Gears + Gearing - Motion Control Tips

When to use gears to change the inertia ratio of a motor-driven system

May 15, 2019 By Danielle Collins Leave a Comment

In any system where a motor drives a load to achieve precise positioning, velocity, or torque, the ratio of the load inertia to the motor inertia plays a significant role in determining the motor’s ability to effectively and efficiently control the load, especially during acceleration and deceleration portions of the motion profile.

In this context, the inertia we’re referring to is mass moment of inertia (sometimes referred to as rotational inertia), which is an object’s resistance to change in rotational speed. An object’s mass moment of inertia is determined by its mass and geometry — specifically, the radius between the object’s center of mass and the point around which the object rotates.

Adding a gear set or gearbox between the motor and the load can improve the load-motor inertia ratio.
Image credit: Omron Industrial Automation

If the inertia of the load is significantly higher than the inertia of the motor, the load will essentially try to “drive” the motor, and the motor will have a difficult time achieving the desired position (or speed or torque). In an attempt to control the load, the motor will draw higher current, which decreases efficiency and increases wear on the motor and electrical components.

On the other hand, if the inertia of the motor is significantly higher than inertia of the load, it’s likely that the motor is oversized, which has negative implications throughout the system — including higher initial cost, higher operating cost, larger footprint, and the need to oversize other components, such as mounting hardware, couplings, and cables.

If the inertia ratio is too high — that is, if the load inertia is much higher than the motor inertia, causing problems with positioning accuracy, settling time, or control of velocity or torque — the load inertia that is seen by, or reflected to, the motor can be decreased by adding a gear set or gearbox between the motor and the load.

J_L = inertia of load reflected to motor

J_M = inertia of motor

Adding a gear set or a gearbox to a motor-driven system reduces the load inertia by the inverse square of the gear ratio, meaning that even a relatively low gear ratio can have a significant effect on the inertia ratio.

J_L = inertia of load reflected to motor

J_D = inertia of drive (ball screw, belt, rack & pinion)

J_E = inertia of external (moved) load

J_C = inertia of coupling

J_G = inertia of gear set or gearbox

i = gear ratio

Note that the inertia of the gear set or gearbox (J_G) is added to the load inertia, but its effect is typically small compared to the reduction provided by the gear ratio.

In addition to optimizing the load-motor inertia ratio, gearboxes are often used in motion control applications to increase the torque delivered to the load from the motor, but they also decrease the rotational speed delivered to the driven component from the motor, by an amount equal to the gear ratio. This is why gearboxes are often referred to as “gear reducers” or “speed reducers.”

In other words, if a motor running at 1200 rpm is driving a load through a 3:1 gearbox, the rotational speed delivered to the load will be 400 rpm (1200 ÷ 3). This reduction in speed can enable the system to operate at a more favorable location on the motor’s speed-torque curve.

Although it is possible to use a gearbox or gear set that is configured to reduce torque (and increase speed), in motion control applications, a more typical solution would be to choose a smaller motor.

Feature image credit: M. M. Nazari

Forest City Gear launches advanced facility for gear-blank production

April 29, 2019 By Lisa Eitel Leave a Comment

Forest City Gear has expanded its turning and milling operations with a state-of-the-art facility designed to greatly improve lead times and quality for the production of precision gear blanks.

This highly productive 8,500 sq. ft. facility is in close proximity to Forest City Gear’s main facility in Roscoe, IL, and now dedicated almost solely to the precision turning and milling operations needed to produce precision gear blanks. That’s very good news for Forest City Gear customers, says Forest City Gear Turning and Milling Supervisor Mike Miller.

“This gives us complete control over the quality and delivery of the blanks (and slugs) that are the ‘near net shape’ starting point for many of the gears we produce,” Miller says. “The types of projects we take on here at Forest City Gear for customers around the world have never been more demanding from a quality and delivery standpoint.”

