Dissertationen zum Thema „Portable coordinate measurement machines“

This study analyzes current trends in metrology in the field of portable coordinate measuring machines and describes current methods for measurement system and process evaluation. Obtained knowledge is applied, in order to evaluate the capability of measurement system, which consists of articulated measurement arm and measurement standard.

Precision measurement of manufactured parts commonly uses contact measurement methods. A Coordinate Measuring Machine (CMM) mounted probe touches the surface of the part, recording the probe’s tip position at each contact. Recently, devices have been developed that continuously scan the probe tip across the surface, allowing points to be measured more quickly. Contact measurement is accurate and fast for shapes that are easily parameterized such as a sphere or a plane, but is slow and requires considerable user input for more general objects such as those with free-form surfaces. Phase stepping fringe projection and photogrammetry are common non-contact shape measurement methods. Photogrammetry builds a 3D model of feature points from images of an object taken from multiple perspectives. In phase stepping fringe projection a series of sinusoidal patterns, with a phase shift between each, is projected towards an object. A camera records a corresponding series of images. The phase of the pattern at each imaged point is calculated and converted to a 3D representation of the object’s surface. Techniques combining phase stepping fringe projection and photogrammetry were developed and are described here. The eventual aim is to develop an optical probe for a CMM to enable non-contact measurement of objects in an industrial setting. For the CMM to accurately report its position the probe must be small, light, and robust. The methods currently used to provide a phase shift require either an accurately calibrated translation stage to move an internal component, or a programmable projector. Neither of these implementations can be practically mounted on a CMM due to size and weight limits or the delicate parts required. A CMM probe consisting of a single camera and a fringe projector was developed. The fringe projector projects a fixed fringe pattern. Phase steps are created by moving the CMM mounted probe, taking advantage of the geometry of the fringe projection system. New techniques to calculate phase from phase stepped images created by relative motion of probe and object are proposed, mathematically modelled, and tested experimentally. Novel techniques for absolute measurement of surfaces by viewing an object from different perspectives are developed. A prototype probe is used to demonstrate measurements of a variety of objects.

Thesis (PH.D.)--Michigan State University. Electrical and Computer Engineering, 2008.
Title from PDF t.p. (viewed on Aug. 11, 2009) Includes bibliographical references (p. 118-121). Also issued in print.

The advent of the industrial revolution has brought a great number of changes in the functioning of various processes in manufacturing industries. The ways and means of working have evolved exponentially with the implementation of advanced technology. Moreover, with the increasing technology, the customer demands have also been varying dynamically due to changes in customer requirements focusing on individual customization. To cope with the dynamic demand, manufacturing industries had to make sure their products are manufactured with higher quality and shorter lead times. Implementation and efficient usage of technology has provided industries with the necessary tools to achieve market demand and stay competitive by growing continuously. The transformation aims to reach the level of zero-defect manufacturing and ensure higher first-time right yield capability with minimum utilization of available resources. However, technological advancements have not developed the quality inspection process of the manufacturing industry at the same level as other processes. Due to this, the quality inspection processes are still human dependent which requires a highly skilled human operator to perform inspection procedures using sensory abilities to detect deviations. Research suggests that human quality inspection is prone to errors due to fatigue as the process is continuous, strenuous, and tedious work. The efficiency of human inspection is around 80% which becomes a chronic problem in safety-critical and high-value manufacturing environments. Moreover, with the increasing level of customization and technology, the products are becoming more complex with intricate shapes and only human inspection is not enough to meet the customer requirements. Especially in the case of automotive industry in Body in White applications, human inspection of outer body panels, engine parts with tighter tolerances alone does not make the cut. Advancements in the field of metrology have led to the introduction of Coordinate measuring machines (CMM), which are classified as contact and non-contact measuring machines. The measurements are performed offline away from the production line, using the sampling method. The contact measuring machines are equipped with touch trigger probe devices that travel all over the part to make a virtual image of the product which is time-consuming but accurate. Whereas the noncontact measuring machines are equipped with laser scanners or optical devices which scan the part and develop a virtual model which is fast but has accuracy and repeatability issues due to external factors. But coordinate measuring machines have proven to be bottlenecks as they were not able to synchronize with the production pace and could not perform aninspection on all the produced parts, which would help in collecting data. The gathered data can be used to analyse root causes and generate trends in defect detection. With the advancements in non-contact measuring systems, automotive industries have also realized the potential of implementing inline measurement techniques to perform quality inspection. The non-contact measuring system consists of a robotic arm or setup which is equipped with a camera, sensors, and a complex algorithm to identify defects. This provides the robotic arm with machine vision which is works by taking a series of images of the product from various and process these images to detect deviations using digital image processing techniques. The inline measurement has proven to be accurate, fast, and repeatable to be implemented in synchronization with the production line. Further, the automotive industries are moving towards hybrid inspection systems which capitalize on the measuring speed of the robot and the fast decision-making ability of human senses.

