| Original equipment manufacturers are moving from product-centric to service-oriented.Performance Based Logistics(PBL)plays a vital role in service-oriented implementation cases.In this model,OEMs do not provide spare parts to customers,but ensure that the customer’s equipment is functioning properly,and manufacturers can maximize service profit by achieving availability goals.In contrast,the traditional service model is charged through the service time and the number of spare parts.This shift in service model has brought new challenges to the spare parts logistics system.One of the challenges for the original equipment manufacturers is that excessive spare parts will bring a lot of holding costs and acquisition costs,resulting in capital occupation due to the highly unstable demand,while too few spare parts will lead to the penalty cost of shortage.Another challenge is that as the market expands or contracts expire,equipment installation bases will change more frequently.For example,with the expansion of multiple regional markets,the scale of equipment installation is growing rapidly.In this context,how to optimize spare parts inventory strategy for time-varying installation base has a significant impact on the successful implementation of PBL strategy.The main research work of this paper is as follows:(1)Single-echelon repairable spare parts inventory policy under time-varying demand.The main objective of the model is to optimize the(S-1,S)base inventory strategy for multiitem repairable spare parts in the central warehouse,and we adopt a multi-phase approximation method to deal with the time-varying demand and multi-stage inventory strategies to maximize service performance gains.Considering the constraint of the filling rate of spare parts,the optimal allocation of the number of spare parts in the central warehouse is obtained through a heuristic algorithm based on marginal analysis.(2)Two-echelon repairable spare parts inventory policy under time-varying demand.The two-echelon inventory system consists of a central warehouse and multiple regional warehouses.In practice,in order to improve the service performance of the PBL,manufacturers usually place multiple regional warehouses close to their equipment in order to quickly replace faulty parts.The main objective of the model is to optimize the(S-1.S)base inventory strategy for repairable spare parts in central warehouses and multiple regional warehouses.During the market expansion phase,the installation scale of equipment in multiple regions is increasing,and the time-varying demand of spare parts is determined by the gradual installation of equipment and the random failure of equipment.We adopt a multi-phase approximation method to deal with the time-varying demand and multi-stage inventory strategies in order to maximize the benefits of service performance.Considering the constraint of the filling rate of spare parts,the optimal allocation of the number of spare parts in the central warehouse and multiple regional warehouses is obtained through a heuristic algorithm based on marginal analysis.(3)Taking the spare parts inventory system of two CT machines of D medical group as an example,the heuristic algorithm based on marginal analysis was used to obtain the optimal spare parts inventory strategy of single-echelon time-varying demand and two-echelon timevarying demand.Through examples,the model established in this paper conforms to the actual development law.Under the premise of ensuring the availability of the system,the cost of spare parts can be greatly reduced,ensuring the normal operation of equipment and the best guaranteed cost.This provides a reference value for the management of spare parts inventory management.The sensitivity analysis of the parameters is carried out under the optimal allocation of spare parts.The simulation results show that the model can significantly improve the decision-making related to inventory allocation.In this paper,the inventory model of repairable spare parts takes into account that the maintenance demand is time-varying,and the time-varying maintenance demand is due to the gradual installation of equipment.Assuming that the maintenance capability of spare parts is limited,the maintenance center adopts M/M/c/∞/nk queuing model.According to the model property,a heuristic algorithm based on marginal analysis is proposed. |
