Gearbox Guide

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Bevel gears are typically constructed from cast iron, aluminum alloy or other steel materials but varybetween manufacturers.

Note: Gears made from steel materials can be noisy when coming into contact with other gears and

also make them prone to wear.

Applications of Bevel Gears

Bevel gearboxes use bevel gears and are mainly used in right angle applications with the shafts in aperpendicular arrangement.

• Print Press • Power Plants

• Automobiles

• Steel Plants

• Hand Drills

• Differential Drives

Advantages of Bevel Gears

• Right angle configuration

• Durable

Disadvantages of Bevel Gears

• Axes must be able to support forces

• Poorly cut teeth may result in excessive vibration and noise during operation

Helical Gearbox

Helical Gears

Helical gears are cut at angles which allow for gradual contact between each of the helical gear teeth.This type of innovation provides for a smooth and quiet operation. Gearboxes using helical gears areapplicable in high horsepower and efficient applications.

Figure 3: Helical Gearbox

Physical Properties

Helical gears are typically constructed from cast iron, aluminum allow or iron material but may varydepending on the manufacturer.



Applications of Helical Gears

Helical gears are widely used in applications which require efficiency and high horsepower.

• Oil Industry

• Blowers

• Food and Labeling


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• u ers

• Elevators

Advantages of Helical Gears

• Can be meshed in parallel or cross orientation

• Smooth and quiet operation

• Efficient

• High horsepower

Disadvantages of Helical Gears

• Resultant thrust along axis of gear

• Additives to lubrication

Spur Gearbox

Spur Gears

Spur gears are made with straight teeth mounted on a parallel shaft. The noise level of spur gears isrelatively high due to colliding teeth of the gears which make spur gear teeth prone to wear. Spur gears come in a range of sizes and gear ratios to meet applications requiring a certain speed or torque output.

Figure 4: Spur Gearbox

Physical Properties

Spur gears are typically constructed from metals such as steel or brass, and plastics such as nylon or polycarbonate. The material used to construct spur gears may vary depending on the manufacturer.



Applications of Spur Gears

Spurs gears are used in applications requiring a decrease in speed with high output torque.

• Cut-to-Length

• Packaging

• Speed Control • Construction

• Power Plants

Advantages of Spur Gears

• Cost-effective

• High gear ratios

• Compact

• High torque output

Disadvantages of Spur Gears

• Noisy

• Prone to wear

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Worm Gearbox

Worm Gears

Worm gears are able to withstand high shock loads, low in noise level and maintenance-free but areless efficient than other gear types. Worm gears can be used in right angle configuration. The wormgearbox configuration allows the worm to turn the gear with ease; however, the gear cannot turn theworm. The prevention of the gear to move the worm can be used as a braking system. When the wormgearbox is not active, it is held in a locked position.

Figure 5: Worm Gearbox

Physical Properties

Worm gears are typically constructed of aluminum, stainless steel and cast iron. The material usedvaries depending on the manufacturer.

Applications of Worm Gears

Worm gears are used in applications requiring high speeds and loads and can be configured for right-angle applications.

• Mining

• Rolling Mills

• Presses

• Elevators/Escalator Drive Systems

Advantages of Worm Gears

• High precision

• Right-angle configurations

• Braking system

• Low noise

• Maintenance-free

Disadvantages of Worm Gears

• Limitations

• Nonreversible • Low efficiency

Planetary Gearbox

Planetary Gears

Planetary gearboxes are named so due to their resemblance to the solar system. The components of a planetary gearbox include a sun gear, ring gear and planetary gears. The sun gear is the centralgear which is fixed in the center, ring gear (annulus ring) which is the outer ring with inward-facingteeth, and the planetary gears which rotate around the sun gears and mesh with both the sun and ringgear.


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Figure 6: Planetary Gearbox

Physical Properties

The sun, ring and planetary gears of a planetary gearbox are constructed of aluminum, stainless steelor brass. The material used varies depending on the manufacturer.



Applications of Planetary Gearboxes

Planetary gearboxes are used in applications requiring low backlash, compact size, high efficiency,resistance to shock, and a high torque to weight ratio.

