Resources

Motion, Drive & Actuation

Frameless Torque Motor Selection Guide

Prepare rotor, stator, thermal path, hollow shaft, encoder and joint packaging inputs for frameless robot joint sourcing.

Who should use this

Humanoid, robotic arm and compact actuator teams packaging motors inside custom joints.

Hardware decision

The guide frames the mechanical and thermal information needed before a frameless motor quote, CAD request or drive system review.

Prepare before RFQ

Bring stator and rotor dimensions, shaft or hollow-bore requirement, torque constant, thermal path, encoder and brake strategy, reducer interface, air-gap or clearance context, assembly tolerance and cable routing constraints.

Start related joint hardware review Start related hardware review

When to use this guide

Start here if the hardware question affects sourcing, files or RFQ review.

  • The motor will be built into a custom joint rather than purchased as a housed servo motor.
  • Joint packaging, thermal path, encoder mounting or hollow shaft requirements affect sourcing.
  • You need file access for mechanical fit review but final joint design remains under your engineering control.

Key engineering decisions

Stator and rotor envelope

Capture outer diameter, inner diameter, stack length, air gap or clearance context, shaft path, bearing strategy and available joint volume.

Thermal path

State how heat leaves the stator, expected duty cycle, ambient range and any housing or liquid-cooling assumptions.

Feedback, brake and reducer interface

Identify encoder integration, brake packaging, reducer ratio, mounting tolerance and axial stack-up before requesting drawings.

Cable routing

Define phase cable, sensor cable, bend exposure and connector exit direction early, especially for humanoid limbs.

RFQ preparation checklist

Include these inputs before asking for quote or document review.

  • Stator OD / ID and length
  • Rotor or hollow-shaft requirement
  • Torque constant or torque target
  • Thermal path and duty cycle
  • Encoder and brake integration
  • Reducer compatibility
  • Air gap, clearance, assembly tolerance and cable routing
  • Required controlled CAD / STEP request

Engineering file considerations

Document access depends on file type and review context.

  • Native CAD, full drawings and internal motor design files are not automatically released.
  • STEP/STP access may be approved for mechanical fit review after context is checked.
  • Thermal or performance estimates do not certify final joint behavior.
Review Engineering Files workflow Read Access Policy

Not covered by this guide

Complete joint design
Thermal simulation or certification
Final joint performance validation
Responsibility for customer housing machining or assembly errors

Ready to attach this guide to a real request?

Use the guide checklist to submit one RFQ with product, file and subsystem context. Controlled access may apply to STEP/STP, native CAD, full drawings and supplier-sensitive records.

Use guide for RFQ preparation