Bonfiglioli A-series gearbox selection and maintenance

Bonfiglioli A-series helical bevel gear reducer selection and maintenance engineering guide

In the field of industrial transmission, helical bevel gear reducers have become the preferred choice for many heavy-duty applications due to their high efficiency, high torque density, and flexible installation methods. Bonfiglioli's A-series (Spiral level gearmotors) has undergone years of technological iteration, covering a torque range of 100-14000 Nm with modular design, high-precision gear grinding, and diverse output forms. This article is based on the official technical manual, and systematically elaborates on the practical application points of this series of reducers from the dimensions of engineering selection, mechanical installation, lubrication maintenance, load verification, and fault diagnosis, providing an operable technical reference for on-site engineers.

Overview of Product Series and Interpretation of Technical Parameters

The A series adopts a combination of helical gears and bevel gears for transmission, which can achieve right angle output with input and output shafts perpendicular. Its core advantages lie in:

Torque range: 100~14000 Nm, with a total of 12 machine bases (A 05 to A 90).

Power coverage: At an input speed of 1400 min ⁻¹, the mechanical power reaches 0.22-150 kW.

Speed ratio range: 5.4~1715 (multi-stage combination).

Output form: Foot or flange installation, key bonded hollow shaft, keyless shrink disc, metric/imperial solid shaft, spline hollow shaft (DIN 5480), suitable for various load connections.

Input interfaces: IEC/NEMA motor adapter, servo motor adapter, solid input shaft.

Key points of selection project: Based on the required output torque M ₂ and output speed n ₂ of the load, combined with the input speed n ₁, calculate the reduction ratio i=n ₁/n ₂, and then check the table to select the rated output torque M ₙ ₂ ≥ calculated torque M ꜀ ₂ (M ꜀ ₂=M ₂ × f ₛ, where f ₛ is the service coefficient). The service coefficient needs to be retrieved from the chart based on the load type (uniform, moderate impact, heavy impact), daily operating hours, and start-up frequency.

Selection calculation process and examples

Step 1: Determine the service coefficient f ₛ

Based on the load characteristics (acceleration quality factor K, divided into K1~K3 curves) and the number of starts and stops per hour, combined with the daily operating hours, refer to Table A2 to obtain f ₛ.

Typical values: uniform load, 8 hours per day, with few startups f ₛ ≈ 1.0~1.2; When subjected to heavy impact and frequent start stop, it can reach 2.0 or above.

Step 2: Calculate the required input power P ᵣ₁

Given the output torque M ₂ and output speed n ₂, as well as the dynamic efficiency η₀ (A series 2nd stage about 0.94, 3rd stage about 0.91, 4th stage about 0.89), then:

Pᵣ₁ = (M₂ × n₂) / (9550 × η₀) [kW]

When selecting, it is necessary to ensure that the rated power of the motor P ₙ ≥ P ᵣ₁. If it is a non continuous working system (S2-S8), it can be multiplied by the power enhancement factor f ₘ (refer to Table A7).

Step 3: Select the machine base and speed ratio

Find a model from the selection table (such as A 10, A 20, etc.) that is close to the calculated speed ratio and has a rated torque of ≥ M ꜀ ₂. For example, if an output torque of 800 Nm, an output speed of 20 min ⁻¹, and an input of 1400 min ⁻¹ are required, then i ≈ 70, check the corresponding model of the A 50 series.

Attention: For dual speed motors or special operating conditions (such as lifting or translation), please contact the technical department.

Mechanical installation and alignment specifications

Correct installation is the key to ensuring the lifespan of the gearbox. The manual specifies the following key points:

1. Installation base and fastening

The installation surface must be flat, and the anchor bolts must be tightened with torque (refer to tables B11 and B12). For the A series, different machine bases correspond to different bolt specifications (such as M8, M10, M12, etc.).

If flange installation (B5 or B14) is used, it is necessary to ensure that the flange mating surface is clean and free of paint or burrs.

2. Assembly of output shaft coupling

Hollow shaft fit tolerance: The standard is G7 (hollow shaft) and h6 (equipment shaft). If slight interference is required, j6 can be used.

When outputting with a solid shaft, the inner hole of the coupling or pulley should be machined to ISO H7 tolerance to avoid bearing damage caused by excessive interference.

During installation, it is necessary to use the threaded hole on the shaft end to match the puller, and it is strictly prohibited to strike, otherwise it will damage the gears and bearings.

3. Installation of hollow shaft locking disc (shrink disc)

If a shrink disc (model suffix "US" or "UH") is selected, the bolts should be tightened multiple times according to the manufacturer's recommended torque sequence to ensure even locking force and avoid journal slippage.

4. Ventilation valve and oil level

After installation, the position of the vent valve and oil level plug must be adjusted according to the actual installation orientation (such as horizontal, vertical, inverted). Manual B2 and B3 provide a detailed list of oil plug position numbers (such as C, L, S, T) corresponding to different installation positions (R, D, H, S, VA, VB). Be sure to configure according to the actual installation orientation, otherwise it may cause oil leakage or insufficient lubrication.

5. Rust prevention and protection

Clean the mating surface and apply an antioxidant (such as Mobilarma 248) before installation.

When painting, it is necessary to protect the oil seal lip and processing surface to prevent the paint from hardening and causing seal failure.

Lubrication Management and Maintenance Strategy

The A-series small machine bases (A102~A303) use synthetic oil for lifelong lubrication (long life), without the need for oil change; Other models require users to add mineral oil or synthetic oil.

