Cycloidal gearboxes or reducers consist of four simple components: a high-speed input shaft, an individual 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 an eye on the cycloidal cam lobes engages cam fans in the housing. Cylindrical cam followers become teeth on the inner gear, and the number of cam supporters exceeds the number of cam lobes. The second 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 increasing torque and reducing quickness.
Compound cycloidal gearboxes provide ratios ranging from as low as 10:1 to 300:1 without stacking phases, as in regular planetary gearboxes. The gearbox’s compound reduction and will 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 treatment, and finishing processes, cycloidal variations share basic design concepts but generate cycloidal motion in different ways.
Planetary gearboxes are made of three simple 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 equipment attaches to the insight shaft, which is linked to the servomotor. The sun gear transmits electric motor rotation to the satellites which, subsequently, rotate in the stationary ring gear. The ring equipment is portion of the gearbox housing. Satellite gears rotate on rigid shafts linked to the planet carrier and cause the planet carrier to rotate and, thus, turn the output shaft. The gearbox gives the output shaft higher torque and lower rpm.
Planetary gearboxes generally have single or two-gear stages for reduction ratios which range from 3:1 to 100:1. A third stage can be added for even 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 amount 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 form. If backlash and positioning precision are crucial, then cycloidal gearboxes provide most suitable choice. Removing backlash can also help the servomotor manage high-cycle, high-frequency moves.
Following, consider the ratio. Engineers can do this by optimizing the reflected load/gearbox inertia and rate for the servomotor. In ratios from 3:1 to 100:1, planetary gearboxes offer the greatest 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. However, if the required ratio goes beyond 100:1, cycloidal gearboxes hold advantages because stacking stages is unnecessary, Cycloidal gearbox therefore the gearbox can be shorter and less expensive.
Finally, consider size. Most manufacturers provide square-framed planetary gearboxes that mate exactly with servomotors. But planetary gearboxes grow 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 greater than 100:1, respectively.
Conversely, cycloidal reducers are bigger in diameter for the same torque yet are not for as long. The compound reduction cycloidal gear train handles all ratios within the same bundle size, therefore higher-ratio cycloidal gear boxes become actually shorter than planetary variations with the same ratios.
Backlash, ratio, and size provide engineers with a preliminary gearbox selection. But choosing the right gearbox also consists of 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 execute properly and offer engineers with a stability of performance, existence, 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 work in virtually any industry that uses servos or stepper motors. And even though both are epicyclical reducers, the differences between the majority of planetary gearboxes stem more from gear geometry and manufacturing procedures instead of principles of procedure. But cycloidal reducers are more diverse 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 additional.
Great things about 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 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 concise size
• Quiet operation
The need for gearboxes
There are three basic reasons to employ a gearbox:
Inertia matching. The most common reason for choosing the gearbox is to control inertia in highly powerful circumstances. Servomotors can only just control up to 10 times their very own inertia. But if response period is critical, the engine should control significantly less than four occasions its own inertia.
Speed reduction, Servomotors run more efficiently at higher speeds. Gearboxes help keep motors working at their optimum speeds.
Torque magnification. Gearboxes provide mechanical advantage by not only decreasing velocity but also increasing result torque.
The EP 3000 and our related products that use 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 couple of internal pins, keeping the reduction high and the rotational inertia low. The wheel incorporates a curved tooth profile instead of the more traditional involute tooth profile, which gets rid of 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 equipment mesh. That provides several overall performance benefits such as for example high shock load capability (>500% of ranking), minimal friction and wear, lower mechanical service factors, among numerous others. The cycloidal design also has a huge output shaft bearing period, which provides exceptional overhung load features without requiring any extra expensive components.
Cycloidal advantages over additional 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 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 since 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 industrial marketplace, in fact it is a perfect fit for applications in weighty industry such as oil & gas, major and secondary metal processing, industrial food production, metal reducing and forming machinery, wastewater treatment, extrusion equipment, among others.