Julian D Booker

Industrial practice in designing for quality

The improvement of the quality of design and the reduction of failure related cost is seen as a crucial competitive requirement for UK manufacturing industry. To achieve these goals, industry must adopt current methods in support of design for quality (DFQ) for analysing potential problems and predicting quality, and integrate these effectively with the appropriate stages of their new product development process. The utilisation and success rate of these techniques in UK companies is, however, relatively low compared to those in countries such as the USA and Japan. In this paper, the fundamental concepts and key areas of opportunity in design improvement using the main DFQ support techniques are reviewed and a framework for their application and integration is presented to support concurrent product development. The typical experiences and problems concerning the application and implementation of techniques are discussed and areas where new research should be directed are touched on so that DFQ techniques may better enhance industrial practice in the achievement of high quality products.

Designing for assembly quality: strategies, guidelines and techniques

Component design decisions and choice of assembly technology ultimately impact on the final quality of a product. Problems may arise when a component’s design puts limits on the technical performance of an assembly operation. Recently, efforts have been focused on predicting component quality levels through variability and process capability measures at the design stage, but the variability associated with assembly operations is rarely considered in the context of quality. This paper reviews the current assembly-orientated design techniques available to detect potential quality problems and identifies the key issues relating to assembly quality, including the relationship between the components, operations and assembly technologies used. An approach is presented for highlighting potential assembly variability problems early in the design process and its application is demonstrated through the use of an industrial case study.

Analysis of Semipermeable Containment Sleeve Technology for High-Speed Permanent Magnet Machines

This paper presents an alternative permanent magnet rotor containment technology. The use of a semipermeable material in a laminated structure is shown to result in a significant improvement in magnetic loading for a given thickness of containment compared to the use of magnetically inert materials such as carbon fiber or Inconel, while minimizing eddy current losses in the containment layer. An analytical model is presented for determining the air-gap field delivered from a permanent magnet array with a semipermeable containment. The analysis is validated through finite element analysis. The fabrication of a prototype machine is detailed and the results presented show good agreement with the analysis. The validated modeling process is used to assess the potential of the new technology.

A statistical study of the coefficient of friction under different loading regimes

Shrink-fits are common engineering fastening systems that comprise a cylindrical hub and shaft locked together by a radial pressure due to interference in size at their interface diameter. Frictional forces at the interface allow the transmission of a torque or resistance to axial movement in the assembly. The measurement of the coefficient of friction under simulated shrink-fit conditions is difficult and time consuming. A flexible experimental approach is presented that can test over a range of pressures, sizes, loading directions, i.e. torsion, compression and tension, and which has the ability to detect changes in the normal load applied due to loading direction. A series of statistical validation studies are conducted on 15 mm diameter low carbon steel specimens to verify theoretical formulations that suggest the coefficient of friction is different for the different loading regimes, and also identifies the surface roughness measured axially or radially as being contributory to the final coefficient of friction value. The experimental approach is applied to a novel laminate sleeve for an electrical machine in order that high confidence is achieved in measuring the coefficient of friction under realistic service conditions.

Case studies in probabilistic design

Deterministic design fails to provide the necessary understanding of the variability associated with the properties of materials, manufacturing tolerances and inservice loading. Probabilistic design offers much potential in this area, providing an effective way of determining product life-time estimates, reducing failure costs and aiding the process of weight optimization in product design, but has yet to be taken up widely by manufacturing industry. In this paper, case studies are used to explore some important probabilistic design concepts and introduce methods that allow reliability performance measures to be assessed for product designs early in the product development process. The methods described are used in conjunction with Failure Mode and Effects Analysis to facilitate the setting of reliability targets for design proposals.

Performance of a Prototype Traveling-Wave Actuator Made From a Dielectric Elastomer

The primary aim of the research is to demonstrate the fabrication and operation of a traveling wave actuator made from a silicone dielectric elastomer. Multiple folded stack configurations of a silicone are assembled to create individually controllable regions in a single device, allowing a traveling-wave pattern of electrical stimuli to be applied to each active region. The prototype actuator is sandwiched between two friction surfaces allowing motion in response to the traveling wave. A number of issues related to the research and development of the prototype actuator are considered, including traveling-wave principle, folded stack design, actuator fabrication, and electrical control. A prototype is tested with a bespoke multiple-channel high-voltage converter to assess the performance characteristics of stroke, force, and frequency. Practical velocities and forces are achieved; however, a number of challenges are discussed in order to increase performance to comparable levels exhibited by commercial actuators with high-force long-stroke capabilities.

