Constructive heuristics for the minimization of core waiting time in permutation flow shop problems

In job scheduling literature many different objectives and constraints have been discussed so far, mainly the objectives of minimizing makespan or total completion time. However, considering an efficient production system other time measures might be interesting as well, e.g. idle time of machines or waiting time of jobs. These time periods refer to either the utilization of a production systems and/or throughput of jobs. Therefore, idle time and waiting time are indicators for the efficiency level of a production system. In our work, we refer to minimizing waiting time between machines (core waiting time) in a permutation flow shop environment and develop suitable constructive heuristics based on the well-known heuristic of Nawaz, Enscore and Ham. An improvement algorithm is applied additionally. The heuristics are evaluated with benchmark instances, while the beam-search-based constructive heuristic for minimizing total completion time is used as an upper bound.