The movement of more than one piece from operation to operation. Single piece or small lot production is nearly always better. Batch production is used for baking operations, for example, when installation of a smaller oven is not yet technologically or economically feasible. Batch operations are depicted as starbursts on value stream maps as sources of waste.
Little's Law can be exploited to reduce lead time of by reducing batch sizes. We have eliminated batch production in client processes by replacing ovens, paint booths, acid baths, steam cleaning and blast cleaning rooms with right-sized equipment, and by shortening changeover times for machining and other operations.