Modern injection molding machines are widely equipped with “servo energy-saving systems”.
However, in real production environments, some machines still exhibit high noise near the mold area and unstable pressure during clamping and holding phases.

Industry Context: When Servo Upgrades Do Not Deliver Expected Performance

Although servo motors and drives are upgraded, many systems retain traditional pump configurations.

In such cases, the hydraulic system may show:

Noticeable noise during operation, especially at the mold area

Pressure deviation during low-speed holding

Flow fluctuation affecting injection consistency

These issues indicate that the performance limitation lies in the hydraulic power source rather than the control system.

Root Cause: Pump Performance Limits in Wide Speed and Frequent Start/Stop Operation

Injection molding machines operate under:

Frequent start/stop cycles
Wide speed variation
Low-speed holding with sustained pressure

Traditional external gear pumps or older designs often struggle in this environment:

Volumetric efficiency drops at low speed, causing actual pressure to fall below setpoints

Flow pulsation leads to unstable clamping and injection behavior

Noise remains relatively high despite servo control

Core Requirement: Stable Pressure Across Wide Speed Range

For servo injection systems, the hydraulic pump must provide:

High volumetric efficiency at low speed

Stable pressure during holding and cooling

Sufficient flow at higher speeds for rapid clamping and injection

Low pulsation for precise servo control

Solution Platform: FG Series High-Pressure Internal Gear Pumps

FG internal gear pumps are increasingly used as the main pump in servo injection molding machines.

Key Technical Parameters

Speed range: 200–3000 r/min
Rated pressure: 31.5 MPa
Maximum pressure: up to 35 MPa

This range supports both high-speed movement and low-speed pressure holding.

Displacement Selection for Injection Applications

FG1 (25–40 mL/r) is typically used for small and medium injection machines

FG1 (40–50 mL/r) or FG2 (64–80 mL/r) is selected for larger clamping forces and higher shot volumes

Structural Advantages

Internal gear design provides low flow and pressure pulsation

Improved volumetric efficiency across a wide speed range

Lower noise characteristics compared with conventional pump designs

Practical Selection Method

In system design, engineers often follow a structured approach:

Calculate required flow based on clamping force, shot volume, and cycle time

Select appropriate displacement within FG1 or FG2 range

Define servo operating range at approximately 600–2400 r/min

Reserve 200–300 r/min for stable low-speed holding operation

This ensures both energy efficiency and stable hydraulic performance.

Performance Improvements in Operation

After adopting FG pumps in servo systems, users typically observe:

Pressure values tracking setpoints more closely during holding

Smoother clamping and injection motion

Reduced flow fluctuation and improved process consistency

Lower noise levels around the machine

These improvements enhance both product quality and operator experience.

Engineering Value: Completing the Servo System

A servo system is only as effective as its hydraulic power source.

FG internal gear pumps provide:

Stable pressure and flow across the entire speed range

Low pulsation for precise servo control

Reduced noise for improved working conditions

Reliable performance under frequent start/stop operation

Summary

In servo injection molding machines, upgrading the motor alone is not sufficient.

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

True energy efficiency
Stable pressure control
Smooth machine operation
Lower noise levels

Only when both the control system and the hydraulic pump are optimized together does the term “servo injection machine” fully reflect its intended performance.