Using a design by features CAD system for process capability modelling

Process capability modelling offers a method of matching the shape, technological and cost capabilities of manufacturing equipment to the requirements of components, singly or as groups. This provides the basis of planning tools useful in the capital intensive business of the construction of new manufacturing facilities or the reconfiguration of existing ones. The success of this modelling approach is dependent upon having an appropriate representation of the design geometry. The representation must be such that all geometric inquiries raised by the process capability modelling are either explicitly held within some data representation or alternatively can be derived algorithmically by reference to a geometric model. The representation must also be capable of withstanding the rigours of use within the wider context of implementing an important part of the CAM interface within a CIM environment. This paper describes a feature-based representation based on a feature taxonomy which uses External Access Directions (EAD) as the characterizing aspect of geometry. These EADs become potential machining directions for a collection of features on a component, and are used as an essential link into generative process planning activities. The representation has been used in conjunction with process planning and process capability modelling applications. This paper concentrates on the latter, where the feature representation has been embedded within a proprietary geometric modeller which has been provided with a purpose-built user interface. A feature-based component model is created by the geometric modeller and accessed by functions which enable flexible component grouping and matching to process capability through the concept of a composite component. Subsequent process component grouping within the context of particular manufacturing systems strategies (cellular manufacture, flow-line, etc.) ultimately results in functional machine descriptions and variants

Shadow-scanned human representations for car seat design

Modelling of the human body has a long history as an essential component of computer aided design systems which provide ergonomic analysis of workplaces and equipment. A current Brite-Euram project is concerned with life-cycle aspects of car seating from design through manufacturing and eventual re-cycling. Loughborough University is responsible for driver comfort assessment which is being carried out through road and laboratory trials, the results of which are to be incorporated within the SAMMIE computer aided ergonomics design system. The human body is infinitely variable in shape and dimension and this leads to particular difficulty in generating initial shape representations and subsequently manipulating these to represent individuals or general populations. This paper is principally concerned with a method for capturing shape information and transforming it into a CAD surface representation. The capture method uses a shadow scanning technique where the human body can be scanned in a matter of minutes and ordered coordinate information provided. This information has been processed for input into the DUCT surface modeller where some data reduction can take place before being output in the form of IGES B-Spline surfaces. These surfaces are then processed into a quadrilateral mesh representation that can be handled by the PHIGS functionality implemented within SAMMIE

Tools for User-Centred Design

User-Centred Design aims to involve users at all stages of the design of products. Some of the basic principles are briefly considered together with their relationship to ergonomics. Tools for the application of User-Centred Design are discussed including specific tools such as digital human modelling, personas, manikin characters, inclusive design and human behavioural modelling

Emulation of modular manufacturing machines using CAD modelling

Designing, testing and debugging a machine control system which controls mechatronic hardware elements can be a complex, time consuming and costly procedure. It is often extremely difficult for the system builder to envisage in advance the effects of small changes to the control system logic, with potentially dangerous results if the hardware consists of heavy machinery. It is also rare that a system builder will arrive at a working prototype on the first attempt and discovering the reasons for incorrect operation without a suitable means of comprehending the problems can be an arduous task. This paper describes an approach which supports the designing, testing and debugging of modular manufacturing machines using 3D graphical models of the machine hardware. The paper emphasises the underlying methodology of the approach, which involves collecting timing data from the executing control system under development, then emulating the operation of the machine by using this data to drive a graphical model of the hardware. The term “emulation” is used to mean modelling using data captured from the real machine as opposed to “simulation” which synthesises data. The work builds on previous research at the MSI Research Institute concerned with the control of modular machines. Two new extensions to this work are described here, which form the basis of the emulation capability. The first is the addition of the ability to execute the control system without the mechatronic hardware elements present whilst still retaining the operational behaviour of the application. The second is the mechanism for collecting the run-time data which defines these operational characteristics, to drive the machine emulation. The features of the custom 3D modeller are presented and its use for machine emulation is described. An example of a real control system under development is given to illustrate the complete process. The research objectives of the work described here are concerned with the fundamental problems designers encounter when trying to prototype the control systems of modular machines. The research has shown that the ability to execute the control system with or without the mechatronic hardware elements present can be a considerable advantage if supported by a CAD-based emulation system

