Determining a Suitable Mathematical Model to Predict the Repair and Maintenance Costs of Earthmoving Machines (Crawler tractor)

Repair and maintenance expenses as one of the variable costs, are necessary for improving the quality and quantity of machine performance. Records of such costs, can be affect predicting repair and maintenance expenditures. Mathematical modeling reduces the volume of these data and provide a better and more percision economical planning for managers. In order to fit those data and obtaining the relationship between accumulated hours of work and repair and maintenance costs, this study was conducted on selected 16 crawler tractors which are active in Earthmoving operations in the co-operative of Jahad Nasr in East Azarbaijan Province, Iran. Required information including operation hours and all costs by considering inflation rates were gathered over the period of ten years from 1997 to 2006. The regression analysis was done on four mathematical models (linear, quadratic, exponential and power), based on significance of coefficients for these models and maximum of. Therefore, the best and final model was quadratic which predicts lower costs than the other models mentioned previously. The reason may be atributed to the nature of quadratic model as well as the lower wages of repair and maintenance personnels in the region.