Shape Inspection Research Articles

Effect of the long-term storage methods on the stability of cartilage biomechanical parameters

Long-term stability of the tissue product in terms of mechanical parameters is a key factor for its expiration date. For the investigation of storage effects on the cartilage tissues the experimental mechanical loading test combined with XCT scanning for the irregular shape inspection was performed. The samples were preserved according to three different protocols using the deep-freezing and two types of saline solution preservation. The stability of the biomechanical parameters was tested within annual intervals. All samples were subjected to uni-axial compression loading using the in-house developed compact table top loading device in displacement-driven mode. Based on the measurements, the results are represented in the form of stress-strain curves and quantified as elastic modulus and ultimate compression stress. It can be concluded that no significant difference was found in neither the mechanical properties of the samples nor in the effects of each preservational method.

Feature shape inspection of metal parts by matching X-ray projection images with CAD model projections

X-ray computed tomography (CT) provides a three-dimensional (3D) volume image of the scanned object and can be applied for nondestructive inspection of industrial materials. The object surface extracted from the X-ray CT volume is examined by comparing it with the pre-obtained computer-aided design (CAD) mesh model of the scanned object. However, industrial materials often contain heavy metals that significantly attenuate X-rays and cause CT artifacts in CT images, preventing an accurate shape extraction. This study proposes a method that extracts the geometric features of two-dimensional (2D) X-ray projection images and matches them with pre-obtained 3D CAD meshes. The proposed method is based on the principle that most of the geometric features of the object, such as edges, in the X-ray 2D projection images are captured and can be directly compared with CAD meshes. We first extract the features in each of the 2D projection images as X-ray feature projections. Subsequently, CAD mesh contours are projected onto 2D mesh feature projections and matched with the X-ray feature projections. Finally, 3D feature shapes of the CAD mesh are obtained by back-projecting the matching results. The proposed method requires only a small number of projection images, thus reducing computational time while maintaining shape accuracy.

UAV-based bridge geometric shape measurement using automatic bridge component detection and distributed multi-view reconstruction

UAV cameras combined with image-based reconstruction are promising non-contact tools for bridge shape inspection while computational efficiency is low, particularly on large-scale image sets. This paper describes an efficient image-based reconstruction pipeline for bridge geometry measurements. A full bridge three-dimensional reconstruction task is decomposed into multiple distributed tasks of reconstructing bridge sub-models using sub-image sets. A deep learning-based object detection method combined with Euclidean clustering is proposed to automatically generate cropped sub-image sets. An image mask generation technique based on 3D-to-2D mesh projection is used to keep valid pixels for camera pose estimation. The proposed method was validated in a laboratory test for arch shape measurement and in a field test for suspension cable shape measurement. The results show significant improvement about computational efficiency without accuracy reduction, compared with conventional image reconstruction methods.

Matching of CAD model projections and X-ray projection images for shape inspection of metal assemblies

X-ray computed tomography (CT) facilitates non-destructive inspection of the interior of mechanical assemblies. However, industrial materials often contains heavy metals; which causes in CT artifacts in CT images and prevents accurate segmentation or shape measurement. To overcome this issue, in this study, we proposed a new inspection method that uses X-ray projection images and CAD meshes. We extracted characteristic features as edges and curved surfaces as feature images and used those for component alignments and shape measurements. The idea behind this is that these characteristic 3D features are captured as crease pixels in 2D projection images; thus, they can be extracted and compared with CAD meshes directly without conducting actual CT reconstructions. Furthermore, we conducted preliminary tests with some metal parts, which indicated that our approach can effectively inspect multi-material mechanical assemblies.

In-line quality control utilizing close-range photogrammetry and a CAD-model

This paper presents an overview of a measurement system that is designed for in-line shape inspection of metal sheet components in real-time utilizing pre-calibrated close-range photogrammetry and a CAD-model. The system is currently designed to measure parts thrown out on a conveyor belt that moves at about 1 m s−1 at a frequency of 0.5 Hz or less without fixturing. Detected features on the components in the camera images are used to align the CAD-model, describing the nominal shape, to the images from which required deviations are computed using photogrammetry. The measurement volume of the current system is 500 × 800 × 200 mm3 and absolute measurements are performed with an accuracy in the order of 0.1 mm. The in-line functionalities of the system have been verified at several real production sites in Sweden. In this paper, the basic components of the system are described together with a few results from real tests.

