Getting the most out of gearboxes

All factory equipment requires some degree of maintenance, monitoring, and replacement, but some need much more than others. One group of high-maintenance components are gearboxes. They are traditionally high wear items, thanks to their usual task: converting high-speed, low-torque power from electric motors into the low-speed, high-torque power needed by machinery.

Still, gearboxes remain widespread and popular because, as one of the tried and true rules of thumb in the power-transmission industry says, “Speed is cheap, torque is expensive.” And relying on motors to generate the torque required by many loads (called direct-drive technology) is usually more expensive than generating the torque with a motor/gear reducer combination. So most engineers specify gearboxes in their designs. Plus, gearboxes can eliminate other mechanical components, such as bearings, belts, chains, and pulleys, thus simplifying and bringing down the cost of motion-control applications.

Engineers should also use the most-efficient gearbox that meets their application’s needs. Such gearboxes use less energy, which saves money and the environment. It also means the motor doesn’t have to generate as much power, so designs can use smaller, less-expensive motors which don’t take up as much space. Efficiency also means less heat generation, which prolongs the life of a gear reducer as well as the oil in it. Excess heat can be also a safety issue. Hot-running gear reducers have been known to burn distracted or less-than-careful employees.

But what type of gearing is most efficient?

Comparing gearing
There are quite a few reasons to consider the various types of gearing. Each type, however, has distinct pros and cons.

Worm gearing: It’s inexpensive, especially for right-angle applications. Worm gearing is self-locking, which eliminates the need for motor brakes in some applications. Worm gearing is also quiet and relatively smooth when running in only one direction.

Worm-gear efficiency tops out at 65 to 80%. Worm gears usually experience sliding friction, which wastes energy, creates heat, and increases tooth wear, all of which shorten the life of a gearbox. And when worm gears are used in applications in which the motor reverses, backlash grows as the teeth wear over time.