The 4WRA6 is a series of direct-operated proportional directional valves manufactured by REXROTH. It is designed as a subplate-mounted component and is typically used to control both the direction and flow rate of hydraulic fluid in a system, thereby managing the direction and speed of hydraulic actuators.

• Direct-Operated Design: The valve spool is moved directly by proportional solenoids without the need for a pilot pressure stage.
• Spring-Centered Spool: When the solenoids are de-energized, the spool returns to and is maintained in the center position by compression springs.
• Mounting: Subplate mounting with porting interface according to ISO 4401.
• Two Configurations: Available with external control electronics (4WRA type) or with integrated onboard electronics (OBE) (4WRAE type).
• Flow Control: Provides proportional flow control with a progressive flow characteristic (metering notch) in addition to direction control.

The key difference lies in the location of the control electronics.

• 4WRA: Requires an external, separate amplifier to function. The amplifier processes the input signal (e.g., from a PLC) and provides the necessary power to the valve's solenoids.
• 4WRAE: Features Integrated OnBoard Electronics (OBE). The control electronics are built into the valve, allowing it to accept standard analog input signals (e.g., ±10 V or 4-20 mA) directly.

A typical 4WRA6 model code is structured as follows:

• 4WRA: Series designation for proportional directional valve without OBE. "E" after WRA (4WRAE) indicates integrated electronics.
• 6: Nominal size (06). Alternative size is 10.
• W / E / etc.: Spool symbol/type (e.g., W, E, EA), which defines the flow characteristics and center position condition.
• 07 / 15 / 30: Nominal flow rate in liters per minute at a pressure drop (Δp) of 10 bar. For size 06, common values are 7, 15, or 26/30 L/min.
• 2X: Component series (20-29).
• G24: Supply voltage (24 V DC).
• K4 / K31: Electrical connection type (e.g., without plug, with specific component socket).
• V: Seal material (e.g., FKM for mineral oil).
• A1 / F1 (for 4WRAE): Control value input type (A1 for ±10V, F1 for 4-20mA).

• Maximum Operating Pressure: Up to 350 bar for P, A, B ports.
• Maximum Flow: Varies with model (e.g., 42 L/min for some 4WRAE6 models).
• Recommended Fluid Cleanliness: ISO 4406 20/18/15.
• Voltage: Typically 24 V DC.

These valves are used in various industrial hydraulic systems requiring precise control, such as:

• Plastic injection molding machines.
• Presses and bending machines.
• Mobile equipment.
• Industrial automation systems where proportional control of speed and direction is needed.

Common problems and their potential causes include:

• Valve does not shift or responds slowly: Check solenoid coil for burnout or open circuit; check power supply voltage; check for contamination causing the spool to stick.
• Internal Leakage: Worn spool or seals, or contamination causing improper sealing.
• Valve sticking: Often due to inadequate fluid cleanliness, insufficient lubrication, or internal damage.
• Excessive noise: Can be caused by excessive vibration, voltage fluctuations, or issues with the solenoid.
• No function despite signal: Check the amplifier (for 4WRA), wiring, and connections between the control unit and the valve.