YAG Laser Rod 3D Corrective Process Optimization through Tool Influent Function Shape Inspection

Due to the increasing demands on the quality of solid-state laser active media production based on yttrium aluminum garnet Y3Al5O12 in the form of rods with precisely machined faces, the possibilities of applying subaperture 3D corrective polishing in this segment of optical production were studied. For the considered laser rod diameters of up to 10 mm, the corrective process had to be optimized to achieve a stable, suitably shaped tool influence function at the full width at half maximum of approximately 1.5 mm, enabling 3D shape corrections with sufficient lateral resolution. For this purpose, a number of experiments were performed using both tools based on a flexible elastic membrane inflated by compressed air and tools with a viscoelastic head, and the effect of the tool-polished surface interaction was studied and analyzed.

A Statistical Approach to Three-Dimensional Shape Inspection of Micro-Solder Balls

This article presents an optical technique for the three-dimensional (3D) shape inspection of micro-solder balls used in ball grid array (BGA) packaging, before attaching them to a board or film. This technique uses an optical source comprising spatially arranged light-emitting diodes (LEDs), and the results are derived based on the specular reflection characteristics of the BGA balls. A vision system is designed to acquire the reflected image from the micro-solder balls. For shape inspection, the locations of the LED point-light-source reflections are determined via image processing, and defects in 3D BGA shapes are detected using statistical information of the relative positions of multiple BGA balls captured in the images. Experiments were conducted to validate our proposed method, and the results revealed that it allows for simultaneous inspection of multiple BGA balls placed arbitrarily in a glass dish, without the need for precise ball-position control.

Shape distortion analysis of drawing die by optical 3D scanning

The contribution dealing with analysis of drawing die shape distortion using optical 3D scanning. The wear of drawing die has a significant influence on the shape stability of the produced tubes. Early identification and determination of wear on the drawing die leads to elimination of production errors. Metrological measuring systems can be used to analyse shape distortion. The optical 3D scanner GOM ATOS II TripleScan SO MV170 (measuring volume: 170 × 130 × 130 mm; camera resolution 2448 × 2050 px (5 Mpx); measuring point distance: 0.07059 mm) was used for experimental measurement of drawing die. The 3D scanned weared drawing die was compared with the reference CAD model. The result of the comparison is the colour deviation map of drawing die’s shape and various inspection sections.

Inspection behaviour and inter-individual cooperation in juvenile qingbo: the effects of prior predator exposure and food deprivation

The predation pressure and food availability to which individuals are exposed during their life histories shape inspection behaviour in animals. In this study, we aimed to test whether such behaviours varied with prior experience (predation, starvation or both treatments) or measurement condition (with or without the presence of a predator; here, the snakehead fish, Channa argus) in the fish species Spinibarbus sinensis, known as qingbo. Unexpectedly, prior predator experience showed no significant effect on inspection behaviour as demonstrated by either the frequency or the duration of each activity outside shelter or on cooperation as demonstrated by the inter-individual distance or synchronization of speed. This may have been due to the different adjustments in behaviour among individuals (more shelter use vs. more inspection), the predator treatment used in the present study (exposure to caged predator rather than direct predation) and/or a species-specific strategy in the qingbo. The starved fish displayed shorter inspection latency, increased inspection behaviour and greater cooperation when measured without the predator; however, when measured in the presence of the predator, the starved fish showed increased inspection frequency but shorter inspection duration, possibly due to the compromise between energy needs and predation risk. Similar to those of the predation group, the fish from the double-treated group showed no difference in inspection behaviour compared to the control group under the predator-absent condition, while the high-frequency, short-duration inspection behaviours remained the same as in the starved group. These findings suggested that the adjustment of inspection behaviour and related cooperation are rather complicated according to either predator experience or food deprivation, partially due to the inter-individual differences in behavioural adjustment and/or different environmental conditions.

Impact of Applied Anti-Reflective Material on Accuracy of Optical 3D Digitisation

Using optical 3D digitisation for dimensional and shape inspection of work-pieces became a trend recently. Before a 3D scanning process starts, surface of the measured part must usually be coated with a thin layer of anti-reflective material. Such surface coating can be performed by means of a wide range of products with various composition and application method. It is however important to know how the matt coating affects the quality and accuracy of digitization, what the structure and thickness of a coating are. The thickness of a coating may vary significantly from product to product and according to our research, it ranges between units and hundreds of µm. This article presents results of an extensive research of seven matt coating products commonly used in practice. The measurement was carried out on cylindrical and spherical elements using ATOS optical 3D scanner and an electron microscope. Thereafter, the measurement results were analysed to define how the applied coating product along with the material of measured object affect the work-piece dimensional properties. The ease of coating removal was evaluated in the research as well.