• Slewing Drives

• Lifts

• Cranes

• Machine Tools

• Automotive

Advantages of Planetary Gears

• High power density

• Compact

• Highly efficiency in power transmission

• Greater stability

• Load distribution among planetary gears

Disadvantages of Planetary Gears

• High bearing loads

• Complex design

• Inaccessibility

Types of Gearmotors

As the name states, a gearmotor consist of an electric motor (brushless, brush, AC, servo) and gear reducer, also

referred to as a gearbox, integrated into a simple package. A gearmotor combination reduces complexity andlowers costs in designs requiring high torque low speed output. Gearmotors can be manufactured to be integral or be combined as separate components. Gearmotors which have the motor and gear reducer sharing the same shaftis what is meant by integral. Anaheim Automation offers a wide selection of stepper gearmotors, brushlessgearmotors, DC gearmotors and AC gearmotors integrated with either spur, planetary or worm gears.

Gearmotors are used in many applications in industrial applications as well as in everyday household appliances.Industrial applications include cranes, lifts, jacks and conveyor machines. Everyday household appliancesgearmotors are used in are washing machines, mixers, clocks, hand tools like drills and dryers.

How do Gearboxes Work?

All gearboxes work in a similar fashion. The directionsthe gears rotate are dependent on the input direction


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. ,gear is rotating in a clockwise direction, the gear itengages will rotate counterclockwise. This continuesdown the line for multiple gears. The combination of different size gears and the number of teeth on each

gear plays a significant role in the output torque andspeed of the shaft. High gear ratios allow for moreoutput torque and lower speeds, while lower gear ratiosallow for higher output speed and less output torque.

A planetary gearbox works relatively the same. A planetary gearbox system is constructed with three main

components: a central sun gear, a planet carrier (carrying one or more planet gears) and an annulus (an outer ring).The central sun gear is orbited by planet gears (of the same size) mounted to the planet carrier. The planet gears aremeshed with the sun gear while the outer rings teeth mesh with the planet gears. There are several configurations for a gearbox system. Typical configurations consist of three components: the input, the output and one stationarycomponent.

For example: one possible configuration is the sun gear as the input, the annulus as the output and the planet carrier remaining stationary. In this configuration, the input shaft rotates the sun gear, the planet gears rotate on their ownaxes, simultaneously applying a torque to the rotating planet carrier that in turn applies torque to the output shaft(which in this case is the annulus). The rate at which the gears rotate (gear ratio) is determined by the number of teeth in each gear. The torque (power output) is determined by both the number of teeth and by which component inthe planetary system is stationary.

How are Gearboxes Controlled?

The output of a motor (i.e. stepper, brushless, AC and brush motors) is used as the input of the gearbox and controlsthe speed at which the gearbox rotates. The configuration below illustrates the driver controlling the external motor,which is connected as the input shaft of the gearbox. As a result, when the driver is powered, the motor shaft rotatesinside the gearbox causing the output shaft of the gearbox to rotate. The output speed and torque is dependent onthe internal configuration of the gearbox.

How to Select the Appropriate Gearbox

When considering a gearbox, many factors need to be considered to meet specific application requirements:

Gear Ratio

Gear ratios are defined as the correlation between the numbers of teeth of two different gears. Commonly,the number of teeth a gear has is proportional to its circumference. This means that the gear with a larger circumference will have more gear teeth; therefore the relationship between the circumferences of the twogears can also give an accurate gear ratio. For example, if one gear has 36 teeth while another gear has 12teeth, the gear ratio would be 3:1.

Output Torque

Output torque is dependent on the gear ratio used. To obtain a high output torque, a large gear ratio would be

selected. Using a large gear ratio will lower the output shaft speed of the motor. Inversely, using a lower gear ratio, a smaller output torque value would be delivered into the system, with a greater motor speed at theoutput shaft. This statement illustrates the relationship that both torque and speed are inversely proportional toone another.

Speed (RPM)

Speed is proportional to the gear ratio of the system. For example, if the input gear has more teeth than theoutput gear, the result will be an increase in speed at the output shaft. On the other hand, having the reversescenario with more gear teeth at the output compared to the input will result in a decrease of speed at theoutput shaft. In general, the output speed can be determined by dividing the input speed by the gear ratio. Thehigher the ratio the lower the output speed will be and vice versa.

Gear Arrangement

Gear arrangement is an ingenious engineering design that offers various benefits over the traditional fixed

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axis gear system design. The unique combination of both power transmission efficiency and compact sizeallows for a lower loss in efficiency. The more efficient the gear arrangement, (i.e. spur, helical, planetary andworm) the more energy it will allow to be transmitted and converted into torque, rather than energy lost in heat.

