Product Overview
The A6VM series bent-axis axial piston variable motors are a flagship product line within the Bosch Rexroth hydraulic transmission platform, classified as all-purpose high-pressure motors. Featuring a bent-axis design with axial tapered piston rotary groups, these motors are specifically engineered for hydrostatic drives in both open and closed circuits. Designed to fully comply with Rexroth A6VM Series 63 mounting and interface standards, these motors offer 100% direct interchangeability with original Rexroth units—enabling plug-and-play replacement without any管路 modifications or adapter plates, significantly minimizing downtime and retrofit costs.
The A6VM series covers a wide displacement range from 28 to 1000 cc/rev, with size 55 representing a compact and efficient member of the family. The bent-axis compact design delivers exceptional power density, with displacement infinitely variable from Vg max down to Vg min ≈ 0. Every unit undergoes 100% factory testing under simulated real-world working conditions, validating pressure, flow, volumetric efficiency, and control characteristics before shipment—ensuring reliable operation from the very first start.
Model Code Interpretation:
A6VM55EP2/63W-VZB020HB
A6VM – Series code: Bent-axis axial piston variable motor
55 – Displacement size: 54.8 cm³/rev
EP2 – Control type: Electric proportional control, with proportional solenoid
63 – Series number: Series 63
W – Rotation: Bidirectional
VZB020HB – Specific configuration code
A6VM55HD1D/63W-VAB020B
A6VM – Series code: Bent-axis axial piston variable motor
55 – Displacement size: 54.8 cm³/rev
HD1D – Control type: Hydraulic proportional control
63 – Series number: Series 63
W – Rotation: Bidirectional
VAB020B – Specific configuration code
A6VM80HA1T/63W-VZB380A-K
A6VM – Series code: Bent-axis axial piston variable motor
80 – Displacement size: 80 cm³/rev
HA1T – Control type: Automatic control, high-pressure related
63 – Series number: Series 63
W – Rotation: Bidirectional
VZB380A-K – Specific configuration code
Technical Specifications
A6VM55EP2/63W-VZB020HB
Model: A6VM55EP2/63W-VZB020HB
Type: Bent-axis axial piston variable motor (Series 63)
Displacement (Vg max): 54.8 cm³/rev
Nominal Pressure: 400 bar
Maximum Pressure: 450 bar
Maximum Speed (at Vg max): 4450 r/min
Maximum Speed (at Vg < Vg max): 7000 r/min
Maximum Inlet Flow: 244 L/min
Torque Constant: 0.87 Nm/bar
Maximum Torque (Δp=400 bar): 349 N·m
Control Type: EP2 – Electric proportional control (24V/12V proportional solenoid)
Weight: Approx. 26 kg
Housing Material: High-strength cast iron
Medium: Mineral oil, synthetic hydraulic oil
NOT suitable for HFA hydraulic fluids
Operating Temperature Range: -25°C to +90°C
Rotation: Bidirectional (viewed on drive shaft)
A6VM55HD1D/63W-VAB020B
Model: A6VM55HD1D/63W-VAB020B
Type: Bent-axis axial piston variable motor (Series 63)
Displacement (Vg max): 54.8 cm³/rev
Nominal Pressure: 400 bar
Maximum Pressure: 450 bar
Maximum Speed (at Vg max): 4450 r/min
Maximum Speed (at Vg < Vg max): 7000 r/min
Maximum Inlet Flow: 244 L/min
Maximum Torque (Δp=400 bar): 349 N·m
Control Type: HD1D – Hydraulic proportional control
Weight: Approx. 26 kg
Housing Material: High-strength cast iron
Medium: Mineral oil, synthetic hydraulic oil
NOT suitable for HFA hydraulic fluids
Operating Temperature Range: -25°C to +90°C
Rotation: Bidirectional (viewed on drive shaft)
A6VM80HA1T/63W-VZB380A-K
Model: A6VM80HA1T/63W-VZB380A-K
Type: Bent-axis axial piston variable motor (Series 63)
Displacement (Vg max): 80 cm³/rev
Nominal Pressure: 400 bar
Maximum Pressure: 450 bar
Maximum Speed (at Vg max): 3900 r/min
Maximum Speed (at Vg < Vg max): 6150 r/min
Maximum Inlet Flow: 312 L/min
Torque Constant: 1.27 Nm/bar
Maximum Torque (Δp=400 bar): 509 N·m
Control Type: HA1T – Automatic control, high-pressure related
Weight: Approx. 50 kg
Housing Material: High-strength cast iron
Medium: Mineral oil, synthetic hydraulic oil
NOT suitable for HFA hydraulic fluids
Operating Temperature Range: -25°C to +90°C
Rotation: Bidirectional (viewed on drive shaft)
Key Technical Advantages
1. 100% Direct Interchangeability – Zero Modification Required
The A6VM series is engineered to exact Rexroth A6VM Series 63 mounting and interface specifications, with identical dimensions, port locations, and shaft end configurations. End users can replace original units directly without any管路 modifications or adapter plates—transforming unplanned downtime into scheduled, rapid maintenance while significantly reducing spare parts procurement costs and equipment downtime losses.
2. Bent-Axis Compact Design – High Power Density with Stepless Control
The bent-axis compact design and high-strength bearing system deliver high power density and low moment of inertia. Displacement can be steplessly adjusted from Vg max down to Vg min ≈ 0. By eliminating gear-shifting mechanisms, smaller pumps can be used to achieve a wide speed range, significantly reducing system cost and space requirements. The wide control range enables the variable motor to satisfy the requirement for both high speed and high torque.
