Investigation and development of an advanced virtual coordinate measuring machine

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel UniversityDimensional measurement plays a critical role in product development and quality control. With the continuously increasing demand for tighter tolerances and more complex workpiece shapes in the industry, dimensional metrology often becomes the bottleneck of taking the quality and performance of manufacturing to the next level. As one kind of the most useful and powerful measuring instruments, coordinate measuring machines (CMMs) are widely employed in manufacturing industries. Since the accuracy and efficiency of a CMM have a vital impact on the product quality, productivity and manufacturing cost, the evaluation and improvement of CMM performance have always been important research topics since the invention of CMM. A novel Advanced Virtual Coordinate Measuring Machine (AVCMM) is proposed against such a background. The proposed AVCMM is a software package that provides an integrated virtual environment, in which user can plan inspection strategy for a given task, carry out virtual measurement, and evaluate the uncertainty associated with the measurement result, all without the need of using a physical machine. The obtained estimate of uncertainty can serve as a rapid feedback for user to optimize the inspection plan in the AVCMM before actual measurement, or as an evaluation of the result of a performed measurement. Without involving a physical CMM in the inspection planning or evaluation of uncertainty, the AVCMM can greatly reduce the time and cost needed for such processes. Furthermore, as the package offers vivid 3D visual representation of the virtual environment and supports operations similar to a physical CMM, it does not only allow the user to easily plan and optimise the inspection strategy, but also provide a cost-effective, risk-free solution for training CMM operators. A modular, multitier architecture has been adopted to develop the AVCMM system, which incorporates a number of functional components covering CMM and workpiece modelling, error simulation, inspection simulation, feature calculation, uncertainty evaluation and 3D representation. A new engine for detecting collision/contact has been developed and utilized, which is suitable for the virtual environment of simulated CMM inspections. A novel approach has been established to calculate errors required for the error simulation, where the data are obtained from FEA simulations in addition to conventional experimental method. Monte Carlo method has been adopted for uncertainty evaluation and has been implemented with multiple options available to meet different requirements. A prototype of the proposed AVCMM system has been developed in this research. Its validity, usability and performance have been verified and evaluated through a set of experiments. The principles for utilising the AVCMM in practical use have also been established and demonstrated. The results have indicated that the proposed AVCMM system has great potentials to improve the functionalities and overall performance of CMMs.ORSAS and the School of Engineering and Design of Brunel University

Knowledge Capture in CMM Inspection Planning: Barriers and Challenges

Coordinate Measuring Machines (CMM) have been widely used as a means of evaluating product quality and controlling quality manufacturing processes. Many techniques have been developed to facilitate the generation of CMM measurement plans. However, there are major gaps in the understanding of planning such strategies. This significant lack of explicitly available knowledge on how experts prepare plans and carry out measurements slows down the planning process, leading to the repetitive reinvention of new plans while preventing the automation or even semi-automation of the process. The objectives of this paper are twofold: (i) to provide a review of the existing inspection planning systems and discuss the barriers and challenges, especially from the aspect of knowledge capture and formalization; and (ii) to propose and demonstrate a novel digital engineering mixed reality paradigm which has the potential to facilitate the rapid capture of implicit inspection knowledge and explicitly represent this in a formalized way. An outline and the results of the development of an early stage prototype - which will form the foundation of a more complex system to address the aforementioned technological challenges identified in the literature survey - will be given

The evaluation of a novel haptic machining VR-based process planning system using an original process planning usability method

This thesis provides an original piece of work and contribution to knowledge by creating a new process planning system; Haptic Aided Process Planning (HAPP). This system is based on the combination of haptics and virtual reality (VR). HAPP creates a simulative machining environment where Process plans are automatically generated from the real time logging of a user’s interaction. Further, through the application of a novel usability test methodology, a deeper study of how this approach compares to conventional process planning was undertaken. An abductive research approach was selected and an iterative and incremental development methodology chosen. Three development cycles were undertaken with evaluation studies carried out at the end of each. Each study, the pre-pilot, pilot and industrial, identified progressive refinements to both the usability of HAPP and the usability evaluation method itself. HAPP provided process planners with an environment similar to which they are already familiar. Visual images were used to represent tools and material whilst a haptic interface enabled their movement and positioning by an operator in a manner comparable to their native setting. In this way an intuitive interface was developed that allowed users to plan the machining of parts consisting of features that can be machined on a pillar drill, 21/2D axis milling machine or centre lathe. The planning activities included single or multiple set ups, fixturing and sequencing of cutting operations. The logged information was parsed and output to a process plan including route sheets, operation sheets, tool lists and costing information, in a human readable format. The system evaluation revealed that HAPP, from an expert planners perspective is perceived to be 70% more satisfying to use, 66% more efficient in completing process plans, primarily due to the reduced cognitive load, is more effective producing a higher quality output of information and is 20% more learnable than a traditional process planning approach