Another application factor to be taken into account is load distribution. Since the load being transmitted isshared among multiple planets, the torque capacity is increased. The higher number of planets in a gear system will increase the load ability and enhance torque density. Gear arrangements improve stability androtational stiffness because of a balanced system, but it is a complex and more costly design.

Figure 8: Fixed-Axis vs. Planetary Gear System

In Figure 8, the gear arrangement on the left is a traditional fixed axis gear system with a pinion driving alarger gear on an axis parallel to the shaft. On the right, is a planetary gear design system with a sun gear (pinion) surrounded by more than one gear (planet gears) and is encompassed in an outer ring gear. The twosystems are similar in ratio and volume, but the planetary gear design has three times the higher torquedensity and three times the stiffness due to the increased number of gear contacts.

Fixed Axis Gear System:

Volume = 1, Torque = 1, Stiffness = 1

Planetary Gear System:

Volume =1, Torque = 3, Stiffness = 3

Other gear arrangements as mentioned in the Types of Gearboxes segment of this guide are bevel, helical,cycloid, spur and worm.

Backlash

Backlash is the angle in which the output shaft of a gearbox can rotate without the input shaft moving, or thegap between the teeth of two adjacent gears. It is not necessary to consider backlash for applications whichdo not involve load reversals. However, in precision applications with load reversals like robotics, automation,CNC machines, etc., backlash is crucial for accuracy and positioning.

Advantages of a Gearbox

• Low noise level

• High effic iency

• High reduction ratios

• Increase in output torque

• Decrease in output speed • Durable

Disadvantages of a Gearbox

• More costly than other drive systems

• Proper lubrication is necessary for smooth running

• Poorly cut teeth may result in excessive vibration and noise during operation

• Quality matters and adds to cost

Troubleshooting

Problem: Gearbox Becomes Hot

Solution: The exterior temperature of the gearbox may become hot due to several reasons. Please refer to the

following information, take the necessary steps to solve this issue. If the gearbox temperature is excessive, please

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consult the manufacturer.

1. Ambient temperature is above advised level - If the ambient temperature is too high, it maydiminish the efficiency of the gearbox. Install a cooling fan or move the application to a more viablelocation.

2. Proper ventilation - Proper ventilation is necessary, not only for the gearbox but for allelectrical/mechanical equipment to function properly. Ensure that there is adequate air flow in the areaof the equipment to allow for system cooling.

3. Improper shaft alignment - The first step is to check the alignment of the input shaft of the motor to

the gearbox. It is necessary that the input shaft of the motor be aligned with the gearbox to ensure theproper use of the gearbox.

4. Overload - Decrease the load of the gearbox and observe if the temperature lowers. If not, your application may require a larger gearbox model.

5. Lubrication – Poor lubrication for the bearings and gears. Consult with the manufacturer regardingwarranty information.

6. Improperly mounted bearings - Reassembly may be required of the gearbox. Consult with themanufacturer regarding warranty information.

Problem: Loud/Vibration Noise

Solution: Loud or vibration noises can be due to many different sources discussed in this section.

1. Improper installation - Improper installation may be a result of loose bolts or misalignmentbetween the motor and gearbox. Tightening loose bolts and aligning the motor and gearbox may solvethe issue of excessive noise.

2. Input speed too high - Lowering the input speed may help reduce the noise.

3. Overload - Decreasing the load may help reduce the noise. If not, a larger-sized model gearbox willbe required.

4. Worn or damaged bearings - Worn or damaged bearings may need to be replaced. Consult withthe manufacturer regarding warranty information.

5. Lubrication - Gears/bearings need to be properly lubricated for cohesiveness. Consult with themanufacturer regarding warranty information.

Problem: Input/Output Shafts Do Not Rotate

Solution: Before going through the below instructions, ensure the motor shaft rotates to isolate any problem with the

motor or gearbox.

1. Proper installation - Ensure that all bolts connecting the motor to the gearbox are securelyfastened.

2. Gear teeth are worn - Need to replace worn gears. Consult your dealer for warranty information.

3. Gears in locked position - Gears may need to be replaced due to wear and tear. Another possibility would be that a foreign object may need to be removed from within the gearbox, causingthe gears to be in the locked position. Consult your dealer for warranty information.

Problem: Gear Teeth Wear

Solution: Wear and tear on gearboxes is natural occurrences. Proper use and system maintenance can help extend

their lifetime of the gearbox.

