5 Zoning
As an alternative to single order picking, the order picking area can be divided into zones. Each order picker is
assigned to pick the part of the order that is in his assigned zone. Compared to other planning issues, the
zoning problem has received little attention despite its important impact on the performance of order-picking
systems. Possible advantages of zoning include the fact that each order picker only needs to traverse a smaller
area, reduced traffic congestion, and furthermore the possibility that order pickers become familiar with the
item locations in the zone. The main disadvantage of zoning is that orders are split and must be consolidated
again before shipment to the customer. Two approaches can be used to cope with this. The first approach is
that of progressive assembly of an order. Using this approach one order picker starts on the order. When he
finishes his part, the tote and pick list (or any other means that are used) are handed to the next picker, who
continues the assembly of the order. Hence an order (or batch of orders) is only finished after having visited
all relevant zones. This system is also called pick-and-pass. The second approach for zoning is parallel (or
synchronised) picking, where a number of order pickers start on the same order, each order picker in his own
zone. The partial orders are merged after picking. In practice, zoning is partially based on product properties,
like size, weight, required temperature and safety requirements.
Little literature on zoning is available. A generic discussion on zoning is given in Speaker (1975). De Koster
(1994) models a zoned pick-and-pass system as a Jackson queuing network which allows rapid estimation of
5 ZoningAs an alternative to single order picking, the order picking area can be divided into zones. Each order picker isassigned to pick the part of the order that is in his assigned zone. Compared to other planning issues, thezoning problem has received little attention despite its important impact on the performance of order-pickingsystems. Possible advantages of zoning include the fact that each order picker only needs to traverse a smallerarea, reduced traffic congestion, and furthermore the possibility that order pickers become familiar with theitem locations in the zone. The main disadvantage of zoning is that orders are split and must be consolidatedagain before shipment to the customer. Two approaches can be used to cope with this. The first approach isthat of progressive assembly of an order. Using this approach one order picker starts on the order. When hefinishes his part, the tote and pick list (or any other means that are used) are handed to the next picker, whocontinues the assembly of the order. Hence an order (or batch of orders) is only finished after having visitedall relevant zones. This system is also called pick-and-pass. The second approach for zoning is parallel (orsynchronised) picking, where a number of order pickers start on the same order, each order picker in his ownzone. The partial orders are merged after picking. In practice, zoning is partially based on product properties,like size, weight, required temperature and safety requirements.
Little literature on zoning is available. A generic discussion on zoning is given in Speaker (1975). De Koster
(1994) models a zoned pick-and-pass system as a Jackson queuing network which allows rapid estimation of
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