Characterising the performance of selected electrical machine insulation systems

This paper presents results from an analysis of alternative slot liner materials used in the construction of electrical machines. The slot liner material has a vital safety critical function within a machine assembly, providing electrical insulation between the winding body and stator core pack. Performance measures for the slot liner material include the dielectric breakdown voltage, tensile strength, thermal conductivity and thermal class, amongst others. There is a large variety of slot liner materials available on the market with the material properties altered to suit a particular application. Some of these material properties are strongly dependent on the components and processes employed in construction of the complete winding assembly e.g. type of the winding impregnation and/or method used in impregnation of the stator/winding assembly. Consequently, the manufacturer provided data is usually inadequate when comparing various insulation systems and their individual elements for a particular machine construction. This research is focused on the conductive heat transfer phenomenon from the winding body into the machine periphery in context of the slot liner material used, for a given impregnation type and method. The repeatability of the winding manufacture process is also investigated. Three alternative slot liner materials with different thermal conductivity and ability of absorbing varnish impregnation have been chosen for prototyping of representative stator/winding hardware exemplars. This has been supplemented with a batch manufacture of the stator-winding hardware exemplar for a selected slot liner material. The proposed experimental approach allows for the complete insulation system to be evaluated accounting for the assembly and manufacture nuances. The results suggest that the use of a particular slot liner has an impact on the winding heat transfer and also implications regarding appropriate manufacture and assembly processes used, i.e. some of the materials require special handling. The experimental work has been supplemented with theoretical analysis to provide a more comprehensive insight into the winding heat transfer phenomena.

Design and development of an active Gurney flap for rotorcraft

The EU’s Green Rotorcraft programme will develop an Active Gurney Flap (AGF) for a full-scale helicopter main rotor blade as part of its ‘smart adaptive rotor blade’ technology demonstrators. AGFs can be utilized to provide a localized and variable lift enhancement on the rotor, enabling a redistribution of loading on the rotor blade around the rotor azimuth. Further advantages include the possibility of using AGFs to allow a rotor speed reduction, which subsequently provides acoustic benefits. Designed to be integrable into a commercial helicopter blade, and thereby capable of withstanding real in-flight centrifugal loading, blade vibrations and aerodynamic loads, the demonstrator is expected to achieve a high technology readiness level (TRL). The AGF will be validated initially by a constant blade section 2D wind tunnel test and latterly by full blade 3D whirl tower testing. This paper presents the methodology adopted for the AGF concept topology selection, based on a series of both qualitative and quantitative performance criteria. Two different AGF candidate mechanisms are compared, both powered by a small commercial electromagnetic actuator. In both topologies, the link between the actuator and the control surface consists of two rotating torque bars, pivoting on flexure bearings. This provides the required reliability and precision, while making the design virtually frictionless. The engineering analysis presented suggests that both candidates would perform satisfactorily in a 2D wind tunnel test, but that equally, both have design constraints which limit their potential to be further taken into a whirl tower test under full scale centrifugal and inertial loads.

A survey-based methodology for prioritising the industrial implementation qualities of design tools

The early use of design tools in new product development has a significant impact on competitive business performance. However, their implementation by companies is not always successful. The main aim of this paper is to enhance research methodology for the development of new design tools to aid successful industrial implementation. A survey of existing research associated with the development and implementation of a wide range of design tools is reviewed, and categorised in terms of their ideal attributes, why, how and when they should be implemented, who should be involved, and where they are best positioned in the product development process. Known issues considered as implementation barriers are also presented in terms of practitioner and manager perspectives. Priority implementation issues are further identified from requirements analysis and the implementation history of four specific design tools at different implementation statuses. These qualities are then discussed in the context of enhancing research methodology for design tool development.

Joining process selection in support of a proactive design for assembly

Abstract There is extensive evidence to suggest that many industrial products are designed with far too many parts. Design for assembly (DFA) case studies indicate that, in many designs, large proportions of excess components are only used for joining. In many cases an excessive number of incorrect joining processes are used, possibly due to a lack of knowledge of such factors as availability, cost and functional performance of alternatives. Selection methodologies exist for some individual joining technologies. However, selecting the most appropriate technology is usually left to the designer through a non-formalized judgemental approach. This paper introduces a new methodology for identifying the most appropriate joining technology and its specific process variants, through both a paper-based methodology and software implementation, as a part of a proactive approach to DFA. The underlying strategy adopted is described and the selection process itself and its application to industrial case studies is demonstrated.