Why to Use a Gearbox and How to Select It?

With the many industrial gearboxes available today, it’s important to match the proper type of gearbox with the drive, motor, and load. When a machine needs a servo system (drive and motor), the gearbox type is critical for accurate and repeatable motion.


Why use a gearbox?


Servomotors often drive loads directly without the need for a gearbox, but in many applications it’s advantageous to use a gearbox between the motor and load.


One main reason to use a gearbox is torque multiplication. It lets designers use smaller servo systems that consume less energy. Instead of buying relatively large servo drives and motors, designer can use smaller components, saving space and money.


Output torque increases in direct proportion to the gear ratio, and top speed of the output shaft decreases. If an application can withstand the reduced speed, a relatively small servo system can supply high torque.


Gearboxes can also address inertia mismatches. For high performance servo systems — those with high dynamic responses or low overshoot, for example – the ratio between the reflected load inertia and motor inertia should be as low as practical, ideally under ten-to-one. A precision gearbox reduces the reflected inertia by the square of the reduction ratio. For instance, using a 25:1 gearbox reduces the load’s reflected inertia by a factor of 625, a significant improvement.


In some cases, gearboxes simply resolve issues relating to mechanical fit. For example, if directly mounting the motor interferes with another mechanical component, a right-angle gearbox may solve the problem.


Compared to most other gear reducers, a precision gearbox provides better accuracy and repeatability. Furthermore, the gearbox’s high efficiency lets it deliver maximum power available from the servo system—features often a necessity in servo applications.


Selecting Gearboxes and Servo Systems


A servo system coupled with a planetary gearbox is expected to provide precise motion, but this requires all components be carefully matched. Although it’s possible to buy the servo drive, motor, and gearbox from different suppliers, it’s not recommended as this requires a great deal of research and comparison to ensure all components will work together. Purchasing components from a single supplier — especially one that has carefully matched the components and will stand behind the specific combination of parts in question—offers several advantages.


The supplier has done all the research and confirms compatibility. Most suppliers will extend a more favorable warranty on such purchases. Plus, they can provide the approved mounting hardware to connect the components.


Some suppliers provide online tools for selecting servo systems and compatible gearboxes, easing the specification effort. These selection guides aid the design and provide specific recommendations for closely matched components that can be purchased as a system. In these cases, engineers can be certain the systems they specify are compatible in all critical areas, and that the components will come with the required mounting bushings and keys.


In fact, some selector tools let designers enter their torque and speed requirements, and then automatically filter a list of available motor-and-gearbox sets. Engineers can enter torque data in metric or imperial values, or the designer can select a particular servomotor size. Designers enter speed data as discrete values, or pick a gear ratio. Finally, the engineer can choose a preferred physical orientation—inline, right-angle gearing, or both.


The resulting list of available systems includes pricing information, a factor often critical to the selection process. After choosing a motor/gear combination, the designer moves to a page with full specifications for the selected servo system, the gearbox, and the combination.


One caveat: Even though a selector can make the specifying process easier, engineers and designers should always verify that a system meets their needs and gets applied correctly.


Accumulated many years of experiences in the mechanical transmission and high-quality manufacturing technology, Jia Cheng Precision Machinery Co., Ltd. was established a professional gearbox production and sales company. “Quality First, Customer Satisfaction First” is the company’s philosophy to continuously improve its production processes, timely and efficiently to provide customers with satisfied services. If you are interested in our gearboxes, welcome to visit the website of Jia Cheng and feel free to contact us to learn more information.


Article Source: http://machinedesign.com/mechanical-drives/how-specify-and-apply-precision-gearboxes-servosystems