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

Incorporation of form deviations into the matrix transformation method for tolerance analysis in assemblies

Comunicación presentada a MESIC 2019 8th Manufacturing Engineering Society International Conference (Madrid, 19-21 de Junio de 2019)Mathematical models for tolerance representation are used to assess how the geometrical variation of a specific component feature propagates along the assembly, so that tolerance analysis in assemblies can be carried out using a specific tolerance propagation method. Several methods for tolerance analysis have been proposed in the literature, being some of them implemented in CAD systems. All these methods require modelling the geometrical variations of the component surfaces: parametric models, variational models, DoF models, etc. One of the most commonly used models is the DoF model, which is employed in a number of tolerance analysis methods: Small Displacement Torsor (SDT), Technologically and Topologically Related Surfaces (TTRS), Matrix Transformation, Unified Jacobian–Torsor model. However, none of the DoF-based tolerance analysis methods incorporates the effect of form deviations. Among the non DoF-based methods, there are two that include form tolerances: the Vector Loop or Kinematic method and the Tolerance Map (T-Map) model, although the latter is still under development. In this work, a proposal to incorporate form deviations into the matrix transformation method for tolerance analysis in assemblies is developed using a geometrical variation model based on the DoF model. The proposal is evaluated applying it to a 2D case study with components that only have flat surfaces, but the proposal can be extrapolated to 3D cases

Comparison of Discrete Part Verification Using Coordinate Measuring Machine and Articulated Arm Coordinate Measuring Machine

Quality assurance is key in manufacturing and assembling processes and is usually implemented by specifying and controlling tolerances and surface finish of important features, in discrete product manufacturing industry. Much of product verification and inspection for single parts and assemblies are considered to be non-value added, and hence, the processes and procedures must be constantly improved to achieve better savings in time and cost. Coordinate Measuring Machines (CMMs) are the gold standard for geometry verification of parts in the industry, for their consistency and accuracy. Articulated Arm CMMs (AACMMs) use a scan/arm configuration, and as such are considered not accurate enough in part verification. And yet, they can result in many time-savings and ease of operation. If developed suitably, these can be used quite viably in situations that do not demand high accuracies. It is the aim of this thesis to investigate how the AACMMs compare to the traditional gantry CMMs in flatness verification. Flatness verification is the most fundamental of geometry verification employed in the industry. The success achieved in form verification can be extended to investigate further geometries, and AACMMs can be developed as an economical alternative to the more traditional CMMs in industry. Specifically, this thesis investigated the flatness of surfaces generated by milling (roughing and finishing). Experiments were conducted on three rectangular blocks of Steel 1018 and three more of Aluminum 6061 of specific dimensions. The CMM employed was used to collect data using three sampling strategies: Hammersley, Halton Zaremba, and Aligned systematic methods. The AACMM was also used to collect the flatness data on each plate through a scan. A commercial Geomagic® Control X™ was used to find flatness deviation between measured data and the CAD model for each of the rough and finish surfaces. Statistics from the distribution of gap distance and deviations were presented through the study. The accuracy was noted in each case. The results developed verified that AACMM is not as accurate as of the traditional CMM in measuring flatness. All the same, the results were sufficient to suggest that AACMM can be used as a viable and faster alternative to the CMM in flatness verification

Feature Cluster Algebra and Its Application for Geometric Tolerancing

abstract: The goal of this research project is to develop a DOF (degree of freedom) algebra for entity clusters to support tolerance specification, validation, and tolerance automation. This representation is required to capture the relation between geometric entities, metric constraints and tolerance specification. This research project is a part of an on-going project on creating a bi-level model of GD&T; (Geometric Dimensioning and Tolerancing). This thesis presents the systematic derivation of degree of freedoms of entity clusters corresponding to tolerance classes. The clusters can be datum reference frames (DRFs) or targets. A binary vector representation of degree of freedom and operations for combining them are proposed. An algebraic method is developed by using DOF representation. The ASME Y14.5.1 companion to the Geometric Dimensioning and Tolerancing (GD&T;) standard gives an exhaustive tabulation of active and invariant degrees of freedom (DOF) for Datum Reference Frames (DRF). This algebra is validated by checking it against all cases in the Y14.5.1 tabulation. This algebra allows the derivation of the general rules for tolerance specification and validation. A computer tool is implemented to support GD&T; specification and validation. The computer implementation outputs the geometric and tolerance information in the form of a CTF (Constraint-Tolerance-Feature) file which can be used for tolerance stack analysis.Dissertation/ThesisM.S. Mechanical Engineering 201

Efficiency improvement of product definition and verification through Product Lifecycle Management

