Top Ten Gearbox and Electric Motor Noise Questions

10. Why is my gearbox & electric motor squeaky? Frankly we have never heard of one of our types of gearbox & electric motor described as squeaky! It would mean that there is a serious problem with a part of the system rubbing against one another.

9. What causes gearbox whine? Gear whine is created by the gears as they mesh and is amplified by resonances in the housing’s ribs, beams, and sides.

8. How does the gearbox housing amplify noise? Vibration is generated at the gear mesh because of time-varying mesh stiffness, manufacturing errors and assembling errors. This vibration is transmitted to the housing through shafts and bearings. The radiated noise is induced from the vibration of the housing.

7. Why does my gearbox rattle? Gearbox rattle is a sound that is excited by the driving source such as the electric motor.

6. What causes gearbox noise? Gearbox noise isn’t just a gear problem – it’s a system problem. Physical interactions between gears can excite system dynamics, so most gear noise doesn’t originate from the gears.

5. How do bearings cause gearbox noise? The asymmetric gear noise spectrum arises from amplitude and frequency modulation of gear-mesh excitation produced by low-frequency manufacturing and assembly errors. Gearbox and electric motor sounds from gear mesh, bearing rotation, lubricant movement, motor vibrations and interaction of the housing all contribute to the overall sound generated.

4. Can you prevent gearbox noise? It’s impossible to eliminate all gearbox noise, because it’s impossible to cut perfect gears. Even if one could, it’s impossible to limit the effect of system dynamics. One can only minimize and control gearbox noise to the extent that it won’t be considered problematic or audible.

3. How do you reduce gearbox & electric motor noise? To solve gearbox & electric motor noise problems, the first step is to determine the type of noise that is objectionable. What’s considered gear noise depends on the speed of operation. Use qualitative and quantitative terms to describe how design factors and manufacturing mistakes play into the noise equation. Then discuss with the design team (and potential suppliers) the problems of gear noise, dynamics, measurement, and modeling.

2. What is gearbox noise? Gear noise is generated by tooth-to-tooth load transfer that causes pressure-pulse trains radiating through the gearset and motor housing. The noise’s frequency is the product of gear rotational speed and the number of gear teeth. Most types of gear noise occur at tooth mesh frequency or harmonics in the audible range. Gearbox noise can be very annoying — even when it isn’t the most significant noise source. That’s because it occurs as pure tones that the human ear can detect even at 10 dB lower than the overall noise level.

1. How do you diagnose a noisy gearbox & electric motor? To minimize noise, all gearbox & electric motor components should be optimally tuned to each other. Three types of gear tooth transmission errors are spacing errors, random errors, and elastic deformations, which combine with mean profile deviations. Gear resonance can be reduced by identifying excitation mechanisms; using finite element analysis to determine the natural frequencies of individual gears; eliminating torsional modes from operating range; detuning and damping helical and bevel gears; and identifying remaining resonant problems with other elements of the gearmotor such as the housing and electric motor.

Contact: Gabriel Venzin, President of ABM DRIVES INC.
ABM Greiffenberger U.S. Subsidiary
394 Wards Corner Road · Suite 110, Loveland, OH 45140 · USA
Phone: +1 513 576-1300
Email: [email protected]

Thank you for your kind attention!

Choosing manufacturing partners

When choosing partners during a machine build, remember that there are two methods for choosing a gearbox, gear motor and/or an electric motor source. Either pick a standard component that might or might not fit a specific application or choose a competent partner to engineer and manufacture a component that fits the application exactly.

Standard solutions are suitable if a design engineer doesn’t have the time or engineering resources to have a custom version engineered — or if it needs a quick setup. New modular approaches to design and construction let manufacturing engineers get reasonably priced custom motors even in modest volumes.

No matter the approach to component selection, be sure to continually improve the design/drive system by comparing predictions of performance with measurements. Then use the result of the analysis to improve the next iteration.

ABM Drives

About the author

Gabriel Venzin is President of ABM DRIVES INC., ABM Greiffenberger U.S. Subsidiary, Cincinnati, Ohio. Call Gabriel at +1-513-576-1300 or email [email protected].