The application factor (Ka) is used to properly size a gearbox when the transmitted load is not perfectly constant.

 

In most industrial machines, the torque transmitted through the drivetrain varies due to:

 

• acceleration and deceleration

• duty cycles

• load variations

• motion reversals

• occasional mechanical shocks

To account for these additional stresses, ISO and DIN standards introduce the application factor Ka.

 

The torque used for gearbox sizing therefore becomes

 

Design Torque = Nominal Torque × Ka

 

The values indicated below are typical guidelines and should be considered minimum values, since each application has its own specific operating conditions.

 

For further information, please refer to the following standards:

 

• ISO 6336

• DIN 3990

• DIN 3991

 

Typical Application Factor Values

 

Ka = 1.1

 

Servo operation with smooth load and moderate acceleration.

 

Typical applications:

 

• positioning axes

• indexing rotary tables

• inspection and vision systems

• automated measuring equipment

• light assembly machines

 

Ka = 1.25 – 1.35

 

Servo applications with frequent cycles and moderate dynamics.

 

Typical applications:

• plasma cutting machines

• printing machines

• packaging machines

• labeling machines

• dispensing systems

• light automated conveyors

• paper handling systems

 

Ka = 1.5 – 1.7

 

Dynamic applications with significant acceleration.

 

Typical applications:

• pick-and-place robots

• Cartesian robots

• tool changers for machine tools

• fast axes in printing machines

• positioning systems for industrial machinery

 

Ka = 1.7 – 2.0

 

Highly dynamic servo applications.

 

Typical applications:

 

• delta robots

• high-speed packaging machines

• high-dynamic laser cutting machines

• high-speed sorting systems

 

Ka ≈ 2.0

 

Dynamic traction or motion applications.

 

Typical applications:

 

• AGV / AMR drive wheels

• automated logistics systems

• rotary axes in special machines

• high-acceleration manipulators

 

Ka > 2.0

 

Applications with severe loads or significant mechanical shocks.

 

Typical applications:

 

• plastic extrusion machines

• crushers

• heavy presses

• forming machines

 

Influence of Mechanical Shocks

 

When applications are subject to mechanical shocks, DIN 3990 recommends using higher application factors.

 

Load condition	Typical factor
Moderate shocks	Ka ≈ 1.35
Medium shocks	Ka ≈ 1.60
Heavy shocks	Ka ≈ 1.85

 

 

Influence of Ambient Temperature

 

Ambient temperature may affect the thermal capacity of a gearbox and therefore its torque capability.

 

The following correction factors may be used as a general guideline:

 

Ambient temperature	Non-ventilated gearbox	Ventilated gearbox
T < 25°C	Kt = 1.00	Kt = 0.90
T < 35°C	Kt = 1.10	Kt = 1.00
T < 45°C	Kt = 1.25	Kt = 1.15

 

 

Gearbox Sizing in Servo Applications

 

In modern servo-driven systems such as laser cutting machines, printing machines, packaging equipment, robotics, and AGVs, gearbox selection does not depend only on nominal torque.

 

It is also recommended to consider:

 

• RMS torque over the duty cycle

• inertia ratio between motor and load

• gearbox torsional stiffness

• Backlash and lost motion.  If your application requires that backlash remains stable over time, you should never exceed the nominal torque of the gearbox.

• overall system dynamic stability

 

These parameters directly influence:

 

• positioning accuracy

• servo stability

• motion quality