He continues: “If we start off a project with turned blanks out of tolerance, or waiting for blanks from a supplier, this can ultimately create a devastating production bottleneck when operations upstream are sitting idle waiting for product to arrive.”

According to Miller, the facility (with its four late-model CNC lathes, three CNC machining centers, and dedicated Zeiss CMM) easily meets current capacity requirements, and gives the company much additional room to grow. Two Mazak Quick Turn 250 Turning Centers will arrive later this year to expand capacity, and future plans call for the addition of a 5-axis machining capability for the production of small planetary housings and carriers.

Since 1955, Roscoe, Ill. based, family-owned Forest City Gear has been one of the gear industry’s leading sources for the development, manufacture and inspection of the highest quality gears, for use in applications that range from medical devices to motorcycles, airplanes to automation, even including the Mars Curiosity Rover.

For more information, visit www.forestcitygear.com.

New stainless steel washdown gearboxes from ATLANTA Drive Systems

April 25, 2019 By Miles Budimir Leave a Comment

ATLANTA Drive Systems’ new range of stainless steel washdown gearboxes are suitable for use in demanding applications in the food & beverage, meat & poultry, marine, chemical and pharmaceutical industries. They are ideal for applications that have direct contact with food products that require washdown under high pressure and are available with ATEX and IP69k protection.

They are offered in three levels of corrosion protection depending on the environment they are exposed to: Coated Aluminum (Z-Series), Stainless Steel Shielded (L-Series) and Stainless Steel (I-Series).

The gearboxes are available in reduction ratios from 5:1 to 102:1, with output torque capacities up to 480 lb.ft and input powers up to 5.4 hp. Stainless steel motors are also available for use with these gearboxes.

Unit design benefits include: housings with smooth surfaces, stainless steel 316L output shafts, viton seals with stainless steel 316L shield, hardened and ground gearing, all stainless steel 316L hardware, closed stainless steel 316L protection cap with o-ring, and fully modular IEC and NEMA C motor flanges.

For more information, visit www.atlantadrives.com.

Apex Dynamics USA offers AFX precision planetary gearboxes (and AFXR right-angle version)

April 24, 2019 By Lisa Eitel Leave a Comment

AFX high-precision planetary gearboxes from Apex Dynamics USA bring speed and continuous capability to the AF series. The gearboxes include a low-friction output bearing and low friction input and output sealing provides lowered startup / no load running torque, and lower heat generation. AFX high-precision planetary gearboxes are:

High torque and high precision
Components with long service life
Low-noise options for applications needing quiet operation

In addition, the planetary gearboxes exhibit limited temperature rise and are suitable for continuous-running applications.

In addition, Apex Dynamics USA offers the AFXR — a right-angle version of its precision planetary-gearbox line. Apex AFXR series planetary gearboxes have a 90° input that transmits through a helical bevel gear. The planetary gearboxes feature an extremely short and light (yet rigid) housing and full compatibility with standard motor adapters.

Highest precision, highest torque, and quiet operation are provided by 100% optimized helical gearing. The series comes in ratios including 12:1, 16:1, 28:1, 32:1, 48:1, and 64:1. AFXR right-angle gearboxes also have more mounting capabilities with AFR100A and AFR140A options.

As with the AFX-series planetary gearboxes, low-friction bearings and input and output sealing provide lowered startup and no-load running torque — and minimal heat generation. For more information, visit Apex Dynamics USA at apexdynamicsusa.com.

Apex Dynamics USA supplies unmatched planetary gearheads to the industry. The manufacturer’s breakthrough patented technology is covered by more than six patents; its high-precision helical reducers are sold at reasonable prices and are offered with the only tip-to-toe five-year warranty in the industry today. This warranty includes the seals and bearings.

Through continued research and development along with high volume production and unsurpassed technology, Apex Dynamics USA produces quality product at the best value. Build-to-stock manufacturing ensures quick delivery … which also lowers costs through quantities of scale. More than 100,000+ units are in stock and these products mount to virtually any motor manufactured. Apex Dynamics USA also guarantees on-time delivery, or the component is free.

