3 minute read
Selecting the right gear
Selecting the right gear
Helical gears, bevel gears, parallel shaft gears and worm gears each account for 20% of the global industrial gear market. Despite the market dominance of these four gear types’, choosing a gear unit involves several design factors that depend on the application and operating conditions. Marek Lukaszczyk, European and Middle East Marketing Manager at WEG, introduces each gear type along with their defining features.
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Gears are among the most important industrial machinery elements – often used in conjunction with an electric motor. Their main purpose is to transmit the right amount of force to ensure a machine’s smooth running. The right gear type also allows deceleration without negatively impacting and stressing the mechanics. With all this to consider, how do endusers and machine builders know which gear type to use?
HELICAL GEARS
Helical gears are among the best-known gear types and are the most cost-effective. The teeth on a helical gear cut at an angle to the face of the gear. When two of the teeth start to engage, the contact is gradual — starting at one end of the tooth and maintaining contact as the gear rotates into full engagement. This gear unit has a longer design, mainly due to the way that the input and output axes are arranged in one line, meaning it is used where sufficient space is available.
BEVEL GEARS
If the axial installation space is limited, a bevel gear is typically used. Bevel gears are used on shafts with intersecting axes, and in some cases on shafts where axes do not intersect. These are used to change the direction of a shaft’s rotation.
Among defining characteristics, bevel gears have teeth that are available in straight and spiral shapes. If the tooth profile is straight, then the two mating gears’ teeth come in sudden contact, imposing impact load on the tooth increasing vibration, noise, and wear rate. Teeth that are cut in the form of a spiral curve of the bevel gear blank can offer gradual contact. This minimises the detrimental effects of straight teeth and offers a longer gear life.
PARALLEL SHAFT GEARS
Parallel shaft gears are usually a multi-stage helical gear unit with parallel shafts, compromising an output shaft, which allows the gear to have easy accessibility to mount onto an existing shaft. The input and output shafts are offset and parallel to each other – as far as possible, compared to the conventional helical gear. Due to their design, their axel dimensions are compact and therefore good at saving space.
WORM GEARS
Despite their low-efficiency level, worm gears are commonly used due to their wide range of applications and large ratios. By design, the worm gear consists of the worm and worm wheel. Just like the bevel gear, the input and output shafts are set at a right-angleposition. Also, the number of teeth in the gear wheel corresponds to the number of gears in the worm.
As multiple teeth of the wheel may be engaged simultaneously, high torques can be transmitted with this unit. Despite this, these gears can operate quietly due to the continuous sliding. Lubrication and additional cooling for high power outputs can result in better efficiency to combat friction on the worm’s flanks and on the wheel.
Choosing a gear unit that works well with your application is a priority. These four main gear types can cover a wide range of operational functions within machinery, which can be modified and adapted based on bespoke needs.
