Servo energy-saving retrofit has been on the upgrade roadmap of many factories for years.
The principle is straightforward: replace the original asynchronous motor and fixed-displacement pump with a servo motor and speed control to reduce energy consumption and noise.

However, in practice, many retrofitted machines fail to achieve the expected results.

Industry Context: When Servo Retrofit Falls Short

Even after upgrading the motor and drive and tuning parameters multiple times, engineers often observe:

Energy savings lower than theoretical expectations

Pressure instability during pressing and holding

Persistent noise, despite the servo system

These issues suggest that upgrading only the motor side does not address the root cause.

Root Cause: Conventional Pumps Are Not Designed for Servo Operation

Traditional gear pumps and vane pumps are optimized for fixed-speed operation.
When used in servo systems, especially at low speed, several limitations appear:

Volumetric efficiency drops significantly at 200–400 r/min

Internal leakage increases, reducing effective pressure output

Flow and pressure pulsation become more pronounced

As a result, the servo control system must compensate with wider safety margins, reducing overall efficiency.

Core Approach: Treat Pump and Servo as a Unified System

To achieve real performance gains, modern retrofit solutions combine:

Servo motor + FG series high-pressure internal gear pump

rather than upgrading the motor alone.

This ensures that both the drive and the hydraulic source are matched to variable-speed operation.

Retrofit Engineering Method

A typical retrofit process follows a structured approach.

Step 1: Define Duty Cycle and Pressure Requirements

Maximum working pressure (commonly 20–25 MPa, up to 28–30 MPa in some cases)

Required flow during fast approach

Pressure stability requirements during slow pressing and holding

Step 2: Select FG Pump Family and Displacement

FG1 (25–40 mL/r) for single-cylinder presses with moderate stroke and cycle time

FG1 (40–50 mL/r) or FG2 (64–80 mL/r) for multi-cylinder or higher-flow systems

Rated pressure: 31.5 MPa
Maximum pressure: up to 35 MPa

These specifications exceed the requirements of most legacy machines.

Step 3: Match Servo Drive and Speed Range

FG pumps operate within a wide speed range of 200–3000 r/min:

High speed provides sufficient flow for fast approach

Low speed maintains stable volumetric efficiency for pressing and holding

This allows the servo system to regulate flow through speed control effectively, without being limited by leakage or pulsation.

Performance Improvements After Retrofit

After integrating FG pumps into servo retrofits, engineers typically report:

Pressure curves that closely follow setpoints, especially during pressing and holding

Cleaner motor current curves with fewer spikes, improving actual energy efficiency

Noticeable noise reduction, replacing sharp pump noise with a smoother background sound

These improvements reflect better coordination between the drive system and the hydraulic source.

Engineering Value: A Repeatable Retrofit Solution

For technical managers planning plant-wide upgrades, the FG series provides more than incremental improvement.

It delivers a standardized hydraulic solution that integrates:

Energy efficiency
Pressure stability
Noise reduction

into a single, repeatable system architecture.

Summary

Servo retrofit success depends on both the motor and the hydraulic pump.

By combining servo drives with FG internal gear pumps, manufacturers can achieve:

Energy savings closer to theoretical expectations

Stable pressure control across the entire cycle

Reduced noise and improved working conditions

Consistent performance across multiple machines

For future retrofit projects, selecting the appropriate displacement within FG0, FG1, or FG2 enables a scalable and repeatable upgrade path without redesigning the hydraulic source each time.