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What Is a Gearmotor and What Are Its Uses?

Waunakee, WI , 2018-10-29

There are many considerations to be made when selecting the right motor for a specific application. What kind of horsepower, efficiency, useful life, starting torque, speed regulation, noise rating and maintenance requirements desired are among the critical motor parameters and ratings to be considered and prioritized in the selection process. Even more critical is the desired speed, torque output and size limitations of the motor. These typically immutable features can pose a problem when using a standalone motor because the relationship between motor size and required speed (rpm) is inversely proportional while maintaining a specific power output. Therefore, a sizeable standalone motor may be required for a slow speed application yet there may not be enough physical space to mount the motor due envelope constraints.

This particular challenge can be overcome with a gearmotor, which is in simple terms is a gearbox integrated with a motor. When integrating a gearbox, also referred to as a gear reducer or speed reducer, to a motor, you can exchange the high-speed low torque characteristics of a small motor with the low speed and high torque characteristics of a large motor yet still only requiring the smaller motor.

There are various types of gears and motors that can be used in a gearmotor combination. The most common motors used for gearboxes are Permanent Magnet DC Motors, AC Induction Motors, and Brushless DC Motors. The Brushless DC Motor is a high-end motor equipped with excellent efficiency, horsepower, useful life and speed regulation and low maintenance and sound profile. The permanent magnet DC motor also can operate at high speeds and moderate horsepower, although it inherently requires more maintenance and has a shorter useful lifespan. At lower speeds and horsepower applications the AC induction motor provides high efficiency, long lifecycle and low maintenance costs.

Often, a gearbox that is coupled to a motor will contain multiple types of gears working together. Below are the most common types of gears found in today’s gearmotors:

1. SPUR – Spur gears are the most widespread types of gears, they are inexpensive to manufacture, easy to operate, efficient and reliable at low speeds. The teeth on spur gears are straight. The gears are most often positioned in series on parallel shafts to achieve large gear reductions. Since the entire length of the gear tooth engages and collides all at once, each impact makes loud noises and causes vibration, which is why spur gears are not used in machinery like cars. Spur gears are found in everyday devices such as washing machines, screwdrivers and windup alarm clocks. A normal gear ratio range is 1:1 to 6:1.

2. HELICAL - Helical gears operate more smoothly and quietly than spur gears due to the way the teeth interact. The teeth on a helical gear are cut at an angle or ‘helix’ to the face of the gear. When 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. Helical is the most commonly used gear in transmissions. Although helical gears require more maintenance and are more expensive to manufacture than spur gears, they are often the optimal choice with the greater benefits of ease of operation, good torque capacity and smoother and quieter operation. Its normal gear ratio range is 3:2 to 10:1.

3. WORM - Worm gears are used in applications where large gear reductions, torque and breaking is required. The worm is mounted on a shaft and has shallow angled teeth that contact with a gear. The worm is designed to turn the gear, but the gear cannot turn the worm, thus motion can only be in one direction. The shallow angle of the worm provides high friction between the gears to lock in place. Worm gears are found in applications such as conveyor systems. A cost-effective solution, worm gears offer high ratios in a single reduction, the ability to handle shock loads and low noise. Gear ratio ranges of 5:1 to 300:1 are typical.

4. BEVEL – Bevel gears change the direction of a shaft’s rotation, typically at 90-degree angles but can be designed to work at other angles. The tooth-bearing faces are pitched and conically shaped. Bevel gears have teeth that are cut in various ways such as straight, spiral, or hypoid shape. Straight teeth have similar characteristics to spur gears and spiral to helical gears. Depending on the cut of the teeth gear ratios can range from 3:2 to 200:1.

There are certainly many options to choose from when integrating a motor and gearbox, but certain combinations provide more reliable, efficient and cost-effective solutions based on specific industry applications. When selecting your desired gearmotor, two distinct methods can be applied:

Method 1: Select your motor and gearbox separately.

Method 2: Choose a pre-engineered gearmotor.

There are many advantages when selecting Method 2. Most of the design and testing work has already been performed by the manufacturer. At NORD DRIVESYSTEMS, highly qualified engineers using rigorous design and testing processes have done the work to greatly reduce the design time and project risk for their customers. NORD DRIVESYSTEMS customers are guided through the selection process where predesigned gearmotor performance curves and gearmotor characteristics are referenced with ease to select a gearmotor with the precise speed and torque characteristics needed. Once selected, the NORD DRIVESYSTEMS delivers a fully integrated motor and gearbox in a compact UNICASE housing design which provides a torsionally rigid housing with superior dependability and long service life.