1. Proper installation - Ensure that all bolts connecting the motor and the gearbox are securelyfastened.

2. Excessive load - Wear and tear on the gear is caused by contact with other gears. Reducing theload will lower the tension the gears make with one another. If a higher load is required, using a larger gearbox may be necessary.

3. Input speed too high - Lowering the input speed may help reduce the amount of wear and tear on

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.

4. Ambient temperature is above the advised level - If the ambient temperature is too high, it maydiminish the efficiency of the gearbox. Installing a cooling fan, or moving the application to a moreviable location may resolve this application.

Cost of a Gearbox

The price of a gearbox varies and is typically affected by size, accuracy specifications, backlash, and the gear ratio,as well as the specific manufacturer. Gearboxes with a backlash in the range of 30 arc-minutes may cost as low as$500. The cost for gearboxes with a backlash value under 5 arc-minutes will cost more than gearboxes with highbacklash values. Below is a list of gearbox products offered by Anaheim Automation. Comprehensive specificationsand pricing is available on our website at AnaheimAutomation.com, for each of the offered types:

• Economy Gearboxes

• High-Grade Gearboxes

• Right-Angle Planetary Gearboxes

• Rotating Output Flange Gearboxes

Formulas

Motor Torque x Gear Ratio = Torque at the Wheel

Input Shaft Speed (RPM) / Gear Ratio = Output Shaft Speed

Gear Ratio = Teeth on one gear : Teeth on a second gear

Example: If one gear has 60 teeth and a second gear has 20 teeth the gear ratio would be 3:1

Where are gearboxes used?

Advancements in technology and the evolution of gears have made more efficient and powerful gearboxes to bedeveloped and manufactured at lower costs. Toothed gear systems have evolved from fixed axis gear systems tonew and improved gears including helical, cycloid, spur, worm and planetary gear systems. Gearboxes are widelyused in applications that require desired output speed (RPM), control the direction of rotation, and to translate torqueor power from one input shaft to another.

Gearboxes are used in a variety of industries:

• Aerospace – In the aerospace industry, gearboxes are used in space and air travel, i.e. airplanes,

missiles, space vehicles, space shuttles and engines.• Agriculture – In the agriculture industry, gearboxes are used for plowing, irrigation, pest and insect

control, tractors and pumps.• Automotive – In the automotive industry, gearboxes are used in cars, helicopters, buses and

motorcycles.• Construction – In the construction industry, gearboxes are used in heavy machinery such as

cranes, forklifts, bulldozers and tractors.• Food Processing – In the food processing industry, gearboxes are used in conveyor systems, the

processing of meat and vegetable products, and packaging applications.• Marine Industry – In the marine industry, gearboxes are used on boats and yachts.

• Medical – In the medical industry, gearboxes are used in surgical tables, patient beds, medical

diagnostic machines, dental equipment and MRI and CAT scan machines.• Power Plants – In power plants, gearboxes are implemented in transformers, generators and

turbines.

Quiz

1. What is backlash on a gearbox? A. The angle the output shaft of a gearbox can rotate without the input shaft moving.

B. The angle the input shaft of a gearbox can rotate without the output shaft moving.

C. The angle the gears inside the gearbox can rotate.

2. What type of gearbox would be used for right angle applications? A. Bevel gearbox

B. Planetary gearbox

C. Worm gearbox

D. Helical earbox

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.

E. A and C

3. Gearboxes can be controlled by _________ motors? A. Stepper

B. Brushless

C. Brush

D. AC

E. All of the above

4. The output speed of a gearbox is proportional to _____________?

A. Input shaft speed B. Gear arrangement

C. Gear ratio

D. Torsional stiffness

5. What is NOT an advantage of a gearbox? A. High efficiency

B. Increase/decrease of output torque

C. Increase/decrease of output speed

D. Less costly

6. If a brushless motor, rated for 4000 RPM, is combined with a gearbox with a gear ratio of 3:1, what will bethe speed of the output shaft?

A. 4000 RPM

B. 12000 RPM C. 1333 RPM

7. What is the difference between helical gears and spur gears? A. Helical gears are cut at angles while spur gears are cut straight.

B. Helical gears are cut straight and spur gears are cut at angles.

C. Helical gears are noisier than spur gears.

8. A gear train contains 2 spur gears. The input gear has 25 teeth and the output gear has 200 teeth.Calculate the gear ratio.

