We discuss the design problem of a repair shop in a single echelon repairable multi-item spare parts supply system. The repair shop consists of several parallel multi-skilled servers, and storage facilities for the repaired items. The effectiveness of repair shops and the total cost of a spare part supply system depend highly on the design of repair facility and the management of inventory levels of the spare parts. In this paper, we concentrate on a design scheme known as pooling. A repair shop can be considered as a pooled structure if the spare parts can be divided into clusters such that each part type is unambiguously assigned to a single cluster (cell). Nonetheless, it is both an important and tough combinatorial optimization question to determine which type of spares to pool together. We propose a sequential solution heuristic to find the best pooled design by considering inventory allocation and capacity level designation of the repair shop. The numerical experiments show that the suggested solution approach has a reasonable algorithm run time and yields considerable cost reductions. Copyright 2018 by SCITEPRESS - Science and Technology Publications, Lda. All rights reserved.

The goal of this paper is to propose a novel mixed integer programming (MIP) formulation for the deadlock-free job shop scheduling problem with limited capacity buffers. Two scenarios are considered; the presence of a central buffer, and unit capacity input buffers for the machines. Due to the complexity of the problem, an operations insertion heuristic based on rank matrices is also proposed to solve the problem. In this heuristic, rank matrices are used to generate the schedules and to check for deadlock situations and machine blocking considering the presence of a central buffer. To evaluate the performances of the mathematical models and the heuristic, comparisons to other approaches reported in literature are conducted.

An efficient search algorithm for finding optimal deadlock-free schedules in FMS modeled by S/sup 4/R nets is presented. The algorithm is based on the branch and bound principle, the depth first search and truncation techniques based on the structure theory of Petri nets. It is applied to the timed S/sup 4/R net extended with priority rules. The efficiency of the proposed approach is illustrated using an example from the literature.

The effect of routing flexibility on the performance of the manufacturing system is studied. A deadlock-free scheduling algorithm, developed for S/sup 4/R nets is used for experimentation. The issues addressed in the paper include extending the S/sup 4/R nets with additional places to take into account machine breakdowns, and the derivation of the set of uncontrolled minimal siphons of the extended net from the set of the original net. Finally, an experimental study is conducted for performance evaluation.