Heuristic scheduling

Abstract

Any form of heuristic scheduling in a factory is bound to create endless hustle and bustle in pursuit of one minor detail after another. Everyone then seems pressed for time and convinced that the factory, to say nothing of himself, is vastly overloaded. ‘Inevitably so’, is the managerial view, ‘since there is (usually) a full year’s work on the order book’. Nevertheless the accumulated down-time and the number of unscheduled hours booked to direct labour suggest rather strongly that all is not quite as cosy as it seems. No waiting time, of course—no chance of that with so much work on hand. Yet despite all this effort no one seems quite certain what tomorrow or, if on piecework, the next job will bring. Hence such frequent queries as ‘How do I get hold of that?’ and ‘What does the thing look like?’. Any manager in that situation has to be a kind of walking encyclopaedia with a quick answer to every problem. On the other hand such answers tend to be short-lived in that they merely engender fresh questions (almost without pause). No wonder that workshops then evolve their own dispatch decision rules, somewhat at odds with those decreed by the management:

• Jobs requiring the same auxiliary tools are combined to save set-up time and so make the rate more easily.

• Tightly rated jobs and jobs involving a high percentage defective are ignored for as long as possible.

• Certain people acquire a kind of customary right to specific jobs and keep special tools aside for the purpose.

• Whatever happens to be on top of the pile is done first.