How to Select an Integrated Robot Joint

1. Start With the Joint Requirement

Define what the robot joint must do before comparing integrated joint products.

Capture:

• - Continuous output torque
• - Peak output torque
• - Target output speed
• - Acceleration profile
• - Motion range
• - Payload
• - Gravity load
• - External loads
• - Duty cycle
• - Positioning requirement
• - Force / torque control requirements
• - Available diameter and length
• - Target joint mass
• - Hollow passage requirement
• - Bus voltage
• - Communication interface
• - Environmental conditions
• - Target build quantity
• - Prototype or production stage

Separate requirements from preferences.

A compact joint may be preferred, but torque-speed capability, thermal limits, bearing loads, communication compatibility, and mechanical integration must be confirmed before a candidate is shortlisted.

2. Confirm What Is Actually Integrated

"Integrated robot joint" is not a standardized architecture.

Different products may include different combinations of components.

Two products with similar external dimensions can represent very different levels of integration.

Do not compare them as equivalent until the included functions are confirmed.

3. Define the Required Output Torque

The integrated joint should be sized using the output-side load requirement.

Distinguish between:

• - Continuous torque
• - Peak torque
• - Acceleration torque
• - Gravity load
• - Shock load
• - Holding torque
• - Transient collision or impact events

Do not select a joint using peak torque alone.

A high peak-torque value may represent only a short-duration electrical or thermal limit.

4. Check Output Speed and Motion Profile

The joint must satisfy both torque and speed requirements.

Check:

• - Rated output speed
• - Maximum output speed
• - Continuous operating speed
• - Acceleration
• - Deceleration
• - Direction reversal
• - Dwell time
• - Repeated cycle frequency

A joint that meets torque requirements but cannot maintain the required motion speed is not a valid candidate.

For dynamic robots, evaluate the entire motion profile rather than one maximum-speed number.

5. Understand the Reducer Architecture

Integrated joints commonly use reducer architectures such as:

• - Harmonic / strain-wave
• - Planetary
• - Cycloidal
• - Other proprietary architectures

The reducer influences:

• - Ratio
• - Backlash
• - Torsional stiffness
• - Efficiency
• - Shock resistance
• - Backdrivability
• - Output speed
• - Thermal behavior
• - Service life

Read How to Select a Reducer for a Robot Joint and Harmonic vs Planetary Reducers for Robot Joints for more detail on reducer selection.

Do not assume reducer type from marketing language if the architecture is not explicitly documented.

6. Evaluate the Integrated Motor

Even when the motor is internal and not separately selectable, its characteristics still affect joint performance.

Relevant motor information may include:

• - Motor type
• - Rated voltage
• - Continuous current
• - Peak current
• - Torque constant
• - Speed constant
• - Winding configuration
• - Thermal limits
• - Rotor inertia
• - Temperature sensing

If motor-level information is not publicly disclosed, do not infer it from a similar standalone motor.

Keep the field open and request supplier confirmation when it materially affects the design.

Read How to Select a Motor for a Robot Joint for the motor-side selection process.

7. Backlash and Torsional Stiffness

Integrated joint precision depends on more than encoder resolution.

Backlash and torsional stiffness directly affect joint-level positioning and control behavior.

Check:

• - Reducer backlash
• - System backlash
• - Torsional stiffness
• - Compliance under load
• - Repeatability
• - Direction reversal behavior

A high-resolution encoder cannot remove mechanical compliance or reducer backlash.

For precision and force-controlled applications, evaluate sensing and mechanics together.

8. Encoder and Feedback Architecture

Integrated joints may use different sensing architectures.

Examples include:

• - Motor-side encoder
• - Output-side encoder
• - Dual encoder
• - Absolute encoder
• - Incremental encoder
• - Magnetic encoder
• - Optical encoder

Do not treat encoder resolution as equivalent to finished-joint positioning accuracy.

9. Driver and Control Interface

Some integrated joints contain the motor driver and control electronics.

Others require an external drive.

Confirm:

• - Driver included or external
• - Bus voltage
• - Continuous current limits
• - Peak current limits
• - Position control
• - Velocity control
• - Torque control
• - Current control
• - Supported feedback modes
• - Command update rate if published
• - Communication interface
• - Configuration tools
• - Firmware requirements

Do not assume that an integrated driver supports the control mode required by the robot.

A joint intended for position control may not automatically provide the torque-control behavior required by a force-controlled robot.

10. Communication and Electrical Integration

Confirm the exact interfaces exposed by the joint.

Depending on the product, these may include industrial or embedded communication interfaces.

Only display communication protocols when they are explicitly documented for the exact product.

Check:

• - Power input
• - Communication interface
• - Connector type
• - Cable routing
• - Grounding
• - Shielding
• - Feedback signals
• - Fault outputs
• - Emergency-stop integration where applicable

Do not infer protocol support from another model in the same family.

