Mechanical Technology January 2016

⎪ Structural engineering materials, metals and non-metals ⎪

Materials engineering in practice: the product-centred approach In this month’s column from Wits’ School of Chemical and Metallurgical Engineering Tony Paterson discusses the advantages of moving from a sequential approach to fabrication to a product-centred approach, based on reciprocal interdependence between the parties involved at every stage, from design, though material processing and manufacture.

all other work centres. The key issue is the need to achieve mutual cooperation and adjustment between all the centres of expertise. Why do we not follow this route? Whilst engineering is taught as a science, it is in fact an applied science. The sim- plified models taught may be simple or complex to analyse but usually fall into the known-known box of Figure 3. These models form a valuable reference base from which to work. However, applied science represents the art of engineering. The key skills required are judgement and compromise. Judgement considers both theory and applied knowledge, while compromise is necessary where required outcomes clash. Judgement is almost always required when unforeseen operational circumstances arise. In the context of materials, for exam- ple, operational circumstances define the load and load effects to which a structure will be exposed during its working life. In essence, anything that results in a stress in the material may be regarded as the material response to a load. However, in practice it would appear that, par- ticularly with the advent of systems, computer assists and specifications, the applied science that is engineering is being regarded as a pure science. For instance the Chemical Manufacturers’ Association defines mechanical integrity as “the establishment and implementa- tion of written procedures to maintain the on-going integrity of the process equipment.” [www.twi-global.com/ technical-knowledge]. This supports the sequential interdependence concept shown in Figure 1. Whilst system thinking, computer models and appropriate input or output specifications are valuable tools which should be embraced, they do not replace the need for expert input, this coming from a range of disciplines as we seek to develop lighter structures. Metaphorically tossing a problem over a contractual wall may only serve to shift blame rather than to gain from the opportunities of col- laboration using expertise from various sources. What makes engineering con- tinually interesting is that it is an applied

T he Chrysler plant in Kokomo, Indiana produces gearboxes. This includes design, casting, machining and assembly. Chrys- ler’s philosophy of placing its best and brightest on the factory floor is probably not unique and similar practices support Japanese manufacture, but in South Africa, the factory floor is not as highly regarded. The rationale is that, as monies are made or lost on the factory floor based on the performance of the end product in the market, looking for nascent problems before they emerge and for opportuni- ties for improvement make commercial sense. The administrative offices in these facilities are sparsely occupied, with all the necessary performance communica- tion reduced to dashboards. Locally we seem to prefer a top-down approach, with substantial administra-

tive offices and/or contract-based rela- tionships. This represents a sequential interdependence between discrete work centres, where coordination is achieved through planning and control, often through rigid procedures. This, illustrated in Figure 1, results in contractual rela- tionships with independent work centres linked via contracts. It works reason- ably well in an industrial production environment. Sequential interdependence, however, rarely results in effective communication. This is required for effective performance in project engineering passing through workshops and jobbing shops where products vary. Figure 2 shows an alter- native product-centred approach. The end product is the focus of success for all technical decisions. The correspond- ing communication structure is shown interacting with the product and with

Figure 1: Sequential interdependence between independent work centres. Coordination is achieved through planning and control via contracts.

Figure 2: The product-centred

approach and reciprocal interdependence enables each party to be dependent on each other. Coordination is achieved through mutual cooperation and adjustment based on end product goals.

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Mechanical Technology — January 2016