Apex Dynamics USA now sells only high-precision 42-mm helical planetary gearhead in industry

April 24, 2019 By Lisa Eitel Leave a Comment

Apex Dynamics USA now sells the only high-precision 42-mm helical planetary gearheads in the industry. The Apex Dynamics inline and right-angle helical gearheads include model AB/AF/ABR/AFR 42 (42-mm square) gearheads in an array of single-stage ratios — including 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, and 10:1.

Standard double stages range from 15:1 to 200:1.

Unique operating features of the patented gearheads include:
• Acceptance of to 10,000 rpm
• 5 arc-min. and 3 arc-min. of backlash (depending on model)
• Footprint of 42 mm² … and less than 60 mm in length

This line of 42-mm helical planetary gearheads has versatile motor-mounting capabilities to allow mounting to all servo and stepper motors.

In regards to safety features, IP rating, and housing material — the gearheads include a stainless-steel output housing and are rated at IP65. They come with a five-year warranty. They are also guaranteed a two-week delivery. For more information, visit Apex Dynamics USA at www.apexdynamicsusa.com.

New high torque planetary gearboxes from Nanotec

March 29, 2019 By Miles Budimir Leave a Comment

For applications that require high torque, Nanotec offers new planetary gearboxes in two sizes and many reductions: the GP42 gearbox is designed for all motors with NEMA 17-flange as well as the DF45 external rotor motors from Nanotec.

The GP56 gearbox can be combined with all brushless dc and stepper motors in sizes NEMA 23 and 24 (56/60 mm). To increase efficiency and service life when subjected to high axial and radial loads, the GP56 is also available with a reinforced output bearing and planetary gears on needle bearings.

Both gearbox series are offered in one- and two-stage versions with a rated torque between 1.8 and 23.5 Nm. Their maximum gear backlash is 0.95°.

By using simulation-based design, the toothing, materials and hardening processes could be significantly improved. The high-torque gearboxes achieve a considerably higher torque than gearboxes of comparable design. In addition, their modular structure enables fast and easy adaptation to individual customer requirements.

For more information, visit www.nanotec.com.

New RH-N gearbox kits from Nabtesco Motion Control are pre-engineered offering

January 28, 2019 By Lisa Eitel Leave a Comment

Nabtesco Motion Control now offers pre-engineered RH-N gearbox kits. RH-N kits use the manufacturer’s newest RV-N series of gearboxes … to 20% smaller and 30% lighter than the original RV-E series. RH-N gearbox kits make for turnkey motion solutions that trim lead, engineering, and installation times. The RH-N directly bolts onto servomotors without the need of additional components, as the gearbox kits eliminate the need to manufacture and machine motor plates and housings.

More specifically, RH-N kits include an RV-N-series gearbox; oil seals and O rings; RH-N middle flange and RH-N motor flange; all necessary fasteners; and input pinion. In fact, the input pinion requires no machining … so installers can simply bolt the design together.

Suitable applications for the RH-N include and array of servomotor-driven designs … and in fact, Nabtesco’s value-added gearbox-kit solution works on all RV-N series gear reducers with standard ratios.

RH-N Kits are designed and manufactured in the U.S. with a two-week lead time on all non-stocked items … though one Nabtesco Motion Control objective for 2019 is to increase stock levels to allow for JIT delivery.

Nabtesco Motion Control can design and manufacture various configurations from the RV-N gearbox body. Fully assembled RH-N variations (in the form of fully completed assemblies of the kit and gearbox excluding grease) are available. Oil seals are properly installed and all bolts torqued to the proper specs.

