January 2021

34 n GEARS AND GEARBOXES January 2021 www.drivesncontrols.com Which type of industrial gear should you choose? G ears are among the most important elements used in industrial machinery – often in conjunction with an electric motor. Their main purpose is to transmit the right amount of force to ensure the smooth running of a machine. The right gear type also allows deceleration to occur without negatively impacting and stressing the mechanics. With all this to consider, how do you choose the best type of gear for your application? Helical, bevel, parallel shaft and worm gears each account for 20% of the global industrial gear market. Helical gears are perhaps the best-known type of gear and 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. Because of the way that the input and output axes are arranged in a line, these gears are long, so are used where sufficient space is available. If the axial installation space is limited, bevel gears are usually preferred. They can be used on shafts with intersecting axes and, in some cases, on shafts where the axes do not intersect. They can be used to change the direction of a shaft’s rotation. Among their defining characteristics, bevel gears have teeth that are available in straight and spiral shapes. If the tooth profile is straight, then the teeth of two mating gears come into sudden contact that imposes impact loads on the tooth, leading to increased vibration, noise and wear rates. Teeth that are cut in the form of a spiral curve on the bevel gear blank can achieve gradual contact, reducing the detrimental effects of straight teeth and offering longer lives. Parallel shaft gears are usually multi-stage helical gears with parallel shafts, with an output shaft that is easier to mount onto an existing shaft. The input and output shafts are offset and parallel to each other – as far as possible, compared to a conventional helical gear. Due to their design, their axle dimensions are compact and they can therefore save space. Worm gears consists of a worm and worm wheel. Like the bevel gear, the input and output shafts are set at a right-angles to each other. The number of teeth in the gear wheel corresponds to the number of gears in the worm. Because multiple teeth of the wheel may be engaged at the same time, high torques can be transmitted. Despite this, these gears can operate quietly due to their continuous sliding operation. Despite having a relatively poor efficiency, worm gears have a wide range of applications and offer large ratios. Lubrication and additional cooling for high-power outputs can improve efficiency to combat friction on the flanks of the worm and wheel. Choosing a gear unit that works well with your application is a priority. The four main types of gear can be modified and adapted based on the needs of the application. n Choosing industrial gears involves several factors that depend on the application and operating conditions. Marek Lukaszczyk, WEG’s European and Middle East marketing manager, outlines the four main types of gear and their defining characteristics. Choosing the best type of gearbox for an application can be confusing SEW Eurodrive recently assembled and delivered this gearbox for an end-user in the sand and gravel industry in just one day, following a gear failure on a scrubber system known as a trommel. In this machine, a large cylindrical drum rotates the material in the first stage of a washing operation that processes 350 tonnes an hour. The replacement parallel-helical gearbox, with additional fan cooling, was rated at 36kNm. The X-series box was ordered for the UK-based end-user by Brammer Buck & Hickman using a new SEW Eurodrive service that assembles and delivers items in one day in emergency situations such as this.