Development of Bolt Tap Shape Inspection System Using Computer Vision Technology

컴퓨터 비전 기술은 인공지능의 한 분야로 인간의 눈의 기능을 기계가 수행 할 수 있도록 카메라로부터 영상 이미지 를 취득하고, 알고리즘을 통하여 분석하고 판별한 후 생산부품의 양품과 불량을 판별하는 부품 검사에 많이 적용되고 있다. 볼트 생산 시스템에서 생산되는 볼트 탭의 유무를 컴퓨터 비전 기술을 적용하여 자동으로 불량품을 선별하는 장치를 개발하 였다. 형상검사 방법으로는 라인 스캔방식으로 검사영역의 시작점과 끝점의 위치를 파악하여 높이를 측정하는 방법을 사용 하였으며, 볼트 탭의 유무를 판별하기 위한 방식으로는 원형 스캔방식으로 검사영역의 평균 밝기 값의 차이를 측정하여 유 사도를 구하는 방식을 사용하였다. 두 종류의 볼트 탭의 검사 성능실험에서 총 검사에 소요되는 시간은 분당 300개 검사가 가능하며, 완벽한 검사 정확도를 나타내어 생산라인에서 검사의 정확성과 효율성을 입증하였다.

Virtual projective shape matching in targetless CAD-based close-range photogrammetry for efficient estimation of specific deviations

A concept for targetless, computer-aided design (CAD)-based, close-range photogrammetry for online shape inspection is introduced. The shape of an object, which is arbitrarily located on a conveyor belt, is to be measured and compared with its nominal shape as defined by a CAD model. For most manufactured objects, deviations are only measured at a few given comparison points. These deviations can be estimated using local photogrammetry based on a priori geometrical information given by the CAD model and the comparison points. Our method results in faster output with higher precision, because we do not generate a shape representation of the entire measured object using typical photogrammetric methods. Images depicting the object from convergent angles are captured by an array of cameras in a precalibrated network, and the CAD model is matched and aligned, within the projective geometry of the camera network, to the depicted object in the images without the use of targets. An algorithm for solving this virtual projective targetless shape matching problem is presented.

Shape Inspection of Gear Prototypes Using Reverse Engineering Method

Reverse engineering is a technology that enables acceleration of data collecting for CAD, CAM, CAE systems, which also means shortening time of development, construction and components production. It is a transfer process of a physical component to a digital format. Generally, the technology of reverse engineering means a conversion of analogue data to digital data that are further processed. Every single industry branch rising their requirements on accuracy, dimension, quality, etc. Therefore, digitisation is applied in many production fields such as an automotive industry, aircraft or shipping, medicine, industrial design, design, etc.An article deals with an analysis of prototype models of gears in various stages of production. The realized inspection of a shape of prototype gears lied in uploading of a digitised referential CAD model (the gear after heat treatment and machining), subsequent setting up of digitised prototype gears (the gear after the machining, gear after heat treatment) in respect of this referential CAD model, a control of their dimensions and forming a colour map of deviations in chosen points.

DIMENSIONAL VERIFICATION AND QUALITY CONTROL OF IMPLANTS PRODUCED BY ADDITIVE MANUFACTURING

Purpose: Development of computer technology and alternative manufacturing methods in form of additive manufacturing leads to the manufacture of products with complex shapes. In the field of medicine they include, inter alia, custom-made implants manufactured for a particular patient, such as cranial implants, maxillofacial implants, etc. With regard to the fact that such implants are inserted into a patient’s body, it is necessary to perform the verification, including the shape and dimensional verification. The article deals with the application of the industrial computer tomography within the process of inspection and verification of selected custom-made implant types. Methodology/Approach: The Department of Biomedical Engineering and Measurement performs the verification of medicinal products manufactured by the additive manufacturing technologies from the Ti-6Al-4V (Grade 5) titanium alloy, using the coordinate measuring machine Carl Zeiss Contura G2 and the industrial computed tomography machine Carl Zeiss Metrotom 1500. These equipment fulfil the requirements for the identification and evaluation of dimensions of both, the external and the internal structures. Findings: The article presents the possibilities of the computed tomography utilisation in the inspection of individual implant manufacture using the additive manufacturing technologies. The results indicate that with the adjustment of appropriate input parameters (alignment), this technology is appropriate for the analysis of shape deviations, when compared with the CAD model. Research Limitation/implication: With the increasing distance of measured object from X-ray source, the machine’s resolution function decreases. Decreasing of resolution has a minor impact on the measured dimensions (relatively high tolerances), but has a significant impact on the evaluation of porosity and inclusions. Originality/Value of paper: Currently, the verification of a manufactured implant can be carried out using 3D scanners and the industrial computed tomography. The use of 3D scanners is appropriate for the shape inspection, for example the shape of an implant’s outer surface. The computed tomography is the only method for evaluation of shape deviations, defectoscopy and dimensional analysis in one measurement.

