Description
D656-065D: Product Overview
The MOOG D656-065D is a two-stage electrohydraulic servo valve from the D656 Series, designed for high-precision control of hydraulic actuators in dynamic systems. In an automation architecture, it serves as the critical interface between electronic controllers (e.g., PLCs, motion controllers) and hydraulic actuators (e.g., cylinders, motors), converting low-power electrical command signals into proportional hydraulic flow and pressure. The D656 Series is recognized for its high dynamic response and reliability in closed-loop systems, making it suitable for applications requiring micrometer-level positioning, velocity, or force accuracy—such as aerospace flight simulators, material testing rigs, and industrial robotics. This valve operates on a nozzle-flapper pilot stage and a sliding spool main stage, ensuring stable performance across varying loads. It is typically integrated into systems with feedback from position/force sensors, where adjustments to the input signal maintain desired actuator behavior, critical for avoiding overshoot or instability in high-performance machinery.
Moog D656-065D
D656-065D: Technical Specifications
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Model Number: D656-065D
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Manufacturer: Moog Inc.
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Product Type: Electrohydraulic Servo Valve (Two-Stage)
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Valve Configuration: 4-way spool (symmetrical flow paths, spring-centered)
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Nominal Flow: 25 GPM (94.6 L/min) @ 1000 psi (69 bar) differential pressure
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Maximum Pressure: 3000 psi (207 bar) per port
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Input Signal: ±10VDC (standard), ±40mA (via optional G123 series amplifier)
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Response Time: <15 ms (step input to 90% flow)
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Resolution: <0.1% of full scale (hysteresis <0.5%)
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Operating Temperature: -20°C to +80°C (-4°F to 176°F) (fluid-dependent)
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Fluid Compatibility: Petroleum-based oils (ISO VG 32/46), phosphate ester synthetic fluids (e.g., Skydrol)
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Weight: 2.5 kg (5.5 lbs, valve body only)
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Dimensions: 165mm (L) x 89mm (W) x 114mm (H) (approximate)
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Certifications: CE, ISO 9001 (manufacturing standard)
Core Features & Customer Value
High-Precision Flow/Pressure Control: The two-stage design (nozzle-flapper pilot + sliding spool) delivers linear flow output proportional to the input signal, with resolution <0.1% of full scale. For engineers, this enables micrometer-level positioning of actuators in semiconductor manufacturing equipment or wind tunnel test rigs, where accuracy directly impacts product quality.
Fast Dynamic Response: A <15 ms response time allows the valve to adjust flow rapidly during transient conditions (e.g., sudden load changes). In robotic assembly arms, this minimizes lag between controller commands and end-effector movement, improving assembly consistency.
Robust Construction for Harsh Environments: The valve body is machined from stainless steel with hardened spool lands, resisting wear from contaminated fluids (common in construction machinery). For maintenance teams, this extends service life to 10,000+ operating hours, reducing replacement costs.
Flexible Signal Compatibility: While optimized for ±10VDC inputs, it integrates with optional Moog G123 amplifiers to accept ±40mA or digital (EtherCAT) signals. This adaptability simplifies retrofitting legacy systems (e.g., upgrading analog controls to digital in paper mills) without replacing the valve.
Stable Performance Across Loads: Internal feedback mechanisms compensate for pressure fluctuations, maintaining consistent flow output even when system pressure varies by ±20%. In material testing machines, this ensures accurate force application regardless of specimen stiffness.
Moog D656-065D
Typical Applications
The D656-065D is deployed in systems requiring precise hydraulic actuation:
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Aerospace: Flight simulator actuators (controlling pitch/roll/yaw), landing gear deployment systems.
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Test & Simulation: Hydraulic test rigs (fatigue testing of components), wind tunnel vanes (airflow control).
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Industrial Robotics: Precision assembly arms (part insertion), material handling systems (load positioning).
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Manufacturing: Plastic injection molding machines (clamp force control), metal stamping presses (ram positioning).
In a flight simulator facility, for example, the valve controls hydraulic actuators that simulate aircraft control surfaces. Its fast response (<15ms) ensures the simulated aircraft reacts to pilot inputs within 20ms of real-world aircraft, critical for pilot training realism.
