Planetary gearboxes from AMG – series, applications and selection

A planetary gearbox is a reducer that uses a sun gear, planet gears and a ring gear to reduce speed and increase output torque. Sharing the load between several planet gears allows a compact design, which is why this type of gearbox is widely used with servo drives and stepper motors.

AMG Automatyka offers GearKo planetary gearboxes designed for different types of axes – from classic positioning drives and rack & pinion systems to rotary tables and designs that require a central through-hole. The individual families differ in torque range, gear ratios, output type and design features, so it is best to start the selection from the application rather than from the gearbox size.

How does a planetary gearbox work?

The basic mechanism consists of:

• a sun gear connected to the input,
• planet gears,
• a planet carrier,
• an internally toothed ring gear.

In a typical reduction configuration, the motor drives the sun gear and the torque is distributed among several planet gears meshing with the ring gear. The motion of the carrier then becomes the output motion of the gearbox.

This makes it possible to:

• reduce rotational speed,
• increase torque,
• keep a compact design,
• limit the inertia of additional transmission components,
• match the motor to the characteristics of the driven mechanism.

The gear ratio alone is not enough for selection, however. In a precision axis, torque, backlash, stiffness, input speed and shaft loads must be analysed together. These are the parameters that determine how to choose a planetary gearbox for a precision application.

Where are planetary gearboxes used?

A planetary gearbox is usually located between the motor and the machine mechanism itself. Its job is to match the drive characteristics to the required motion.

Typical applications include:

• positioning axes,
• linear gantries,
• robots and manipulators,
• rotary and indexing tables,
• pick-and-place systems,
• packaging and assembly machines,
• conveyors,
• cutting and printing systems,
• rack drives.

Not every one of these applications needs the same type of reducer, though. That is why the GearKo range includes several distinct design families.

Which planetary gearbox series does AMG offer?

AMG offers the TB/TBR, TD/TDR, TE/TER, TF, TCB/TCBR/TCE, TDP and TM/TMN families. Instead of treating them as similar gearboxes in different sizes, it is better to look at each one in terms of a specific application.

Series	Characteristics	Typical application
TB/TBR	Wide range of sizes and torques	General-purpose automation axes
TD/TDR	Flange output, focus on stiffness and smooth running	Positioning axes, gantries, tables
TE/TER	Precision versions for demanding axes	Pick-and-place, indexing, positioning
TF	High axial and radial load capacity	Heavily loaded axes, tables and manipulators
TCB/TCBR/TCE	Modular family for integration with various drives	CNC, robotics, warehouse automation
TDP	Gearbox integrated with a pinion	Rack & pinion, gantries
TM/TMN	Large through-hole, crossed-roller bearing	Rotary tables, positioners, robot axes

Exact torque, ratio and backlash values should always be checked for the specific size and version, as the ranges differ between series and gearbox stages.

TB/TBR – a versatile family for many types of drives

TB/TBR planetary gearboxes cover a wide range of sizes and torques. This makes them a good starting point when selecting a reducer for many classic automation axes.

The series is used, among others, in:

• assembly machines,
• packaging equipment,
• robots,
• positioning tables,
• conveyors,
• cutting and printing systems.

It is a particularly interesting option when a single gearbox family has to cover several different drive sizes and gear ratios.

TD/TDR – for axes requiring high stiffness and smooth operation

The TD/TDR series uses a flange output, and the design is aimed at applications where stiffness and vibration reduction matter.

Typical applications include:

• gantries,
• indexing tables,
• manipulators,
• pick-and-place systems,
• dispensing,
• rack & pinion drives.

Compared with TB, the range of available ratios is more focused, so TD/TDR is worth considering mainly when the system requires a specific way of mounting the output and high mechanical stiffness.

TE/TER – for precision axes and low-vibration applications

TE/TER gearboxes are designed for precision automation axes where low vibration and accurate motion control are particularly important.

They can be used, among others, in:

• indexing tables,
• pick-and-place systems,
• gantries,
• dispensing,
• positioning systems.

With this family it is especially important to check the parameters for a specific size – backlash, torque and ratio values differ between versions, so a single value should not be applied to the whole series.

TF – when the gearbox has to carry higher shaft loads

The TF planetary gearbox was designed with an emphasis on axial and radial load capacity.

This matters in applications where the output shaft is subjected not only to torque, but also to additional forces from:

• a pinion,
• an arm,
• a table,
• a gripper,
• a working element mounted directly on the output.

The TF series can therefore be a good direction when designing heavily loaded axes, indexing tables, gantries and manipulators.

TCB/TCBR/TCE – a modular design for different types of machines

The TCB/TCBR/TCE family makes it possible to build systems matched to different motor and mechanical configurations.

Applications include:

• positioning axes,
• robots,
• CNC machines,
• gantries,
• warehouse automation,
• packaging machines,
• conveyors.

