## 3 Simulation Model Results
### Design of the Simulation Model--Case Study  
The design of the simulation model and the actual simulation were performed in order to verify and confirm the theoretical model, using a real case study, in the manufacture of bearing ring type cylindrical parts, requiring adequate knowledge of the modelled object. The model was designed according to the events and processes that take place in the system and the technological operations (processing of flat surfaces, processing of running channels, turning, grinding, and superfinishing/honing) needed to achieve the analyzed part and the constraints imposed on manufacturing.  
The use of modern state-of-the-art software in designing and studying advanced production systems represents an important step towards digitizing the production and integrating it into the industry of the future: Industry 4.0. Using Tecnomatix/Siemens Product Lifecycle Management Software Inc. (2015) [44], the plant simulation module performed the system simulation with discrete events on a case study--a flexible manufacturing system (Figure 4).  
The goal was to achieve the simplest possible model of the designed system. The manufacturing system model (Figure 4) is based on an example of a real production department by using the Tecnomatix Plant Simulation software/Siemens, the input data being collected directly from the respective process. Data on costs, energy consumption, and labor were not taken into account.  
The simulation technique can graphically model asynchronous/synchronous concurrent events, manufacturing processes, real-time control systems, and real-time decision concepts within a flexible manufacturing system. The simulation model presents a detailed description of the alternative of flexible manufacturing systems considered, having the role of reproducing the dynamic performances of the system. The relevant evaluation criterion (average waiting time of the parts in the system) is then deduced from these dynamic observations.  
The manufacturing flow was organized on the principle of workstation compatibility. Following this criterion, the principle of technological compatibility and functional compatibility as well as the related information exchange were respected.  
Finally, the general structure of the FMS was determined by allocating partial functions to some physical elements--component subsystems: machine tools, information transmission, transformation and processing stations, elements for handling, transport, storage, energy transmission and distribution systems, and its transformation, etc. Then, the necessary connections between them were established in order to obtain the general system operation.  
The analyzed process contains 8 workstations and handling elements of industrial robot type and transport with conveyor as well as storage elements at the system entrance and exit. Only one work shift was considered for the analysis. Logistics and equipment such as loading station, conveyor, industrial robot, sorting station, and loading station were also designed and integrated in the system.  
Figure 4: The sequence from the simulation in Tecnomatix of the designed system.