Coordinate Measuring Machine (CMM) inspection planning and knowledge capture – formalising a black art

In manufacturing, the automated elicitation of engineering knowledge is a major challenge due to the increasing knowledge-intensive processes and systems used in industry. Capturing and formalizing engineering knowledge is a highly costly and time-consuming task. The existing literature covers little in this field, leaving unanswered the technical difficulties of capturing and representing knowledge in Coordinate Measuring Machine (CMM) inspection planning applications. This work presents the Inspection Planning and Capturing Knowledge (IPaCK) system, a novel paradigm for the automated capturing and formalising of human centred expertise in the field of CMM planning. The proposed solution is an innovative physical setup using a simple tracked hand-held probe that facilitates intuitive planning of a CMM measurement strategy as a user interacts with a real component. As the sequence is generated, in real time a motion tracking-based digital tool logs user activity throughout the task. A post processor then converts log file data into multiple formalised outputs representing the knowledge created and utilised during the CMM inspection planning task. Experienced CMM inspection planners validated IPaCK’s potential to produce knowledge representations of CMM planning strategies that were useful, relevant and accurate. A comparison of planning strategies resulted in the detection of measurement patterns; embedding both inspection planning knowledge and experience, constituting the first known implementation of automatically capturing best practice and defining benchmarks to evaluate future planning strategies. A task completion time (TCT) comparison against a conventional CMM showed that IPaCK facilitates faster measurement planning and part programming. On using the system, novice planners rated IPaCK and its knowledge representations to provide significant metacognition support to CMM planning and training. Experienced planners confirmed IPaCK’s knowledge capture capability and that the formats were industry acceptable, relevant and beneficial in inspection planning tasks. IPaCK could be at the heart of the next generation of CMM inspection planning systems; one that automatically captures and formalises inspection planning knowledge and experience in multiple outputs. This thesis presents the underpinning science and technology to realise the implementation

Quality and inspection of machining operations: Review of condition monitoring and CMM inspection techniques 2000 to present

In order to consistently produce quality parts, many aspects of the manufacturing process must be carefully monitored, controlled, and measured. The methods and techniques by which to accomplish these tasks has been the focus of numerous studies in recent years. With the rapid advances in computing technology, the complexity and overhead that can be feasibly incorporated in any developed technique has dramatically improved. Thus, techniques that would have been impractical for implementation just a few years ago can now be realistically applied. This rapid growth has resulted in a wealth of new capabilities for improving part and process quality and reliability. In this paper, overviews of recent advances that apply to machining are presented. Moreover, due to the relative significance of two particular machining aspects, this review focuses specifically on research publications pertaining to using tool condition monitoring and coordinate measurement machines to improve the machining process. Tool condition has a direct effect on part quality and is discussed first. The application of tool condition monitoring as it applies to turning, drilling, milling, and grinding is presented. The subsequent section provides recommendations for future research opportunities. The ensuing section focuses on the use of coordinate measuring machines in conjunction with machining and is subdivided with respect to integration with machining tools, inspection planning and efficiency, advanced controller feedback, machine error compensation, and on-line tool calibration, in that specific order and concludes with recommendations regarding where future needs remain

