Worm gear reducers are commonly used in industrial, heavy equipment, and consumer products. Although these reducers are relatively inefficient, they can provide high reduction ratios and are often self-locking.
worm gear
It consists of a worm (sometimes called a worm gear) and a gear (sometimes called a worm wheel). It is 90° to a non-parallel, non-intersecting axis. The worm is similar to a screw with a V-shaped thread, and the gear is similar to a spur gear. The worm is a typical drive component that, together with its thread, propels the gear.
Like a ball screw, the worm on a worm gear can have a single or multiple starting points—meaning there are multiple lines or helices on the worm. For a single-starting-point worm, with each complete rotation (360°), the worm advances one tooth of the gear. So a gear with 24 teeth will provide a gear reduction of 24-1.
For a worm gear with multiple starting points, the gear reducer is equal to the number of teeth on the gear divided by the number starting from the worm (unlike most other types of gears, the gear reducer is a function of the diameters of the two parts).
In a worm gear drive, the worm can have one starting (thread) or multiple starting mechanisms.
The meshing of worm gears and gears is a mixture of sliding and rolling motions, but at high reduction ratios, sliding contact dominates. This sliding motion generates friction and heat, limiting the efficiency of worm gears to between 30% and 50%.
To reduce friction and heat, different metals are needed to manufacture worm gears and gears.
For example, worms might be made of hardened steel, while gears might be made of bronze or aluminum.
While sliding contact reduces efficiency, it provides very quiet operation (using different metal materials for the worm and gear also contributes to quiet operation). This makes worm gears suitable for applications where noise is minimized, such as elevators. Furthermore, using softer materials for the gears means they can absorb shock loads, as experienced in heavy equipment or crushers.
The main advantages of worm gears are their ability to provide high reduction ratios and correspondingly high torque multiplication. They can be used in low- to medium-speed applications. Furthermore, because their reduction ratio is based on the number of teeth, they are more compact than other types of gears. Like fine-pitch lead screws, worm gears are typically self-locking, making them ideal for longitudinal motion applications.
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