In higher education, the emphasis of teaching is shifting to the application of knowledge in practical situations. Case studies are an ideal means to achieve this objective.

Through a case study, students learn to investigate and work out a practical problem step by step: the ‘learning by doing’ principle. Beside insight into the actual problem, another important objective is the development of competence in the performance of a simulation study.

The case studies and related models can also be used for experimentation purposes, enabling students to perceive complex systems in an entertaining manner and to test their own ideas. The simulation study which led to the creation of the model is skipped. The case study and the models form the basis of the ‘playing’ part.

case1A trailer manufacturer wants to gain insight into the feasible output of a new assembly line before he starts building. This is a classical example of a production line where the effect of a failure in one of the links of the production process can have tremendous consequences.

Note: This case study is appropriate for a first approach with the software and can perfectly be used during a first exercise session with ED.

case2The purpose of this case study is to investigate the effect of different queuing strategies on customer waiting times and queue lengths for the 8 checkouts of a supermarket. The case study displays five different strategies, with simple to complex modelling structures. The first strategy consists of building a M/M/8 system; secondly the service time is assumed to depend on the number of groceries. Further, concepts such as express checkout are introduced. In the last strategy, the number of opened checkouts is determined by the length of the queue. This is the prototype of a familiar queuing system.

case3Five production lines supply their products in boxes to a transport system which contains 4 side conveyors and one main conveyor. Boxes on the main conveyor have priority over boxes on the side conveyors. A number of questions regarding the transport system’s capacity is asked: what point denotes the limit of the production increase? Where do problems resulting from a production increase appear? Does increasing the speed of the conveyors have any effect? This is a typical example of a transport system with accumulating conveyors.

case4The company Neduco wants to build a new warehouse. How many docks and forklift truck drivers are necessary? How large does the pallet unloading area have to be? In this case study, the student himself/herself has to give concrete form to the management’s wish for enough docks, forklift truck drivers and unloading area. This will lead to the studying of various scenarios relating to the required number of docks and forklift truck drivers.

case5An airport wishes to increase the processing of airplanes at an airport pier by moving the delayed airplanes to a central dispatch location where they are being processed separately. What is the effect of this new structure on the queues and waiting times of airplanes at the pier? How large does the dispatch location have to be? Additionally, the effect of introducing a specially trained customs team that becomes responsible for problem handling is investigated, does the specialization of teams enable costs savings? This case study represents a queuing problem with complications. By cutting back the teams, the situation shifts from an infinite capacity to one team, which is indeed faster, but turns out to become a bottleneck itself.

case6This case study is the classical example of a job shop problem. The job shop introduced here is carried out with 4 product types, each with various routings, and 5 machine groups of different size and capacity. The objective is to determine and display the waiting and throughput times. In a second scenario, priority rules are investigated. The outcome is structured in such a way that it can easily be generalized to other job shop problems.

case7The municipality of a medium-sized town wishes to have a so-called Compact Dynamic Bus Station built. For the fulfilment of the bus schedule, logistics principles are used for the station processes. The core question is: how many platforms and buffer locations are required? In this extensive case study, the schedule of 38 bus lines is rendered in an Excel file during 4 peak hours and involves 275 buses. This file can be copied to ED or can be used from Excel via a DDE-link. Both techniques are studied.

case8A carpenter's factory produces windows and window frames according to customers' orders. The production process is composed of 10 steps: sawing, milling, hinge fixing, spraying, etc. A customer order consists of a quantity of windows or window frames and of an agreed delivery week. The order portfolio of for a given year is made up of 100 customer orders.

The first objective of the case study is to model the process and the fulfillmentfulfilment of this portfolio through the time. To this end, actual delivery dates and planning can be compared to each other. The second objective is development of this model towards a measurement tool. This is made possible by the production of GanntGantt charts for the production planning, the testing of priority rules with consideration of the delivery date, or the effect of the intermediate planning of an urgent order.

This case study illustrates the advanced possibilities of simulation as an operational planning tool.

case9A manager of a company offering emergency road service wants to improve the performance of their call centers. Four strategies are compared to find a balance between cost and waiting times. An interesting strategy to consider is to allow controlled overflow between the existing four call centers. This strategy is compared to the existing situation of four separate call centers, a central call center and a shortest-queue policy.

case10An airport wants to determine the minimum number of desks at Passport Control and at Customs to have acceptable waiting times for passengers. The passengers do not arrive in a continuous stream; each time a plane arrives, a cluster of passengers simultaneously enters the airport. At Passport Control, a distinction is made between EU, non-EU and biometric passports. Several strategies are compared for distributing the three classes over the desks. The variability of the passengers walking speeds and the speed of the baggage handling system are taken into account.

case11This case study concerns a Monte Carlo simulation rather than a discrete event simulation. An airport wishes to maximize profit by tuning the capacity of its parking areas. The available parking space is divided into long- and short term parking areas, parts of which can be permanently reserved for personnel. A second instrument for the airport to influence profit are the daily rates of the parking areas.

case12When do passengers arrive at the check-in desk for their flight? The arrival pattern will have major consequences for the airlines desk planning. This case study comes with a ready made 3D model incorporating several queuing strategies, such as centralized and per-desk queuing and dynamic opening/closing of desks. Students do not have to build the model but can focus on investigating the effects of different arrival processes and different queuing strategies.

case13In this case study we deal with an inventory and manufacturing system. Simulation is applied to improve the use of inventory, balancing storage and order cost against loss of sales when products are out of stock. The replenishment strategies for four lines of finished products constructed out of eight component types can be adjusted individually to find an optimal strategy.

case14Should we pool servers or not? This question is important in many applications such as customer service operations, call centers, hospitals, etc. In this case study a simple but instructive example of parallel queues is investigated which helps to gain insight into this question. Both queuing theory and simulation help answer this question.

case15In this case study we investigate to pool or not to pool the MRI scanners of the Radiotherapy department of a hospital. Due to different service requirements for emergency and regular patients separation of capacities might be preferable over pooling.