## 2 Materials and Methods: Architectural Configurations for the Case Study
### The Hydraulic System
#### 2.1.1 System Structure and Technical Requirements  
The main technical requirements for the actuator during operation are two: the minimum thrust force that the rod must exert during the blanking of the semi-finished product and the maximum duration of the entire working cycle of the press. The system considered as a case study for pressing semi-finished brass products consists of a hydraulic press with a system for feeding/unloading parts that includes a rotary table with four stations, a robot manipulator, and a conveyor belt, as shown in Figure 1.  
The typical blanking work cycle is divided into two macro-phases. The first includes the rod quick descent, the blanking, the expulsion of the piece, and the rode quick rise. In this first macro-phase the cylinder is actively involved in the work cycle. The second, on the other hand, involves only the rotation of the table for loading the parts to be machined. In this case the cylinder rod does not perform any movement and remains in a waiting state. The duration of this second macro-phase is usually set by the end user of the machine and is 0.3 s in the process considered as a case study. It is, therefore, obvious that the constraint on the maximum duration of the blanking cycle determines a limit on the maximum duration of the first macro-phase, in which the cylinder is in motion. In addition to the specifications for the minimum force that must be generated during operation and for the maximum duration of the working cycle, a third limitation is established. This defines the limit mass of the tool that can be anchored to the free end of the actuator rod. The numerical values of the above parameters are summarized in Table 3.  
The entire process consists of five individual phases: quick descent (QD), blanking (B), expulsion (E), quick rise (QR), and table rotation (TR). During the blanking phase, pressure and velocity have a rather complex trend, that should be determined either experimentally or by simulating the process. For the purposes of this work, i.e., the functional comparison between the different system architectures in terms of energy efficiency, the impact of the variation in these two quantities during the blanking phase on the overall energy consumption values is limited. The discussion is, therefore, made under the simplified assumption that the speed of the load is uniform, and corresponds to the average value during the cutting operation and that the oil pressure is constant and corresponds to the maximum value reached during blanking. First of all, it is necessary to define the main project specifications, which include the translation speed of the cylinder rod, the stroke, and the delivery pressure for each working phase. The choice of values for the translation speed is arbitrary and limited only by mechanical or other constraints. The stroke is defined as a function of the thickness of the semi-finished product to be sheared in the shearing phase and of the characteristics of the system in the other phases. For the feeding pressure, a pressure level is chosen that is considered sufficient to maintain the control of the valves, to compensate for the load losses distributed in the tubes, and to overcome the resistance of any load at the free end of  
Figure 1: Pressing system considered as a case study and main constituent elements. The vertical hydraulic cylinder of the press is located in the dashed square. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Parameter** & **Value** & **Unit** \\ \hline Minimum blanking force & 294,300 & (N) \\ Rotation phase duration for the rotary table & 0.3 & (s) \\ Maximum duration of the entire processing cycle & 1.4 & (s) \\ Maximum duration of operation for the actuator & 1.1 & (s) \\ Maximum mass of the tooling anchored to the rod & 80 & (kg) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Technical requirements for the hydraulic system. the cylinder rod. In Table 4, the values of these parameters are given for each phase of the blanking cycle.