Cycloidal gearboxes or reducers contain 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 compound reducers, the first track of the cycloidal cam lobes engages cam supporters in the casing. Cylindrical cam followers act as teeth on the internal gear, and the amount of cam supporters exceeds the number of cam lobes. The second track of compound cam lobes engages with cam supporters on the output shaft and transforms the cam’s eccentric rotation into concentric rotation of the result shaft, thus raising torque and reducing acceleration.
Compound cycloidal gearboxes offer ratios ranging from only 10:1 to 300:1 without stacking phases, as in standard Cycloidal gearbox 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 slow quickness 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 basic design concepts but generate cycloidal motion in different ways.
Planetary gearboxes are made of three basic force-transmitting elements: a sun gear, three or more satellite or planet gears, and an internal ring gear. In an average gearbox, the sun gear attaches to the input shaft, which is linked to the servomotor. The sun gear transmits engine rotation to the satellites which, subsequently, rotate within the stationary ring equipment. The ring gear is part of the gearbox casing. Satellite gears rotate on rigid shafts linked to the earth carrier and cause the earth carrier to rotate and, thus, turn the output shaft. The gearbox provides output shaft higher torque and lower rpm.
Planetary gearboxes generally have solitary or two-equipment stages for reduction ratios ranging from 3:1 to 100:1. A third stage could 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 internal 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 first consider the precision needed in the application form. If backlash and positioning accuracy are necessary, then cycloidal gearboxes offer the best choice. Removing backlash can also help the servomotor handle high-cycle, high-frequency moves.
Following, consider the ratio. Engineers can do this by optimizing the reflected load/gearbox inertia and quickness for the servomotor. In ratios from 3:1 to 100:1, planetary gearboxes provide best torque density, weight, and precision. In fact, few cycloidal reducers provide ratios below 30:1. In ratios from 11:1 to 100:1, planetary or cycloidal reducers can 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 expensive.
Finally, consider size. Many manufacturers offer square-framed planetary gearboxes that mate exactly with servomotors. But planetary gearboxes grow in length from solitary to two and three-stage designs as needed gear 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 larger in diameter for the same torque yet are not for as long. The compound decrease cycloidal gear train 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 an initial gearbox selection. But selecting the most appropriate gearbox also consists of 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 execute properly and provide engineers with a balance of performance, lifestyle, 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 even though both are epicyclical reducers, the variations between most planetary gearboxes stem more from gear geometry and manufacturing processes rather than principles of operation. But cycloidal reducers are more varied and share small in common with one another. 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
Great things about cycloidal gearboxes
• Zero or very-low backlash remains relatively constant during lifestyle 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 choosing the gearbox is to control inertia in highly dynamic circumstances. Servomotors can only control up to 10 times their own inertia. But if response period is critical, the engine should control significantly less than four instances its own inertia.
Speed reduction, Servomotors run more efficiently in higher speeds. Gearboxes help keep motors working at their ideal speeds.
Torque magnification. Gearboxes offer mechanical advantage by not merely decreasing velocity 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 made up of an eccentric roller bearing that drives a wheel around a set of inner pins, keeping the decrease 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 style introduces compression forces, instead of those shear forces that would can be found with an involute gear mesh. That provides a number of overall performance benefits such as high shock load capability (>500% of ranking), minimal friction and use, lower mechanical service elements, among many others. The cycloidal style also has a huge output shaft bearing period, which provides exceptional overhung load features without requiring any extra expensive components.
Cycloidal advantages over various other styles of gearing;
Able to handle 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 requires minimal maintenance following installation. The EP may be the most reliable reducer in the industrial marketplace, in fact it is a perfect suit for applications in heavy industry such as oil & gas, principal and secondary steel processing, commercial food production, metal slicing and forming machinery, wastewater treatment, extrusion equipment, among others.