# Decision Support Simulation Method for Process Improvement of Intermittent Production Systems
## 1 Introduction  
Continuous improvement of production processes based on customer demands is necessary in order to increase or maintain competitiveness. The only companies that can stay competitive in the long term are those that are able to carry out continuous improvements and adapt to external environmental changes in all the companies' areas [1]. If we take into consideration the sweeping changes in the transformation of production systems in the last 50 years and the developmental possibilities that arise from the technological progress, we can see that process improvement is a very important research area [2]. The general trends are the satisfaction of unique customer demands, as well as a reduction in production lead time [3,4]. These trends create some new challenges that can only be overcome with intensive improvement of intermittent production systems. Process improvement can refer to the production systems to be realized. Intermittent production systems are especially complex because in the material flow routes for products/product families the technological equipment's operation time and changeover time often differ, as do the applied unit load making devices [4,5]. In practice, improvement can be realized by using the lean philosophy's device system [5,6]. However, the application of simulation modeling technology is becoming more prominent because of the processing's increasing complexity and developmental demand. We can explain simulation as a method for making a computer model on the basis of the real/planned systems; consequently, we examine these systems' status changes [3]. We can classify the simulation models according to several aspects. If the simulation model's input data contain stochastic variables, we can speak about a stochastic simulation model; otherwise, the simulation model is deterministic [7]. We can distinguish discrete and continuous simulation models on the basis of another classification aspect. The system's status will be changed in the discrete points of time in the case of thediscrete model and at every point of time in the case of the continuous model [8; 9]. Basically, the discrete simulation models are used for the production areas [10; 11]. Simulation modeling has been applied in both continuous production systems [12; 13] and intermittent production systems (for example: process improvement [14], production scheduling [10], etc.). Besides the examination of production systems, simulation modeling has been applied in other areas as well (for example: disaster logistics [15], port logistics [16], air circulation in a tennis hall [17], and electric distribution [18]). The objective of the simulation examinations can be the determination of selected system parameters at different model settings [19; 20], simulation examination of real-time systems [21; 22; 23], or optimizing the workings of assigned systems [24; 25] for intermittent manufacturing systems. Such examinations have been carried out by discrete event controlled simulation modeling [19; 20; 21; 22; 23; 24] or Petri nets [26; 27; 28; 29]. Discrete event controlled simulation modeling has become increasingly important due to its applicability and flexibility. However, the studies have only examined the production processes of one product family (in which the examined products' material flow routes are the same) and/or contain several simplifications. These studies do not explain how we can create a simulation investigational model in the case of the most complex intermittent manufacturing systems. There is a need for a simulation investigational model for intermittent production systems that is able to analyze the logistical processes of more than one product family simultaneously, where the parameters of the logistical processes can differ from each other (e.g., operation times, changeover times, batch sizes, or types of the unit load forming devices), as well as having numerous material flow nodes and backflows.