In this series, the choice of version should be based on the data sheet of the specific model and the required mounting method.

TDP – a planetary gearbox for rack drives

In a classic rack & pinion axis, the gearbox has to be connected to a separate pinion. TDP integrates the planetary gearbox with a helical pinion.

This reduces the number of separately selected parts and simplifies the connection between the reducer and the rack.

The series is particularly useful in:

• gantries,
• long linear axes,
• tables and positioning systems,
• robots,
• drives using a gear rack.

Depending on the application, the module and the number of teeth of the pinion are also selected to match the appropriate gear rack.

TM/TMN – for rotary tables and axes requiring a through-hole

In some designs the centre of the axis must remain free because it has to carry:

• electrical cables,
• pneumatic lines,
• process media,
• signal harnesses.

The TM (TMN) planetary gearbox is designed for such applications.

Its characteristic features are a large through-hole and a crossed-roller bearing. As a result, it is particularly suitable for:

• rotary tables,
• positioners,
• indexers,
• robot axes,
• tool heads.

How to choose the right planetary gearbox series?

It is best to start not from a table of models, but by answering a few questions about the axis.

What torque is required?

Determine the operating torque and the peak values that occur during acceleration and braking.

It is not enough to compare the maximum motor torque with the value stated for the gearbox. The whole duty cycle matters.

What gear ratio is required?

The gear ratio results primarily from the relationship between the motor speed and the required output speed.

If a servo motor runs at 3,000 rpm and the mechanism needs about 500 rpm:

i ≈ 3000 / 500 = 6

A ratio of about 6:1 will therefore be needed as a starting point.

How important is backlash?

In an axis with frequent changes of direction, backlash directly affects positioning accuracy.

However, you should not automatically choose “the lowest possible backlash”. A higher precision class makes sense when the entire mechanism requires it – including guides, couplings, the rack or the screw.

How heavily is the output shaft loaded?

If a pinion, table or arm is mounted directly on the gearbox, check not only the torque but also the permissible radial and axial loads.

In such an application, a design like the TF may be more suitable than a reducer selected only on the basis of the gear ratio.

Is a special design needed?

The machine geometry alone may narrow down the choice:

• rack & pinion drive → TDP,
• central through-hole → TM/TMN,
• high output loads → TF,
• demanding positioning axis → TD/TDR or TE/TER,
• wide range of versions → TB/TBR.

Only after this stage is it worth comparing specific sizes.

How to match a gearbox to a servo motor or stepper motor?

The mechanical connection between the gearbox and the motor requires matching, among other things:

• shaft diameter,
• shaft length,
• motor flange,
• hole pattern,
• the required adapter sleeve or hub.

That is why it is worth stating the exact motor model in your enquiry right away.

GearKo gearboxes can work with a variety of drives. At AMG you can also select a servo drive, stepper motor or JVL integrated stepper motor at the same time, so the gearbox can be analysed as part of a complete axis rather than as a separate component.

What data should you prepare before selecting a gearbox?

For an initial selection, a few basic pieces of information are usually enough:

• motor model,
• operating and peak torque,
• motor speed,
• required gear ratio or output speed,
• required accuracy,
• type of load,
• mounting method,
• environmental conditions.

This makes it possible to rule out series that do not fit the design straight away and move on to comparing specific models.

Choose the gearbox for the whole axis, not just for the torque

The GearKo families cover different design needs. TB/TBR offers a wide choice of versions, TD/TDR and TE/TER are aimed at precision axes, TF handles higher shaft loads, TDP simplifies rack drives, and TM/TMN solves the need for a central through-hole.

That is why choosing a planetary gearbox is best started by defining torque, speed, gear ratio, backlash and mounting method. Only then is it worth narrowing down to a specific series and size.

This approach reduces the risk of choosing a gearbox that has the right ratio but does not fit the loads, geometry or dynamics of the particular machine.

FAQ

Which planetary gearboxes are available from AMG?

The range includes the TB/TBR, TD/TDR, TE/TER, TF, TCB/TCBR/TCE, TDP and TM/TMN families. They differ in torque range, output design and intended use.

Which series is suitable for a rack drive?

The TDP is particularly well suited to this application, as the gearbox is integrated with a helical pinion.

Which gearbox works well in a rotary table?

If a central through-hole is needed, consider the TM/TMN. For other table designs, series with a flange output may also be suitable.

How to choose a gearbox for a quiet, precise axis?

Start by comparing TD/TDR and TE/TER, but the final choice should result from the torque, gear ratio, backlash, speed and loads of the specific axis.

Can the gearbox be mounted on any servo motor?

Full compatibility should not be assumed without checking the dimensions. The flange, shaft and adapter components must be matched to the specific motor model.

Does AMG manufacture GearKo gearboxes?

No. The manufacturer of the gearboxes is GearKo, while AMG supplies them on the Polish market and supports the selection of the right series for the drive.