In complex machines, hydraulic schematics often resemble dense network maps.
A main cylinder drives the core process, while ejectors, clamps, tilting mechanisms, lubrication systems, and other auxiliary motions operate simultaneously within the same system.

When all circuits share a single conventional pump, power distribution becomes difficult to control.

Industry Context: Power Competition in Multi-Circuit Systems

Typical issues in single-pump multi-circuit systems include:

Auxiliary circuits activating during main cylinder operation, causing sudden pressure and flow fluctuation

Interference between circuits, making system tuning and stability control more complex

Limited scalability, where adding new functions requires redesigning the entire hydraulic power unit

These challenges arise because multiple circuits compete for the same flow and pressure source.

Core Requirement: Independent Yet Coordinated Power Supply

To improve system stability, hydraulic design must achieve:

Priority supply for the main process cylinder
Controlled and independent operation of auxiliary circuits
Scalable architecture for future function expansion

This requires separating power distribution at the source level rather than managing conflicts downstream.

Solution Platform: FG21 Dual Internal Gear Pump Architecture

FG21 dual internal gear pumps provide a practical way to reorganize hydraulic power supply.

Structural Configuration

FG21 integrates two pumps on a single shaft:

Front pump: typically an FG1 or FG2 with medium to large displacement, dedicated to the main high-pressure circuit

Rear pump: smaller displacement (25 / 32 / 40 / 50 / 63 mL/r), supplying auxiliary circuits such as ejectors, clamps, tilting mechanisms, and lubrication

Both pumps share the same motor and operate within a speed range of 200–3000 r/min

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

This configuration supports multi-circuit systems with both high-pressure and variable-flow requirements.

Design Method for Multi-Circuit Systems

In practical system design, engineers typically apply the following approach:

Connect the primary process cylinder exclusively to the front pump to ensure stable pressure and flow

Group auxiliary circuits on the rear pump, separating them from the main power path

Use sequencing valves and logic control at the manifold level to coordinate motion instead of allowing circuits to compete directly

This approach improves both stability and controllability.

Performance Improvements in Operation

After implementing FG21 dual pump architecture, several benefits are observed:

Main cylinder motion becomes stable and predictable, unaffected by auxiliary circuit activation

Auxiliary circuits operate independently, simplifying system tuning and fault diagnosis

System expansion becomes easier, as new auxiliary functions can be integrated into the rear pump circuit without redesigning the main power unit

Engineering Value: Power Source-Level System Structuring

FG21 does not simply increase capacity; it restructures how hydraulic power is distributed.

It enables:

Clear separation between critical and non-critical circuits
Reduced interaction and interference between functions
More efficient troubleshooting through circuit-level isolation
Built-in flexibility for future upgrades

Summary

For multi-circuit hydraulic systems, stability and scalability depend on how power is distributed at the source.

FG21 dual internal gear pumps provide:

Dedicated power supply for main cylinders
Independent support for auxiliary circuits
Simplified system tuning and maintenance
Flexible expansion capability for additional functions

For machine builders offering standardized platforms with customized options, FG21 effectively creates a structured and expandable hydraulic architecture, ensuring that core performance remains stable while allowing auxiliary functions to evolve.