WAREHOUSE LAYOUT DESIGN:
MINIMIZING TRAVEL TIME WITH A GENETIC AND
SIMULATIVE APPROACH - METHODOLOGY AND CASE STUDY
Filippo Queirolo
Flavio Tonelli
DIP
University of Genoa
Via all’Opera Pia 15
I-16145 Genoa - Italy
E-mail: tonelli@itim.unige.it
Maurizio Schenone
DSPEA
Polytechnic of Turin
Corso Duca degli Abruzzi 24
I-10129 Turin - Italy
E-mail: schenone@athena.polito.it
Paolo Nan
Ivan Zunino
SACS Savona
Via Cadorna 2
I-17100 Savona - Italy
E-mail: sacs_savona@yahoo.it
KEYWORDS
Genetic algorithms, simulation, warehouse, layout design.
ABSTRACT
This paper deals with the warehouse layout optimization
problem with respect to the distance reduction and the
travel time minimization. The authors also searched for a
flexible tool in order to optimize layout functionally to the
fluctuations in demand and inventory level. The addressed
optimization problem is a constrained optimization problem
on an integer domain and it is shown to be NP-hard. The
wide applicability of evolutionary computation and its good
performances on a variety of different optimization
problems have led to a strong interest in this type of
algorithm. A heuristic genetic algorithm have been
developed and a system for the effective assignment of the
storage area to the different class of items is presented. The
system is based on the association of a genetic algorithm
and a deterministic simulation model.
Computational experiments are conducted to verify the
effectiveness of the algorithm. They were made by applying
the proposed tool to a real industrial case concerning an
Italian soft drinks company.
As a result, the authors intend to provide a tool for
warehouse layout and operations optimization that could be
attractive for operation management researchers and
realistically applicable by practitioners.
INTRODUCTION
Warehousing can be defined by three functions: i)
receiving goods from a source; ii) storing goods until they
are needed by a customer (internal or external); iii)
retrieving the goods when requested.
Storing material for an internal customer implies the need
for work-in-process storage, whereas storing goods for an
external customer may imply the need for finished products
storage. However, the functions of warehousing remain the
same and successful warehouse layouts must accomplish
the following objectives, regardless of material being
stored: maximize the use of space, maximize the use of
equipment, maximize the use of labor, maximize
accessibility to all items, maximize protection of all items.
Although the objectives of warehouse layout and operation
are easily recognized, warehouse layout problems are often
complicated by a large varieties of products needing
storage, varying areas of required storage space and drastic
fluctuations in product demand.
Optimal approaches to warehouse layout problems often
consider a single objective (e.g. maximize floor space
utilization) and/or provide a solution to a static problem.
Warehouse design problems are further complicated by
alternative storage methods and equipment.
CA.RE. PROJECT
Frequently large companies, characterized by advanced
production planning and control methodologies and an high
technological level, are supported by small-medium
enterprises (SMEs) which, in many cases, when not
integrated in efficient industrial districts or linked to a
consolidated network, can show remarkable structural
limitations and low competitiveness. In this scenario,
research activities devoted to improve ICT systems of
SMEs are useful. This work has been developed within the
CA.RE. project and it is just related to the whole re-
organization of a SME, working in the large consume
goods market, producing and selling soft drinks for the
Italian and the French markets.
Importance of Finished Goods Warehouse Management
In several cases inventory management has a strong impact
on the economics of a large-consume good company. Even
if inventory management is primary related to demand
forecasting and master scheduling, material handling is a
critical issue of this process since the total lead time depend
on it. Moreover it’s a not value-added time-consuming
activity. For this reason finished goods allocation within the
storage areas is here addressed as a critical activity and it’s
deeply analyzed in order to reach an effective allocation of
the finished goods. The reduction of the global storage cost
through the minimization of the total travel time is the main
goal of the proposed system, named Z-Sim.
Proceedings 14th European Simulation Symposium
A. Verbraeck, W. Krug, eds. (c) SCS Europe BVBA, 2002