Custom Planetary Gearbox Engineering

When a Catalog Gearbox Does Not Fit the Project

A planetary gearbox project does not need to start from an existing SigGear model number.

You may already have:

• a motor that must be kept
• a fixed installation diameter or length
• an output-speed target
• a torque or load requirement
• a required shaft or flange
• an existing mechanism drawing
• a current gearbox that does not meet the project requirement

SigGear designs and manufactures miniature and compact planetary gearboxes and can review a project using existing gearbox platforms as engineering starting points before evaluating modified or custom configurations.

Send Your Motor or Drawing Request Engineering Review

Common Custom Planetary Gearbox Requests

Depending on the selected gearbox platform and engineering feasibility, project-specific review may include:

• reduction ratio
• gearbox diameter and axial length
• motor matching
• motor shaft and input interface
• output shaft shape and length
• mounting flange or mounting pattern
• housing and installation structure
• encoder or brake integration where applicable
• cable and connector configuration where applicable
• backlash target
• radial and axial load conditions
• duty cycle and operating condition

Changing one requirement may affect other parameters such as torque, speed, efficiency, size, service life, thermal behavior or cost. Final feasibility must therefore be confirmed as a complete configuration rather than one parameter at a time.

I Already Have a Motor

This is a common starting point.

If the motor has already been selected, send the motor drawing or the information available for:

• motor type
• nominal voltage
• rated and peak power
• rated / no-load speed
• shaft diameter
• usable shaft length
• shaft flat, key or pinion requirement
• mounting-hole pattern
• locating pilot diameter
• available total assembly length

SigGear can then review the motor-to-gearbox interface together with the required output speed, torque and installation envelope.

The supply configuration can be:

• planetary gearbox only
• motor only
• matched motor + gearbox assembly

View the 32P Motor Integration Guide

I Know the Output Speed but Not the Gear Ratio

The exact ratio does not need to be defined before the first discussion.

If the motor speed and desired output speed are known, they provide a starting point for ratio selection:

preliminary reduction ratio ≈ motor speed / desired output speed

The final configuration still needs to account for the available stage ratios, torque requirement, gearbox input-speed limit, efficiency, duty cycle and motor operating point.

If the motor speed is not yet fixed, send the application and target output motion first.

I Do Not Know the Required Torque

A project can still start before the torque value is fully defined.

Useful inputs can include:

• load or payload
• arm length or linkage geometry
• wheel diameter
• pulley or screw information
• friction or resistance that must be overcome
• acceleration requirement
• motion cycle
• whether the axis works against gravity
• a sketch or CAD screenshot of the mechanism

The engineering review can then identify what needs to be calculated, estimated or tested before selecting the gearbox.

Existing SigGear Planetary Platforms

SigGear manufactures an 8-42 mm planetary gearbox series covering miniature and compact gearbox frame sizes, which can also serve as engineering starting points for project-specific configurations.

The current public range includes:

8P / 10P / 12P / 14P / 16P / 20P / 22P / 24P / 28P / 32P / 36P / 42P

Each frame size has its own available ratios, stage configurations, torque limits, efficiency, dimensions and other operating limits. Values must be confirmed from the relevant model page rather than transferred between frame sizes.

Browse the 8-42 mm Planetary Gearbox Series

32P as a Public Engineering Reference

The 32P is currently one of the clearest public examples of how a SigGear planetary gearbox can be evaluated for integration.

Its public Engineering Pack includes:

• technical datasheet
• mechanical-interface reference
• motor-integration guide
• simplified 4-stage STEP model

The public STEP is intended for packaging, mounting and early mechanical design-in. Controlled configuration-specific drawings are used for final release.

View 32P View 32P Engineering Resources

What Can Be Modified?

Depending on the selected gearbox platform and engineering feasibility, a project may involve changes to the motor interface, ratio, output shaft, flange, mounting arrangement, housing, encoder or brake configuration. Not every modification is available for every gearbox size, and the final configuration must be reviewed as a complete system.

Motor + Gearbox Integration Engineering Prototype → Design-In → Production

Typical Project Situations

Custom planetary gearbox engineering may be relevant when:

The motor is already fixed

The gearbox must be adapted around an existing motor shaft, pilot, mounting pattern, speed and available assembly length.

The gearbox must fit an existing mechanism

The project has a fixed diameter, length, mounting surface or output location that a catalog configuration does not match directly.

The output shaft is application-specific

The project requires a different shaft geometry, shaft length, flange or mounting arrangement.

The output speed is known but the transmission is not

The engineer knows how fast the mechanism should move but has not selected the stage count or ratio.

The product needs a motor + gearbox assembly

The project needs the motor and gearbox evaluated together instead of sourcing the two parts separately.

The project is moving from prototype toward production

A preliminary gearbox configuration needs to be refined around the actual motor, housing, loads, mounting and operating cycle before the design is frozen.

Engineering Review Path

A typical custom planetary gearbox project can move through:

Application / Existing Motor / Drawing
→ Feasibility Review
→ Frame Size and Ratio Evaluation
→ Motor and Interface Review
→ Configuration Drawing
→ Prototype or Sample
→ Application Test
→ Parameter / Interface Refinement
→ Design Confirmation
→ Pilot Preparation
→ Production

The exact sequence depends on how mature the customer's design already is.

What to Send First

You do not need to prepare a long specification sheet before contacting SigGear.

Start with the information you already have:

1. Application — what the mechanism needs to do
2. Motor — drawing or motor model if one has already been selected
3. Output target — speed and torque / load if known
4. Space — maximum diameter, length or installation envelope
5. Interface — shaft, mounting or drawing if these are already defined
6. Project stage — concept, prototype, pilot or production planning
7. Quantity — prototype quantity and expected production volume if known

If some of these are unknown, send the drawing, mechanism or product concept first. The missing engineering inputs can be identified during the review.

Applications

Miniature and compact planetary gearboxes can be evaluated for products such as:

• humanoid and service robots
• quadruped robots
• robotic arms
• dexterous hands and grippers
• exoskeletons
• UAV and drone mechanisms
• robotic lawn and outdoor equipment
• electric curtains and smart-home mechanisms
• smart sanitary and household mechanisms
• medical and laboratory equipment
• precision instruments
• compact automation mechanisms
• other products that require a small motor and reduction gearbox

These are application areas where planetary transmission may be relevant. They are not statements that SigGear has a public customer case in every listed application.

Need a Different Transmission Structure?

A planetary gearbox is not always the correct answer.

If the required torque, packaging, load condition or joint architecture suggests another approach, SigGear can also review cycloidal and integrated actuator solutions.

Open Custom Precision Transmission Engineering Browse Cycloidal Joint Modules

Discuss Your Planetary Gearbox Project

Send the motor, drawing, available space or motion requirement you already have.

Wanrong Wang
International Sales / Sales Engineer, SigGear
wangwanrong@siggear.com

Request Engineering Review Send Your Motor or Drawing