11. Check Output Bearing Loads

The integrated joint may also serve as a structural joint element.

Confirm whether it can directly support:

• - Radial load
• - Axial load
• - Overturning moment
• - Combined loads

Some joints contain an integrated cross-roller bearing or another output-bearing architecture.

Others still require external structural support.

This distinction can materially affect:

• - Housing design
• - Joint diameter
• - Stiffness
• - Mass
• - Assembly complexity
• - Service life

If output-bearing capacity is not published, treat it as an open engineering question.

12. Thermal Behavior Is a System Constraint

An integrated joint places several heat-generating elements in a compact volume.

Potential heat sources include:

• - Motor
• - Reducer losses
• - Driver electronics
• - Brake
• - Bearings

Thermal performance can therefore become the limiting factor even when torque capability appears sufficient.

Check:

• - Continuous operating torque
• - Continuous current
• - Motor temperature
• - Driver temperature
• - Case temperature
• - Ambient temperature
• - Cooling method
• - Conduction path
• - Duty cycle
• - Thermal derating
• - Over-temperature protection

A peak torque specification does not establish continuous joint capability.

The relevant question is whether the joint can perform the required repeated motion without exceeding thermal limits.

13. Evaluate Mechanical Envelope and Mass

Integrated joints are often selected to simplify packaging, but complete dimensions still matter.

Check:

• - Outer diameter
• - Total length
• - Output flange
• - Input / mounting flange
• - Hollow-bore diameter
• - Shaft geometry
• - Mounting bolt pattern
• - Cable exit
• - Connector clearance
• - Brake extension if applicable
• - Total mass

Evaluate the installed envelope, not only the cylindrical body.

Connector orientation, cable bend radius, mounting hardware, and link geometry may increase the actual space required.

14. Check Hollow Passage and Cable Routing

Many robot joints require cables, hoses, or structural elements to pass through the joint axis.

A hollow joint architecture can simplify routing.

Confirm:

• - Hollow-bore diameter
• - Usable passage diameter
• - Rotating versus stationary cable path
• - Cable bend radius
• - Connector dimensions
• - Internal obstruction
• - Maximum joint rotation

A published hollow-shaft diameter should not automatically be treated as the usable cable-routing diameter.

Confirm the actual internal passage and assembly constraints.

15. Evaluate Backdrivability and Joint Behavior

Backdrivability can matter for:

• - Collaborative robots
• - Force interaction
• - Legged robots
• - Manual positioning
• - Impact response
• - Energy efficiency

But backdrivability depends on the complete joint:

Motor → Reducer ratio → Reducer architecture → Friction → Bearings → Control mode → Brake

Do not classify a joint as backdrivable solely from reducer type.

If backdrive torque or friction data is important and not published, request it from the supplier.

16. Evaluate Reliability and Service Life

Integrated joints combine several potential life-limiting components.

Service life may depend on:

• - Reducer fatigue
• - Bearing life
• - Lubrication
• - Motor insulation
• - Encoder reliability
• - Driver electronics
• - Connector durability
• - Thermal cycling
• - Shock and vibration

Ask whether life data applies to:

• - The reducer only
• - The actuator assembly
• - The complete integrated joint

Do not treat subsystem life as complete-joint life unless supplier documentation explicitly supports it.

17. Environment and Protection

The operating environment may affect joint selection.

Relevant conditions include:

• - Dust
• - Water
• - Outdoor exposure
• - Humidity
• - Corrosion
• - Vibration
• - Shock
• - Temperature
• - Repeated thermal cycling

If an IP rating or environmental qualification is published, confirm whether it applies to:

• - The complete joint
• - The housing only
• - A specific installation condition

Do not infer environmental protection from appearance or enclosure style.

18. Integrated Joint vs Separate Motor + Reducer Architecture

Neither architecture is universally better.

Integrated joints can reduce integration time, while separate components can provide greater architectural flexibility and sourcing control.

19. Compare Multiple Integrated Joint Candidates

Before design freeze, compare several technically viable candidates using the same joint requirement.

Comparison template — populate each column using published model-level specifications.

For actual product records, unavailable specifications should be shown as:

Not publicly disclosed

Do not infer missing values from another model or product family.

20. Supplier and Sourcing Constraints

An integrated joint can increase supplier dependence because multiple functions are bundled into one product.

Before design freeze, review:

• - Exact model availability
• - Prototype quantity
• - Lead time
• - MOQ
• - CAD files
• - Dimensional drawings
• - Electrical documentation
• - Communication documentation
• - Torque-speed curves
• - Thermal information
• - Bearing load data
• - Encoder documentation
• - Firmware / configuration software
• - Customization options
• - Replacement availability
• - Future production capacity
• - Second-source options
• - Supplier technical support

Do not assume price, lead time, MOQ, inventory, production capacity, or future availability when those values are not published.

Use Request Quote to capture missing commercial and technical information.

21. Integrated Joint Selection Checklist