Cycloidal gearboxes
Cycloidal gearboxes or reducers consist of four fundamental components: a high-speed input shaft, an individual 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 track of the cycloidal cam lobes engages cam followers in the housing. Cylindrical cam followers become teeth on the inner gear, and the amount of cam fans exceeds the amount of cam lobes. The next track of compound cam lobes engages with cam followers on the output shaft and transforms the cam’s eccentric rotation into concentric rotation of the output shaft, thus raising torque and reducing swiftness.
Compound cycloidal gearboxes provide ratios ranging from as low as 10:1 to 300:1 without stacking stages, 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 number for followers or rollers in the sluggish quickness output shaft (flange).
There are several commercial variations of cycloidal reducers. And unlike planetary gearboxes where variations derive from gear geometry, heat therapy, and finishing processes, cycloidal variations share fundamental design concepts but generate cycloidal motion in different ways.
Planetary gearboxes
Planetary gearboxes are made of three basic force-transmitting elements: a sun gear, three or even more satellite or world gears, and an internal ring gear. In an average gearbox, the sun gear attaches to the input shaft, which is connected to the servomotor. The sun gear transmits engine rotation to the satellites which, in turn, rotate within the stationary ring equipment. The ring gear is area of the gearbox housing. Satellite gears rotate on rigid Cycloidal gearbox shafts connected to the planet carrier and cause the earth carrier to rotate and, thus, turn the output shaft. The gearbox gives the result shaft higher torque and lower rpm.
Planetary gearboxes generally have solitary or two-gear stages for reduction ratios ranging from 3:1 to 100:1. A third stage could 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 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 initial consider the precision needed in the application. 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.
Next, consider the ratio. Engineers can do this by optimizing the reflected load/gearbox inertia and acceleration for the servomotor. In ratios from 3:1 to 100:1, planetary gearboxes offer the greatest 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. However, if the required ratio goes beyond 100:1, cycloidal gearboxes hold advantages because stacking phases is unnecessary, so the gearbox can be shorter and less expensive.
Finally, consider size. Most manufacturers provide square-framed planetary gearboxes that mate specifically with servomotors. But planetary gearboxes develop in length from solitary to two and three-stage styles as needed gear ratios go from significantly less than 10:1 to between 11:1 and 100:1, and then to higher 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 deal size, therefore higher-ratio cycloidal equipment boxes become also shorter than planetary variations with the same ratios.
Backlash, ratio, and size provide engineers with a preliminary gearbox selection. But deciding on the best gearbox also entails bearing capability, torsional stiffness, shock loads, environmental conditions, duty routine, and life.
From a mechanical perspective, gearboxes have grown to be somewhat of accessories to servomotors. For gearboxes to perform properly and provide engineers with a stability of performance, lifestyle, and worth, sizing and selection ought to be determined from the load side back to the motor as opposed to 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 the majority of planetary gearboxes stem more from gear geometry and manufacturing processes rather than principles of procedure. But cycloidal reducers are more varied and share little in common with each other. There are advantages in each and engineers should think about the strengths and weaknesses when choosing one over the additional.
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 remains relatively constant during existence 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 choosing the gearbox is to regulate inertia in highly powerful situations. Servomotors can only control up to 10 times their personal inertia. But if response time is critical, the motor should control significantly less than four times its own inertia.
Speed reduction, Servomotors operate more efficiently at higher speeds. Gearboxes help keep motors working at their ideal speeds.
Torque magnification. Gearboxes offer mechanical advantage by not only decreasing swiftness 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 primary 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 removes shear forces at any point of contact. This design introduces compression forces, instead of those shear forces that would can be found with an involute gear mesh. That provides numerous performance benefits such as high shock load capacity (>500% of rating), minimal friction and use, lower mechanical service elements, among numerous others. The cycloidal style also has a sizable output shaft bearing period, 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 in comparison 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 electric motor for longer service life
Just ridiculously rugged since all get-out
The overall EP design proves to be extremely durable, and it needs minimal maintenance following installation. The EP is the most dependable reducer in the commercial marketplace, in fact it is a perfect fit for applications in large industry such as for example oil & gas, primary and secondary steel processing, commercial food production, metal reducing and forming machinery, wastewater treatment, extrusion tools, among others.