Servo Hydraulic Power Units: Energy Saving Up to 60% on Injection Moulding

Coupling an IE3 servo motor with a high-efficiency internal gear pump allows LIFTHYDRAU servo hydraulic power units to achieve field-verified energy savings of 50–60% on plastic injection moulding lines. This article shares benchmark data from three customer sites in Vietnam, Türkiye and Mexico.

Why Injection Moulding Machines Consume So Much Energy

Conventional injection moulding machines typically use fixed-displacement or variable-displacement pumps driven by asynchronous motors. During holding pressure, cooling and mould-opening dwell phases, the motor continues running at rated speed while hydraulic oil returns to the tank through the relief valve — energy that is entirely converted into waste heat. In real production, the portion of the moulding cycle that genuinely requires full flow usually accounts for only 30–40% of total cycle time, while the system operates at low or zero effective output for the remainder. This is the fundamental reason servo hydraulic power units can deliver such substantial savings: oil on demand, speed on demand.

System Architecture: Matching the IE3 Servo Motor to the Internal Gear Pump

The core of a LIFTHYDRAU servo hydraulic power unit lies in coordinated motor and pump control. An IE3 efficiency-class asynchronous servo motor maintains high efficiency even in part-load ranges, working with the drive to achieve closed-loop speed and torque regulation. Compared with external gear designs, the internal gear pump offers lower flow pulsation and higher volumetric efficiency, sustaining stable output even at low speeds — which makes it highly compatible with the variable-speed duty of servo drive systems.

When the machine enters the holding pressure phase, servo motor speed drops to the minimum required to maintain pressure, pump output flow falls accordingly, and the system no longer relies on relief valve discharge. During cooling, the motor approaches standstill and energy consumption approaches zero. Across the entire moulding cycle, motor power tracks the actual load curve dynamically rather than running at constant output. This control logic is the technical basis for the 50–60% savings figures.

Vietnam Site: Home Appliance Housing Moulding Line

An appliance manufacturer in Vietnam operates a moulding workshop with multiple machines around 250 tonnes clamping force, primarily producing washing machine drums and air conditioner housings. Before retrofit, average hydraulic system power consumption per machine was approximately 18.5 kW over 22 operating hours per day. After installing a LIFTHYDRAU servo hydraulic power unit, measured average power dropped to 7.4 kW — a 60% saving. Cooling time accounts for a relatively large share of the moulding cycle at this plant, and the substantial relief losses of the conventional system during cooling were eliminated entirely. At local industrial electricity rates, annual savings per machine reach approximately RMB 42,000, with a payback period under 14 months. Oil temperature also fell noticeably, extending hydraulic oil change intervals from 4,000 hours to over 8,000 hours.

Türkiye Site: Precision Automotive Component Moulding

An automotive component supplier in Türkiye runs moulding lines producing interior clips and connectors, with clamping forces between 180 and 350 tonnes. The plant's existing variable pump system required frequent pressure and flow adjustment under precision moulding conditions, and response lag caused part weight variation. After installing servo hydraulic power units, energy consumption fell 52% and moulding repeatability improved markedly. Field data showed average power of 21.3 kW per 350-tonne machine before retrofit, falling to 10.2 kW afterwards. With Türkiye's higher and more volatile industrial electricity prices, the savings case was even stronger. After completing the first pilot machine, the plant extended the retrofit to all 11 machines in the workshop.

Mexico Site: Large Logistics Pallet Moulding

A plastics manufacturer in Mexico produces logistics pallets and returnable crates, with clamping forces generally above 500 tonnes — heavy-tonnage, long-cycle duty. Before retrofit, average hydraulic system power per machine reached 34.7 kW, and hydraulic oil temperature ran persistently high, requiring supplementary cooling in summer. After installing LIFTHYDRAU servo hydraulic power units, average power fell to 14.6 kW, a saving of approximately 58%. Large-tonnage machines have long holding pressure phases, and the servo system's advantage in low-speed pressure holding is fully amplified. Oil temperature stabilised within a reasonable band, and cooling water consumption dropped by roughly 35%.

Common Conclusions from Three Sites

Across the Vietnam, Türkiye and Mexico sites, savings consistently fell in the 50–60% band — not by coincidence. The energy structure of an injection moulding machine's hydraulic system sets the upper bound of retrofit benefit, while actual savings depend on original system efficiency, the share of holding and cooling time in the cycle, and machine load factor. At all three sites, non-full-flow operation accounted for over 60% of the moulding cycle, providing ample room for servo savings.

Notably, payback periods at all three projects stayed between 12 and 20 months. Even setting aside extended oil life and reduced cooling water consumption from lower oil temperatures, electricity savings alone justify the retrofit decision. For injection moulders, servo hydraulic power units have shifted from an energy-saving option to a standard line configuration.

Selection and Retrofit Recommendations

Servo hydraulic retrofits are not a simple matter of swapping pump and motor. The original system's working pressure, flow curve, tank volume and cooling capacity must be verified to ensure the servo pump set's output characteristics match the moulding process. Volumetric efficiency of the internal gear pump at low speed is a key indicator that directly determines holding-phase stability. Servo drive parameters must also be tuned in coordination with the machine controller to achieve fast pressure and flow response. For workshops with multiple machines running in parallel, starting with a single pilot machine to validate savings data and part consistency before wider rollout is recommended.