Gear Ratio = 200/25 = 8:1

FAQ

Q. Are planetary and spur gearboxes bi-directional?

A. Yes, planetary and spur gearboxes are designed to be used for bi-directional operation. The direction the input

shaft rotates and gear arrangement of the gearbox will determine the rotation of the output shaft.

Q. Can Anaheim Automation’s motors be combined with a gearbox?

A. Anaheim Automation’s motors can be assembled with a gearbox to meet the necessary requirements of an

application. Motors and gearboxes can be purchased separately or be purchased as an assembled unit.Customization is available. Minimum purchase requirements and a Non-Cancellable/Non-Returnable agreement willapply.

Q. What is the lifetime of Anaheim Automation’s motors and gearboxes?

A. Yes, planetary and spur gearboxes are designed to be used for bi-directional operation. The direction the input

shaft rotates and gear arrangement of the gearbox will determine the rotation of the output shaft.

Q. What type of gearbox would be used for right angle applications?

A. A bevel and worm gearboxes are mainly utilized in right angle applications. They offer high efficiency and low gear

ratios. A straight bevel gearbox with straight cut teeth are utilized in slow speed applications, whereas spiral bevelgearboxes with curved teeth are utilized in high performance, high speed applications. Worm gearboxes are alsoavailable with right angle configurations. They are able to sustain high shock loads, low in noise, maintenance-freebut are less efficient than bevel gearboxes.

Q. Can gearboxes be backdriven?

A. Some gearboxes, such as spur gearbox can be backdriven, while some, such as the worm gearbox cannot be

backdriven.

Q. How many planet gears are there in a gearbox?

A. The amount of planetary gears in a gearbox differs based on specific application requirements. Most planetary

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gearboxes consist of two or more planetary gears.

Q. What is the difference between straight cut gears and helical gears?

A. Straight cut gears have straight and tapered teeth, and are used for low speed applications. Helical gears are cut

at angles to allow gradual contact between the gear teeth. This allows for smooth and quiet operation. Helical gearsare applicable in high horsepower and efficient applications.

Glossary

Figure 8: Fixed-Axis vs. Planetary Gear System

Addendum – the height of the gear tooth above the pitch circle diameter.

Backlash – the angle the output shaft of the gearbox can move without the input shaft moving.

Base Circle – an imaginary circle used in involute gearing to generate the involutes that form the tooth profiles.

Bevel Gears – used for right-angle applications. There are two types of bevel gears which are straight and spiral.

Bore – the diameter of the hole in a sprocket, gear, bushing, etc.

Center distance – distance between the axes of two meshed gears.

Circular Thickness – the thickness of the tooth on the pitch circle.

Dedendum – the depth of the tooth below the diameter of the pitch circle.

Diametrical Pitch – the teeth per inch of the diameter of the pitch circle.

Differential Gear – a bevel gear which allows two shafts to rotate at a different speed.

Gear – a wheel with teeth that meshes with another wheel with teeth to translate motion.

Gear Center – the center of the pitch circle.

Gear Ratio – the ratio between the numbers of teeth of meshing gears.

Gear Train – two or more gears meshed by their teeth. A gear train generates power speed through the meshed

gears rotating.

Helical Gear – a gear with the gear teeth cut at angles.

Line of Contact – the line or curve along which two tooth surfaces are tangent to each other.

Involute – the curve which describes a line which is unwound from the circumference of the gear.

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Pitch Circle – the curve of intersection of a pitch surface of revolution and a plane of rotation.

Pitch Diameter – the diameter of the pitch circle.

Pitch Radius – the radius of the pitch circle.

Planetary Gears – a system that consists of three main components: the sun gear, ring gear, and two or more

planet gears. The sun gear is the located in the center, the ring gear is the outermost gear, and the planet gears arethe gears surrounding the sun gear inside the ring gear.

Pressure Angle – the angle between the line of action and the normal to the surface of the tooth.

Spiral Bevel Gears – shafts which are perpendicular to each other and are used in right-angle applications.

Spur Gear – connect parallel shafts which have involute teeth that are parallel to the shaft.

Sun gear – a gearwheel that rotates around its own axis and has other gears (planet gears) that rotate around it.

Torsional Stiffness - the measure of the amount of torque that a radial shaft can sustain during its rotation in a

mechanical system.

Working Depth – the max depth a tooth of one gear extends into the tooth gear of mating gear.

Worm Gear – a gear with one or more teeth with screwed threads.

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Gearbox Guide