Vibration Monitoring of Gearbox Using Vibro-60 and Computer Aided Data Acquisition

Experiment No: Vibration Monitoring of Gearbox Using Vibro-60 and Computer-Aided Data Acquisition

1.0 Aim and objectives of Vibration Analysis of Gear Fault

1.1 Aim: The aim of this experiment is to conduct vibration analysis for a motor-gearbox system with some intended damaged on the gear tooth.

1.2 Objectives:

- To run the motor-gearbox system and capture the time and frequency domain Waveform using vibro-60 and computer-aided data acquisition
- To identify the GMF or gear-mesh frequency and its sidebands and harmonics due to faults
- To analyse the frequency and time-domain waveform depicting gear fault.

2.0 Theoretical background

Gear mesh frequency, which is also called tooth mesh frequency, is the frequency at which gear teeth mate together in a gearbox. There are three important frequencies involved in gearboxes: input speed, gear mesh frequency, and output speed. Gearboxes will always have a strong vibration component at the gear mesh frequency. Gear mesh frequency and output speed can be written as:

Gear mesh frequency = number of teeth x shaft speed
Output speed = input speed x input teeth/output teeth
When a gearbox has two or more teeth mesh stages, the calculation of the forcing frequencies become more challenging because there are multiple shaft speeds and gear mesh frequencies. It is thus more difficult to analyze specific faults. The most common failures in gearboxes are due to: Gear misalignment , Over load on tooth, Tooth wear, Gear eccentricity, Damaged teeth Time domain or waveform is a very powerful tool to diagnose gear faults. There is a pulse (spike) in waveform as each tooth meshes.

Procedure
- Turn ON the power supply of the motor
- Use the tachometer to determine the speed of the motor or gear box shaft
- Turn the Speed controller (potentiometer) to increase the speed
- Mount the accelerometer of the vibro-60 and measure the vibration level in velocity and acceleration.
- Do this measurement in three positions(V,H,A) and for two bearings. One bearing on the pinion side and the other bearing on the gear side.
- Use the same steps, but at this time use the DAQ system.
- Turn ON the DAQ or Data Acquisition Unit, the PC and open the LABVIEW Software
- Record the speed in RPM of either motor or gearbox.
- Capture the time and frequency domain waveform
- Be sure to capture the GMF, its harmonics and sidebands. If necessary change

The scale of the horizontal axis of the frequency domain waveform.