A study on lot-size dependence of the energy consumption per unit of production throughput concerning variable lot-size

Recently, in order to reduce energy consumption while maintaining productivity in lines, industries require pre-evaluation methods and production management methods that consider these aspects simultaneously. A pre-evaluation method that considers both productivity and energy consumption and simultaneously calculates productivity and energy consumption during the planning of a manufacturing system has already been proposed. In addition, with production management methods that consider productivity and energy consumption, the lot-size dependence of energy consumption per unit of production throughput has been formulated and verified. On the other hand, because the needs of consumers have become more diverse, mass customized or high-mix low-volume manufacturing systems, in which lot sizes vary, have been developed. We defined the condition in which lot size is not varied as "constant lot-size", whereas the condition in which lot size is varied as "variable lot-size". We define the variable lot-size that lot sizes are not constant during a certain continuous production time. However, production management methods that consider variable lot size have not developed. Therefore, we propose a formulation for the lot size dependence of the energy consumption per unit of production throughput for variable lot sizes. The key parameter of this formulation is the average lot size, as the throughput and energy consumption per unit of production throughput are independent of the lot size distribution. We also carry out case studies using a discrete event simulation to verify the proposed formulation.