Profit-oriented disassembly-line balancing

As product and material recovery has gained importance, disassembly volumes have increased, justifying construction of disassembly lines similar to assembly lines. Recent research on disassembly lines has focused on complete disassembly. Unlike assembly, the current industry practice involves partial disassembly with profit-maximization or cost-minimization objectives. Another difference between assembly and disassembly is that disassembly involves additional precedence relations among tasks due to processing alternatives or physical restrictions. In this study, we define and solve the profit-oriented partial disassembly-line balancing problem. We first characterize different types of precedence relations in disassembly and propose a new representation scheme that encompasses all these types. We then develop the first mixed integer programming formulation for the partial disassembly-line balancing problem, which simultaneously determines (1) the parts whose demand is to be fulfilled to generate revenue, (2) the tasks that will release the selected parts under task and station costs, (3) the number of stations that will be opened, (4) the cycle time, and (5) the balance of the disassembly line, i.e. the feasible assignment of selected tasks to stations such that various types of precedence relations are satisfied. We propose a lower and upper-bounding scheme based on linear programming relaxation of the formulation. Computational results show that our approach provides near optimal solutions for small problems and is capable of solving larger problems with up to 320 disassembly tasks in reasonable time

Equivalence of the LP relaxations of two strong formulations for the capacitated lot-sizing problem with setup times

The multi-item capacitated lot-sizing problem (CLSP) has been widely studied in the literature due to its eminent relevance to practice such as constructing a master production schedule. The incorporation of setups crafts CLSP with a realistic feature demanded by practice. In this paper we present a complete proof for the linear equivalence of the shortest path formulation (SP) and the transportation formulation (TP) formulations for the CLSP with setups. Our proof is based on the linear transformation from TP (SP) to SP (TP). We explicitly consider the zero demand case in our proof since it is frequently observed in the real world and test problem instances used in the literature

Equivalence of LP relaxations of two strong formulations for the capacitated lot-sizing problem with setups

The multi-item capacitated lot-sizing problem (CLSP) has been widely studied in the literature due to its eminent relevance to practice such as constructing a master production schedule. The incorporation of setups crafts CLSP with a realistic feature demanded by practice. In this paper we present a complete proof for the linear equivalence of the shortest path formulation (SP) and the transportation formulation (TP) formulations for the CLSP with setups. Our proof is based on the linear transformation from TP (SP) to SP (TP). We explicitly consider the zero demand case in our proof since it is frequently observed in the real world and test problem instances used in the literature