Note: Nabtesco Motion Control RD2-S and RD2-R use legacy RV-E series gearboxes. The newer RV-N series comes in sizes that are far larger (for much higher maximum rated torques). The manufacturer anticipates a migration to the RV-N Series (and the RH-N kits) for two reasons:

RV-N series gearboxes are smaller, lighter and more powerful than the traditional RV-E series
Pre-engineered solutions help design engineers as detailed above

For more information on RH-N Kits (and to provide feedback or submit requests) visit this deep link on nabtescomotioncontrol.com.

Laser marking now part of Gear Motions production

January 7, 2019 By Lisa Eitel Leave a Comment

Gear Motions now has a fiber laser marking machine which was recently installed at its Nixon Gear Division in Syracuse.

The Beamer Laser Systems Model FL53 uses a 50-watt high powered LED laser to mark products quickly and safely. The machine offers fast cycle times and a wide range of marking intensities. It has a 12.5 x 26-in. total marking field and can accommodate a part up to 3.5 ft long with the side panels attached, and even larger parts when the panels are removed.

An optional 5C collet indexer was also purchased for radial marking of shaft-type parts.

This is the first time that Gear Motions has been able to offer laser marking as a manufacturing service. Previously, operations such as dot peening and engraving were used as a method of marking parts for customers. Laser marking produces a higher quality mark with a better visual appearance, which is particularly desirable for customers that may resell their gears at retail. It can also provide a more data-dense marking solution, via 2D bar codes, QR codes , and so on. for those customers that need it.

Gear Motions is now able to meet the laser marking requirements of its existing customers without sending to an outside vendor. This will streamline the entire process and make complete gear manufacturing even quicker and more efficient. The company can now also offer this value-add service to attract new business from customers that need laser marking on their precision-made gears and may also consider laser mark only business in the future.

Gear Motions, Inc. is an employee-owned company, with gear manufacturing facilities in Syracuse and Buffalo, NY. Specialists in precision ground gears, the company manufactures custom cut and ground gears for OEMs all around the world. Products include precision ground helical gears, spur gears, pump gears, bevel gears and worm gears, as well as multiple types of sprockets, timing pulleys, shafts and splines. For more information, visit gearmotions.com.

Gearbox service factor and service class explained

December 14, 2018 By Danielle Collins Leave a Comment

Sizing a gearbox (or gearmotor) for an industrial application typically begins with determining the appropriate service factor. In simple terms, the service factor is the ratio of the gearbox rated horsepower (or torque) to the application’s required horsepower (or torque). Service factors are defined by the American Gear Manufacturers Association (AGMA), based on the type of gearbox, the expected service duty, and the type of application.

Image credit: Cone Drive

While service factors may seem to be very specific, with thousands of combinations of gearbox types and applications each assigned its own numerical value, the criteria used to determine these values are based not on testing and empirical data, but rather on extensive review and analysis of gearbox manufacturers’ experience.

In general, the horsepower (or torque) rating of a gear tooth is based on the durability of the gear surface — its resistance to pitting — or on its bending fatigue. As the service factor of a gearbox is increased, the relationship between the gear teeth life (based on durability of the gear surface) and load is proportional to the increase in service factor, raised to the 8.78 power. In other words, if the service factor is increased by 30 percent (from 1.0 to 1.30, for example), the gear tooth life will increase 10 times (1.30^8.78 = 10.01).

To determine the gearbox service factor, start by consulting a set of tables or charts provided by the manufacturer, based on the type of gearing (worm, spiral bevel, helical, etc.). These tables list a wide range of applications (conveyors, cranes, winders, saws, blowers, etc.), each with (typically) three levels of service duty the gearbox is expected to see: zero to 3 hours per day; 3 to 10 hours per day; or greater than 10 hours per day. Each of these application-service duty combinations is assigned a recommended service factor.

Service factors by application type and gearbox service duty, per AGMA guidelines.
Image credit: Regal Beloit Corporation

Remember, the gearbox service factor is much like a safety factor to ensure the gearbox meets the application requirements, taking into account typical operating conditions known to exist for various types of applications. Once the AGMA-recommended service factor is determined, consider other, non-typical, working conditions that can cause additional stress and wear on the gear teeth, bearings, or lubrication. If any of these conditions exist, increase the service factor accordingly to ensure a sufficient safety margin and life of the gearbox.

