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

STEP-based Conceptual Framework for Measurement Planning Integration

AbstractMeasurement aims to check the product conformance or to control the manufacturing processes’ parameters. It needs to be planned in an integrated and interoperable manner with other manufacturing activities. Integration of measurement planning is based on the information provided by the design phase. This paper aims to assist the interoperability of the measurement plans through introducing the resource-independent measurement specifications (RIMS) concept. The paper presents a conceptual framework for representing a STEP-based measurement features from the coordinate metrology perspective. The proposed framework supports the direct formulation of the measurement process specifications in an operation-based manner and the realization the process control functionality of the measurement processes

Tolerancing and Sheet Bending in Small Batch Part Manufacturing

Tolerances indicate geometrical limits between which a component is expected to perform its function adequately. They are used for instance for set-up selection in process planning and for inspection. Tolerances must be accounted for in sequencing and positioning procedures for bending of sheet metal parts. In bending, the shape of a part changes not only locally, but globally as well. Therefore, sheet metal part manufacturing presents some specific problems as regards reasoning about tolerances. The paper focuses on the interpretation and conversion of tolerances as part of a sequencing procedure for bending to be used in an integrated CAPP system

Automating Tolerance Synthesis: A Framework and Tools

This paper describes CASCADE-T—a new approach to tolerance synthesis that uses a complete representation of the conditional tolerance relations that exist between features of a part under design. Conditional tolerances are automatically determined from functional requirements and shape information. Tolerance primitives based on the virtual boundary requirements approach to tolerance representation are composed to form more complex tolerance relationships. Artificial intelligence techniques, including a constraint network, frame-based system, and dependency tracking are used to support flexible and detailed computation for tolerance analysis and synthesis

Explicitly representing the semantics of composite positional tolerance for patterns of holes

Representing the semantics of the interaction of two or more tolerances (i.e. composite tolerance) explicitly to make them computer-understandable is currently a challenging task in computer-aided tolerancing (CAT). We have proposed a description logic (DL) ontology based approach to complete this task recently. In this paper, the representation of the semantics of the composite positional tolerance (CPT) for patterns of holes (POHs) is used as an example to illustrate the proposed approach. This representation mainly includes: representing the structure knowledge of the CPT for POHs in DL terminological axioms; expressing the constraint knowledge with Horn rules; and describing the individual knowledge using DL assertional axioms. By implementing the representation with the web ontology language (OWL) and the semantic web rule language (SWRL), a CPT ontology is developed. This ontology has explicitly computer-understandable semantics due to the logic-based semantics of OWL and SWRL. As is illustrated by an engineering example, such semantics makes it possible to automatically check the consistency, reason out the new knowledge, and implement the semantic interoperability of CPT information. Benefiting from this, the ontology provides a semantic enrichment model for the CPT information extracted from CAD/CAM systems

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

Model-based definition in computer aided tolerance analyses

Recent advancements in means of data collection and utilization have stepped forward to the realization of model-based definition approaches in product and production development processes. This realization is further facilitated by the presentation of open-source standards for model-based definition including STEP AP 242 and QIF 3.0. As a result, engineers are empowered with a significant amount of data to improve the development processes, particularly the tolerancing and metrology processes. This paper evaluates the opportunities enabled in the era of tolerance analyses, particularly computer-aided tolerance analyses by model-based design approaches particularly through the utilization of STEP AP 242 and QIF 3.0 standards. The main breakthrough in these standards is the semantic representation of tolerancing data in the models. However, the existing methods of modeling and analyzing tolerance information are diverse and not all these methods can utilize the new standards in the same manner. The potential usages of the new standards in different tolerance modeling techniques are reviewed. Furthermore, the research gaps and wishes for further improvements in the tolerance analysis era through model-based definition are discussed

Toward Meaningful Manufacturing Variation Data in Design - Feature Based Description of Variation in Manufacturing Processes

AbstractThe need to mitigate the effects of manufacturing variation already in design is nowadays commonly acknowledged and has led to a wide use of predictive modeling techniques, tolerancing approaches, etc. in industry. The trustworthiness of corresponding variation analyses is, however, not ensured by the availability of sophisticated methods and tools alone, but does evidently also depend on the accuracy of the input information used. As existing approaches for the description of manufacturing variation focus however, almost exclusively, on monitoring and controlling production processes, there is frequently a lack of objective variation data in design. As a result, variation analyses and tolerancing activities rely on numerous assumptions made to fill the gaps of missing or incomplete data. To overcome this hidden subjectivity, a schema for a consistent and standardised description of manufacturing variation is suggested. It extends existing ISO GPS annotation by information about influences on the manufacturability of a chosen design solution and in this way enables the systematic acquisition of variation data meaningful for design practice