1. Lubricating oil selection

According to the ambient temperature and load, refer to Table A3: ISO VG 150 mineral oil or ISO VG 150 synthetic oil is used for light loads (0-20 ℃); Medium load (20-40 ℃) using ISO VG 220 or 320; Overload recommendation ISO VG 400/460.

Mineral oil and synthetic oil cannot be mixed.

2. First oil change cycle

After running for about 300 hours for the first time, the lubricating oil should be replaced and the interior should be rinsed with a cleaning agent to remove wear particles during running in.

Then divided by oil temperature: when the oil temperature is below 65 ℃, change the oil every 8000 hours; 4000 hours at 65-80 ℃; 2000 hours at 80-95 ℃ (synthetic oil can be extended to 15000-25000 hours).

3. Oil level inspection

Regularly check the oil level through the oil level plug (the gearbox must be in the correct installation position). If the oil level is low, add oil of the same brand and model.

4. Long term storage protection

If stored for more than 60 days, the processing surface needs to be coated with rust proof oil; After more than 6 months, the ventilation plug should be placed at a high position and filled with an appropriate amount of oil (if not pre filled before leaving the factory). Before use, replace it with the correct amount and viscosity of oil.

Radial load and axial load verification

The manual provides a complete radial load calculation method to ensure the service life of the shaft and bearings.

1. Radial load calculation

Determined by the transmitted torque M ₁ (input) or M ₂ (output), sprocket/gear/pulley pitch diameter d, and load factor K ᵣ (sprocket K=1, gear K=1.25, V-belt K=1.5~2.5):

R꜀ = (2000 × M × Kᵣ) / d [N]

2. Allow radial load

The selection tables in the manual provide the allowable radial loads R ₙ₁ (input shaft) and R ₙ₂ (output shaft) at the midpoint of the standard shaft extension. If the load application point is not at the midpoint (x from the shoulder), it needs to be converted according to the formula:

R ₓ=R ₙ× a/(b · x) (where x<c, a, b, c are constants, refer to Table B8)

Verification condition: R ꜀ ≤ R ₓ.

3. Axial load

Allowable axial load A ₙ=0.2 × R ₙ (input or output). If the axial load is large or acting simultaneously with the radial load, contact the technical department.

Engineering Tip: If the allowable radial load of the selected model is insufficient, you can choose the option of reinforced bearings (A series can choose "Reinforced bearings"), or increase the machine base size.

Thermal power and heat dissipation verification

For continuous operation or high ambient temperature conditions, it is necessary to verify the thermal power P ₜ of the reducer (Table B15). When the mechanical input power exceeds P ₜ, auxiliary heat dissipation measures (such as forced fans, cooling coils) need to be taken. The manual provides the thermal power values of each machine base in the A series at different input speeds, for example, A102 has a P ₜ=3.5 kW at 1400 min ⁻¹ and 3.0 kW at 2800 min ⁻¹.

Verification: If the actual transmitted power P ₁>P ₜ, a larger machine base or additional cooling device needs to be selected.

Anti run back option

For inclined conveyors or elevators, an optional backstop (option AL or AR) can be installed to prevent the output shaft from reversing. The manuals B10a and B10b specify the applicable machine bases (A102 to A904) and their corresponding rotation directions. When placing an order, the rotation direction should be specified (AL is counterclockwise, AR is clockwise, observe the output shaft end). If not specified, default AR.

Attention: The backstop is only suitable for unidirectional rotation and cannot be used to prevent reverse rotation caused by electrical reverse connection.

Common troubleshooting reference

Phenomenon 1: High oil temperature (>95 ℃)

Check if the oil level is too high or too low; Check if the thermal power exceeds the standard; Confirm if the ambient temperature exceeds 40 ℃ (with a derating of 2.5%/K required).

Check for external heat source radiation or poor ventilation.

Phenomenon 2: Oil leakage from the output shaft

Check whether the oil seal is aging or the shaft neck is worn; Confirm if the ventilation valve is blocked, causing an increase in internal pressure; Verify if the installation orientation is correct (incorrect oil plug position configuration).

When replacing the oil seal, be sure to protect the shaft neck to avoid scratches.

Phenomenon 3: Abnormal vibration or increased noise

Check if the anchor bolts are loose; Check if the coupling alignment exceeds the tolerance; Check if the gears are damaged due to overload or foreign objects entering.

The radial load formula in the manual can be used to verify whether the actual load exceeds the allowable value.

Phenomenon 4: Motor overload or gearbox jamming

Check if the load exceeds the rated torque; Check if there is any mechanical brake or reverse brake misoperation; For dual speed motors, the instantaneous impact torque during switching may reach up to 200% of the rated value. It is necessary to confirm whether the instantaneous peak torque is within the allowable range (it is recommended to limit it to within 200%, and using two-phase power supply switching can reduce the impact).

Suggestions for installing accessories and spare parts

Torque arm: For hollow shaft output, a torque arm must be installed (see section 20.0 of the manual), and its installation dimensions and bolt specifications are given according to the machine base.

Installation kit: Different machine bases can be equipped with standard installation, through installation (MPSV), anti vibration installation (MNVIB), and DIN rail installation (MDIN) to adapt to different cabinets or on-site environments.

Spare parts: stock oil seals, O-rings, vent valves, and locking plate bolts to reduce downtime losses.