This master thesis deals with the use of measuring stations in an automatic machining lines. An overview of the methods of measuring engineering products in engineering practice with a focus on automation of measurement is described. The basic principles of function of these machines, their construction and materials are described. The largest part describes coordinate measuring machines, which continue to evolve and offer more and more possibilities for automatic measurement. The practical part is aimed at documenting the sample situation of measurements on this type of equipment and evaluating the possibility of its integration into the automatic machining line.

This diploma thesis deals with the proposal of internal methodology for measurement of products and parts on CMM UPMC Zeiss at CMI Brno. The first part of this work analyzes the current state of knowledge in the field of accurate measurement on coordinate measuring machines (CMM), which includes the definition of basic metrological concepts, methodology for determining and expressing uncertainties of measurement and a general description of CMM. The diploma thesis also contains a detailed description of the UPMC 850 CARAT S-ACC device from the company Zeiss and summarizes the requirements for the testing laboratory in accordance with the standard ČSN EN 17 025: 2018. The next part of the work is focused on defining and determining the measurement uncertainties for this CMM and on developing a testing procedure for measurements on this machine. The final part of this thesis summarizes the achieved results and recommendations for practice.

Les travaux présentés dans ce mémoire sont centrés sur l'amélioration de la qualité des mesures réalisées sur machine à mesurer tridimensionnelle (MMT) en milieu industriel. En particulier nous nous intéressons au diagnostic et à la correction des défaillances de la chaine de mesure. Dans un premier temps, nous proposons un travail d'expertise des savoir-faire des utilisateurs sous la forme d'une analyse des modes de défaillance et de leur criticité (amdec) des maillons de la chaine de mesure, ainsi qu'une analyse d'un ensemble de procédures qualité industrielles usuelles. Une étude bibliographique des solutions présentées dans la littérature complète l'expertise menée. Suite à ces travaux, nous avons défini la structure et les fonctionnalités d'un superviseur de MMT adapté aux contraintes d'utilisation des MMT en milieu industriel. Nous proposons des indicateurs qualité, ainsi que des procédures adaptées pour leur évaluation. Le superviseur, enrichi avec les indicateurs et procédures expérimentés doit mener a la maitrise de la qualité des mesures réalisées sur MMT. Les indicateurs de qualité calculés et suivis pour la supervision, offrent des perspectives en vue de l'évaluation des incertitudes sur les mesures.

碩士
大葉大學
機械工程研究所碩士在職專班
94
Today, industrial parts need more accurate dimensions for manufacturing processes than those in the past. These industrial parts with high precision need more reliable and accurate measuring equipments to do the measurement tasks for quality control. Coordinate measuring machines have been predominatly used to generate measurement points for a surface. The measurement data are analyzed to yield geometric tolerance information for the surface features such as flatness. With the availability of tolerance information, it is necessary to check if the surface is within the specifield limit. In this paper, I compare the effectiveness of Hemmersley sequence sampling, Halton-Zarmba sequence sampling and the Aligned systematic sampling. The mathematical model is used for the measuring points of the workpiece. The experiment is used to find the optimal number of measuring points and an appropriate sampling method to measuring coplanarity with Gage Repeatability and Reproducibility analysis.

碩士
淡江大學
航空太空工程學系碩士班
96
The development of a product includes varying engineering processes that include dimensional verification, especially in the stages of first article and test production. The product’s manufacture can cooperate with the system engineering concept and combine every engineering step in an integrated manner. Quantity verification plays the role of “checking” and ‘feedback” in a product’s system life cycle. However, Coordinate Measuring Machine (CMM) is essential to size measurement and its variety and accuracy also can help product’s development. CMM is also important in reverse engineering technology. We can use CMM to get geometry characteristics of the product and using reverse engineering software to make curves and reconstruct the planes to re-model its original shapes. The experiment of this research can be divided into two parts, including size measurement and surface reconstruction. Use CMM to compare the dimensional variation of mouse and projector with its original design. Furthermore, apply the surface reconstruction function of CATIA to analysis the surface error of the projector. The result of this study shows, about 50%~60% of 3C products’ average dimensional variation is within 1%, but all of their variation is within the range of tolerance. On the other hand, the dimensional variation of mechanic sample is only less than 0.2%. It is possibly can conclude that higher dimensional variation of the electronic product is due to their more complicate shapes for the modern design and manufacturing processes. This thesis is applying CMM to study the differences of ordinary electronic products’ dimensional variation and surface reconstruction between initial design and after re-modeling by using CAD software. This work is trying to find these product’s key design characteristics. This research is expecting to achieve verification and feedback function in system engineering methodology of products develop stages by using measurement and reverse engineering method.