Some conditions that may require an increase in the service factor are:

Elevated temperatures
Extreme shock loads or vibrations
Non-uniform loads (cutting versus conveying, for example)
Cyclic loads (frequent starts and stops)
High peak versus continuous loads

Once the appropriate gearbox service factor is determined, multiply the service factor by the horsepower (or torque) required for the application, and the result is the output horsepower (or torque) required by the gearbox.

How does service class differ from service factor?

In some cases, manufacturers cite gearbox “service classes” rather than service factors. Service classes are designated as I, II, or III, and are generally translated to numerical service factors of 1.0, 1.4, and 2.0, respectively, to be used in gearbox sizing calculations. It’s common that even if a manufacturer publishes service classes for general application types, they also publish the more specific service factors for specific applications as well.

Suggested service factors based on service class.
Image credit: STOBER Drives Inc.

Why don’t some catalogs list gearbox service factors?

Servo-rated gearboxes require detailed sizing to choose inertia, output torque, and speed for proper servo system operation.
Image credit: Wittenstein

Using service factor to guide the selection of a gearbox is appropriate for applications driven by traditional AC induction motors. But because gearbox output torque, speed, and inertia are much more critical for the proper operation of a servo system, sizing a so-called “servo-rated” gearbox requires a more detailed and exact method. For gearboxes that are used in servo systems, the primary emphasis in the sizing process is on required torque and inertia match.

Geared stepper motors drive movements of Breakfast Brixel moving architectural wall

November 13, 2018 By Lisa Eitel Leave a Comment

A new architectural wall called the Breakfast Brixel is making some installations more dynamic. The system is built from dozens of digitally controlled rotating bricks that act as pixels to create waves, stripes, and undulating shapes on the moving walls. Brixel installations can even run customizable artwork and facades to evolve in response to real-time data and software commands.

Breakfast engineers designed everything from scratch — PCBs included — and employ geared stepper motors to rotate the bricks.

In addition, the center support shaft of each Brixel column allows each brick to spin endlessly in either direction without tangled wires or the use of slip rings.

“A computer runs a fully featured application in the background. It sends data to the Brixels with movement commands that include speed and direction. We can also set custom acceleration and deceleration curves at any time on the fly when the Brixels are moving. This lets us create beautiful and organic displays — such as wind animations,” explained Breakfast CTO and cofounder Mattias Gunneras.

For high-level programming of animations and interactive movements, controls were dynamically scripted was Python, OpenCV-Python, and Numpy. In addition, for Brixel Silhouette — a Brixels mode that causes the wall to rotate bricks to mirror the shapes and movements of people in front of the installation — Breakfast engineers used 3D simulation for testing through a VR headset. That let the team get a feel for the displays before a prototype physical installation was ready.

“We’re using stitched-together 3D depth cameras to create a point cloud of the scene in front of the installation,” said Gunneras. With this technique, we can create the mirroring effect to map a person … regardless of how close they stand to the installation.”

Breakfast Brixel walls are customizable to work as facades, railings, dividers, and fences. The design allows an unlimited number of rows and columns.

When there’s nobody standing in front of the installation, kinetic animations and relevant information can play across the installation in the form of letters created by positive and negative colors and space.

Brixel walls can display an array of digitally programmed visuals and movements. The bricks come in an array of sizes, shapes, materials, and colors.

A Linux controller sits at the heart of each installation to execute programs that process visual data and pass high-level data to the bricks. Data goes via RS-485 connections to controller PCBs at the bottom of each column. Each controller PCB then sends the data over serial lines up the columns to each individual brick. Brixel installations are controllable and updated via a web-based app running off the Linux controller — for access from any mobile device. Users can upload content, create playlists, and set schedules.