Abstract:
A Transportation problem of galvanized steel coils from manufacturer to customers is a daily delivery planning that different coils ordered from each customer were combined as coil groups for loading each coil group on the same truck. The total number and total weight of the coils for each group must not exceed the maximum loading capacities of the truck. Every coil group should have the total weight at least the minimum weight for transportation cost calculation of each shipment. Then the planner will assign logistic providers from three possible companies to carry which groups of coil to their corresponding customers. Three logistic providers have different transportation cost and different minimum monthly shipping proportion by weight as identified in their service contract. Therefore, the problem becomes the allocation problem of coil groups to each logistic provider with minimizing transportation cost as objectives and total shipping weight for each company as restriction. This research proposed a mixed-integer linear programming model (MILP) for coil shippment daily scheduling to minimize transportation cost. The OpenSolver software with CBC optimizer was used to find the solution from the proposed MILP model. The performance of the model was evaluated by comparing with the real coil transportation data set of 59 days in three months. The data set has the average number of customer equal to 11 customers per day, the average total number of coil equal to 153 coils per day, and the average total weight equal to 1,353 tons per day. The results revealed that the MILP was able to find all feasible solutions. The transportation cost was decreased 178,161 baths per month. The monthly shipping proportions by weight for all logistic providers were conformed to their contracts. The total weight associated with transportation cost from the shipping weight less than the minimum limit was reduced 180.7 tons per month or 34.1%.