Robot arm and wrist engineering review
Precision arm axes and compact wrists share a joint-actuator interface, but their limiting requirements can differ. Build a model-specific shortlist from the installed load, motion cycle, error budget and service routing.
Evaluate ZHR-H harmonic models when reduced lost motion is an important design input; evaluate ZHR-P planetary configurations against the same load and integration requirements. Neither family name establishes arm payload, wrist accuracy, impact limits or safe holding. Qualification requires the selected configuration's data and a representative assembly test.
Reviewed September 18, 2026 · Engineering selection guidance
| Decision area | Shoulder / elbow / precision arm axis | Compact wrist / tool orientation axis |
|---|---|---|
| Load case | Link masses, payload location, reach, gravity orientation and acceleration | Tool center of gravity, eccentric moment, process forces and orientation changes |
| Precision | Loaded joint error and its contribution to end-effector error throughout the workspace | Tool orientation and position error under the actual tool load and thermal state |
| Thermal duty | Extended-reach holds, repeated accelerations and the mounting heat path | Repeated fine motions, tool holds and cooling in the enclosed end assembly |
| Mechanical integration | Output bearing forces and moments, link stiffness, fixing and datum surfaces | Installed mass, axial length, connector clearance and tool flange loads |
| Routing and travel | Harness motion and service access through the full working envelope | Limited or continuous rotation, power/data/service routing and bend or twist limits |
| Stop requirements | Allowed arm motion after a stop, bus loss or power loss, with the payload attached | Allowed tool movement and retention behavior; separate holding mechanism if required |
Start with the perpendicular distance from each joint axis to the load's line of action. For a static point load, torque magnitude about that axis is force multiplied by the perpendicular lever arm. Calculate the contribution from the tool, payload and downstream links for each pose; then add the dynamic and process-load cases in the system model.
For a hypothetical 2 kg load and g = 9.81 m/s², a perpendicular lever arm of 0.40 m contributes 7.85 Nm of static torque. At 0.08 m, the same load contributes 1.57 Nm. This simplified example excludes link weight, acceleration, friction and process forces. It is not a ZHR rating, a model recommendation or a design margin.
Send a torque-speed-time trace when available, including peak duration and repeated holds. Keep external bearing forces and overturning moments separate from commanded output torque; one torque number cannot verify every part of the load path.
Define whether the requirement is absolute position accuracy, repeatability or orientation error. State the measurement position, payload, approach direction, speed and thermal condition. A low backlash number alone does not account for elastic deflection, feedback location, calibration or the arm structure.
For a wrist, also verify routing space before selecting continuous rotation. Hollow routing, slip rings and brakes are configuration features to confirm, not assumed contents of an integrated joint.
Compare H14, H17, H20 and H25 using the exact reduction ratio. The public interface boundary is CAN / RS485; confirm the selected interface, command set and controller compatibility.
Compare H-series model dataRead the source specificationsCompare exact configurations. P17 is available as 36 V with one magnetic encoder or 48 V with two. P60 is CAN only with no native EtherCAT; verify other interfaces by model.
Compare P-series model dataReview P17 configuration sourcesUse public STEP models and dimension images for layout. Request the matching drawing revision, tolerances, bearing limits, torque-speed data and protocol documentation before releasing production parts.
Open technical downloadsDownload the inquiry checklistA catalog torque rating does not establish an arm's payload or suitability for human interaction. Test stop and holding behavior in the installed system. Confirm any required brake, fault response and protective measures rather than inferring them from the reducer architecture.
Copy the following details into the message field of the selected series' inquiry form. If the actuator family is undecided, state the design priority and ask which configurations can be evaluated against it.
Mark unknown values explicitly. For P17, specify 36 V single-encoder or 48 V dual-encoder. Request the document revision applicable to the selected configuration.
Use the payload center of gravity, link masses, arm posture, acceleration and process forces to calculate a torque-speed-time profile for each axis. Payload mass alone does not define actuator torque or a validated arm payload rating.
No. The complete error budget also includes loaded stiffness, structural deflection, feedback, calibration and temperature. Define accuracy and repeatability under specified tool loads, reach, speed and measurement conditions.
Compare exact ZHR-H and ZHR-P configurations against tool moment, torque-speed demand, installed mass, envelope, output bearing loads and routing. Confirm the required travel, interface and holding behavior before choosing a model.
Use public CAD and dimension images for preliminary integration. Request the drawing revision, tolerances, load limits, connector information and selected configuration before approving production parts.
Related application guidance: humanoid hip, knee and ankle requirements · robotic hand and finger actuation.