Cycloidal gearboxes or reducers consist of four fundamental components: a high-speed input shaft, a single or compound cycloidal cam, cam followers or rollers, and a slow-speed output shaft. The input shaft attaches to an eccentric drive member that induces eccentric rotation of the cycloidal cam. In substance reducers, the first tabs on the cycloidal cam lobes engages cam supporters in the casing. Cylindrical cam followers act as teeth on the internal gear, and the number of cam supporters exceeds the amount of cam lobes. The next track of substance cam lobes engages with cam fans on the result shaft and transforms the cam’s eccentric rotation into concentric rotation of the result shaft, thus increasing torque and reducing rate.
Compound cycloidal gearboxes provide ratios ranging from as low as 10:1 to 300:1 without stacking stages, as in regular planetary gearboxes. The gearbox’s compound reduction and can be calculated using:
where nhsg = the amount of followers or rollers in the fixed housing and nops = the number for followers or rollers in the slower rate output shaft (flange).
There are several commercial variations of cycloidal reducers. And unlike planetary gearboxes where variations derive from gear geometry, heat treatment, and finishing procedures, cycloidal variations share fundamental design concepts but generate cycloidal movement in different ways.
Planetary gearboxes are made up of three simple force-transmitting elements: a sun gear, three or more satellite or planet gears, and an interior ring gear. In a typical gearbox, the sun equipment attaches to the insight shaft, which is connected to the servomotor. Sunlight gear transmits motor rotation to the satellites which, subsequently, rotate within the stationary ring gear. The ring gear is area of the gearbox housing. Satellite gears rotate on rigid shafts connected to the planet carrier and cause the earth carrier to rotate and, thus, turn the result shaft. The gearbox provides result shaft higher torque and lower rpm.
Planetary gearboxes generally have single or two-gear stages for reduction ratios which range from 3:1 to 100:1. A third stage could be added for actually higher ratios, nonetheless it is not common.
The ratio of a planetary gearbox is calculated using the next formula:where nring = the amount of teeth in the inner ring gear and nsun = the number of teeth in the pinion (input) gear.
Comparing the two
When deciding among cycloidal and planetary gearboxes, engineers should first consider the precision needed in the application form. If backlash and positioning accuracy are crucial, then cycloidal gearboxes provide most suitable choice. Removing backlash can also help the Cycloidal gearbox servomotor deal with high-cycle, high-frequency moves.
Following, consider the ratio. Engineers can do this by optimizing the reflected load/gearbox inertia and speed for the servomotor. In ratios from 3:1 to 100:1, planetary gearboxes provide best torque density, weight, and precision. Actually, few cycloidal reducers provide ratios below 30:1. In ratios from 11:1 to 100:1, planetary or cycloidal reducers can be used. However, if the mandatory ratio goes beyond 100:1, cycloidal gearboxes hold advantages because stacking levels is unnecessary, so the gearbox could be shorter and less expensive.
Finally, consider size. Many manufacturers provide square-framed planetary gearboxes that mate specifically with servomotors. But planetary gearboxes grow in length from one to two and three-stage designs as needed gear ratios go from less than 10:1 to between 11:1 and 100:1, and then to greater than 100:1, respectively.
Conversely, cycloidal reducers are larger in diameter for the same torque yet are not as long. The compound reduction cycloidal gear train handles all ratios within the same bundle size, therefore higher-ratio cycloidal equipment boxes become actually shorter than planetary versions with the same ratios.
Backlash, ratio, and size provide engineers with a preliminary gearbox selection. But choosing the right gearbox also requires bearing capability, torsional stiffness, shock loads, environmental conditions, duty cycle, and life.
From a mechanical perspective, gearboxes have become somewhat of accessories to servomotors. For gearboxes to perform properly and provide engineers with a stability of performance, life, and worth, sizing and selection ought to be determined from the load side back to the motor instead of the motor out.
Both cycloidal and planetary reducers work in any industry that uses servos or stepper motors. And although both are epicyclical reducers, the differences between many planetary gearboxes stem more from gear geometry and manufacturing procedures instead of principles of operation. But cycloidal reducers are more diverse and share small in common with each other. There are advantages in each and engineers should consider the strengths and weaknesses when choosing one over the other.
Benefits of planetary gearboxes
• High torque density
• Load distribution and sharing between planet gears
• Smooth operation
• High efficiency
• Low input inertia
• Low backlash
• Low cost
Benefits of cycloidal gearboxes
• Zero or very-low backlash remains relatively constant during lifestyle of the application
• Rolling instead of sliding contact
• Low wear
• Shock-load capacity
• Torsional stiffness
• Flat, pancake design
• Ratios exceeding 200:1 in a concise size
• Quiet operation
The necessity for gearboxes
There are three basic reasons to use a gearbox:
Inertia matching. The most typical reason for selecting a gearbox is to regulate inertia in highly dynamic situations. Servomotors can only control up to 10 times their own inertia. But if response period is critical, the motor should control less than four moments its own inertia.
Speed reduction, Servomotors run more efficiently in higher speeds. Gearboxes help to keep motors working at their optimum speeds.
Torque magnification. Gearboxes provide mechanical advantage by not only decreasing acceleration but also increasing result torque.
The EP 3000 and our related products that make use of cycloidal gearing technology deliver the most robust solution in the most compact footprint. The main power train is made up of an eccentric roller bearing that drives a wheel around a set of inner pins, keeping the reduction high and the rotational inertia low. The wheel incorporates a curved tooth profile rather than the more traditional involute tooth profile, which removes shear forces at any stage of contact. This design introduces compression forces, instead of those shear forces that would exist with an involute gear mesh. That provides a number of functionality benefits such as high shock load capability (>500% of rating), minimal friction and use, lower mechanical service factors, among many others. The cycloidal design also has a large output shaft bearing period, which provides exceptional overhung load features without requiring any extra expensive components.
Cycloidal advantages over additional styles of gearing;
Capable of handling larger “shock” loads (>500%) of rating in comparison to worm, helical, etc.
High reduction ratios and torque density in a compact dimensional footprint
Exceptional “built-in” overhung load carrying capability
High efficiency (>95%) per reduction stage
Minimal reflected inertia to motor for longer service life
Just ridiculously rugged because all get-out
The entire EP design proves to be extremely durable, and it requires minimal maintenance following installation. The EP is the most dependable reducer in the commercial marketplace, and it is a perfect suit for applications in heavy industry such as oil & gas, principal and secondary steel processing, industrial food production, metal cutting and forming machinery, wastewater treatment, extrusion tools, among others.