Failure Modes and Effects Analysis (FMEA) in maintenance and diagnostics

Failure Modes and Effects Analysis (FMEA) is a tool that has long been used at various stages of the product life cycle but is most commonly used in the engineering design and manufacturing planning stages. Some work has been done on conceptual design stages but very little, if any, research has been conducted to understand how FMEA might be used during the service of the product. Furthermore, the feedback of performance knowledge (in the form of FMEA data) from the in-service product use to conceptual and engineering design is a potentially valuable but un-exploited activity. This can be seen as a possible method of implementing Design for Service. Diagnostic service tools (manuals, computer diagnostics, etc) are usually created as a post-production activity, but reuse of FMEA knowledge generated during design could be used in a concurrent activity. Additional benefits are gained from improved accuracy of the FMEA and the maintenance of up-to-date product knowledge. A system for computerised interactive FMEA generation from FMEA elements has been created from the research. An object-oriented FMEA model has been adopted and expanded to generate the FMEA elements and diagnostic FMEA. The use of an object-oriented FMEA environment and FMEA object libraries promotes the reuse of existing information and has increased data availability for the diagnostic tool development. The Diagnostic Service Tool (DST) is an extended application from the automated FMEA generation. Existing failure mode data is used to determine further characteristics of parts failure. As a result, a tool in the form of diagnostic software is created which is practical for real life use. The prototype software was evaluated in a field service application using four automatic transmission problem cases. The results showed that there was significant difference in repair times between the conventional repair manuals and DST. The research has demonstrated that the prototype software is successful in providing effective field service centered tools to the Field Service and in turn a method of providing feedback to the Designer. Hence, knowledge sharing between Engineering and Field Service can be carried out continuously to provide a significant improvement in product development

Feature technology - an overview

Manufacture is an objective that has become more urgent within the wider context of a total Computer Integrated Manufacturing environment. In seeking this integration it is recognised that the diversity of activities and consequent needs for data can best be served by a single representation for design, design analysis and manufacturing planning, and that a strong candidate for this descriptive role is a Feature Representation. This paper briefly overviews the primary methods of the use of features through Feature Recognition and Design by Features, particularly in the process planning application area

Feature technology : an overview

The proper integration of the activities of computer-aided design (CAD) and computer-aided manufacture (CAM)is an objective that has become more urgent within the wider context of a total computer integrated manufacturing (CIM) environment. In seeking this integration it is recognized that the diversity of activities and consequent needs for data can best be served by a single representation for design, design analysis and manufacturing planning, and that a strong candidate for this descriptive role is a feature representation. This paper briefly overviews the primary methods of the use of features through feature recognition and design by features, particularly in the process planning application area

Towards understanding of human behaviour in crowded spaces

Human behaviour in the real world is important information for developing human behaviour models and simulations. However, it is difficult to capture ‘real’ human behaviour since each human has unique char-acteristics. As part of the AUNT-SUE (Accessibility and User Needs in Transports - Sustainable Urban Environments) project, this research is aimed at understanding individual human behaviour in crowded spaces based on video observation analysis. The video observation analysis employed a video observation method where a multi-mode transportation system in Malaysia was selected as a case study. The observa-tion focus was at an exit door where considerable variety of human movement and behaviour could be observed. Six hours of video recording was conducted covering weekdays, weekends, peak and off-peak times. Almost 19,000 individual humans were observed and categorised into six different behaviours that were determined from the three major human movements of free, opposite direction and same direction movement

The logical and geometric modelling of a universal machine control reference architecture

This paper reports on new research into the computer modelling and simulation of the UMC (Universal Machine Control) Reference Architecture. A key factor in the UMC Reference Architecture is the provision of aset of software configuration tools to facilitate the building of modular machines and machine control structures. In this respect the roles of geometric solid modelling and logical control modelling are emphasised in the paper

The impact of manikin family configuration on accommodation

The complexity in considering human anthropometric diversity in multivariate problems commonly leads to a situation where more people are excluded by the design than was the objective. Ergonomists and product designers would benefit from tools and methods that make it less demanding to assess and achieve the expected accommodation level of the product in multivariate design problems. One approach is to employ computer manikin families in human simulation tools. This paper discusses how different configurations of two manikin families affect the way they represent targeted users