3. Multiple Control Options for Flexible Adaptation Across Industries
The A6VM series offers more than 7 control types—EP electric proportional control, HD hydraulic proportional control, HA high-pressure related automatic control, DA hydraulic remote control, HZ hydraulic two-point control, EZ electric two-point control, and more:
EP2 Electric Proportional Control (A6VM55EP2): Enables precise electric displacement adjustment via proportional solenoid, supporting 12V/24V supply. Offers precise control, energy savings, and rapid response—ideal for remote automatic control or integration with electronic control systems.
HD1D Hydraulic Proportional Control (A6VM55HD1D): Provides proportional displacement adjustment via pilot oil pressure. Control oil can be directly drawn from the high-pressure side. Simple, reliable structure—ideal for hydraulic pilot control in mobile machinery.
HA1T High-Pressure Related Automatic Control (A6VM80HA1T): Requires no external pilot oil source—automatically adjusts displacement based on motor high-pressure side pressure, enabling constant torque/power control and simplifying system design. Ideal for high-load, high-precision machinery such as cranes.
4. High-Speed Capability with Long-Life Bearing System
Approved for very high-speed operation. Equipped with a compact, robust long-life bearing system featuring an excellent power-to-weight ratio and superior starting characteristics. Size 55 achieves 4450 r/min at Vg max and 7000 r/min at Vg < Vg max. Optimized hydraulic circuits and low-friction structures ensure high starting efficiency and smooth operation.
5. Compact Design with Modular Architecture
The bent-axis compact design and high-strength bearing system deliver high power density and low moment of inertia, balancing long service life with fast dynamic response. Modular components support rapid maintenance and upgrades, with optional flushing and boost-pressure valves available.
6. 100% Factory Testing Under Simulated Working Conditions
Every A6VM series unit undergoes rigorous factory testing under simulated real-world conditions, validating pressure, flow, volumetric efficiency, control response characteristics, and thermal performance across the full operating range. Test media match actual operating conditions, ensuring each unit is ready for immediate installation and reliable operation upon delivery—eliminating the risk of “dead on arrival” components.
Application Areas
The A6VM series variable motors are widely deployed across the following industries and equipment types:
A6VM55EP2/63W-VZB020HB (Electric Proportional Control) :
Construction Machinery: Medium/small excavator travel/swing drives
Agricultural Machinery: Combine harvester travel drives
Industrial Equipment: Injection molding machines, conveyors
Specialty Vehicles: Municipal vehicle hydraulic systems
A6VM55HD1D/63W-VAB020B (Hydraulic Proportional Control) :
Marine & Shipbuilding: Deck crane hydraulic systems
Construction Machinery: Crane hoisting/swing mechanisms
Road Construction: Roller travel drives
Mining Equipment: Rock drilling rigs
A6VM80HA1T/63W-VZB380A-K (High-Pressure Related Automatic Control) :
Crane Machinery: Large crane hoisting mechanisms
Construction Machinery: Rotary drilling rig power heads
Road Construction: Asphalt paver hydraulic drives
Komatsu PW170ES and similar construction equipment
Expert Maintenance Tips
1. Hydraulic Fluid Cleanliness Management
The A6VM series utilizes bent-axis axial piston designs with minimal clearances between pistons and cylinder bores, making them highly sensitive to fluid contamination. It is recommended to install filters with ≤10μm filtration rating, maintaining fluid cleanliness to ISO 4406 19/17/14 or better. NEVER use HFA hydraulic fluids—the A6VM series is not suitable for HFA fluids. Recommended oil viscosity is 16–36 mm²/s (at operating temperature).
2. EP2 Electric Proportional Control Tuning (A6VM55EP2)
The EP2 control is an electric proportional control with proportional solenoid. Before wiring, verify that the control system voltage matches the coil specifications (12V or 24V) to avoid coil burnout from voltage mismatch or sluggish control response. The control signal is current-based; PWM regulation is recommended.
3. HD1D Hydraulic Proportional Control Tuning (A6VM55HD1D)
The HD1D control is a hydraulic proportional control type. During commissioning, verify that the pilot oil supply pressure is stable and cleanliness is adequate. The control characteristic is proportional to the pilot pressure—fine-tune the pilot pressure setting according to actual operating conditions. Control oil can be directly drawn from the high-pressure side.
4. HA1T High-Pressure Related Automatic Control Tuning (A6VM80HA1T)
The HA1T control is an automatic control, high-pressure related type. No external pilot oil source is required—displacement is automatically adjusted based on motor high-pressure side pressure. During commissioning, verify that system working pressure is within the HA1T control setting range. Sizes 28–200 all support HA1T control.
5. Air Bleeding and Pre-filling Before Start-up
Always bleed air from the motor housing via the highest vent port before initial start-up or after extended shutdown periods to prevent cavitation damage. Ensure the motor housing is completely filled with hydraulic fluid prior to starting.
6. Coupling Alignment Requirements
Maintain shaft alignment within 0.05 mm concentricity and 0.5° angular deviation between the drive shaft and the load shaft. Excessive misalignment will lead to premature bearing wear and shaft seal leakage. The use of flexible couplings is recommended to compensate for minor installation deviations.
7. Case Drain and Backpressure Control
Ensure the case drain line is unrestricted with no flow restrictions. For sizes 28–200, continuous case backpressure must not exceed 10 bar. Excessive case backpressure will cause shaft seal damage and premature bearing failure. The drain line should return directly to the reservoir, not in parallel with the return line. Note that the case drain temperature may be higher than the circuit or reservoir temperature.
8. Periodic Inspection and Maintenance
Inspect shaft seals for leakage and listen for abnormal operating noise every 1,000 operating hours or every 6 months (whichever comes first). If reduced volumetric efficiency or insufficient output torque is observed, timely overhaul of the piston assembly and valve plate is recommended.