Feature Extraction Based 3D Model Registration for Surface Finish Quality Evaluation

Engineers and designers constantly strive to design machines that have high life cycle, can run faster, and can manufacture products having higher geometrical accuracy. However, manufacturing processes often produce parts with surfaces that are unsatisfactory from the viewpoint of geometrical precision or quality of surface texture. In general, electronic, optical, and tactual methods are used for exploring and evaluating the surface texture and the surface geometry. With the advancements in the reverse engineering technology, computer based numerical analysis of the data obtained from 3D imaging devices, referred to as registration, has also emerged as a tool for shape inspection. Registration expedites shape inspection by augmenting the process of error measurement. The existing registration methods suffer from problems that limit the extensive use of the existing approaches, thereby making them application specific. In this research, we propose a novel approach for reducing the number of data points used for registration without compromising with registration accuracy. We propose a segmentation based registration approach that utilizes the features extracted from the models, thus reducing the data size. The registered data sets can be compared to each other for evaluating the differences in shape. The difference information can further be used to appropriately modify the manufacturing process parameters for obtaining highly accurate products.

Shape reconstruction and inspection using multi-planar X-ray images

Computer-aided manufacturing is widely used to create products from computer-aided design (CAD) models. The different characteristics of each manufacturing process can lead to product defects. Therefore, it is necessary to inspect the shape and dimensions of a manufactured product against the original CAD model for quality assurance. While the conventional laser-based three-dimensional (3D) scanning allows reconstruction of the external shape of an object, X-ray imaging can capture the internal shape. Aided by digital radiographic techniques, X-ray images can be captured within a few milliseconds. In this study, we used multiple X-ray images of an object to reconstruct its geometry and topology. Each of the two-dimensional (2D) X-ray images was processed to detect object edges. Using the geometric calibration information of the X-ray imaging system, the 3D vertices of the object were reconstructed. The topology, edges connecting vertices, was reconstructed by re-projecting the vertices to the X-ray images. The reconstructed object shape was statistically analyzed to understand the effects of the number of views and the parameters used in the reconstruction process on the accuracy of the reconstructed geometries. For our target objects, images from more than seven different views were used to successfully reconstruct the full shape of the object.

Image analysis algorithm and verification for on-line molecular sieve size and shape inspection

An online machine vision inspection method is proposed to implement feedback control of molecular sieve growth process in rotary drum granulation. An experimental platform, comprising of a high-resolution digital camera and an image analysis system, has been developed to confirm the validity of the method on particle size distribution (PSD) and sphericity measurements. Experiments were performed with non-uniform molecular sieve particles (1–3mm diameter) obtained from production line. The particle images are first obtained through digital camera and are then processed by image analysis system. After separating the overlap particles and removing non-target particles of the images, the molecular sieve size and shape are computed in less than 0.9s. The validity of the size measuring accuracy is confirmed through comparing with the results from micrometer. The experimental results show that the repetitive precision of the proposed inspection system is about±1%, the diameter measurement error between image method and micrometer is about±3%, single image inspection speed is around 0.9s/frame. The proposed method is reliable to provide feedback information for control system in rotary drum granulation.

Blade Blending and Torsion Deformation Analysis Based on its Coordinate Measurement Data

Blade is one of the most important components of an aero engine; its geometric shape should be inspected carefully in the production stage to ensure that it satisfies the tolerance specification. Blending and torsion deformation are basic items of blade geometric shape inspection. Coordinate Measurement Machine (CMM) has been widely used to perform the blade geometric shape measurement. Some sampling strategies for blade CMM measurement are discussed and one kind of blade blending and torsion deformation calculation method considering the CMM probe radius compensation is presented. Experiments based on simulation data and real measurement data are performed to verify the adopted sampling strategy and deformation calculation method.

3D Ship Shape Inspection Approach using Laser Vision Systems for Automatic Ship Loader

3D Ship Shape Inspection Approach using Laser Vision Systems for Automatic Ship Loader

Output-only modal parameter identification for force-embedded acceleration data in the presence of harmonic and white noise excitations

Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.