From Conventional Hydraulics to Servo-Hydraulics: 86.4% Energy Savings in a Copper Tube End-Forming Machine
An Industrial Case Study Using Siemens SimoHyd, SINAMICS S120, SIMOTICS 1FK7 and SIMATIC S7-1500T
Energy consumption in hydraulic machinery is strongly influenced by the way hydraulic power is generated and controlled. Conventional hydraulic power units commonly operate an electric motor and pump at relatively constant speed, while the actual process demand varies throughout the machine cycle. During periods of low hydraulic demand, excess flow and pressure may be dissipated through throttling, bypassing, or other control mechanisms. As a result, a considerable amount of electrical energy can be converted into heat rather than useful mechanical work.
This case study describes the modernization of the hydraulic drive system of a copper tube end-forming machine using Siemens SimoHyd servo-hydraulic technology. The new system combined a SIMATIC S7-1500T technology controller, SINAMICS S120 servo drive, SIMOTICS 1FK7 servo motor, and a servo-driven hydraulic pump.
During an eight-hour production shift, the conventional hydraulic configuration consumed approximately 2,144.4 kWh, while the servo-hydraulic system consumed approximately 291.3 kWh under the evaluated operating conditions. This corresponds to an observed reduction in electrical energy consumption of approximately 86.4%.
The Application: Copper Tube End Forming
Copper tube end-forming machines are used to mechanically expand, shape, or form the ends of copper tubing for subsequent joining, assembly, or manufacturing processes.
The forming operation requires substantial hydraulic force during specific stages of the machine cycle. However, maximum hydraulic power is not required continuously.
A typical operating sequence includes workpiece positioning, tool approach, rapid movement, forming under high force, pressure holding, tool return, unloading, and preparation for the next cycle. The hydraulic demand therefore changes considerably throughout the operating cycle, creating an important opportunity for energy optimization.
Limitations of the Conventional Hydraulic System
In a conventional hydraulic power unit, an induction motor typically drives the hydraulic pump continuously or near continuously. The motor may therefore consume significant electrical power even when the machine requires little hydraulic flow.
When the pump produces more flow than the process requires, the excess hydraulic energy must be controlled elsewhere in the system. Depending on the architecture, this can involve pressure-relief valves, proportional valves, throttling elements, or circulation back to the tank.
The fundamental problem is that the hydraulic power unit may continue producing energy even when the process cannot use it. This can lead to unnecessary electrical energy consumption, increased oil temperature, higher thermal losses, increased cooling requirements, additional stress on hydraulic components, and continuous operation of the electric motor and pump. For machines with highly intermittent hydraulic demand, these losses can become particularly significant.
Servo-Hydraulic Architecture
The redesigned system replaced the conventional fixed operating concept with a servo-controlled hydraulic power generation system based on Siemens SimoHyd technology.
The principal automation architecture consisted of a Siemens SIMATIC S7-1500T controller, SINAMICS S120 servo drive, SIMOTICS 1FK7 servo motor, and a servo-driven hydraulic pump.
Instead of continuously operating the hydraulic pump at a fixed motor speed, the servo drive allows pump speed and therefore hydraulic flow to be adjusted dynamically according to the process requirement.
The operating principle can be summarized as hydraulic demand → motion/control command → servo motor speed and torque → pump flow and pressure. This allows the hydraulic power source to react directly to the machine cycle.
During rapid movement, the servo system can command a higher pump speed to generate the required flow. During high-force forming, the control system can provide the torque necessary to generate the required hydraulic pressure. During low-demand or waiting stages, motor speed can be substantially reduced instead of continuously producing unnecessary hydraulic flow.
The servo drive therefore transforms the hydraulic power unit from a continuously operating energy source into a demand-oriented actuator.
Role of the SIMATIC S7-1500T
The SIMATIC S7-1500T technology controller formed the central control layer of the system. Its role was not limited to conventional PLC sequencing. The controller coordinated the machine sequence together with the servo-hydraulic operation, allowing hydraulic power generation to be synchronized with the actual requirements of the forming process.
This type of architecture is particularly useful because the PLC has knowledge of the machine’s operating state. The controller can determine when the machine is approaching the workpiece, beginning the forming operation, entering a pressure-holding phase, retracting the tooling, or waiting for the next production cycle.
This information can be used to request only the hydraulic performance necessary for each stage. The result is a coordinated electromechanical and hydraulic control system rather than a hydraulic power unit operating independently from the process.
SINAMICS S120 and SIMOTICS 1FK7
The SINAMICS S120 drive system was used to control the SIMOTICS 1FK7 servo motor driving the hydraulic pump.
Servo motors differ fundamentally from motors used in many conventional hydraulic power units because their speed and torque can be changed rapidly and precisely according to control demand.
For servo-hydraulic applications, this capability provides two major advantages. First, hydraulic flow can be controlled through pump speed, allowing pump speed to be reduced when flow demand decreases. Second, the motor can generate controlled torque when the hydraulic system requires pressure for the forming operation.
The combination allows electrical energy to be supplied much more closely in proportion to the mechanical and hydraulic work required by the process.
Energy Consumption Comparison
Energy consumption was evaluated over an eight-hour production shift. The conventional hydraulic system consumed approximately 2,144.4 kWh, while the Siemens SimoHyd servo-hydraulic system consumed approximately 291.3 kWh.
Figure 1. Project HMI showing the energy comparison between the conventional hydraulic system and the Siemens SimoHyd servo-hydraulic solution.
The observed energy reduction was calculated as (2,144.4 − 291.3) / 2,144.4 × 100, resulting in approximately 86.4% lower electrical energy consumption.
