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Cycloidal gearbox

Cycloidal gearboxes
Cycloidal gearboxes or reducers contain four simple components: a high-speed input shaft, a single or compound cycloidal cam, cam followers or rollers, and a slow-speed output shaft. The insight shaft attaches to an eccentric drive member that induces eccentric rotation of the cycloidal cam. In substance reducers, the first an eye on the cycloidal cam lobes engages cam fans in the casing. Cylindrical cam followers act as teeth on the internal gear, and the amount of cam fans exceeds the amount of cam lobes. The next track of substance cam lobes engages with cam followers on the result shaft and transforms the cam’s eccentric rotation into concentric rotation of the result shaft, thus raising torque and reducing speed.

Compound cycloidal gearboxes offer ratios ranging from only 10:1 to 300:1 without stacking levels, as in standard planetary gearboxes. The gearbox’s compound reduction and can be calculated using:

where nhsg = the number of followers or rollers in the fixed housing and nops = the quantity for followers or rollers in the slow rate output shaft (flange).

There are several commercial variations of cycloidal reducers. And unlike planetary gearboxes where variations are based on gear geometry, heat therapy, and finishing procedures, cycloidal variations share basic design principles but generate cycloidal movement in different ways.
Planetary gearboxes
Planetary gearboxes are made up of three fundamental force-transmitting elements: a sun gear, three or even more satellite or planet gears, and an internal ring gear. In a typical gearbox, the sun gear attaches to the input shaft, which is connected to the servomotor. Sunlight gear transmits electric motor rotation to the satellites which, subsequently, rotate within the stationary ring equipment. The ring equipment is part of the gearbox housing. Satellite gears rotate on rigid shafts connected to the planet carrier and trigger the earth carrier to rotate and, thus, turn the result shaft. The gearbox gives the output shaft higher torque and lower rpm.

Planetary gearboxes generally have single or two-gear stages for reduction ratios ranging from 3:1 to 100:1. A third stage can be added for actually higher ratios, but it is not common.

The ratio of a planetary gearbox is calculated using the following formula:where nring = the number of teeth in the inner ring gear and nsun = the amount of teeth in the pinion (input) gear.
Comparing the two
When deciding between cycloidal and planetary gearboxes, engineers should 1st consider the precision needed in the application form. If backlash and positioning Cycloidal gearbox accuracy are necessary, then cycloidal gearboxes offer the most suitable choice. Removing backlash can also help the servomotor manage high-cycle, high-frequency moves.

Next, 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 offer the best torque density, weight, and precision. Actually, not many cycloidal reducers provide ratios below 30:1. In ratios from 11:1 to 100:1, planetary or cycloidal reducers may be used. Nevertheless, if the mandatory ratio goes beyond 100:1, cycloidal gearboxes hold advantages because stacking phases is unnecessary, so the gearbox could be shorter and less costly.
Finally, consider size. Most manufacturers offer square-framed planetary gearboxes that mate exactly with servomotors. But planetary gearboxes develop in length from single to two and three-stage designs as needed equipment ratios go from significantly less than 10:1 to between 11:1 and 100:1, and to greater than 100:1, respectively.

Conversely, cycloidal reducers are larger in diameter for the same torque but are not as long. The compound reduction cycloidal gear train handles all ratios within the same package size, so higher-ratio cycloidal equipment boxes become even 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 entails bearing capacity, torsional stiffness, shock loads, environmental conditions, duty routine, and life.

From a mechanical perspective, gearboxes have become somewhat of accessories to servomotors. For gearboxes to execute properly and offer engineers with a balance of performance, life, and worth, sizing and selection should be determined from the load side back to the motor instead of the motor out.

Both cycloidal and planetary reducers are appropriate in any industry that uses servos or stepper motors. And although both are epicyclical reducers, the differences between the majority of planetary gearboxes stem more from equipment geometry and manufacturing procedures instead of principles of procedure. But cycloidal reducers are more varied and share small in common with each other. There are advantages in each and engineers should think about the strengths and weaknesses when selecting one over the other.

Benefits of planetary gearboxes
• High torque density
• Load distribution and posting 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 existence of the application
• Rolling rather than 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 common reason for selecting a gearbox is to regulate inertia in highly powerful situations. Servomotors can only control up to 10 times their own inertia. But if response period is critical, the electric motor should control significantly less than four moments its own inertia.

Speed reduction, Servomotors run more efficiently at higher speeds. Gearboxes help keep motors working at their ideal speeds.

Torque magnification. Gearboxes offer mechanical advantage by not merely decreasing acceleration but also increasing output torque.

The EP 3000 and our related products that utilize 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 internal pins, keeping the reduction high and the rotational inertia low. The wheel includes a curved tooth profile rather than the more traditional involute tooth profile, which eliminates shear forces at any stage of contact. This design introduces compression forces, instead of those shear forces that could can be found with an involute gear mesh. That provides several efficiency benefits such as high shock load capability (>500% of ranking), minimal friction and put on, lower mechanical service elements, among many others. The cycloidal design also has a huge output shaft bearing span, which provides exceptional overhung load features without requiring any additional expensive components.

Cycloidal advantages over additional styles of gearing;

Capable of handling larger “shock” loads (>500%) of rating compared to worm, helical, etc.
High reduction ratios and torque density in a concise dimensional footprint
Exceptional “built-in” overhung load carrying capability
High efficiency (>95%) per reduction stage
Minimal reflected inertia to engine for longer service life
Just ridiculously rugged because all get-out
The overall EP design proves to be extremely durable, and it needs minimal maintenance following installation. The EP may be the most dependable reducer in the commercial marketplace, and it is a perfect fit for applications in heavy industry such as oil & gas, main and secondary metal processing, industrial food production, metal cutting and forming machinery, wastewater treatment, extrusion products, among others.

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