Analysis of laser scanning and strategies for dimensional and geometrical control (original) (raw)

Comparison between non contact and contact scanning systems for dimensional control

In the last years, the presence of non contact scanning systems has increased continuously in the industry. The main reason is that these systems lead to an important reduction in the inspection time and consequently a reduction in manufacturing costs while maintaining quality levels. The advantages of these systems are well known, such as the high speed data acquisition and the high number of captured points. However there exist some disadvantages, like the poor (undefined) accuracy when comparing with traditional touch trigger probe inspection systems. For this reason, scanning systems are mainly used in Reverse Engineering, heritage conservation or multimedia applications (movies, video games, etc.). In metrological applications, their validity has not been tested, in terms of geometric and dimensional tolerance control and accuracy. This work deals with this problem, performing a comparison between two scanning systems. To carry out this comparison, a laser triangulation sensor ...

Method for analyzing probe scanned surfaces

Probe scanning is widely used in modern dental industry, which is why it is important for the scanning process to be accurate for both hardware and software. Due to the wide range of scanner manufacturers with different types of surface registration algorithms it is of interest to in an analytical way evaluate the successfulness of the scanning. If the surface is registered in a successful way it also increases the probability of fortunate reengineering of the intended object based on the scanning. The rationale of the study is that a well represented scanning result is essential for the manufacturing, internal fit and strength of a coping. The purpose of this paper is to propose a general method that enables analysis of the successfulness of the representation of probe scanning, and an optimization of the scanning. Twenty-four scans of a premolar preparation die were made in order to demonstrate the cause and effect relationship between alignment, central revolution axis of the probe and the representation of the result. Three scans were made for each of 8 alignments of the die. First the central revolution axis of the scanner was set in the concavity between the 2 convexities of the die. In the second scan, the central revolution axis of the scanner was set slightly to the left of the higher convexity of the die. For the third scan, the central revolution axis was set on the maximum of the higher convexity. The fundamental idea of the method is that, by confining a triangulated surface representation, from the scan and the scanned object, to surfaces based on the probe tip geometry, a value for the accuracy of each triangle can be determined. When the position of the central revolution axis and the alignment were optimized the poor areas with a predefined tolerance between 0.05 mm and 1.25 mm than were reduced by a factor of 14. By optimizing scanning, better scan results can be achieved, which is desirable for the internal fit, strength and manufacturing of the coping.

Automated dimensional inspection planning using the combination of laser scanner and tactile probe

Measurement, 2012

Combining multiple sensors on CMMs (Coordinate Measuring Machines) is useful to fulfill the increasing requirements on both complexity and accuracy in dimensional metrology. Yet, the methodology to plan measurement strategies for systems combining different types of sensors is still a major challenge. Such planning is commonly done in an interactive way. This paper presents a methodology which can create inspection plans automatically for CMM inspection combining a touch trigger probe and a laser scanner. The inspection features are specified based on the extracted geometry features and the associated PMI (Product and Manufacturing Information) items from a CAD model. A knowledge based sensor selection method is applied to choose the suited sensor for each inspection feature. For touch trigger measurements, the sampling strategy considers the measurement uncertainty calculated by simulation. A geometry-guide method is developed for collision-free probing path generation. For laser scan measurements, the required view angles and positions of the laser scanner are determined iteratively, based on which the scan path is generated automatically. The proposed methodology is tested for several cases and validated by measurement experiments. The methodology provides suited planning results and can be used for automated dimensional inspection, i.e. Computer Aided Quality Control (CAQC). Highlights  We develop an inspection planning system for CMM measurements  Laser scanner and tactile probe are combined in that system  CAD model is used to guide the inspection planning for each inspection feature  Inspection path is generated automatically for both sensors *Highlights

A Uniform Approach for Utilizing Synergy between Inspection Technologies and Computational Methods

Cirp Annals-manufacturing Technology, 2006

Emerging scanning technologies currently capture diverse data that includes geometrical and physical properties (i.e. normals, material and color). Yet, existing inspection computational methods do not satisfy industry demands. This paper proposes a new approach for inherently handling diverse data and utilizing the synergy between inspection technologies and digital processing methods. Two methods were developed: a Hierarchical Space Decomposition Model (HSDM), which sorts the sampled data, and a 3D Geometrical Bilateral Filter (3D GBF) that utilizes the diverse data. These methods provide efficient data reduction while preserving sharp features. The feasibility of this approach is demonstrated on the diverse data.

Non-contact whole-part inspection

Recent advances in optical scanning devices enable us to collect millions of sample points of reasonable individual accuracy on a part to be inspected. There are obvious advantages of non-contact inspection methods: speed, coverage, ease of operation, price, etc. One may ask why non-contact methods are not even more widespread in dimensional measurement. In fact the automatic extraction of actual dimensional and GD&T values from non-contact measurement data is not an easily repeatable and reproducible procedure. What is the reason for this?

