⚡️ Electric Servo Drive Systems for Industrial Presses: Energy Efficiency and Precision ⚡️

[Hasan S. Cemkan]

🛠️ Engineering Challenges in Heavy Metal Forming​

Industrial metal forming processes demand precise control, high force density, and repeatability, while also having to operate under grid constraints and fluctuating energy costs. In conventional mechanical and hydraulic presses, continuous idling, unbuffered peak power demands, and uncontrolled kinetic deceleration lead to high electrical installation costs and significant energy losses. Drive system manufacturer Baumüller addresses these operational challenges by developing specialized electric servo drives and hybrid servo-hydraulic architectures for screw presses and hydraulic forming machines in the automotive, aerospace, and general metal fabrication industries.

⚙️ Shared DC Link Architecture for Screw Presses​

In collaboration with synchropress, Baumüller designed an intelligent drive system used in machines with pressing forces ranging from 100 kN to 10,000 kN. The drive architecture in the synchropress 4M system replaces traditional overhead drive configurations with four geared spindles mounted in alignment with direct shaft connections to the press table. This axial arrangement eliminates auxiliary gear stages and reduces the machine's overall footprint requirements.

Synchronization between the four independent axes is managed by Baumüller b maXX 5100 active line rectifier units and b maXX 5500 axis controllers. The core engineering mechanism relies on a common direct current (DC) link connecting regenerative rectifiers to b maXX 5300 or b maXX 5500 inverter units. Integrated capacitor banks within the common DC bus buffer the cyclic power surges that occur when the ram contacts the workpiece. As a result, the facility's connected electrical line rating can be sized for average power demand rather than peak power demand, reducing electrical infrastructure expenditures.

Furthermore, the DC link recovers kinetic energy generated during ram deceleration. After the forming stroke, kinetic braking energy is converted into electrical energy, buffered directly in DC capacitor storage, and returned to the drive bus to power the subsequent operating cycle. This closed energetic loop directly reduces the overall kilowatt-hour consumption per formed part.

💧 Demand-Responsive Servo Hydraulics for High-Force Forming​

For hydraulic forming applications, Turkish press manufacturer Hürsan Pres has integrated Baumüller drive technology into its SERVO press series, launched at the end of 2024. The implemented servo-hydraulic system combines Baumüller DSD2 dynamic servo motors, b maXX 5500 servo converters, and integrated servo-hydraulic software modules running directly on the drive microprocessor. The system operates via a fixed displacement hydraulic pump directly coupled to the servo motor shaft. Fluid pressure and volumetric flow are entirely controlled by dynamically modulating the motor's rotational speed.

Unlike conventional induction motor-driven hydraulic power units, the servo pump provides volumetric flow strictly on demand. During non-productive phases of the cycle, such as pressure holding pauses, part loading, and dwell intervals, the servo motor reduces speed or stops entirely. This operating principle eliminates throttling losses in bypass valves, reduces thermal stress on the hydraulic oil, and shortens overall cycle times due to faster pressure build-up dynamics.

📈 The Future of Energy Efficiency and Precision​

Industrial press manufacturers are increasingly replacing traditional flywheel clutches and asynchronous valve-controlled power units with servo-electric systems to comply with energy efficiency benchmarks like ISO 50001 and regional industrial decarbonization initiatives. In screw press applications, conventional mechanical clutch drives exhibit cycle-to-cycle force variations of up to 5% due to friction clutch wear and thermal expansion. Direct multi-spindle electric synchronization limits ram tilt to micro-radian tolerances, extending die life in precision forging and coining operations.

Compared to standard fixed-speed hydraulic systems, which routinely exhibit energy efficiencies below 40% due to continuous oil circulation and heat dissipation, servo-pump systems operate with hydraulic efficiencies exceeding 70% to 80%. Common DC link architectures with capacitive or kinetic buffering represent an industry-standard strategy for smoothing peak grid demands in cyclic machinery, often reducing plant transformer sizing requirements by 30% to 50% compared to unbuffered, direct-on-line drive designs.