Product Overview
The A2FM series bent-axis fixed-displacement piston 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 A2FM Series 61 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 A2FM series covers an ultra-wide displacement range from 5 to 1000 cc/rev, including sizes 28, 32, 45, 56, 90, 107, and 180. The bent-axis compact design delivers exceptional power density and total efficiency, including a very high starting efficiency critical for operations requiring immediate response. The 7/9-piston design effectively reduces flow pulsation, maintaining low vibration and low noise during extended high-speed operation. Every unit undergoes 100% factory testing under simulated real-world working conditions, validating pressure, flow, and sealing performance before shipment—ensuring reliable operation from the very first start.
Model Code Interpretation:
A2FM28/61W-VPB020
A2FM – Series code: Bent-axis fixed displacement piston motor
28 – Displacement size: 28.1 cm³/rev (geometric displacement)
61 – Series number: Series 61
W – Rotation: Bidirectional (viewed on drive shaft)
VPB020 – Specific configuration code (shaft end, mounting flange, port options)
Technical Specifications
A2FM28/61W-VPB020
Model: A2FM28/61W-VPB020
Type: Bent-axis fixed displacement piston motor (Series 61)
Geometric Displacement: 28.1 cm³/rev
Nominal Pressure: 400 bar
Peak Pressure: 450 bar
Maximum Speed: 6300 r/min
Weight: Approx. 9.5 kg
Mounting Flange: ISO 3019-2 100B4 HW
Drive Shaft: Parallel keyed shaft DIN 6885
Port Configuration: SAE working ports A and B at side, opposite
Seal Material: FKM (fluoroelastomer)
Housing Material: High-strength cast iron
Medium: Mineral oil and synthetic hydraulic oil (HFD/HFB/HFC)
Operating Temperature Range: -20°C to +90°C (standard seals)
Rotation: Bidirectional (viewed on drive shaft)
A2FM Series Displacement Reference :
A2FM12 – 10.3 cm³/rev
A2FM16 – 16 cm³/rev
A2FM23 – 22.9 cm³/rev
A2FM28 – 28.1 cm³/rev
A2FM32 – 32 cm³/rev
A2FM45 – 45.6 cm³/rev
A2FM56 – 56.1 cm³/rev
A2FM63 – 63 cm³/rev
A2FM80 – 80.4 cm³/rev
A2FM90 – 90 cm³/rev
A2FM107 – 106.7 cm³/rev
A2FM125 – 125 cm³/rev
A2FM160 – 160.4 cm³/rev
A2FM180 – 180 cm³/rev
A2FM Series Pressure Ratings :
Size 5: Nominal pressure 315 bar / Peak pressure 350 bar
Sizes 10–200: Nominal pressure 400 bar / Peak pressure 450 bar
Sizes 250–1000: Nominal pressure 350 bar / Peak pressure 400 bar
Key Technical Advantages
1. 100% Direct Interchangeability – Zero Modification Required
The A2FM series is engineered to exact Rexroth A2FM Series 61 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 and Superior Efficiency
The bent-axis compact design and high-strength bearing system deliver exceptional power density. The bent-axis axial tapered piston rotary group ensures minimal friction losses. Total efficiency is exceptionally high, including a very high starting efficiency—critical for operations requiring immediate response.
3. Wide Displacement Range with Flexible Configuration
The A2FM series offers an ultra-wide displacement selection from 5 to 1000 cc/rev, allowing precise adjustment to specific application requirements. Multiple shaft options (parallel keyed, splined, tapered), mounting flange types, and port configurations are available to suit various system requirements.
4. High-Speed Capability with Low-Noise Operation
Maximum speed reaches 6300 r/min, approved for high-speed operation. The 7/9-piston design effectively reduces flow pulsation, maintaining low vibration and low noise during extended high-speed operation. Optimized hydraulic circuits and low-friction structures ensure smooth operation characteristics.
5. Modular Design with Flexible Function Expansion
Optional integrated pressure relief valve prevents system overload. Optional counterbalance valves (BVD/BVE) , flushing valves, and boost-pressure valves provide additional control and protection mechanisms. Modular components support rapid maintenance and upgrades.
6. 100% Factory Testing Under Simulated Working Conditions
Every A2FM series unit undergoes rigorous factory testing under simulated real-world conditions, validating pressure, flow, volumetric efficiency, and sealing 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 A2FM series fixed displacement motors are widely deployed across the following industries and equipment types:
Construction Machinery: Excavator travel/swing drives, rotary drilling rig power heads
Road Construction Equipment: Roller travel drives, asphalt pavers
Crane Machinery: Crane hoisting mechanisms, swing mechanisms
Mining Equipment: Mining machinery, rock drilling rigs
Agricultural Machinery: Large tractors, combine harvesters
Marine & Shipbuilding: Marine winches, deck machinery
Industrial Equipment: Metallurgical equipment, injection molding machines, conveyors
Expert Maintenance Tips
1. Hydraulic Fluid Cleanliness Management
The A2FM series utilizes bent-axis 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. Mineral oil or synthetic hydraulic oil is recommended. Never use degraded or substandard hydraulic fluids.
2. Case Drain and Backpressure Control
Ensure the case drain line is unrestricted with no flow restrictions. For sizes 10–200, 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.
3. 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.
4. 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.
5. Rotation Direction Confirmation
The A2FM series features bidirectional rotation as viewed on the drive shaft. Verify that the system circuit direction matches the required rotation direction before installation—reversing fluid flow will reverse the motor‘s direction of rotation.
6. 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.
