Typically, general job shop scheduling problems assume that working times of machines are equal, for instance eight hours a day. However, in real factories, these working times are different because the machines may have different processing speeds, or they may require maintenance. That is, one machine may need to be operated only half day whereas other machines may have to be operated for the ...

This report describes a database model currently under development at the Manufacturing System Integration Division (MSID) of the National Institute of Standards and Technology (NIST). The database model contains a set of tables that are mapped onto the machine shop information model developed by MSID. The information model provides neutral data interfaces for integrating machine shop software ...

One of the main restrictions in scheduling problems are the machine (resource) restrictions: each machine can perform at most one job at a time. We explore machine dependencies is shop scheduling problems representing them as graphs. Our study shows that the structure of machine dependency graphs is important in the complexity analysis of shop scheduling problems. We call acyclic a shop schedul...

The Shifting Bottleneck (SB) heuristic is among the most successful approximation methods for solving the Job Shop problem. It is essentially a machine based decomposition procedure where a series of One Machine Sequencing Problems (OMSPs) are solved. However, such a procedure has been reported to be highly ineffective for the Flow Shop problems (Jain and Meeran 2002). In particular, we show th...

The paper considers a three-machine shop scheduling problem to minimize the makespan, in which the route of a job should be feasible with respect to a machine precedence digraph with three nodes and one arc. For this NP-hard problem that is related to the classical flow shop and open shop models, we present a simple 1.5approximation algorithm and an improved 1.4-approximation algorithm.

In the multi-operation scheduling that arises in industrial engineering, each job contains multiple tasks (operations) that require execution in different shops. It is assumed that in each shop there is only one machine to perform the required operations. In this paper, a parallel model of multi-operation scheduling is proposed, in which multiple machines are available in each shop to perform t...

The Flexible Job Shop Scheduling Problem (FJSP) is one of the most general and difficult of all traditional scheduling problems. The Flexible Job Shop Problem (FJSP) is an extension of the classical job shop scheduling problem which allows an operation to be processed by any machine from a given set. The problem is to assign each operation to a machine and to order the operations on the machine...

In this paper, scheduling problems in Flexible Manufacturing Cells (FMC) are studied. The scheduling objective is to minimize the makespan. We used a genetic algorithm (GA) for solving the optimization scheduling problem. We have developed one FMC with industrial characteristics with the objective of studying scheduling problems in these types of manufacturing systems (single machine scheduling...

scheduling is an important subject of production and operations management area. in flow-shop scheduling, the objective is to obtain a sequence of jobs which when processed in a fixed order of machines, will optimize some well defined criteria. the concept of transportation time is very important in scheduling. transportation can be done by robots. in situations that robots are used to transpor...

in this paper, we considered solving approaches to flexible job shop problems. makespan is not a good evaluation criterion with overlapping in operations assumption. accordingly, in addition to makespan, we used total machine work loading time and critical machine work loading time as evaluation criteria. as overlapping in operations is a practical assumption in chemical, petrochemical, and gla...