SKU assignment to unidirectional picking lines using correlations
Date
2015-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Operations Research Society of South Africa
Abstract
A real life order picking system consisting of a set of unidirectional picking lines is inves-
tigated. Batches of stock keeping units (SKUs) are processed in waves defined as a set of
SKUs and their corresponding store requirements. Each wave is processed independently on
one of the parallel picking lines as pickers walk in a clockwise direction picking stock. Once
all the orders for a wave are completed a new mutually exclusive set of SKUs are brought
to the picking line for a new wave. SKUs which differ only in size classification, for example
small, medium and large shirts, are grouped together into distributions (DBNs) and must
be picked in the same wave. The assignment of DBNs to available picking lines for a single
day of picking is considered in this paper. Different assignments of DBNs to picking lines are
evaluated using three measures, namely total walking distance, the number of resulting small
cartons and work balance. Several approaches to assign DBNs to picking lines have been investigated in literature. All of these approaches seek to minimise walking distance only and
include mathematical formulations and greedy heuristics. Four different correlation measures
are introduced in this paper to reduce the number of small cartons produced and reduce
walking distance simultaneously. These correlation measures are used in a greedy insertion
algorithm. The correlation measures were compared to historical assignments as well as a
greedy approach which is known to address walking distances effectively. Using correlation
measures to assign DBNs to picking lines reduces the total walking distance of pickers by 20%
compared to the historical assignments. This is similar to the greedy approach which only
considers walking distance as an objective, however, using correlations reduced the number
of small cartons produced by the greedy approach.
Description
CITATION: Matthews, J. & Visagie, S. E. 2015. SKU assignment to unidirectional picking lines using correlations. Orion, 31(2):61-76, doi:10.5784/31-2-531.
The original publication is available at: http://orion.journals.ac.za
The original publication is available at: http://orion.journals.ac.za
Keywords
Order picking systems, Undirectional picking lines, Assignment problems (Programming)
Citation
Matthews, J. & Visagie, S. E. 2015. SKU assignment to unidirectional picking lines using correlations. Orion, 31(2):61-76, doi:10.5784/31-2-531.