K.K.B. Hon

Performance and Evaluation of Manufacturing Systems

Abstract The monitoring and control of the input and output of manufacturing systems is an essential task for the system optimisation. Performance of manufacturing systems covers a wide spectrum of technology and management activities. This paper reviews the historical evolution of and modern developments in manufacturing performance measurement within a systems framework based on five metrics and five levels from single workstation to the entire manufacturing network. A summary of an industrial survey in the aerospace industry is also included to provide an industrial perspective. The implications of emerging topics of growing importance in sustainability, agility, e-manufacturing, complexity and biomimetics are also discussed.

Selective Laser Sintering of SiC/Polyamide Composites

Abstract This paper presents an experimental study into the production of particulate Silicon Carbide/Polyamide matrix composites via the selective laser sintering (SLS) process. FEPA standard SiC grit, F240, was blended with the commercially available Duraform Polyamide to produce blend compositions of 50 volume percent and 50 weight percent SiC for direct SLS processing. A full factorial experimental approach was applied to examine the effects and interactions of laser power, scan speed, line spacing and layer thickness with regard to the mechanical and physical properties of composite sintered parts. Analysis of results and discussions of parameter interactions and individual main effects especially with regard to part strength are also presented.

Experimental investigation into the selective laser sintering of silicon carbide polyamide composites

Abstract This paper presents an experimental investigation into the production of particulate silicon carbide (SiC) polyamide matrix composites via the selective laser sintering (SLS) process. FEPA standard F240 SiC grit was blended with Duraform polyamide to produce a powder blend composition of 50 wt% SiC for direct SLS processing. A full factorial experimental approach was applied to examine the effects and interactions of key fabrication parameters, with regard to the tensile strength and porosity of the composite SLS processed parts. Output from the factorial analyses is presented and discussed and a comparison between the responses obtained for tensile properties and morphology of the SLS processed parts was also investigated. The optimum energy density for producing parts with maximum strength and minimum porosity was determined experimentally. A further study into the effects of powder blend composition and energy density with regard to tensile strength of composite specimens is also presented. This investigation revealed that the optimum energy density for producing parts of maximum strength was independent of the initial powder blend composition.

New approaches for the nesting of two-dimensional shapes for press tool design

In this paper two approaches to the automatic pairwise clustering of two-dimensional shapes for press tool design are discussed. The first is based on extracting the edge information in the form of edge arrays, which are manipulated to obtain the optimum pairing; while the second applies the non-deterministic concepts of genetic algorithms. The results of applying both approaches are also presented.

Integration of rapid prototyping technology into FMS for agile manufacturing

The problem of inaccuracies of models manufactured by layer manufacturing technology has greatly limited its intended level of exploitations especially in the down‐stream applications and integration into the FMS and CIM. The principles of cellular manufacturing together with various examples of its application and benefits are well documented. Increased competition combined with customer demand for quality, speed, product performance and lower costs are putting an ever‐greater burden on manufacturing. Not only do products need to be launched faster than ever, but also manufacturing needs to be flexible in rapidly retuning its facilities. The move to cellular manufacturing, TQM or CIM or other techniques alone is thus no longer enough. Instead, the challenge is increasingly one of compressing the time it takes to continually “re‐invent” the manufacturing system in order to meet the prevailing demands of the market place. This paper presents a comparative study on the effects of hatch patterns on stereolithography models using epoxy‐based resin in a CIM environment. A unique experimental investigation has been carried out with two new hatch patterns, Divergent Star‐weave, (DSW), and Diagonal Divergent Star‐weave (DDSW), which have significantly improved the stereolithography product quality, and reduced lead time thus yielding a significant tool in agile manufacturing.

Automated Design of Progressive Dies

This paper describes the structure and operation of a prototype intelligent system for progressive die design and manufacturing. The system is developed using X Window ‘C’ programs to create an interface linking the CAD (computer aided design) package, AutoCAD and the expert system shell, Kappa. AutoCAD is used for the input of the piece part geometry, creating the temporary drawings and final design drawings of the tool parts and assembly while Kappa is used to create the knowledge base, the databases of the standard tool parts and the menu system for entering design data. Purpose-built ‘C’ programs are also used for some numerically intensive computations, for example calculating the best material utilization. The system knowledge is based on a structured analysis of present press tool design techniques.

The Nesting of Two-dimensional Shapes using Genetic Algorithms

The general two-dimensional cutting stock problem is concerned with the optimum layout and arrangement of two-dimensional shapes within the spatial constraints imposed by the cutting stock. The main objective is to maximize the utilization of the cutting stock material. This paper presents some of the results obtained from applying a combination of genetic algorithms and heuristic approaches to the nesting of dissimilar shapes. Genetic algorithms are stochastically based optimization approaches which mimic natures evolutionary process in finding global optimal solutions in a large search space. The paper discusses the method by which the problem is defined and represented for analysis and introduces a number of new problem-specific genetic algorithm operators that aid in the rapid conversion to an optimum solution.

A study of cutting forces and surface finish in high-speed machining of AISI H13 tool steel using carbide tools with TiAlN based coatings,

Abstract High-speed machining (HSM) has emerged as a key technology in rapid tooling and manufacturing applications. In this study, the effect of increased spindle speeds on surface finish is examined. Physical vapour deposition (PVD) coated ball-nose micrograin carbide tools are used in finishing cuts for spindle speeds up to 42 000 r/min and a real-time force acquisition system is used to study the orthogonal forces. The importance of orthogonal force components to surface finish prediction and control is explored. The results show that Fz axial force has a very strong correlation with surface finish and that increased spindle speeds lead to far superior surface finish. Multilayer TiAIN coated carbides were found to generate the best surface finish while the uncoated tool and TiAIN + WC/C lubricant coating led to a severe degradation of surface finish at increased spindle speeds.

An Intelligent Object-Oriented Approach to the Design and Assembly of Press Tools

Abstract In recent years, research communities and industries have started to develop knowledge-based tooling design systems to tackle the common difficulties that most companies have. The most widely used strategy is accommodating the know-how into an expert system and linking it with a CAD system. This paper describes the structure and operation of a prototype intelligent system for progressive die design and manufacturing. The system is developed using X Window C programs to create the interface linking the CAD package, AutoCAD, and the expert system shell, Kappa. AutoCAD is used for the input of the piece part geometry, creating the temporary drawings and final design drawings of the tool parts and assembly. Kappa is used to create the knowledge base, the databases of the standard tool parts, and the menu system for entering design data. C programs are also used for some intensive computations, for example, calculating the best material utilisation.

A new approach of group technology part families optimization

Abstract The key question of forming a group technology (GT) based manufacturing system has attracted numerous attempts in applying various optimization techniques. This paper presents a new approach of optimizing GT part family formation by genetic algorithm (GA) which is based on the principles of natural selection. A genetic algorithm model combining a coding design, a penalty factor and a scaling operation was developed for this purpose. Results generated from four case examples and comparisons with three other heuristic methods demonstrated that the genetic algorithm approach provides a powerful and effective numerical tool for the optimization of GT part-families.