How to prevent fatigue fracture of the output shaft of the BL15-17 double-axis cycloidal pinwheel reducer.

The prevention of fatigue fracture of the output shaft of BL15-17 dual axis cycloidal pinwheel reducer requires comprehensive consideration from multiple aspects such as design, materials, manufacturing, installation, use, and maintenance. The following are specific preventive measures:

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Increase the transition fillet radius: The right angle or small fillet at the shoulder of the shaft is a typical source of stress concentration. The transition fillet radius should be increased to R ≥ 3-5mm or 1/10~1/5 of the shaft diameter. If necessary, an "unloading groove" should be used to reduce the stress concentration factor.

Optimize keyway and spline design: The end of the flat keyway should adopt a circular arc transition, and the groove depth should not be too deep. The clearance between the key and the groove should be controlled at 0.01~0.03mm. The spline adopts an involute spline, and the root fillet R is ≥ 0.3mm to avoid stress concentration at the root.

Avoid sudden changes in cross-section: The diameter of the shaft should change smoothly, and the transition of taper should be better than that of step transition. If necessary, add "strengthening protrusions" to reduce local cross-section weakening.

Reasonable selection of materials

Select appropriate materials based on the load level. For medium and low loads (torque ≤ 500N · m), 45 steel can be used; For medium to high loads (torque 500~2000N · m), 40Cr is selected; for high load/impact conditions (torque ≥ 2000N · m), high-strength alloy structural steel such as 42CrMo is used, which has higher strength and toughness and can reduce internal crack sources.

Improve manufacturing processes

Heat treatment: The output shaft is quenched and tempered to obtain a tempered martensite structure, in order to balance strength and toughness. The mating surface of the shaft can also be surface quenched to form a hardened layer, improving local wear resistance and fatigue strength. After quenching, low-temperature tempering is required to eliminate stress.

Surface treatment: Shot peening is used to create a residual compressive stress layer on the surface of the shaft, offsetting the tensile stress during operation and preventing crack propagation. Nitriding treatment can also be carried out to improve the wear resistance and corrosion resistance of the shaft, and enhance fatigue strength. At the same time, the surface roughness of the shaft should be controlled within Ra ≤ 1.6 μ m to avoid tool marks becoming crack sources.

Ensure installation accuracy

When installing the reducer, use a laser alignment instrument to calibrate and ensure that the coaxiality of the input/output shaft is ≤ 0.05mm/m. The bearing press fitting uses a hydraulic press to control the interference fit, avoiding tight interference fit or loose clearance fit. The interference fit between the bearing and the shaft is generally taken as 0.01~0.03mm.

Reasonable use of equipment

To avoid long-term overload operation and impact load on the reducer, a torque limiter can be installed with a set value of about 1.3 times the rated torque. It is prohibited to operate beyond the nameplate load. At the same time, it is recommended to reduce the frequency of frequent starting and stopping, with a recommended limit of ≤ 10 times per day, to minimize fatigue damage to the shaft.