A worm gear reducer is a right angle gear set that gives you the greatest possible amount of speed reduced while being considerably smaller in volume than other types of gear arrangements.
The worm gear arrangement is also known as a worm drive. It is composed of a worm that is combined with a worm gear (WG). Now, a worm is the spirally threaded shaft (similar to a screw) of a WG set. The WG, or worm wheel, is similar to a spur gear but considerably smaller in volume. A WG reducer, like other gear sets or arrangements, can decrease rotational speed or allow the transmission of higher torque. This is usually the perfect choice if you need to reduce motor speed by a large amount in a single step. The normal reduction range for a single worm gear is 5:1 up to 100:1. The WG ratio is based on the number of threads on the worm and the gear’s teeth. The ratio is higher if the number of threads on the worm is less.
There are different types of worm gears:
· Non-throated – both the worm and the worm gear have no throat or grooves carved around their circumferences.
· Single-throated – one element which is usually the driven gear is throated or has grooves. A single moving point on the worm drive is where tooth contact takes place. This line contact allows for higher loads without excessive wear.
· Double Throated – also known as a cone or hourglass. Both the worm and the driven gear have concave teeth. This type of gear set can support the largest amount of weight.
· For maximum mating, worm gears are helically cut
· Converts high speed inputs to low speed and high torque outputs in one simple step
· Pure sliding motion occurs
· Allows for maximum speed reduction
· Excellent for precise movement of load
· Not usually bidirectional
· Normally operates at 900F over ambient
· Has low energy-conversion efficiency
Worm gear reducers are used in a variety of machines. Some of the most usual machines that uses this type of gear set are automotive parts, rolling mills, presses, rudders and conveying engineering. A lot of elevators use WG’s as well because of its small size and non-reversibility. Small electric motors have a high speed and low torque. Using a WG reducer allows them to have more uses or applications.
Factors that affect the efficiency:
· Condition of installation
· Speed of sliding
· Surface quality
· Lead angle of the worm
Because of the heat and friction that occurs when the gears move in a continuous sliding motion, there are different types of lubrication that need to be applied in order to improve its efficiency:
· Compounded mineral oils
· Extreme Pressure (EP) mineral gear oils
· Synthetic WG oils
These oils have different and unique characteristics that make them effective in decreasing temperature and preventing severe wear.
In addition to lubrication, the development of a new technology called double enveloping has greatly enhanced the efficiency of them.