The servo-hydraulic system therefore used only about 13.6% of the electrical energy consumed by the conventional hydraulic configuration during the evaluated eight-hour operating period. The absolute reduction was approximately 1,853.1 kWh per eight-hour shift.
This represents a substantial reduction in electrical energy demand for the machine. However, the result should be interpreted as an application-specific measured outcome. The achievable energy reduction in another hydraulic machine will depend on factors such as machine cycle, pressure profile, pump sizing, idle time, hydraulic architecture, production rate, and the efficiency of the original system.
The 86.4% result should therefore not be interpreted as a universal efficiency figure for all servo-hydraulic applications.
Why Was the Energy Reduction So Large?
The magnitude of the improvement can largely be explained by the highly variable hydraulic demand of the tube-forming process. The conventional system continued consuming energy during portions of the cycle where full hydraulic power was unnecessary.
The servo-hydraulic system, in contrast, could substantially reduce motor operation during low-demand stages and increase it only when the process required additional flow or pressure. This reduces several sources of loss simultaneously.
Reduced Idle Energy Consumption
A conventional pump may continue rotating while the machine is waiting or operating under low load. With servo control, pump speed can be reduced significantly during these periods.
Reduced Throttling Losses
Traditional hydraulic systems often regulate actuator speed by restricting hydraulic flow. The energy associated with the pressure drop across the restriction is converted primarily into heat. By regulating flow directly through pump speed, the servo-hydraulic system can reduce the need for this type of energy dissipation.
Demand-Based Pressure Generation
The system does not need to continuously maintain maximum hydraulic output. Pressure and flow can instead be generated according to the process stage.
Lower Thermal Losses
Hydraulic losses eventually appear largely as heat in the oil. Reducing unnecessary hydraulic power generation consequently reduces thermal loading. This may also decrease the operating demand placed on oil cooling equipment, creating an additional system-level efficiency benefit.
Additional Engineering Benefits
Although energy reduction was the primary measurable outcome of the project, servo-hydraulic architectures can provide several additional engineering advantages.
Improved Process Control
The hydraulic power source becomes an actively controlled part of the automation system. Pump speed and motor torque can be coordinated with specific stages of the machine cycle.
Reduced Heat Generation
Lower hydraulic losses mean less energy must be removed through the machine’s cooling system. Lower oil temperatures may also contribute to more stable system behavior.
Lower Acoustic Noise
Because the pump does not need to run continuously at maximum speed, acoustic noise can be reduced during low-load portions of the production cycle.
Greater Diagnostic Capability
A servo-controlled architecture provides access to electrical parameters such as motor speed, torque, current, drive status, and operating conditions. These signals can be incorporated into the PLC and HMI for monitoring and diagnostics.
Flexible Machine Optimization
Pump behavior can be changed through control parameters rather than exclusively through mechanical or hydraulic modifications. This makes it possible to optimize individual portions of the production cycle through software.
Servo-Hydraulics as a Mechatronic System
One of the most important lessons from this project is that servo-hydraulics should not be considered merely as a more efficient hydraulic pump. The technology changes the architecture of the machine.
A conventional hydraulic system is primarily a hydraulic power system controlled by automation. A servo-hydraulic solution integrates electrical drive technology, motion control, hydraulic power generation, PLC sequencing, pressure and flow control, machine diagnostics, and energy management.
The resulting system is therefore better described as a mechatronic hydraulic powertrain. The hydraulic system remains responsible for generating high force, but the energy supplied to that system is managed dynamically through modern servo-drive technology.
Applications With High Servo-Hydraulic Potential
The largest efficiency improvements are likely to occur in machines where hydraulic demand changes substantially throughout the production cycle.
Potential applications include tube and pipe forming machinery, hydraulic presses, injection molding equipment, metal forming systems, bending machines, clamping systems, test machines, and other cyclic hydraulic production equipment.
Machines that spend significant portions of their operating time at low hydraulic demand may offer particularly strong opportunities for energy reduction.
However, proper engineering analysis remains essential. Pump displacement, required peak pressure, flow demand, servo motor sizing, drive sizing, acceleration requirements, thermal behavior, and control strategy must all be evaluated as part of the system design.
Conclusion
The modernization of the copper tube end-forming machine demonstrates the potential impact of integrating servo-drive technology with industrial hydraulics.
By replacing the conventional hydraulic power architecture with a Siemens SimoHyd-based servo-hydraulic system using a SIMATIC S7-1500T controller, SINAMICS S120 servo drive, and SIMOTICS 1FK7 servo motor, electrical energy consumption during the evaluated eight-hour shift was reduced from approximately 2,144.4 kWh to 291.3 kWh.
This represents an observed reduction of approximately 86.4%.
The significance of the project extends beyond the energy figure itself. It demonstrates how hydraulic systems can be transformed from continuously operating power sources into demand-driven, digitally controlled systems in which electrical, automation, motion-control, and hydraulic engineering operate as a coordinated architecture.
For industrial machines with strongly variable hydraulic demand, servo-hydraulic technology can therefore represent not only an energy-efficiency improvement but also a fundamental redesign of how hydraulic power is generated and controlled.
About the Project
The servo-hydraulic system described in this case study was engineered and implemented for a copper tube end-forming application using Siemens automation and drive technologies.
System architecture: SIMATIC S7-1500T, SINAMICS S120, SIMOTICS 1FK7 and Siemens SimoHyd servo-hydraulic technology.
Measured result: approximately 86.4% lower electrical energy consumption during the evaluated eight-hour production shift compared with the previous conventional hydraulic configuration.