Cycloidal gearboxes or reducers consist of four fundamental components: a high-speed input shaft, an individual or substance 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 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 result shaft, thus increasing torque and reducing speed.
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 slower velocity 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 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 a typical gearbox, the sun gear attaches to the input shaft, which is connected to the servomotor. The sun gear transmits electric motor rotation to the satellites which, in turn, rotate Cycloidal gearbox within the stationary ring equipment. The ring equipment is portion of the gearbox casing. Satellite gears rotate on rigid shafts connected to the earth carrier and trigger the earth carrier to rotate and, thus, turn the output shaft. The gearbox provides result shaft higher torque and lower rpm.
Planetary gearboxes generally have one or two-gear stages for reduction ratios which range 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 first 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 manage high-cycle, high-frequency moves.
Next, consider the ratio. Engineers can do this by optimizing the reflected load/gearbox inertia and swiftness 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 keep advantages because stacking levels is unnecessary, so the gearbox can be shorter and less expensive.
Finally, consider size. Many manufacturers provide square-framed planetary gearboxes that mate specifically with servomotors. But planetary gearboxes develop in length from solitary 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 higher than 100:1, respectively.
Conversely, cycloidal reducers are larger in diameter for the same torque but are not as long. The compound decrease cycloidal gear teach handles all ratios within the same package size, so higher-ratio cycloidal equipment boxes become also shorter than planetary variations with the same ratios.
Backlash, ratio, and size provide engineers with an initial gearbox selection. But choosing the right gearbox also requires 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 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 distinctions between many planetary gearboxes stem more from gear geometry and manufacturing processes instead of principles of operation. But cycloidal reducers are more varied and share little in common with one another. There are advantages in each and engineers should think about the strengths and weaknesses when choosing one over the additional.
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 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 compact size
• Quiet operation
The necessity for gearboxes
There are three basic reasons to employ 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 very own inertia. But if response period 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 to keep motors operating at their ideal speeds.
Torque magnification. Gearboxes offer mechanical advantage by not merely decreasing speed 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 includes 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, rather than those shear forces that could exist with an involute gear mesh. That provides several functionality 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 gives exceptional overhung load features without requiring any additional expensive components.
Cycloidal advantages over various other styles of gearing;
Able to handle 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, principal and secondary steel processing, commercial food production, metal reducing and forming machinery, wastewater treatment, extrusion tools, among others.