Svetan Ratchev

Force and deflection modelling in milling of low-rigidity complex parts

Abstract To remain competitive, high-quality high-value manufacturers constantly seek to improve their product quality and to reduce cost and lead times by producing ‘right first time’ machined components. Producing the right profile in such parts increasingly depends on specialised CAM packages for defining appropriate cutting strategies and tool paths. Despite the significant developments in NC simulation and verification there are still gaps between the theoretically predicted surfaces and the measured surfaces due to a relatively small percentage of machining error types that could be detected and interpreted by the existing software systems. The paper reports on a virtual environment for simulation and prediction of the deflection of thin-walled parts during machining. It aims to increase the understanding of the causes of poor geometric accuracy by considering the impact of the machining forces on the deflection of thin-walled structures. The proposed approach is based on identifying and modelling of key processing characteristics that influence part deflection, modelling of the material removal process using “voxels”, and predicting and correcting the deflection of the parts. The decision making is based on a novel integrated environment using CAD and finite element analysis tools. The reported work is part of an ongoing research on developing an adaptive machining planning environment for modelling, prediction, and selection of process and tool path parameters for rapid machining of complex low-rigidity high-accuracy parts.

An ontology for the definition and validation of assembly processes for evolvable assembly systems

Assembly forms eighty per cent of the cost of manufacturing a product and this is where the greatest competitive advantage can be gained as assembly has not been fully understood in the research community. This paper reports on the development of a specification ontology to describe assembly processes at a level where they can be mapped to individual assembly modules. The ontology is an extension of the process specification language (PSL) defined by NIST. The developed ontology is applied to an existing case to demonstrate the capabilities. It is believed that the development of this ontology will lead to the opening of further channels for research in modular control and modular assembly processes, which are building blocks for evolvable assembly systems

Knowledge based requirement engineering for one-of-a-kind complex systems

The success of requirement specification in new design projects largely depends on an accurate match between customer requirements and company product and process knowledge. Despite the recent developments in the domain there is still a lack of transparency and consistent definition and integration of the activities in requirement engineering (RE). There is also a lack of structured methods for capturing relevant enterprise knowledge and deploying it in support of decision making for requirement specification. This paper reports on the knowledge acquisition and sharing for requirement engineering (KARE) approach for requirement specification of one-of-a-kind complex systems. The approach provides a generic view of key RE processes clustered into three groups of activities: requirement elicitation, analysis and negotiation. The process is supported by a set of knowledge functions aimed at facilitating the requirement engineers in matching customer requirements to product characteristics. The reported research has been developed as part of the ESPRIT collaborative project KARE funded by the European Commission.

Concurrent process and facility prototyping for formation of virtual manufacturing cells

Reports on a new methodology for formation of virtual (“extended”) machining cells using generic capability patterns termed “resource elements”. Resource elements are used to uniquely describe the processing requirements of the component mix and dynamically match them to the processing capabilities of the machining shop. The virtual cell formation methodology is based on four steps: component requirement analysis and generation of processing alternatives; definition of virtual cell capability boundaries; machine tool selection; and system evaluation. The proposed methodology facilitates the dynamic formation of virtual manufacturing structures by providing accurate assessment of the component processing requirements and their matching with the available capabilities of the existing manufacturing facilities.

Towards Web‐enabled design of modular assembly systems

The development of reconfigurable modular production systems is one of the crucial factors for manufacturers to sustain their competitive advantage in areas such as precision assembly. To ensure the effective and cost efficient configuration and successive reconfigurations it is of critical importance to involve all stakeholders in the decision‐making process. The reported research is targeting the development of an integrated Web‐enabled decision‐making environment that supports some of the key assembly system engineering stages from user requirement specification to system implementation. The focus is on the design of assembly workstations based on detailed process requirements with a target of developing highly efficient and cost‐effective solutions. The paper presents an application framework for collaborative distributed design supported by domain ontologies and is illustrated using an industrial case study.

An Agent Based Framework to Support Plug And Produce

The new market trends are very different, so it is crucial to the companies improve the tools and capabilities that allow themselves readjust rapidly and effectively to the news market changes and to the new requirements. In order to facilitate this process, it is proposed in this paper an agent based implementation that can provide to the existent systems the capacity to quickly adapt and reconfigure using standard technology. The proposed framework provides an intelligent tool to autonomously help the configuration when a production operator pretends to introduce a new variant of product in runtime and consult important information provided by the system to monitor execution.

The changing relationship between production and inventory examined in a concurrent engineering context

Abstract This paper examines some of the changes that are occurring in manufacturing companies and in the market in which they operate. Changes include the product design process, reduction in product design time, new technology, new materials and production methods, the availability of better quality data, organisation change including changes in techniques and tools used for planning and control. Changes in the market include increased competitiveness, the need for shorter lead times, shorter product life cycles, pressures on costs and the need for greater responsiveness. The paper discusses these among other changes and suggests that the relationship between production and inventory needs to be reviewed to determine whether and how it should respond. A generalised concurrent engineering context is proposed within which it is suggested that production and inventory planning and control should be included.

Active fixturing: literature review and future research directions

Fixtures are used to fixate, position and support workpieces and represent a crucial tool in manufacturing. Their performance determines the result of the whole manufacturing process of a product. There is a vast amount of research done on automatic fixture layout synthesis and optimisation and fixture design verification. Most of this work considers fixture mechanics to be static and the fixture elements to be passive. However, a new generation of fixtures has emerged that has actuated fixture elements for active control of the part–fixture system during manufacturing operations to increase the end product quality. This paper analyses the latest studies in the field of active fixture design and its relationship with flexible and reconfigurable fixturing systems. First, a brief introduction is given on the importance of research of fixturing systems. Secondly, the basics of workholding and fixture design are visited, after which the state-of-the-art in active fixturing and related concepts is presented. Fourthly, part–fixture dynamics and design strategies which take these into account are discussed. Fifthly, the control strategies used in active fixturing systems are examined. Finally, some final conclusions and prospective future research directions are presented.

Distributed product and facility prototyping in extended manufacturing enterprises

In order to reduce the cost at the early product development stages, the planners need methodologies and tools that would allow them to judge upon the implications of the product design on the required manufacturing processes and facilities for their production. This paper reports on a new theoretical platform and a pilot implementation of a decision-making environment for distributed product and facility prototyping in an extended enterprise. The approach is based on an exchange of requests and information between collaborative autonomous agents that support the design, manufacturing planning and facility formation activities. The decision-making is formalized as iterative matching of design, process and facility attributes using multilevel resource capability representation within the extended enterprise. The system is implemented as an XML/CORBA-based environment for conveying design and manufacture messages across traditional technology boundaries. The reported research aims to provide the designers with a rapid manufacturing feasibility assessment tool to be used at different design and planning stages in extended manufacturing enterprises.

Rapid manufacturing of non-assembly complex micro-devices by microstereolithography

This paper introduces a non-assembly manufacturing case with microstereolithography technology. The design and manufacturing process of a pneumatic thrust bearing is described, and a special tessellation method is developed to further improve the capability of the manufacturing system thus bigger products can also be easily manufactured. Implemented in a layer-by-layer fashion, stereolithography has been used for the rapid manufacturing of complex devices, and it avoids the expensive assembly process in the traditional manufacturing. This paper presents that microstereolithography can produce high-resolution products with intricate details, small openings, and smooth surfaces. The potential of the microstereolithograhy technique is explored for the rapid manufacturing of small and complex objects.