Cycloidal gearboxes
Cycloidal gearboxes or reducers consist of four simple 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 fans in the casing. Cylindrical cam followers become teeth on the internal gear, and the number of cam fans exceeds the amount of cam lobes. The next track of compound cam lobes engages with cam fans 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 amount of followers or rollers in the fixed housing and nops = the quantity for followers or rollers in the gradual rate output shaft (flange).
There are many commercial variations of cycloidal reducers. And unlike planetary gearboxes where variations derive from gear geometry, heat therapy, and finishing processes, cycloidal variations share basic design concepts but generate cycloidal motion in different ways.
Planetary gearboxes
Planetary gearboxes are made of three fundamental force-transmitting elements: a sun gear, three or more satellite or planet gears, and an interior ring gear. In a typical gearbox, the sun gear attaches to the insight shaft, which is connected to the servomotor. The sun gear transmits motor rotation to the satellites which, in turn, rotate in the stationary ring equipment. The ring gear is area of the gearbox casing. Satellite gears rotate on rigid shafts connected to the earth carrier and cause the earth carrier to rotate and, thus, turn the result shaft. The gearbox gives the output shaft higher torque and lower rpm.
Planetary gearboxes generally have single or two-equipment stages for reduction ratios ranging from 3:1 to 100:1. A third stage can be added for also higher ratios, but it is not common.
The ratio of a planetary gearbox is calculated using the next formula:where nring = the amount of teeth in the inner ring gear and nsun = the amount of teeth in the pinion (input) gear.
Comparing the two
When deciding among cycloidal and planetary gearboxes, engineers should first consider the precision needed in the application form. If backlash and positioning precision are necessary, then cycloidal gearboxes offer the most suitable choice. Removing backlash can also help the servomotor deal with high-cycle, high-frequency moves.
Next, consider the ratio. Engineers can do that by optimizing the reflected load/gearbox inertia and quickness 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 can be used. However, if the required ratio goes beyond 100:1, cycloidal gearboxes hold advantages because stacking stages is unnecessary, therefore the gearbox could be shorter and less costly.
Finally, consider size. Most manufacturers offer square-framed planetary gearboxes that mate exactly 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 decrease cycloidal gear teach handles all ratios within the same package size, so higher-ratio cycloidal gear boxes become also 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 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 balance of performance, existence, and value, sizing and selection ought to be determined from the strain 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 distinctions between most planetary gearboxes stem more from equipment geometry and manufacturing procedures instead of principles of procedure. But cycloidal reducers are more diverse and share little in common with one another. There are advantages in each and engineers should think about the strengths and weaknesses when selecting one over the various 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
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 Cycloidal gearbox reasons to use a gearbox:
Inertia matching. The most common reason for selecting a gearbox is to control inertia in highly dynamic situations. Servomotors can only just control up to 10 times their very own inertia. But if response period is critical, the engine should control less than four occasions its own inertia.
Speed reduction, Servomotors run more efficiently in higher speeds. Gearboxes help to keep motors working at their optimum speeds.
Torque magnification. Gearboxes offer mechanical advantage by not merely decreasing quickness 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 primary power train is comprised 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 design introduces compression forces, instead of those shear forces that could can be found with an involute equipment mesh. That provides numerous functionality benefits such as for example high shock load capacity (>500% of ranking), minimal friction and use, lower mechanical service factors, among many others. The cycloidal design also has a huge output shaft bearing period, which gives exceptional overhung load capabilities without requiring any additional expensive components.
Cycloidal advantages over additional 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 compact 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 requires minimal maintenance following installation. The EP is the most reliable reducer in the commercial marketplace, in fact it is a perfect suit for applications in large industry such as for example oil & gas, major and secondary metal processing, industrial food production, metal slicing and forming machinery, wastewater treatment, extrusion tools, among others.