An Environmental Impact and Cost Evaluation of Manufacturing System ― Application to a heat treatment system ―

Application to a heat treatment system

Abstract

Environmental benign manufacturing system has been pursued in manufacturing companies together with the reduction of manufacturing cost, which means the necessity of developing a simultaneous evaluation method of environmental and manufacturing cost. In general, environmental evaluation of the manufacturing system is difficult due to its complexity and peculiarity to each company. In this study, to cope with the problem, a hierarchically structured process flow in manufacturing system is introduced to visualize the manufacturing process. The process flow is composed of unit processes which stand for operations and the data necessary to the evaluation of environmental and cost are put into the lowest lever unit processes. Cost evaluation is carried out by the method of activity based costing. This method simultaneous evaluation of both environmental impact and manufacturing cost is applied to the evaluation of a heat treatment system. The system processes automotive machine parts with the use of either gas soft nitriding or gas carburizing method. In the case of gas soft nitriding the amount of CO2 emission, environmental impact defined by Eco-indicator 95, energy consumption and manufacturing cost per 1kg machine parts are 1.63kg, 5.50×10-3, 18.7MJ and 88.22 yen respectively. On the other hand, the corresponding values of gas carburizing are as follows: 0.655kg, 8.75×10-4, 7.7MJ, 55.36 yen. As the result, the method of gas carburizing is preferable from the viewpoint of environment and cost.