Sequencing rules and due date setting procedures in flow line cells with family setups

Abstract

The purpose of this study is to investigate due date setting procedures and dispatching decisions in a flow line cell with family setups. In this environment, setups are not required when switching from a job in a given family to a job in the same family. However, switching from a job in one family to a job in another family requires a setup. Family setups in this shop are sequence independent. The dispatching decisions in this shop are threefold: (1) when should the decision to switch from one part family to another be made; (2) once the decision to switch families is made, how should the next part family be chosen (next family decision); and (3) how should the jobs within a family be prioritized (next job decision)? If the decision to switch classes can only be made after the current family is exhausted, the rule is called a class exhaustion rule. Otherwise the rule is a truncated rule. The results indicate that the due date setting procedure has a major impact on how dispatching should be performed in the shop. The family exhaustion procedure using the APT next family rule and the SPT next job rule is the best performer for mean flow time. When setup times are long, the SEQ due date rule using the family exhaustion procedure with the FCFS next family and the EDD next job rules performed well for due date criteria. When setup times are short, the EDD/T, Sawicki truncation rule and the family exhaustion rules performed well for due date criteria.

Non-exhaustive family based dispatching heuristics–exploiting variances of processing and set-up times

“…Alternatively, several authors study the relevance of non-exhaustive heuristics, which allow switching families, even when the queue for the current family is not empty. Mosier et al (1984) (Frazier 1996, Mahmoodi et al 1992, Russell and Philipoom 1991. Ruben et al (1993) modify ECON by including a threshold value on queue length.…”

“…Russell and Philipoom (1991) consider several truncation rules for batch formation. Next to due date related truncation rules, they discuss a rule introduced by Sawicki (1973).…”

“…show how most of these rules may be related to the concept of the Weighted Shortest Processing Time Rule (WSPT), see Pinedo (1995). An important example of such a rule is adopted by the exhaustive Minimum Average Set-up and Processing time rule (MASP) heuristic, see (Russell and Philipoom 1991). According to this rule, system set-up is related to the choice of (Mosier et al 1984 can be found by omitting set-up times, and processing times respectively.…”

“…The possibility to further decompose batches is reflected in the notion of "non-exhaustive" policies. Whereas exhaustive policies only change their choice of job family if there are no jobs left within the current family, non-exhaustive policies allow for switching to other job families, even when the current family queue is not empty (Mosier et al 1984, Russell and Philipoom 1991, Mahmoodi and Dooley 1991, and Ponnambalam et al 1999. In this article we will re-assess construction and evaluation of non-exhaustive family based dispatching heuristics for the single machine case.…”

“…Existing non-exhaustive heuristics, however, rely on static parameters, in terms of pre-set time fences (Russell and Philipoom 1991) or batch sizes (Mosier et al 1984, Ruben et al 1993, or link the choice of batch size to queue length at the decision moment (Mosier et al 1984). They do not consider local data on processing times in their decision to split a batch.…”