زمان بندي تعمير محصولات برگشتي به همراه تعيين اندازه و زمان سفارش‌دهي قطعات يدكي آنها در لجستيك معكوس دوسطحي

Repair Scheduling of Returned Products with Spare Parts Lot Sizing and Scheduling in Two Level Reverse Logistics

در اين مقاله، سيستم توليدي دمونتاژ- مونتاژ سه مرحله اي در لجستيك معكوس از مطالعه صنعت هوايي شناسايي و معرفي شده است، همچنين زمان بندي تعمير محصول برگشتي و تعيين اندازه و زمان سفارش انباشته قطعات يدكي به طور همزمان در آن بررسي شده است. تصميم گيرنده، به دنبال كمينه كردن مجموع هزينه ‌ها، شامل ميانگين وزني اتمام كارها (تعمير بالگردهاي برگشتي) و هزينه هاي موجودي قطعات يدكي است. يك مدل يكپارچه از طريق مدل سازي برنامه ريزي عدد صحيح مختلط خطي براي مسيله توسعه داده شده است. سپس حل مدل و حساسيت جواب‌‌ها نسبت به تغييرات پارامترهاي كليدي براي مسيله پايه در صنعت هوايي بررسي شده است. استراتژي هاي مختلف تعمير قطعات يدكي، توسط مونتاژگر، به عنوان سناريوهاي جايگزين با استراتژي تعويض قطعه با قطعات دريافتي از توليدكننده، در 120 مسيله نمونه اي مقايسه شده است. با وجود عملكرد بهتر استراتژي تعمير قطعات مشترك به طور ميانگين، نتايج، مويد لزوم اتخاذ استراتژي‌هاي مختلف در دوره هاي مختلف عمر قطعات برگشتي است.

In this paper a new problem of three stage disassembly-assembly scheduling is introduced and reviewed. This problem, which was arisen from the aviation industry characteristics, is a generalization of the two stage assembly scheduling problem. Products (helicopters) in the aviation industry return to assembler for annual overhaul repair services. In the first stage helicopters are disassembled into their components. After that, the components are sent to their dedicated machines in the second stage for repair operations concurrently. In the second stage, some of the components may require one or more spare parts. Repair operations of the components can be started when their required spare parts are available at that time. After completing all of the component operations, the assemble stage can be started. In this problem we consider repair scheduling of components and lot sizing and scheduling of their required spare parts with the objective of minimizing sum of total completion times of the retuned products and spare parts inventory costs. In this study, an integrated formulation approach has been employed for the problem and a linear MIP was developed. A base case from aviation industry was solved and results were analyzed. The sensitivity analysis of the problem was carried out by changing key parameters of the base case. Selecting a repair strategy or changing to a new strategy is a key decision in the aviation industry. In this study, changing to a new strategy has been compared with three existing repair strategies in 120 problem instances using three types of data sets. Results showed that various strategies could be selected depend on the quality of returned products. The repairing shared items strategy has a better performance in average compared to the other strategies.