compared with the TIG, the welded by fiber laser has narrow heat affected zone (HAZ), small overall residual distortion, fine microstructure, high Vickers hardness. It can be concluded that fiber laser welding is more suitable for welding the thin Ti6Al4V titanium alloy plate than TIG welding; due to the small beam focus characteristics of fiber lasers enabiling deep penetration welding.

Towards quality analysis of MES through CMM data interoperation

The implementation of MBD/MBE (Model-based Design and Engineering) in the product design and manufacturing can effectively support multi-step data interoperation among “Design-Manufacture-Measurement.” Due to the limited data interoperation functions provided by the current CMM software (Coordinate Measurement Machine), most studies of MBD/MBE focused on designing the upstream. In contrast, the downstream (the underlying measurement data utilization) research is less. MES has an essential function in managing the manufacturing quality that analyses the condition and its development trend by collecting the manufacturing process quality data. Insufficient use of the underlying measurement data will lead to limited MES functions, especially for the capability of decision-making in intelligent manufacturing systems. The paper presents a measurement data interoperation method based on the interoperation layer method to support the quality analysis in MES (Manufacturing Execution System), discusses the relevant critical logic and data processing flow of the layer. It is verified that it can provide more comprehensive measurement data for quality management in the workshop.

Impact of thermal gradients on the geometry correction of a bridge coordinate measuring machine

If the problems related to the parts and measurement strategy of Coordinate Measuring Machines (CMMs) are not taken into consideration, temperature variations become the main source of measurement uncertainties. Indeed, they may cause variations in geometry as well as reference point drift. The effect of drift is sometimes minimized by CMM users and is not well quantified in general. The aim of this paper is to present a physical method to determine the evolution of CMM geometry and drift which is based directly on CMM temperature variations and construction parameters, i.e. the position of the axes measurement scales and reference points of each axis. The method is applied to a Zeiss CMM Contura G2. The consequences of these CMM evolutions are simulated in the measurement of a sphere generated by a Renishaw Machine Checking Gauge. The proposed method falls within the framework of an uncertainty assessment methodology performed by multi-level Monte Carlo simulation, where the first level corresponds to the characterization of the CMM evolution.

Path Planning and Setup Orientation for Automated Dimensional Inspection Using Coordinate Measuring Machines

Inspection planning is considered an essential practice in the manufacturing industries because it ensures enhanced product quality and productivity. A reasonable inspection plan, which can reduce inspection costs and achieve high customer satisfaction, is therefore very important in the production industry. Considerations such as preparations for part inspection, measuring machines, and their setups as well as the measurement path are described in an inspection plan which is subsequently translated into part inspection machine language. Therefore, the measurement of any component using a coordinate measuring machine (CMM) is the final step preceded by several other procedures, such as the preparation of the part setup and the generation of the probe path. Effective measurement of components using CMM can only be done if the preceding steps are properly optimized to automate the whole inspection process. This paper has proposed a method based on artificial intelligence techniques, namely, artificial neural network (ANN) and genetic algorithm (GA), for fine-tuning output from the different steps to achieve an efficient inspection plan. A case study to check and validate the suggested approach for producing effective inspection plans for CMMs is presented. A decrease of nearly 50% was observed in the travel path of the probe, whereas the CMM measurement time was reduced by almost 25% during the actual component measurement. The proposed method yielded the optimum part setup and the most appropriate measuring sequence for the part considered.

Pose calibration of line structured light probe based on ball bar target in cylindrical coordinate measuring machines

Non-contact measurement has shown great advantages in term of high efficiency measurement. In order to obtain the 3D point cloud efficiently, line structured light probe has been widely used in coordinate measurement machine, which is mounted on the end of the motion axis. However, the installation errors of the probe seriously affect the measurement accuracy. Hence, probe pose error compensation is essential. In this paper, a novel calibration method is proposed to compensate the installation errors. First, the system transformation relationship between the probe coordinate system and the workpiece coordinate system is established. Then, the probe pose is calibrated in the cylindrical coordinate measuring machine. The ball bar is adopted instead of a single sphere to avoid no solution of the probe pose in cylindrical coordinate measuring machines. After obtaining the initial value, an optimal multi-objective function is constructed to optimize the pose errors and sphere centers. The proposed method is easy to operate and has high accuracy which is evaluated in a set of experiments.

Wear and damage in retrieved humeral inlays of reverse total shoulder arthroplasty-where, how much, and why?

Polyethylene (PE) wear and material degradation have been reported as complications in reverse total shoulder replacements (rTSAs). In this regard, scapular notching is associated with more clinical complications. Therefore, the purposes of the study were to quantify the linear and volumetric wear, as a measure for the amount of removed material, and to qualitatively assess the PE damage modes to describe the material degradation in retrieved rTSA humeral PE inlays that contribute to failure of shoulder replacements. Furthermore, this study aimed to evaluate the effect of scapular notching on PE wear and rim damage of the humeral components. The total study population of 39 humeral inlays contains 2 cohorts that were used for the damage mode analysis and for the wear analysis, respectively. The extent and presence of wear damage modes in 5 defined zones were assessed by a grading system for all PE joint replacements. For quantitative wear analysis the most frequent design (n = 17) was chosen. Using a coordinate-measuring machine and postprocessing software, volumetric wear measurements for the retrieved humeral PE inlays were undertaken. Furthermore, prerevision radiographs were analyzed for scapular notching. Finally, retrieval findings were correlated with clinical and radiographic data to consider the effect of notching and to identify risk of failures for these prostheses. Damage on the rim of the humeral PE inlays was more frequent and severe than on the intended articulation surface. Irrespective of the damage mode, the inferior rim zone sustained the greatest amount of wear damage followed by the posterior zone. Burnishing, scratching, pitting, and embedded particles are most likely to occur in the articular surface area, whereas surface deformation, abrasion, delamination and gross material degradation are predominantly present in the inferior and posterior rim zones. The retrieved inlays exhibited a mean volumetric wear rate of 296.9 mm³/yr ± 87.0 mm³/yr. However, if the notched and non-notched components were compared, a significant higher volumetric wear rate (296.5 ± 106.1 mm³/yr) was found for the notched components compared to the non-notched group (65.7 ± 7.4 mm³/yr). Generally, there was a significantly greater incidence of damage and greater amount of wear if scapular notching occurred. The notched components showed a 5-fold increase in PE wear rate. Therefore, scapular notching has a strong effect on PE damage and wear. If scapular notching can be clinically avoided, the PE wear performance is in a similar magnitude as found for hip and knee replacements.

Portable Hybrid Refrigerator Prototype for Agribusiness With Its 3D Real Physical Geometry Scanned and Transferred for Simulation Software

A methodology that starts from the acquisition of real prototype geometries up to simulations to evaluate parameters, improvements, or performance under various conditions is proposed. The authors show a case study of a refrigerator with storage capacity for 50 kg of fruit solar-powered by photovoltaic panels, which reach a temperature of about 4°C. The refrigerator comprises two systems, vapor-compression, and Peltier. The methodology consisted of acquiring by a 3D laser scanner or coordinate measuring machine (CMM) and in some small complex items using 3D photogrammetry scanner. These data were transferred first as a CAD or solid works geometry and subsequently transferred to domains geometry useful for ANSYS or COMSOL simulation software. These models with high-resolution bring the simulations closer to real prototypes. Wireless sensors were installed for temperature and humidity monitoring. The analyses of the energy efficiencies of the prototype were performed. The photovoltaic system was for use in crop areas where there was no access to the urban electric network.