The correct and complete geometrical definition of a product is nowadays a critical activity for most companies. To solve this problem, ISO has launched the GPS, Geometrical Product Specifications and Verification, with the goal of consistently and completely describe the geometric characteristics of the products. With this project, it is possible to define a language of communication between the various stages of the product lifecycle based on "operators": these are an ordered set of mathematical operations used for the definition of the products. However, these theoretical and mathematical concepts require a level of detail and completeness of the information hardly used in usual industrial activities. Consequently in industrial practice the definition and verification of products appears to be a slow process, error-prone and difficult to control. Product Lifecycle Management (PLM) is the activity of managing the company's products throughout their lifecycle in the most efficient way. PLM describes the engineering aspects of the products, ensuring the integrity of product definition, the automatic update of the product information and then aiding the product to fulfil with international standards. Despite all these benefits, the concepts of PLM are not yet fully understood in industry and they are difficult to implement for SME's. A first objective of this research is to develop a model to depict and understand processes. This representation is used as a tool during the application of a case study of a whole set of a GPS standards for one type of tolerance. This procedure allows the introduction of the GPS principles and facilitates its implementation within a PLM process. Until now, PLM is presented on isolated aspects without the necessary holistic approach. Furthermore, industry needs people able to operate in PLM context, professional profiles that are not common on the market. There is therefore an educational problem; besides the technical knowledge, the new profile of engineers must be also familiar with the PLM philosophy and instruments to work effectively in a team. With the aim of solving this problem, this thesis presents a PLM solution that gives the guidelines for a correct understanding of these topic

Modeling and Representation of Geometric Tolerances Information in Integrated Measurement Processes

Modeling and representation of geometric tolerances information across an enterprise is viable due to the advances in Internet technologies and increasing integration requirements from industry. In Integrated Measurement Processes (IMP), geometric tolerances data model must support different models from several well-defined standards: including ASME Y14.5M-1994, STEP, DMIS, and others. In this paper, we propose a layered conformance level geometric tolerances representation model. This model uses the widely applied ASME Y14.5M-1994 as its foundation layer by abstracting most information from this standard. The additional geometric tolerances information defined by DMIS and STEP is incorporated into this model to form corresponding conformance layers that support IMP. Thus, different application domains in an enterprise can use this data model to exchange product information. This model is further transformed with XML Schema that can be used to generate XML instance file to satisfy geometric tolerances representation requirements in IMP

Effective Product Lifecycle Management: the role of uncertainties in addressing design, manufacturing and verification processes

The aim of this thesis is to use the concept of uncertainty to improve the effectiveness of Product Lifecycle Management (PLM) systems. Uncertainty is a rather new concept in PLM that has been introduced with the new technical language, drawn by ISO, to manage Geometrical Product Specification and Verification (GPS) in the challenging environment of modern manufacturing. GPS standards regard in particular design and verification environments, and want to guarantee consistence of information through a technical language which define both specification and verification on sound logical and mathematical bases. In this context, uncertainty is introduced as the instrument that measures consistency: between the designer intentions (specifications) and the manufactured artefact (as it is observed through measurement) as well as between the measurand definition provided by designers (the specification again) and that used by metrologists. The implications of such an approach have been analyzed through a case study dealing with flatness tolerance and paying particular attention to the verification processes based on Coordinate Measuring Machines (CMM). A Design of Experiment (DoE) has been used and results have been analyzed and used to build a regression model that allows generalization in the experiment validity domain. Then, using Category Theory, a categorical data model has been defined which represents the operation based structure of GPS language and uses the flatness research results in order to design a software able to concretize the GPS vision of geometrical product specifications management. This software is able to translate specification requirements into verification instructions, estimate the uncertainty introduced by simplified verification operations and evaluate costs and risks of verification operations. It provides an important tool for designers, as it allows a responsible definition of specifications (designer can simulate the interpretation of specifications and have an idea of the costs related with their verification), and for metrologist, as it can be a guide for designing GPS compliant verification missions or handling the usual verification procedures according to the GPS standards. However, during the study, it has been matured the consciousness that this approach, even if correct and valuable, was not the most suitable to fully exploit the real potential of CMM. Then, aside the GPS oriented work, an adaptive sampling strategy, based on Kriging modelization, has been proposed with very encouraging result

Modelling the integration between the design and inspection process of geometrical specifications for digital manufacturing

Geometrical Product Specifications (GPS) is a technical language which covers the standardization for micro/macro- geometry specifications. In today’s environment of globalization, out-sourcing and sub-contracting is increasing. Geometrical specifications of a product need to be detailed to a degree where nothing is left open to interpretation. To fulfil this, and to meet the requirements of digital manufacturing, it is necessary to integrate the design and inspection process of a geometrical specification. At the technical level, many functional operator/operations are employed in a geometrical specification. These functional operators/operations are based on rigorous mathematics, and they are intricately related and inconvenient to be used directly. Consequently, it is of practical utility to build an integrated information system to encapsulate and manage the information involved in GPS. This thesis focuses on geometrical tolerancing, including form/orientation/ location tolerancing, and its integrated geometry information system. The main contributions are: Firstly, a global data expression for modelling the integration between the design and inspection process of a geometrical tolerance is presented based on category theory. The categorical data model represents, stores and manipulates all the elements and their relationships involved in design and inspection process of a geometrical tolerance, by categories, objects and morphisms, flexibly; the relationships between objects were refined by pull back structures; and the manipulations of the model such as query and closure of query are realized successfully by functor structures in category theory. Secondly, different categories of knowledge rules have been established to enhance the rationality and the intellectuality of the integrated geometry information system, such as the rules for the application of geometrical requirement, tolerance type, datum and datum reference framework and, for the refinement among geometrical specifications. Finally, the host system for drawing indication of geometrical tolerances in the framework of GPS was established based on AutoCAD 2007 using ObjectARX.EThOS - Electronic Theses Online ServiceGBUnited Kingdo