W.A. Knight

Design for disassembly and the environment

Abstract The financial and environmental consequences of disassembly and recycling at the end of a products life are studied. Analyses of a small coffee maker and some large domestic appliances are presented. It is shown that redesign proposals resulting from Design for Assembly analysis are compatible with Design for Disassembly and that significant improvements are achievable. It is also shown that optimization of the disassembly sequence is important in order to maximize any financial benefits, but that to minimize environmental impact considerations additional to Design for Disassembly should be taken into account. Criteria to determine the point at which disassembly should cease are discussed

Computer-Aided Cold Forging Process Design: A Knowledge-Based System Approach to Forming Sequence Generation

Abstract This paper presents some developments on the design of a Knowledge-based system approach to generate technologically feasable preforming sequences for multi-stage cold forging of solid and hollow rotationally symmetric parts. The sequences are intended to be initial designs which need additional analyses and evaluations in order to identify the most appropriate forging sequence. The approach is based upon a backward direction of the generative process and takes advantage of the division of the design rules which govern, respectively, (i) the recognition of operations, (ii) determination of the relevant deformation, and (iii) sequencing and grouping of the different operations.

Product Design for Disassembly and Bulk Recycling

Abstract The recycling of manufactured products depends greatly on the efficiency with which material can be separated from each other. For the long term, recycling can be made more effective by the design of products for greater use of disassembly and recycling. This requires the development of suitable product analysis tools to enable design teams to evaluate the ease of disassembly and recycling of alternative product concepts during the early stages of design. This paper describes the development of product analysis procedures for combined disassembly and bulk recycling such that consequences of material selection upon the end-of-life recovery of materials can be investigated.

Design for Bulk Recycling: Analysis of Materials Separation

Abstract Increased interest in the life cycle design of products has resulted in emphasis on the disassembly and recovery of materials at product end-of-life. For many products the cost of disassembly will outweigh the value of any materials recovered and such products will be processed by bulk recycling involving shredding and mechanical material separation. The efficiency of bulk recycling is influenced by a number of factors including the selection of materials during product design. This paper deals with the analysis of materials separation, which determines the least cost or maximum profit level of materials separation. This can be used for the evaluation of product designs for efficient bulk recycling and the combination of disassembly and bulk recycling.

Computer Aided Design of Multi-Stage Cold Forging Process: Load Peaks and Strain Distribution Evaluation

Summary This paper describes some developments of an interactive program aimed at assisting the user in analysing for suitability the forming sequences for multi-stage cold forging of rotationally symmetric parts. The program capabilities include (i) the automatic analysis of sequences in forging solid as well as hollow parts and recognition of individual operations involved in each step, (ii) the evaluation of the load-peak distribution in the different forming stage-and (iii) the prediction of the strain distribution accumulated in the blanks and the finished part. The program is part of an integrated system consisting of a suite of interactive procedures whose purpose is facilitating all the engineering activities for the process planning functions involved in manufacturing components on automatic multi-station cold forging machines. The major implication of including the developed program in this CAD system is that of providing the user with the tools suitable to perform a complete producibility check and to identify the most appropriate forming sequence.

Design for Assembly Analysis: Extraction of Geometric Features from a CAD System Data Base

Design for assembly analysis procedures require certain geometric properties for each component part and sub-assembly. Algorithms have been developed for extracting this geometric information directly from a CAD system data base. This paper describes the implementation of these procedures and demonstrates their use by application to typical assembly. A wire frame geometric model of each component is developed and then graph theory used to determine automatically such features as part size and symmetry.

A New Approach to the Optimization of Blends Composition in Injection Moulding of Recycled Polymers

The use of recycled polymers is widespread for the injection moulding of many commodity plastic parts. Recycled polymers are usually blended with virgin polymers to obtain the best trade-off between cost and low melt viscosity. This last constraint is necessary to avoid short shots and to minimize the clamp force of the required injection moulding machine and, therefore, the process cost. The current industrial approach to this problem is to select the polymer blend by trial and error. In this paper a new approach to the minimisation of the overall manufacturing cost is proposed. It is based on a rheological model of the blend which has been developed from experimental tests according to the mixture design technique. The approach has been validated through an industrial case study.

Integrated Design Analysis for Product Simplification

A systematic methodology is presented for product structure simplification through an integration of Design for Manufacture and Assembly (DFMA) with the Theory of Invention Problem Solving (TRIZ). A new functional model is combined with a selection of TRIZ problem solving tools that are identified as effective in product structure simplification. DFMA analysis is used to evaluate alternative concepts. Application of the combined approach is illustrated through a case study of a heavy duty stapler.

Design for Manufacture: Expert Processing Sequence Selection for Early Product Design

Summary A method to Systematically map part geometry and material requirements onto sequences of processes and compatible materials is described. The geometrical and material constraints of the design are input information for the system. The system produces a list of practical processing sequences and material combinations. The sequences are ranked according to the difficulty of manufacturing the Dart with particular processes selected and how well a material meets the material requirements for the part.

Economic Impacts during Microelectronics Product Design

Abstract An integral part of product design for manufacture is the use of predictive cost models to quantify the effects of early design decisions. An investigation has been performed to develop a set of detailed cost models to estimate the economic impact of microelectronics integrated circuit (IC) design alternatives. Cost-of-Ownership models, developed for IC fabrication equipment, are extended to the various cost domains in the microelectronics development cycle, including optical lithography and design for test solutions. The developed cost models have been implemented in software tools and these utilised to assess the effects of various design and processing options on overall IC manufacturing costs