Proposal of an Efficiency Index for Supporting System Configuration Design

Demands for various miniature mechanical parts and products such as mobile phones, medical devices and so on, will increase more and more. Contrarily, manufacturing systems for those devices are becoming larger and more complicated. AIST developed the first prototype of a machineable microfactory which consisted of miniature machine tools and robots in 1999 as a countermeasure for the situation. An expected advantage of the microfactory was that the microfactory can reduce environmental impact and costs of miniature mechanical fabrication. However, the effect of the microfactory in reducing environmental impact and costs, or enhancing system efficiency have not been quantified. So, an appropriate index to evaluate microfactories by considering environmental impacts, costs and system throughput, simultaneously, is necessary. In the paper, the authors propose an evaluation index, based on the required time for each process, machine cost, operator’s cost and environmental impact, using the microfactory as an example. The calculation shows that the proposed efficiency index is useful in evaluating the system configuration.