The operational life of a slewing ring is directly affected by the choices made at the procurement stage. By recognizing the following five common mistakes and applying simple preventive measures, you can significantly reduce both maintenance costs and the risk of unscheduled downtime. While these recommendations may apply broadly, every project is unique, and final decisions must always rely on engineering judgment.
1. Ignoring Overturning Moment
Often only axial and radial loads are calculated, while overturning moment (M) multiplies stress on tooth roots during rotation.
Prevention: Include M alongside Fa (axial force) and Fr (radial force) in load calculations. Ensure combined load
P=Fa2+kFr2+(MD)2P = \sqrt{F_a^2 + kF_r^2 + \left(\frac{M}{D}\right)^2}
does not exceed 80% of catalog capacity.
2. Not Measuring Flange Parallelism
If mounting surfaces deviate more than 0.1 mm, axial preload distributes unevenly, leading to pitting at the tooth root within 500 hours.
Prevention: Grind flange flatness within 0.05 mm; use 0.02 mm shims if needed.
3. Incorrect Gear Module Selection
Using a small module (m) under heavy torque raises contact stress and accelerates wear.
Prevention: Select module according to ISO 6336 torque charts. Increasing from module 6 to 8 can reduce contact stress by 17%.
4. Inappropriate Grease and Wrong Interval
Low-viscosity grease causes film breakdown at high temperatures.
Prevention: Use NLGI 2 calcium-sulfonate complex grease with EP additives and base oil viscosity ≥150 cSt @ 40 °C. Relubricate after the first 100 hours and adjust interval ×0.8 in dusty environments.
5. Tightening Bolts in a Single Pass
Applying full torque in one step causes up to 30% variation in preload due to friction scatter.
Prevention: Apply torque in three passes (30% / 60% / 100%) in a star pattern. Reference torques: M20 – 580 Nm, M24 – 1000 Nm, M27 – 1500 Nm.
Quick Checklist:
Was combined load calculated including moment?
Is flange parallelism ≤0.05 mm?
Is gear module compliant with ISO?
Does grease meet viscosity and EP requirements?
Were bolts tightened in three stages?
These five steps eliminate the most critical pitfalls in slewing ring selection and can considerably extend service life. Remember: every application is unique, and the data provided here are examples—not a guaranteed performance specification.