Feature-based hybrid inspection planning for complex mechanical parts

Globalization and emerging new powers in the manufacturing world are among many challenges, major manufacturing enterprises are facing. This resulted in increased alternatives to satisfy customers\u27 growing needs regarding products\u27 aesthetic and functional requirements. Complexity of part design and engineering specifications to satisfy such needs often require a better use of advanced and more accurate tools to achieve good quality. Inspection is a crucial manufacturing function that should be further improved to cope with such challenges. Intelligent planning for inspection of parts with complex geometric shapes and free form surfaces using contact or non-contact devices is still a major challenge. Research in segmentation and localization techniques should also enable inspection systems to utilize modern measurement technologies capable of collecting huge number of measured points. Advanced digitization tools can be classified as contact or non-contact sensors. The purpose of this thesis is to develop a hybrid inspection planning system that benefits from the advantages of both techniques. Moreover, the minimization of deviation of measured part from the original CAD model is not the only characteristic that should be considered when implementing the localization process in order to accept or reject the part; geometric tolerances must also be considered. A segmentation technique that deals directly with the individual points is a necessary step in the developed inspection system, where the output is the actual measured points, not a tessellated model as commonly implemented by current segmentation tools. The contribution of this work is three folds. First, a knowledge-based system was developed for selecting the most suitable sensor using an inspection-specific features taxonomy in form of a 3D Matrix where each cell includes the corresponding knowledge rules and generate inspection tasks. A Travel Salesperson Problem (TSP) has been applied for sequencing these hybrid inspection tasks. A novel region-based segmentation algorithm was developed which deals directly with the measured point cloud and generates sub-point clouds, each of which represents a feature to be inspected and includes the original measured points. Finally, a new tolerance-based localization algorithm was developed to verify the functional requirements and was applied and tested using form tolerance specifications. This research enhances the existing inspection planning systems for complex mechanical parts with a hybrid inspection planning model. The main benefits of the developed segmentation and tolerance-based localization algorithms are the improvement of inspection decisions in order not to reject good parts that would have otherwise been rejected due to misleading results from currently available localization techniques. The better and more accurate inspection decisions achieved will lead to less scrap, which, in turn, will reduce the product cost and improve the company potential in the market

Error compensation and uncertainty evaluation of CMMs based on kinematic error models and gaussian processes

This thesis was submitted for the degree of Masters of Philosophy and awarded by Brunel University London.Given the increasing demand for precision engineering applications, the evaluation of measurement error and uncertainty has been the focus of intensive research to meet the requirements of precision manufacturing processes. Systematic errors of mechanical components affect the accuracy of the production parts. It is therefore best to analyse the geometric accuracy of machine tools before production processes begin. This proposed method is based on simulation in the MATLAB programme, which investigates the influence of the geometric errors of the Coordinate Measuring Machine (CMM) on the calibration. The advantages of this measurement procedure are reduced physical measuring times, reduced measurement uncertainties as well as volumetric measurement, and compensation for CMM geometric errors. In this research, theoretical modelling of the local, kinematic error model and the Gaussian Process (GP) model are presented and explored in depth. These proposed methods are simulations providing an integrated virtual environment in which user can generate the inspection path planning for specific tasks and evaluate the errors and uncertainty associated with the measurement results, all without the need to perform a number of physical CMM measurements. The estimated errors and uncertainty can serve as rapid feedback for users before performing actual measurements or as a prior evaluation of the results of the CMM calibrations. The estimation of CMM geometric errors are usually described using 21 kinematic errors which consist of three positional and three rotational error functions for each of the three axes, along with three squareness errors. This assumes that the method to estimate of these kinematic errors can be generated by performing an artefact measurement such as for a hole or a ball plate in the numbers of the positions of the CMM working region and then matching the kinematic errors to the measured changes in artefact geometry. The process validation of a local, kinematic error model and a GP model has been determined with the design and analysis of CMM measurement using a ball plate as an artefact, calculating the percentage error to compare their effective results. This research project has led to the following contribution to knowledge: Mathematical model development for making effective choices regarding the local, kinematic error model and GP model is performed and formulated; this is verified by particular kinematic errors of the CMM measurements, presenting high accuracy and reliability of the error and uncertainty evaluation performance. The improvement achieved by the proposed method over the traditional approaches between the simulated datasets and actual CMM data measurements has been demonstrated. The numerical simulations with a well-designed strategy providing accurate estimates of the CMM kinematic errors using only a nominal CMM calibration with a ball plate have been validated and evaluated in both approaches. The influences of kinematic errors affected through the measurement process of the CMM on the calibration have been investigated.Royal Thai Government, Ministry of Sciences and Technology and National Institute of Metrology Thailand (NIMT)

Méthode interactive et par l'apprentissage pour la generation de trajectoire en conception du produit

