An investigation into short production runs in spray drying plants of the New Zealand dairy industry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Industrial Management and Engineering at Massey University
The features of short production runs in spray-drying plants of the New Zealand Dairy Industry were examined and some methods developed to help improve productivity in dealing with them. In particular a survey was carried out of the managers of all spray-drying plants in order to establish quantitative and qualitative information on short production runs. It was found that short production runs could be classified into those caused by interruptions to runs, such as mechanical breakdown, those caused by specification changes, and those caused by the decision to run the plant for a limited period, usually as a result of the limited milk available for processing. The effect of capacity utilisation on spray-drying plants and the costs of smoothed milk flow were examined and it was found that smoothed milk flow could not be justified on economic grounds alone. The occurrence of short runs due to specification changes in other industries is documented as are methods to overcome their costs. It was concluded that the major effects in spray-drying plants were likely to be through set-up cost and learning behaviour. However, it was found that neither of these seriously affected cost of powder manufacture, short production runs due to specification changes were dealt with without excess costs over normal manufacture. The relationship between run length and energy consumption and run length and processing rate were examined and quantified. A computer based management information system was developed to assist in the control of costs in general and short production runs in particular in spray-drying plants.