“…Constraints (13)(14)(15) impose the rules for the starting time of each job on each machine; while, as mentioned above, equality (12) gives the completion time of each job on the last machine as a function of its start time and its processing time. Constraint (13) says that between the starting times of consecutive jobs on a machine, there must be enough time for the first (of the two jobs) to be processed.…”
Section: Milp Models For Flowshop With Unlimited Buffermentioning
confidence: 99%
“…Constraint (14) indicates that between the starting times of a job on two consecutive machines, there must enough time for the job to be processed on the first machine. Constraint (15) simply says that the starting time of the first job on the first machine must be non-negative, i.e., the insertion of idle time at the beginning of the schedule is allowed. The remaining constraints were already explained before.…”
Section: Milp Models For Flowshop With Unlimited Buffermentioning
confidence: 99%
“…In the numerical experiments, we considered instances with (n, m) ∈ {(5, 3), (10, 3), (10, 7), (10, 10), (15,3), (15, 7), (15,10), (20, 3)}.…”
Scheduling problems involving both earliness and tardiness costs have received significant attention in recent years. This type of problem became important with the advent of the justin-time (JIT) concept, where early or tardy deliveries are highly discouraged. In this work we examine the flowshop scheduling problem with no storage constraints and with blocking inprocess. In this latter environment, there are no buffers between successive machines; therefore intermediate queues of jobs waiting in the system for their next operations are not allowed. Performance is measured by the minimization of the sum of earliness and tardiness of the jobs. Mixed-integer models that represent these scheduling flowshop problems are presented. The models are evaluated and compared in several problems using commercial known software.
“…Constraints (13)(14)(15) impose the rules for the starting time of each job on each machine; while, as mentioned above, equality (12) gives the completion time of each job on the last machine as a function of its start time and its processing time. Constraint (13) says that between the starting times of consecutive jobs on a machine, there must be enough time for the first (of the two jobs) to be processed.…”
Section: Milp Models For Flowshop With Unlimited Buffermentioning
confidence: 99%
“…Constraint (14) indicates that between the starting times of a job on two consecutive machines, there must enough time for the job to be processed on the first machine. Constraint (15) simply says that the starting time of the first job on the first machine must be non-negative, i.e., the insertion of idle time at the beginning of the schedule is allowed. The remaining constraints were already explained before.…”
Section: Milp Models For Flowshop With Unlimited Buffermentioning
confidence: 99%
“…In the numerical experiments, we considered instances with (n, m) ∈ {(5, 3), (10, 3), (10, 7), (10, 10), (15,3), (15, 7), (15,10), (20, 3)}.…”
Scheduling problems involving both earliness and tardiness costs have received significant attention in recent years. This type of problem became important with the advent of the justin-time (JIT) concept, where early or tardy deliveries are highly discouraged. In this work we examine the flowshop scheduling problem with no storage constraints and with blocking inprocess. In this latter environment, there are no buffers between successive machines; therefore intermediate queues of jobs waiting in the system for their next operations are not allowed. Performance is measured by the minimization of the sum of earliness and tardiness of the jobs. Mixed-integer models that represent these scheduling flowshop problems are presented. The models are evaluated and compared in several problems using commercial known software.
“…Our focus in this survey is on DDM, where a DDM policy consists of a due date setting policy and a sequencing policy. In contrast to most of the scheduling literature [49] [78] [88], where due dates are either ignored or assumed to be set exogenously (e.g., by the sales department, without knowing the actual production schedule), we focus on the case where due dates are set endogenously. Most of the research reviewed here does not consider inventory decisions and hence is applicable to MTO systems.…”
“…These costs include: penalty clauses in the contract, if applicable; loss of goodwill resulting in an increased probability of losing the customer for some or all future jobs; and a damaged reputation which will turn other customers away (Sen and Gupta 1984). The difficulty level of this problem can be assessed by means of a particular case whose solution is undoubtedly complex, namely, the deterministic problem when all jobs are available at the same time with one machine is NP-hard for the criterion of minimizing total tardiness (Du and Leung 1990).…”
This paper addresses the non-preemptive single machine scheduling problem to minimize total tardiness. We are interested in the online version of this problem, where orders arrive at the system at random times. Jobs have to be scheduled without knowledge of what jobs will come afterwards. The processing times and the due dates become known when the order is placed. The order release date occurs only at the beginning of periodic intervals. A customized approximate dynamic programming method is introduced for this problem. The authors also present numerical experiments that assess the reliability of the new approach and show that it performs better than a myopic policy.
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