Another way to compare performance and efficiency is to look at quality. There are two common gear-quality indicators that all engineers understand. One is that too much noise and vibration means low precision and limited life. Rotating machines that are noisy and vibrate can have any number of quality issues: improperly balanced rotating components; mating components with excessive tolerances; and components that are not rigid enough, flexing under load and leading to misalignment.
Noise from helical gearing is approximately 10 to 12 dB(A) lower than that from spur gearing. In human terms, that means 16 helical gear units generate as much noise as eight worm gears or a single spur-gear unit.
The second quality indicator is excessive heat. It equates to low efficiency and wasted energy. Heat generation in rotating machines can also have many causes, including inefficient design, misalignment, incorrect fits, and seal drag. Unfortunately, low-quality gear reducers are major contributors to excessive energy consumption. These gearboxes typically get so hot you cannot keep your hand on them for more than a second or two.
Helical gearing is 20 to 30% more efficient than single-stage worm gearing. That not only means cooler operation. With a 2-hp motor, helical gears can save up to 4,000 kW-hr annually. Or engineers can opt for a smaller motor simply because of lower gear-reducer losses, which saves on the initial investment.