Description
Product introduction
The MOOG D661-431D-4 is a high-precision, pilot-operated electro-hydraulic servo valve designed for demanding industrial automation and motion-control applications. As part of MOOG’s D661 series, the D661-431D-4 combines a two-stage valve architecture (pilot plus main spool) with integrated electronics, offering the dynamic performance and repeatability required for position, velocity, or force control systems.
This valve model features the standardized ISO 4401 Size 05 mounting, enabling compatibility with many industrial hydraulic manifolds and actuators. With a high operating pressure rating (up to approximately 350 bar) and rapid response time, the MOOG D661-431D-4 serves as the electro-hydraulic interface translating analog control signals into precisely controlled hydraulic flow. Its application spans both new-build machines and retrofit programmes where old pilot valves are being upgraded.
In an automation system, the D661-431D-4 plays a critical role by converting control system commands into fluid motion while maintaining tight feedback control and minimal hysteresis. Whether used for cylinder actuation in presses, servo-hydraulic test rigs, or motion platforms, the MOOG D661-431D-4 ensures that system integrators and machine builders achieve higher accuracy, faster cycle times and enhanced reliability.
Core advantages and technical highlights
Functional innovation: The MOOG D661-431D-4 uses a proven two-stage design with MOOG’s ServoJet® pilot stage driving the main spool. This architecture allows high dynamic gain, enabling rapid spool movement and improved flow control precision.
High performance: With a pressure rating up to ~350 bar and standard flow capacities in the 20-200 L/min range, the D661-431D-4 is capable of handling demanding loads and fast actuation requirements. The response time in the lower millisecond range enables high-bandwidth control loops, making it suitable for motion-critical applications.
Reliability and robustness: Integrated electronics and feedback loop design reduce hysteresis and drift over time, delivering repeatable performance and stable behaviour in continuous-duty industrial use. The standardized mounting and established MOOG platform ensure long-term parts availability and service support.
Compatibility and ease of use: The D661-431D-4’s standard interface — ISO 4401 Size 05 — and analog command options (±10 V/±10 mA) make it straightforward to implement in legacy systems or as a drop-in upgrade. This helps reduce redesign effort and simplifies integration for OEMs and service teams.
Optimised system architecture: By selecting a premium valve like the D661-431D-4, machine constructors can achieve fewer hydraulic stages, tighter control loops and better overall machine stability. This equates to reduced maintenance, lower lifecycle cost and enhanced machine uptime.
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