Paul Maropoulos

Recent developments in large-scale dimensional metrology

Abstract With ever-more demanding requirements for the accurate manufacture of large components, dimensional measuring techniques are becoming progressively more sophisticated. This review describes some of the more recently developed techniques and the state-of-the-art in the more well-known large-scale dimensional metrology methods. In some cases, the techniques are described in detail, or, where relevant specialist review papers exist, these are cited as further reading. The traceability of the measurement data collected is discussed with reference to new international standards that are emerging. In some cases, hybrid measurement techniques are finding specialized applications and these are referred to where appropriate.

Open standard, open source and peer-to-peer tools and methods for collaborative product development

This paper reports on a collaborative product development and knowledge management platform for small to medium enterprises. It has been recognised that current product lifecycle management (PLM) implementations are document oriented, have a non-customisable data model and inter-enterprise integration difficulties. To overcome these, an ontological knowledge management methodology utilising the semantic web initiative data formats was added to a PLM and an open source alternative. Shortcomings of centralised architectures are highlighted and a solution using a de-centralised architecture proposed. This is implementable at low cost; the scalability increases in line with user numbers. Ontologies, rules and workflows are reusable and extendable.

Application of product data management technologies for enterprise integration

Product Data Management (PDM) systems and their offspring, Collaborative Product Development and Product Lifecycle Management technologies, aim to bring engineering enterprises together, allowing seamless interoperability between different departments and throughout the extended enterprises. However, there are a number of shortcomings in the current crop of commercially available systems, such as the lack of design knowledge sharing, links with Enterprise Resource Planning systems, knowledge management tools and a generic standard for PDM system implementation. This paper presents a proposed software solution to some of the above problems. In particular, the paper describes methodologies being developed that are aimed at overcoming the lack of analysable product information at the conceptual stage of product design and manufacturing evaluation, along with the integration of such a concept design tool within a distributed environment. A leading PDM system is used to manage all the information and knowledge that is made available to internet/intranet users in a controlled manner. The international standard for exchange of product data model (STEP) is implemented to enable the integration of the design environment with manufacturing and enterprise resource management systems. In addition, the paper also introduces three other recent/ongoing projects, being carried out at Cranfield University, in the application of PDM, knowledge management and STEP standard for integrated manufacturing businesses.

Manufacturing and assembly automation by integrated metrology systems for aircraft wing fabrication

Abstract Discrepancies of materials, tools, and factory environments, as well as human intervention, make variation an integral part of the manufacturing process of any component. In particular, the assembly of large volume, aerospace parts is an area where significant levels of form and dimensional variation are encountered. Corrective actions can usually be taken to reduce the defects, when the sources and levels of variation are known. For the unknown dimensional and form variations, a tolerancing strategy is typically put in place in order to minimize the effects of production inconsistencies related to geometric dimensions. This generates a challenging problem for the automation of the corresponding manufacturing and assembly processes. Metrology is becoming a major contributor to being able to predict, in real time, the automated assembly problems related to the dimensional variation of parts and assemblies. This is done by continuously measuring dimensions and coordinate points, focusing on the products key characteristics. In this paper, a number of metrology focused activities for large-volume aerospace products, including their implementation and application in the automation of manufacturing and assembly processes, are reviewed. This is done by using a case study approach within the assembly of large-volume aircraft wing structures.

Digital Enterprise Technology

Industry is undergoing a rapid transformation internationally, characterized by the liberalization of global markets, increased mobility of people and capital and the constant requirement for exploiting the enabling capability of the internet in order to rapidly add value to products and services. Increased competition has also led to the gradual consolidation of sectors, as companies adopt corporate alliances and mergers in order to manage their spiralling R&D and marketing costs across different markets. Currently, the defence and aerospace sectors are largely consolidated on both sides of the Atlantic and the same is true for the automotive, pharmaceuticals and chemicals industries. The removal of protectionist policies, coupled with the availability of a skilled workforce and comprehensive communication technologies in many parts of the world, has allowed large enterprises to adopt globalization and plan manufacturing and design operations on a truly global basis. The benefit of this approach is that the resources of an enterprise can be fine-tuned to allow competitive operations in traditional major markets, such as the North American and the European regions, as well as cover the varied demands of emerging new markets. In addition, an enterprise can seek to exploit specific scientific skills that may be available in abundance in certain countries, such as design technology and mathematical analysis in Russia and software engineering skills in India. Globalization can be rewarding for industry at an enterprise level, but it can be problematic for the small and medium size enterprises (SMEs) that underpin the operation of larger enterprises and are crucial for the economic growth of specific countries and regions. Initial fears of a massive employment drift to low-wage regions have largely not been realized. A good example of the opposite trend is the recent growth of manufacturing industry in the United States, which was principally sustained by developing business practices that apply computer-based technologies and use a first-class electronic networking and communications infrastructure. Clearly, computer-based methods for design and manufacture, supported by electronic networking and communication infrastructure (e-commerce), represent an essential level of technology required by industry in order to support competitive manufacturing operations on a regional and global basis. Globalization and enterprise consolidation amplify the effects of socio-economic events and market requirements in the industries and economies of the industrialized world, in much more direct and immediate ways than previously. These conditions create the need for:

