01
Start with force at the screw
Joint torque alone is not an axial load. Convert it using the perpendicular moment arm throughout the arm’s motion.
Robotics application · reviewed October 4, 2026
Biped Robot Arm Roller Screw Reference Check
Compare published arm screw ranges; this is not a sizing or safety approval.
Contact EngineeringArm screw reference check
Arm Screw Range Screen
Compare your inputs with one manufacturer’s published linear-actuator examples. This is a reference check, not a screw selection.
3 kN
Maximum force at the screw during the motion cycle. The HJL examples publish 0.6–8 kN maximum thrust.
Published HJL examples list up to 96 mm, with the limit varying by model.
HJL examples list 2, 3.5, 5, or 6.5 mm; lead alone does not establish backdrive behavior.
1 kN
Enter the RMS value from the load cycle. No continuous rating is published in the referenced summary.
Added to the inquiry summary; joint type does not change this reference-range screen.
Enter axial force at the screw, not joint torque. For a simple linkage, force is approximately joint torque divided by the perpendicular moment arm; use the worst case across the full motion and include push and pull loads.
Reference Check
Inputs do not exceed the published maxima and the lead is listed; model fit is not confirmed.
- Peak axial force does not exceed the highest published HJL example (8 kN); this does not confirm a model or duty-cycle fit.
- Stroke does not exceed the longest published HJL example (96 mm); the maximum stroke differs by model.
- The 5 mm lead appears in the published HJL example options; verify which model and rating combination supports it.
- No continuous RMS load rating is published in the referenced summary, so compare the force-time profile with the selected model’s continuous and thermal limits.
This screen does not calculate a minimum screw diameter, dynamic capacity, service life, or safety rating. Those require the full load and speed cycle, geometry, support conditions, and selected supplier data.
Request Engineering ReviewIf an input is invalid, your combination is not represented, or you need a model-specific result, use the engineering contact form and include the load profile and linkage geometry.
What the reference check can tell you
The comparison is useful for identifying questions to take to a supplier. It does not establish a production-ready selection.
02
Check a specific configuration
Published maximum thrust, stroke, speed, and lead options belong to particular actuator models and may not combine arbitrarily.
03
Validate the complete duty cycle
Continuous force, fatigue life, heat, support, and backdrive behavior need the selected assembly’s data and operating cycle.
Published inverted roller-screw actuator examples
One supplier lists the following HJL humanoid-joint modules. These are supplier-published product maxima, not universal roller-screw limits or continuous ratings.
| Model | Max thrust (N) | Max speed (mm/s) | Max stroke (mm) | Listed lead (mm) | Max diameter (mm) | Mass (kg) |
|---|---|---|---|---|---|---|
| HJL08 | 600 | 300 | 38 | 3.5 | 49 | 0.5 |
| HJL12 | 4,000 | 120 / 300 | 72 | 2 / 5 | 62 | 1.3 |
| HJL15 | 8,000 | 120 / 400 | 96 | 2 / 6.5 | 86 | 2.8 |
Source checked October 4, 2026. The published page does not give a continuous RMS rating for these examples. Confirm the exact thrust, speed, lead, stroke, and thermal combination with the supplier before using it in a design.
View the supplier’s HJL specificationsConvert joint torque into actuator force
For a simple linkage, the moment about the joint is the actuator force multiplied by its perpendicular moment arm. As the arm moves, that distance changes, so check the full range of motion.
Approximate static relationship: joint torque = screw force × perpendicular moment arm; therefore screw force ≈ joint torque ÷ r⊥.
This relation is not a dynamic load model. Include gravity, payload, inertia, acceleration, friction, linkage efficiency, and both load directions. A very small moment arm can create a large force demand or a linkage singularity.
A practical selection and validation sequence
The tool makes an early comparison; supplier ratings and the complete mechanism analysis determine whether a design fits.
1. Define the motion and load
Record joint angle, torque, speed, payload, acceleration, and duty cycle. Convert the load to screw force with the actual linkage geometry.
2. Screen the reference envelope
Enter force at the screw, active stroke, and lead. Treat a match to a published maximum as a prompt for review, not proof that that exact combination is supported.
3. Check the candidate assembly
Verify peak and continuous ratings, speed, fatigue life, stiffness, lubrication, temperature, bearings, support, and buckling against the selected supplier’s data.
4. Review the system behavior
Confirm packaging, side-load control, motor and controller limits, measured backdrive behavior, sensing, and the intended human-robot interaction strategy.
