Proposal of a downsized factory and an index to evaluate its system efficiency

Micro mechanical fabrication is one of the important and practical technologies in nowadays manufacturing. Since all the manufacturing technologies should be environmentally conscious, recently, one basic idea was to downsize manufacturing system for micro/meso mechanical fabrication to reduce environmental impact of manufacturing. AIST, Japan developed the first prototype of a desktop manufacturing system named "microfactory", as a countermeasure for the situation. It consisted of miniature machine tools and robot manipulators. The trial was successful, though, whether the system is really "eco-efficient", or not, has not been examined quantitatively. An appropriate index to evaluate manufacturing systems by considering environmental impacts, costs and system throughput, simultaneously, will help the concept to become more popular. In this report the authors propose a system efficiency index named "total performance indicator (TPI)". Using the microfactory as an example, the paper tries to show that the proposed efficiency index is useful in evaluating and designing configurations of manufacturing systems. Comparison with a conventional system indicates that microfactory-like systems are hopeful as environmentally conscious manufacturing systems for micro mechanical fabrication.