Motion System
HANDBOOK
Integrated gearmotors as this one from Parker Automation are often more compact than an assembly with a separate gearhead and motor.
An overview of
GEARMOTORS A GEARMOTOR
integrates a gear reducer and either an ac or dc electric motor into one physical unit. Thanks to its gearset, a gearmotor can deliver high torque at low horsepower or low speed. Most industrial gearmotors incorporate fixed-speed ac motors. However, some gearmotors use dc motors. These dc gearmotors are common in automotive applications — to electronically adjust side-view mirrors and make automatic seat adjustments, for example. Engineers can mix and match motors and gears as needed to best fit application requirements. However, housing design, assembly gearings, gear lubrication, and specific mode of integration of pinion gear and motor-output shaft all affect gearmotor performance. Motor and gear-reducer combinations abound. For example, right-angle wormgear, planetary and parallel shaft gears can combine with permanent-magnet dc, ac induction, or brushless dc motors to form a gearmotor unit. Though it’s possible to combine many different motors and gearsets, not just any one will work for every application, because certain combinations are more efficient and cost-effective than others. Knowing the application and getting an accurate estimation of its required torque and operating speeds is the foundation for successfully integrating a gearmotor into a system.
COMMON GEARMOTOR TYPES AND VARIATIONS As gearmotors can be built on either ac or dc motors, there are a number of choices for the gear reducer. There are five basic 110
DESIGN WORLD — MOTION
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types of gears that can be paired with a motor to form a complete gearmotor. Those are bevel, helical, hypoid, spur and worm types. Another way to classify gearmotors is by the physical arrangement of the final complete unit. So for instance, there are so-called in-line gearmotors where the gear shaft is parallel with the motor shaft, also called a parallel shaft. These can either be offset from the output shaft or completely in line with the output shaft. The other configuration is the right-angle gearmotor, where the output shaft is at a 90-degree angle to the motor shaft.
BENEFITS Gearmotors give better performance than other motor-gear combinations. More importantly, gearmotors simplify design implementation because they save engineers from integrating motors with gears, which in turn reduces engineering costs. If the application requirements are known, engineers can order the right gearmotor from a supplier directly. What’s more, if a gearmotor is sized properly, having the right combination of motor and gearing can prolong operating life and boost overall design efficiency. Another benefit of gearmotors is that they eliminate the need for couplings and potential alignment problems that come with those components. Such problems are common when a design includes the connection of a separate motor and gear reducer — which in turn increases the potential for misalignment and bearing failure, and ultimately reduces useful life. motioncontroltips.com | designworldonline.com
9/12/16 10:34 AM