How to determine whether the screw of ZLYJ250-12.5-2 gearbox is in the resonance speed range

1、 Theoretical pre calculation locking resonance speed range

Estimate the critical speed of the screw using industry standard simplified empirical formulas.

The maximum allowable speed of the input shaft of this model is 1500rpm. After deceleration at a speed ratio of 12.5, the theoretical maximum speed of the screw is 120rpm.

The industry's general safety guidelines require a separation margin of ≥ ± 15% between the working speed and the critical speed. If the working speed of the screw falls within the ± 15% range of the critical speed, it enters the resonance risk zone.

2、 Rapid verification of on-site features

During operation, there are severe periodic vibrations without obvious causes, and the vibration amplitude undergoes sudden changes with small adjustments to the speed, rather than linearly changing with the speed.

In the spectrogram, there is an abnormally prominent peak at the frequency conversion of one time screw, and this peak does not decrease significantly with dynamic balance correction and alignment adjustment.

During the acceleration/deceleration process, the vibration suddenly surges at a fixed speed point, and immediately drops significantly after leaving that speed point.

Accompanied by abnormal low-frequency buzzing, the axial movement of the screw feels significantly increased, and the local temperature rise of the gearbox housing is abnormally high.

3、 Professional testing for precise confirmation

Bump Test: When the machine is stopped, use a hammer to strike the output end of the screw, collect the frequency response signal through a vibration sensor, directly read the natural frequency of the screw system, and convert it into the corresponding resonance speed.

Run up/Coast down test: Control the equipment to slowly increase from the lowest speed to the highest working speed, synchronously collect vibration amplitude, phase, and speed data throughout the process, and draw a Bode plot. If there is a peak vibration and a 180 ° phase transition at a certain speed point, it can be determined that the speed is a resonant speed.

Supplement the collection of vibration data under different loads, eliminate the natural frequency deviation caused by load changes, and ultimately lock in the actual resonance speed range.