Browsing by Subject "Single Machine"

Now showing 1 - 3 of 3

Open Access
An exact approach to minimize single machine total weighted tardiness problem with unequal release dates
(1998) Özdemir, Deniz
In this research, the problem of scheduling a set of jobs on a single machine to minimize total weighted tardiness with unequal release dates is considered. We present a new dominance rule by considering the time depending orderings between each pair of jobs. The proposed rule provides a sufficient condition for local optimality. Therefore, if any sequence violates the dominance rule then switching the violating jobs either lowers the total weighted tardiness or leaves it unchanged. Based on the dominance rule, an algorithm is developed which is compared to a number of heuristics in the literature. Our computational results indicate that the proposed algorithm dominates the competing algorithms in all runs, therefore it can improve the upper bounding scheme and can be used in reducing the number of alternatives in any enumerative algorithm. Furthermore, the proposed dominance rule is incorporated in a branch and bound algorithm in conjunction with lower bounding scheme, branching condition and search strcitegy. To the best of our knowledge, author know of no other published exact approach for l|rj| problem. This enhances contribution of our study in the literature.
Open Access
Scheduling with controllable processing times in a CNC environment
(2002) İlhan, Taylan
Flexible manufacturing systems give a manufacturer some capabilities to consider and solve different manufacturing problems simultaneously instead of one by one in a sequential manner. Using those makes her more competitive in the market. One of those capabilities is controllable processing times. By using this capability, the due date requirements of customers can be satisfied much more effectively. Processing times of the jobs in a CNC machine can be easily controlled via machining conditions such that they can be increased or decreased at the expense of tooling cost. In this study, we consider the problem of scheduling a set of jobs by minimizing the sum of total weighted tardiness, tooling and machining costs on a single CNC machine. This problem is NP-hard since the total weighted tardiness problem is NP-hard alone. Moreover, the problem is non-linear because of the nature of the tooling cost. We proposed a DP-based heuristic to solve the problem for a given sequence and designed a local search algorithm that uses it as a base heuristic.
Open Access
Single CNC machine scheduling with controllable processing times and multiple due dates
(2004) Atan, Mehmet Oğuz
In order to reflect the characteristics of a modern manufacturing environment, elements of customer satisfaction and the competition between firms should be considered simultaneously. Manufacturers should be careful on deciding which orders to accept, and should pay attention on the weighted earliness and tardiness penalties they will be due, while considering the priorities of the customers. Customers that want to minimize the risk of deviation from a delivery date, offer multiple due dates to the manufacturer, each coming with a distinct price for the order that is decreasing as the date gets later. Manufacturers that use flexible manufacturing systems have the capability to control the processing times of jobs, by changing the machining conditions at the expense of tooling costs. In this study, we consider the problem of scheduling a set of jobs on a single CNC machine, while maximizing the total profit that is composed of sum of prices of scheduled jobs less the sum of total weighted earliness/tardiness cost, tooling cost and machining cost. This problem is NP-hard since the total weighted tardiness problem is NP-hard alone. Furthermore, because of the nature of the tooling cost, the problem is nonlinear. We propose a number of ranking rules and scheduling algorithms. Using these rules and algorithms, we construct a single-pass heuristic algorithm that determines the processing times for each job and schedules them simultaneously, to maximize the overall profit.