Locking Reliability and Torque Characteristics in Planetary Gearboxes

1. Locking Mechanism of Planetary Gearboxes

Some customers may express concerns about potential loosening between our full-round input bore gearboxes and D-flat stepper motor shafts due to insufficient locking force. This section demonstrates why our design prevents such issues through two key aspects.

1.1. Clamping Design at Gearbox Input

• Full-round Bore with Radial Clamping

• Principle: The coupling features a complete circular bore. Lateral fastening screws induce elastic deformation for 360° uniform contraction, ensuring full-axis grip.

• Screw Configuration: Dual symmetrical screws create balanced force couples to prevent stress concentration and enhance vibration resistance.

• D-flat Shaft Adaptation: Clamping force converts to normal pressure on the flat surface while maintaining frictional grip on curved sections, providing dual anti-rotation security.

1.2. Torque Capacity

Although the gearbox output end bears higher torque, the motor-gearbox interface only withstands the motor’s output torque—a relatively low value. Our radial clamping design reliably handles this torque without slippage.

Conclusion: Properly tightened connections will not loosen under high torque. Advantages include:

Zero shaft damage (no set screw marks)

Keyless alignment

Rapid assembly

No need for periodic screw retightening

2. Torque Specifications of Planetary Gearboxes

2.1. Two Critical Torque Ratings

Gearbox torque capacity is limited by gear and housing strength, defined by:

• Maximum Continuous Torque: Safe long-term operational limit.

• Instantaneous Peak Torque: Short-term overload threshold to protect against damage.

2.2. Why High-Ratio Gearboxes Have Lower Torque Limits

Example: The EG17-G5 (5:1) allows 10Nm, while the EG17-G10 (10:1) permits only 5Nm.

Technical Reasons:

2.2.1. Gear Size

High-ratio designs use smaller input gears (fewer teeth, reduced module) to drive larger output gears.

2.2.2. Root Bending Stress

Bending stress ∝ applied force / (gear module² × geometric factors).

For identical input torque, smaller input gears endure higher root stress due to reduced cross-sectional area and bending resistance.

2.2.3. Contact (Hertz) Stress

Contact stress ∝ √(force) / √(curvature radius).

Smaller input gears exhibit higher contact stress from their tighter curvature.

2.4.4. Input Shaft & Bearing Limits

High-ratio gearboxes employ thinner input shafts and smaller bearings with lower torsional/load ratings.

Summary

This paper details the technical advantages of our full-round bore planetary gearboxes in locking reliability and torque performance. The patented clamping mechanism (360° uniform contraction + dual-screw balance) ensures secure motor-shaft coupling while eliminating assembly complexities. Clear torque ratings and rigorous stress analysis validate the design’s robustness across ratios, ensuring long-term durability under diverse operating conditions.

Updated on: 29/07/2025