Indoor GPS: system functionality and initial performance evaluation

Indoor GPS (iGPS) is a newly developed laser based measuring system for large scale metrology. The relative portability, reconfigurability and ease of installation make the iGPS suitable for many industries manufacturing large scale products. The system performance depends on both the components characteristics and their physical configuration. Hence, an important consideration for the iGPS is to characterise its real capabilities, pointing out how they can be influenced by the systems configuration and setup. In this paper, the system is introduced and the technical aspects are briefly described. Then, an initial test is performed to establish its repeatability, reproducibility and accuracy.

Modelling and optimization of novel laser multilateration schemes for high-precision applications

A computer simulation technique has been developed to investigate the performance of established and novel laser multilateration schemes. The models focus on analysing the impact of variations in system configuration, optimizing the system self-calibration process and evaluating the volumetric measurement error propagation. Careful optimization of the system configuration and self-calibration planning significantly reduces the uncertainty of system self-calibration and measurement. Comparing the simulated performances of multilateration systems with different number of measurement stations, e.g. four, five and six stations, quantifies the performance improvement obtained by increasing the number of stations. Specific recommendations for optimization of multilateration set-ups and measurement plans and for minimizing measurement uncertainty are set out in the paper. A novel, sequential multilateration set-up for high-precision calibration of small artefacts has been defined, and measurements have been made to support the analysis presented here.

Large-volume metrology instrument selection and measurability analysis

Abstract A wide range of metrology processes are involved in the manufacture of large products. In addition to the traditional tool-setting and product-verification operations, increasingly flexible metrology-enabled automation is also being used. Faced with many possible measurement problems and a very large number of metrology instruments employing diverse technologies, the selection of the appropriate instrument for a given task can be highly complex. Also, as metrology has become a key manufacturing process, it should be considered in the early stages of design, and there is currently very little research to support this. This paper provides an overview of the important selection criteria for typical measurement processes and presents some novel selection strategies. Metrics that can be used to assess measurability are also discussed. A prototype instrument selection and measurability analysis application is also presented, with discussion of how this can be used as the basis for development of a more sophisticated measurement planning tool.

Estimation of uncertainty in three-dimensional coordinate measurement by comparison with calibrated points

This paper details a method of estimating the uncertainty of dimensional measurement for a three-dimensional coordinate measurement machine. An experimental procedure was developed to compare three-dimensional coordinate measurements with calibrated reference points. The reference standard used to calibrate these reference points was a fringe counting interferometer with a multilateration-like technique employed to establish three-dimensional coordinates. This is an extension of the established technique of comparing measured lengths with calibrated lengths. Specifically a distributed coordinate measurement device was tested which consisted of a network of Rotary-Laser Automatic Theodolites (R-LATs), this system is known commercially as indoor GPS (iGPS). The method was found to be practical and was used to estimate that the uncertainty of measurement for the basic iGPS system is approximately 1 mm at a 95% confidence level throughout a measurement volume of approximately 10 m × 10 m × 1.5 m.

Key digital enterprise technology methods for large volume metrology and assembly integration

Digital enterprise technology (DET) is a theoretical framework for collaborative design and production development in the context of a products lifecycle. The DET framework can be used to configure digital product and process development technologies which assimilate design data, at various levels of completeness, with a high degree of real-time measurement feedback from the production environment in order to validate the products tolerance specification and the selected production and assembly processes. This paper describes research focused on the integration of two major facets of DET; process planning and large volume metrology (LMV). The challenges encountered include the representation of early designs of complex products, the definition of high risk areas in the process plan and the generation of accurate, dynamic measurement data from large-scale laser metrology in the production environment. The methods employed demonstrate how DET-based strategies for design, manufacture and integration can utilize recent technology advances in aggregate modelling and planning, tolerance analysis tools and 3D coordinate metrology. Early testing using aerospace products has been very promising and the research findings will benefit manufacturers of high-value, high-complexity products within distributed production networks.