Experimental design3.3.1. Different

Experimental design
3.3.1. Different production strategies
The simulation model was designed to simulate the chocolate
production system for two different production strategies, one
based on production efficiency (PS1) and one based on reduced
batch dispersion (PS2). In PS1 the maximum processing batch size
is always used so that the equipment in the production stage is
always used at full capacity. Since the size of the cocoa bean batches
delivered to the chocolate manufacturer is not necessarily
a multiple of the processing batch size, some cocoa beans are mixed
with the next batch of cocoa beans. This results in having some
batches of finished product produced from two different batches of
raw materials. Instead, PS2 focuses on reducing batch dispersion,
where the chocolate manufacturer avoids mixing the different
batches of cocoa beans. Here, some processing batches might be
smaller in size. As batch processes are involved, this results in some
partially unutilized processes in the chocolate production line, with
a corresponding reduction in production efficiency. On the other
hand, if a safety crisis occurs to a batch of raw materials, a PS2
production strategy would lead to smaller recall sizes compared to
PS1. A graphical illustration of both PS1 and PS2 can be seen in
Fig. 2.
In the remainder of this paper, production efficiency is
measured by the number of processing batches because:
 The number of processing batches equals the number of times
a roasting process is performed and the duration of the roasting
process depends on the roasting grade desired, not on the
amount of nibs processed into the equipment (Jinap, Rosli,
Russly, & Nordin, 1998; de Muijnck, 2005). Therefore less
processing batches mean less time needed for roasting, with
a constant number of equipments; or less equipments needed,
with a constant processing time required. Thus, less processing
batches lead to a higher efficiency.
 Smaller batch sizes (also meaning more batches when processing
a constant raw material amount) were found by other
authors to lead to an increase in production setup times and
costs, resulting in losses of production efficiency (Dabbene &
Gay, 2011; Dupuy et al., 2005; Rong & Grunow, 2010; Wang,
Li, & O’Brien, 2009).
3.3.2. Different traceability systems
The simulation model includes a basic traceability system (TS0),
and two improved traceability systems (TSþ and TSþþ). TS0 fulfils
the European law regarding traceability, thus the actors involved in
the supply chain and located within the European borders follow
the “one step back-one step forward approach” required by law
(European Commission, 2002). That is, the finished chocolate
product is traceable from the supermarket, to the chocolate
manufacturer, to the cocoa exporter. As the cocoa exporter is
assumed to be located outside Europe it is not possible to trace the
cocoa beans further in the supply chain.
TSþ is an extension of TS0, where the local buying stations,
when buying the cocoa beans from the cocoa farmers, mark all
cocoa bags with a unique code and the buying date. Also, when the
cocoa exporter buys the cocoa and mixes bags from different local
buying stations, the original bags remain. This means the cocoa is
delivered to the chocolate manufacturer in the original bags with
the code of the local buying station. These codes are then registered
so that the finished chocolate can be traced up to the local buying
station.