Cycloidal gearbox

Cycloidal gearboxes
Cycloidal gearboxes or reducers consist of four basic 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 compound reducers, the first tabs on the cycloidal cam lobes engages cam supporters in the housing. Cylindrical cam followers act as teeth on the inner gear, and the amount of cam supporters exceeds the amount of cam lobes. The next track of substance cam lobes engages with cam fans on the output shaft and transforms the cam’s eccentric rotation into concentric rotation of the result shaft, thus increasing Cycloidal gearbox torque and reducing rate.

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

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

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

Planetary gearboxes generally have one or two-gear stages for reduction ratios ranging from 3:1 to 100:1. A third stage can be added for also higher ratios, nonetheless 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 number 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. If backlash and positioning precision are crucial, then cycloidal gearboxes offer the best choice. Removing backlash can also help the servomotor manage high-cycle, high-frequency moves.

Following, consider the ratio. Engineers can do that by optimizing the reflected load/gearbox inertia and rate for the servomotor. In ratios from 3:1 to 100:1, planetary gearboxes provide greatest torque density, weight, and precision. In fact, not many cycloidal reducers provide ratios below 30:1. In ratios from 11:1 to 100:1, planetary or cycloidal reducers may be used. However, if the mandatory ratio goes beyond 100:1, cycloidal gearboxes keep advantages because stacking stages is unnecessary, therefore the gearbox could be shorter and less expensive.
Finally, consider size. Many manufacturers offer square-framed planetary gearboxes that mate precisely with servomotors. But planetary gearboxes grow in length from one 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 then to greater than 100:1, respectively.

Conversely, cycloidal reducers are bigger in diameter for the same torque but are not as long. The compound reduction cycloidal gear teach handles all ratios within the same deal 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 cycle, and life.

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

Both cycloidal and planetary reducers work in virtually any industry that uses servos or stepper motors. And although both are epicyclical reducers, the differences between many planetary gearboxes stem more from equipment geometry and manufacturing procedures rather than principles of operation. But cycloidal reducers are more diverse and share little 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.

Great things about 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 stays relatively constant during life of the application
• Rolling instead of sliding contact
• Low wear
• Shock-load capacity
• Torsional stiffness
• Flat, pancake design
• Ratios exceeding 200:1 in a compact size
• Quiet operation
The necessity for gearboxes
There are three basic reasons to use a gearbox:

Inertia matching. The most typical reason for choosing the gearbox is to control inertia in highly dynamic situations. Servomotors can only control up to 10 times their own inertia. But if response time is critical, the engine should control less than four occasions its own inertia.

Speed reduction, Servomotors operate more efficiently in higher speeds. Gearboxes help keep motors working at their optimum speeds.

Torque magnification. Gearboxes provide mechanical advantage by not merely decreasing rate but also increasing result 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 comprised 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 incorporates a curved tooth profile rather than the more traditional involute tooth profile, which eliminates shear forces at any stage of contact. This style introduces compression forces, rather than those shear forces that could exist with an involute gear mesh. That provides several efficiency benefits such as for example high shock load capacity (>500% of rating), minimal friction and put on, lower mechanical service elements, among many others. The cycloidal style also has a sizable output shaft bearing span, which gives 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 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 as 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 industrial marketplace, in fact it is a perfect match for applications in large industry such as oil & gas, principal and secondary metal processing, commercial food production, metal trimming and forming machinery, wastewater treatment, extrusion devices, among others.

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