Compare screw and rotary-joint architectures on the same load case
No architecture is a universal winner. Compare complete assemblies using the same motion, load, package, and service assumptions.
| Dimension | Screw-actuated joint | Rotary geared joint | Design check |
|---|---|---|---|
| Force / torque | Linear thrust is mapped through a linkage. | Torque is delivered at the joint output. | Compare peak and RMS demands over the full motion. |
| Motion envelope | Stroke and linkage geometry set the available motion. | Joint module and transmission set the available motion. | Check range, speed, collision clearance, and end stops. |
| Interaction / backdrive | Depends on screw, motor, bearings, sensors, and control. | Depends on geartrain, motor, sensors, and control. | Use measured assembly data and define the safety strategy. |
| Cost and service | Include screw, supports, linkage, lubrication, and replacement access. | Include transmission, bearings, sensing, and replacement access. | Compare supplier quotes and lifecycle service assumptions. |
Limits and risks to resolve before design release
A reference-range match cannot replace ratings for the chosen product or validation of the complete actuator and arm.
Using joint torque as screw thrust
Risk: The force requirement can change substantially with linkage angle and effective moment arm.
Mitigation: Calculate force across the full range of motion, including push and pull directions and acceleration.
Treating peak thrust as a continuous rating
Risk: Peak capacity does not establish thermal capability, fatigue life, or duty-cycle fit.
Mitigation: Provide the load/speed cycle and request model-specific peak, continuous, thermal, and life limits.
Assuming lead alone proves backdrivability or safety
Risk: The complete actuator includes friction, motor, transmission, sensing, and control behavior.
Mitigation: Define the interaction requirement and request measured backdrive force and system-level safety review.
Choosing architecture from a screening result
Risk: Support conditions, buckling, critical speed, side loads, package, and total system cost are not screened here.
Mitigation: Compare candidate assemblies using the same load profile and review drawings, ratings, and lifecycle cost.
Evidence and scope
The product figures above come from a single supplier’s public HJL actuator page, checked October 4, 2026. SKF’s roller-screw selection guidance says selection depends on load spectrum, speed, acceleration, cycle rate, environment, required life, accuracy, and stiffness; a basic dynamic rating is a nominal fatigue-life input, not a service-life guarantee.
- Techrobots HJL linear actuator specifications (supplier product data; checked October 4, 2026)
- SKF roller-screw selection recommendations (selection method and nominal dynamic rating; accessed October 4, 2026)
- Rollvis planetary roller-screw product overview (manufacturer overview; accessed October 4, 2026)
Supplier claims are identified as such. No independent biped-arm force range, universal load multiplier, or lead-based safety threshold is asserted here. Published examples can change; verify current model data before purchase or design release.
Frequently asked questions
Answers for early actuator comparison and engineering handoff.
Does this page size a biped robot arm roller screw?
No. The screen compares entered peak force, stroke, and lead with one supplier’s published actuator examples. It does not select a screw diameter, verify a load rating, calculate life, or approve a design.
How do I convert arm-joint torque into screw force?
For a simple linkage, actuator force is approximately joint torque divided by the perpendicular distance from the pivot to the actuator force line. That moment arm changes through the range of motion, so evaluate the complete geometry and the worst case.
Does a larger screw lead guarantee backdrivability?
No. Lead changes travel per revolution and the ideal force-to-torque relationship, but friction, preload, motor cogging, gearing, sensing, and control also affect the assembled actuator. Request measured backdrive data for the candidate assembly.
Can I compare the listed maximum thrust directly with my joint torque?
No. Maximum thrust is an axial actuator value, while joint torque depends on linkage geometry and joint angle. Convert the load case to force at the screw first, then verify continuous, peak, speed, thermal, and life ratings for the selected model.
Are the HJL examples universal roller-screw ratings?
No. They are specifications for three integrated actuator examples from one supplier. Their published maxima do not establish continuous RMS ratings or prove that every force, stroke, and lead combination is available.
What should I send for an engineering review?
Send the linkage or CAD, joint torque and speed over the full motion cycle, payload and acceleration assumptions, peak and RMS screw loads, stroke, duty cycle, mounting conditions, environment, and any backdrive or safety requirements.
Request a model-specific engineering review
Share the arm linkage, motion and load profile, stroke, duty cycle, package limits, and interaction requirements so the candidate actuator can be checked against its actual ratings.
Published September 25, 2026 · Reviewed October 4, 2026