Worm gear drives are chosen for the same reasons everywhere: a large reduction ratio in a single stage, a compact right-angle package, and the option of self-locking. The trade-off is that efficiency depends strongly on how the drive is designed and run. Understanding efficiency, heat and maintenance before you buy prevents both an oversized motor and an early failure.
The efficiency of a worm set comes from its lead angle. Power is transmitted through sliding contact between the worm and the worm wheel, so the geometry of the worm dominates the result. Single-start worms give high ratios and can be self-locking, but their small lead angle makes them the least efficient, typically 50-70%. Multi-start worms with larger lead angles reach 85-95% efficiency at the cost of a lower ratio. Specifying the required ratio, input speed and duty cycle lets the designer pick the best compromise.
Material pairing decides how long the set survives under sliding contact. The standard combination is a hardened and ground steel worm running against a bronze worm wheel. The bronze provides the conformability and embedding ability that keep sliding wear under control, while the ground steel worm gives the smooth, accurate surface that bronze needs. Non-standard pairings save money in some applications, but they change both efficiency and wear life, and should be reviewed against the actual duty.
Heat is the enemy of worm gearboxes. Sliding friction turns lost power into heat, so the efficiency number directly sets the thermal rating. A drive that runs continuously, or at high input speed, must be able to dissipate the heat it generates; otherwise the oil thins, the film breaks down and scoring follows quickly. For the same load, a less efficient worm set needs either a bigger housing, external cooling, or a lower duty factor. Stating continuous versus intermittent operation in the inquiry is therefore essential.
Maintenance keeps the efficiency that design provides. Use the oil grade and viscosity the manufacturer specifies, check the oil level regularly, and change it on schedule, because worn oil loses its film strength. Monitor the oil temperature and watch for unusual noise, which usually signals wear or misalignment. For self-locking drives, be aware that self-locking only holds under static load; vibration and shock can still back-drive the worm and must be designed around.
For buyers, the short version is: tell the supplier the reduction ratio, input speed, torque, operating hours per day and ambient temperature. With those values a worm gearbox can be sized for both strength and thermal capacity. At our factory, worm gears and worm shafts are produced in-house, so the geometry, material and finish can be tuned for your exact duty rather than taken from a stock catalogue.