The accessibility is an important factor considered in the validation and verification phase of the product design and usually dominates the time and costs in this phase. Defining the accessibility verification as the motion planning problem, the sampling based motion planners gained success in the past fifteen years. However, the performances of them are usually shackled by the narrow passage problem arising when complex assemblies are composed of large number of parts, which often leads to scenes with high obstacle densities. Unfortunately, humans’ manual manipulations in the narrow passage always show much more difficulties due to the limitations of the interactive devices or the cognitive ability. Meanwhile, the challenges of analyzing the end users’ response in the design process promote the integration with the direct participation of designers.In order to accelerate the path planning in the narrow passage and find the path complying with user’s preferences, a novel interactive motion planning method is proposed. In this method, the integration with a random retraction process helps reduce the difficulty of manual manipulations in the complex assembly/disassembly tasks and provide local guidance to the sampling based planners. Then a hypothesis is proposed about the correlation between the topological structure of the scenario and the motion path in the narrow passage. The topological structure refers to the medial axis (2D) and curve skeleton (3D) with branches pruned. The correlation runs in an opposite manner to the sampling based method and provide a new perspective to solve the narrow passage problem. The curve matching method is used to explore this correlation and an interactive motion planning framework that can learn from experience is constructed in this thesis. We highlight the performance of our framework on a challenging problem in 2D, in which a non-convex object passes through a cluttered environment filled with randomly shaped and located non-convex obstacles.L'accessibilitéest un facteur important pris en compte dans la validation et la vérification en phase de conception du produit et augmente généralement le temps et les coûts de cette phase. Ce domaine de recherche a eu un regain d’intérêt ces quinze dernières années avec notamment de nouveaux planificateurs de mouvement. Cependant, les performances de ces méthodes sont généralement très faibles lorsque le problème se caractérise par des passages étroits des assemblages complexes composées d'un grand nombre de pièces. Cela conduit souvent àdes scènes àforte densitéd'obstacles. Malheureusement, les manipulations manuelles des humains dans le passage étroit montrent toujours beaucoup de difficultés en raison des limitations des dispositifs interactifs ou la capacitécognitive. Pendant ce temps, les défis de l'analyse de la réponse finale des utilisateurs dans le processus de conception promeut l'intégration avec la participation directe des concepteurs.Afin d'accélérer la planification dans le passage étroit et trouver le chemin le plus conforme aux préférences de l'utilisateur, une nouvelle méthode de planification de mouvement interactif est proposée. Nous avons soulignéla performance de notre algorithme dans certains scénarios difficiles en 2D et 3D environnement.Ensuite, une hypothèse est proposésur la corrélation entre la structure topologique du scénario et la trajectoire dans le passage étroit. La méthode basée sur les courbures est utilisée pour explorer cette corrélation et un cadre de planification de mouvement interactif qui peut apprendre de l'expérience est construit dans cette thèse. Nous soulignons la performance de notre cadre sur un problème difficile en 2D, dans lequel un objet non-convexe passe à travers un environnement encombrérempli d'obstacles non-convexes de forme aléatoire et situés

Virtuaaliprototypoinnin implementointi matalan tuotantovolyymin tuotepäivitysprojekteissa

The aim of this master’s thesis was to discover whether virtual prototyping could be utilized in a forest machine company’s product update projects to support the cooperation between design and production departments. The goal was to develop and evaluate an implementation method for virtual prototyping during design phases, which would make the current development process more efficient by reducing the amount of resources spent in physical prototyping in future product update projects. This thesis is part of a jointly funded research project. In the theoretical part of the thesis a literature review considering product development, concurrent engineering, prototyping, and virtual reality technology was undertaken. In addition virtual prototyping, its previous applications, and its impact and requirements on organizational and individual level were researched, providing the theoretical framework for the thesis. The practical part of the research included an analysis of the case company based on the literature review, materials produced during the jointly funded project, and qualitative interviews with 10 employees of the case company. The aim was to become acquainted with the case company’s product development process, current design reviews and communication between design and production departments. As a result, an implementation method for virtual prototyping was developed, which concentrated on the evaluation of assembly properties in collaborative design reviews. The implementation method was tested in one product update project by organizing a collaborative design review and by demonstrating the benefits of virtual prototyping at a virtual reality test facility. An inquiry along with observation and open discussion were utilized to collect feedback about the performance of the implementation method and virtual prototyping in evaluation of assembly properties. The results indicate that the company saw potential in virtual prototyping utilizing collaborative design reviews. As a result, these design reviews will be partly applied in future product upgrade projects. Evaluation of assembly properties was seen as a successful implementation target. The main shortcomings for comprehensive application of virtual prototyping were the need for optimization of 3D models and the product data management’s current status in the case company, which currently does not support the implementation method as well as it could. To gain results from the practical benefits of virtual prototyping, it should be further implemented during future product update projects as a whole