The Usage of Mobile Laser Scanning in Detail Visual Inspection

2020

The Detailed inspection (DET) in general represents an intensive examination of a specific item, installation or assembly to detect damage, failure or irregularity. The Detailed Visual Inspection (DVI) detects measured areas or lengths for a wider range of more closely defined defects on the road. The maximum length that can be recorded depends on the cross-section position method that is being used. The linear defect is considered for length larger than 1m, while the area defect is considered for the area larger than 0.1m 2. There is a wide range of types of defection. For example, major and minor fretting, cracking, chipping loss, local settlements, transverse joint cracking, joint faulting, loss of texture, patching, etc. For successful conduction of detail visual inspection, the highly precise and accurate spatial data are required. The most often used technology is one of the laser scanning aero, mobile or terrestrial.

Target Validation and Image Calibration in Scanning Systems

1st International Conference on Image Processing and Pattern Recognition (IPPR '13), 2013

One of the directions for paper document conservation is conversion to microfilms and scanned images. Since recently microfilming has been abandoned over digitization, there is a need for standards and guidelines for the conversion workflow. The article proposes a set of methodologies for calibrating scanning systems to ensure high quality reproduction of both microfilms and original paper prints, in terms of tonal reproduction, geometric distortion and image sharpness.

Measurement Improvement and Optimization Using Scanning Technology at SAAB AB, Linköping

2010

This master thesis is a development project that is carried out for process improvement and automation for the measurement equipment at "SAAB AB", Linköping focusing on several sections including sheet metal, welding and pipe bending sections. Those are the core sections of the manufacturing of the latest fighter systems from "SAAB AB" such as Gripen, Neuron (unmanned aircraft) and other development projects. SAAB AB has the following issues:  Setup time of different parts in the specified departments is higher for the quality checking.  The quality inspection of different parts is manual and takes much time.  Use of scanning technology to reduce inspection time and increase reliability. The writers of the research work has done a comprehensive investigation and critical analysis of the current condition of the specified departments of "SAAB AB" and made a research work on how to make the process more efficient by implementing automation especially with the use of scanning technology and reduce the huge development cost.

Possibilities of Using Three-Dimensional Optical Scanning in Complex Geometrical Inspection

Strojniški vestnik – Journal of Mechanical Engineering, 2011

Non-contact optical three-dimensional measuring, scanning and digitising are increasingly present in quality assurance systems. Simple scanning procedures, high density of data acquired in a single scan, and the possibility of integrated reverse engineering and inspection, are all advantages of optical scanning compared to conventional measuring methods. Due to the three-dimensional acquisition of measuring data, an optical scanner is often considered to be an alternative possibility for coordinate measuring machines. However, the accuracy of the measured data acquired by optical scanning (even with a high-end system) is still far below the level achieved by high-level coordinate measuring machines. This paper examines the possibilities of using a three-dimensional scanner for workpiece inspection. The first part presents a special field of workpiece inspection in which, even with currently achievable accuracy, optical scanning is a viable solution for the inspection of manufactured parts. In addition, the achievable dimensional accuracy of an optical scanner is tested by scanning several gauge blocks. In conclusion, a head to head comparison with a coordinate measuring machine is made by scanning and verifying a sphere.

Analysis of the Possibilities of Using Low-Cost Scanning System in 3D Modeling

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016

The laser scanning technique is still a very popular and fast growing method of obtaining information on modeling 3D objects. The use of low-cost miniature scanners creates new opportunities for small objects of 3D modeling based on point clouds acquired from the scan. The same, the development of accuracy and methods of automatic processing of this data type is noticeable. The article presents methods of collecting raw datasets in the form of a point-cloud using a low-cost ground-based laser scanner FabScan. As part of the research work 3D scanner from an open source FabLab project was constructed. In addition, the results for the analysis of the geometry of the point clouds obtained by using a low-cost laser scanner were presented. Also, some analysis of collecting data of different structures (made of various materials such as: glass, wood, paper, gum, plastic, plaster, ceramics, stoneware clay etc. and of different shapes: oval and similar to oval and prism shaped) have been done. The article presents two methods used for analysis: the first one-visual (general comparison between the 3D model and the real object) and the second one-comparative method (comparison between measurements on models and scanned objects using the mean error of a single sample of observations). The analysis showed, that the low-budget ground-based laser scanner FabScan has difficulties with collecting data of non-oval objects. Items built of glass painted black also caused problems for the scanner. In addition, the more details scanned object contains, the lower the accuracy of the collected point-cloud is. Nevertheless, the accuracy of collected data (using oval-straight shaped objects) is satisfactory. The accuracy, in this case, fluctuates between ± 0,4 mm and ± 1,0 mm whereas when using more detailed objects or a rectangular shaped prism the accuracy is much more lower, between 2,9 mm and ± 9,0 mm. Finally, the publication presents the possibility (for the future expansion of research) of modernization FabScan by the implementation of a larger amount of camera-laser units. This will enable spots the registration , that are less visible.