Material Production Systems Research Articles

A simulation model of the comminution–liberation of recycling streams: Relationships between product design and the liberation of materials during recycling

End-of-Life (EOL) products can be considered to be industrial ores, since the minerals (materials can be considered as minerals) contained are recovered, processed and reintroduced in the material production systems as industrial ores. Therefore, the principles used in classical minerals processing can be applied to describe the comminution and liberation of EOL products during recycling. Similarly as for natural ores, particle size reduction and liberation have an important role in the quality of the recycling streams and on the possibilities for their further processing and reintroduction in the resource cycles. A simulation model is presented that describes the relationships between product design and the liberation level attained by shredding. The model simulates the comminution and liberation phenomena as a function of the product design variables. From the analysis of experimental samples, sensitivity analysis and simulations, relationships are illustrated and discussed. The breakage behaviour of End-of-Life (EOL) products differs largely from these natural minerals. Therefore, although many definitions can be adapted from classical minerals processing, a different approach is required in the modelling of the comminution–liberation of EOL products. This is the first step in the development of these type of models, and much experimental work is required for further development. The simulation results using a passenger vehicle as example show that during product design, the materials and joints among them can be chosen to obtain the best possible liberation and the lowest possible contamination. Therefore, industrial ores can be ‘designed’ for recycling, to reduce recycling losses and optimise resource efficiency. The aim is to implement this knowledge in the product design stage of defining materials and connections.

Building materials production centers in developing countries

The need for shelter is a growing worldwide problem. In developing countries this need far exceeds the capacity of government agencies to respond. self-help techniques often provide alternative means for lower income people to imporve their own shelter and community services with a minimun of outside assistance. These techniques may often require the introduction of less advanced, but appropriate building technology is important. It is, however, only one part of a comprehensive system needed to produce better housing. In many countries, technology is the least important constraint; more serious concerns are building technology is important. It is, however, only one part of a comprehensive system needed to produce better housing. In many countries, technology is the least important constraint; more serious concerns are managerial and financial obstacles. The Building Materials Production Centers concept is part of a larger shelter development strategy; a Cooperative Development System 1) aimed at promoting low-cost housing in developing countries. The self-help construction that takes place in squatter settlements and rural areas is often poorly served by the formal construction industry material suppliers and must rely on informal material production systems for building materials. Building Materials Production Centers can be established to meet the needs of these settlement areas in a more efficient way at a reasonable cost and at locations where people are improving their own housing and communities.

A unified setting for various models of automated material flow and production systems

A conceptual framework is proposed for the description of discrete-event models of material flow and production systems. It is built in accordance with the traditional view of systems as a set of related objects. Objects express resources, and relations define activities. Various models can be described by the way the state-transition mapping is specified, such as stochastic queuing networks, event-graphs, Petri nets, and discrete-event simulation models. The proposed setting may help building consistent models at various stages of the design of a manufacturing system, and can be used as a basis for a tutorial presentation of existing approaches.