Quick Decision Framework
Start With the Joint Requirements
Compare peak and continuous torque, speed, mass, duty cycle, and the same system boundary for both candidates. Public sources reviewed here do not establish a universal torque density threshold or a matched performance advantage for custom housings.
Validate the Heat Path
A custom structure can act as part of a frameless motor’s heat path, but it does not guarantee lower winding temperature. Test the complete joint at its intended duty and ambient conditions, including nearby gearbox and sensor limits.
Architecture Comparison
Standard module or housing
Catalog assembly boundary
Preserve the supplied interfaces and ratings when they meet the joint envelope and operating requirements.
Application-specific housing
Customer-defined assembly boundary
Combine interfaces only where packaging, load, thermal, or service evidence supports the added design and qualification work.
Conceptual layouts only. Interfaces, heat flow, mass, and performance depend on the selected products and validated assembly; the drawing is not to scale.
Detailed Evaluation Criteria
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| Decision dimension | Standard housing or module | Application-specific housing |
|---|---|---|
| Envelope and interfaces | Use the catalog mounting pattern, shaft, connectors, and service clearances if they fit the joint. | Can combine interfaces or fit a constrained envelope; confirm access, assembly sequence, and replacement path in CAD. |
| Thermal validation | Use supplier ratings only with their stated mounting and duty conditions; verify them in the robot assembly. | May provide a designed conduction path to the frame. Measure winding and adjacent component temperatures at the required duty. |
| Alignment and retention | Follow the selected motor, bearing, and module drawings and preserve their specified datums. | Design the full tolerance stack and retention process for the selected parts and temperature range; do not assume a universal fit. |
| Cost and schedule | Often avoids new housing design and tooling; confirm catalog availability, lead time, and any adapter work. | Adds design, prototype, tooling, and qualification effort. Compare total cost at the forecast quantity; no universal break-even quantity is established here. |
| Ingress and service | Check the module’s declared protection rating and its test conditions against the deployment environment. | Specify the target and acceptance test, then measure seal drag and confirm service access on the assembled joint. |
This is a qualitative decision framework, not a matched test of named products. Public evidence reviewed for this page does not provide comparable mass, cost, temperature, or lifetime data across standard and custom humanoid actuator housings. See the frameless motor installation guide for product-specific integration guidance and the Berkeley Humanoid Lite paper for one research prototype example.
Have candidate drawings or duty requirements? Compare those constraints with the RFQ checklist below.
Compare candidatesMaterial Choice: Use Application Data
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| Material input | Evidence available here | How to use it |
|---|---|---|
| 6061-T6 Aluminum | Hydro’s 2019 extrusion sheet lists typical thermal conductivity of 167 W/m·K at 25°C for 6061-T6/T6511 extrusion. | Treat this as a typical material datum, not finished-housing performance. Include product form, section, contact, coating, and operating temperature in the thermal analysis. |
| 7075-T6 Aluminum | No directly comparable 7075-T6 datasheet or finished-part test is cited on this page. | Request the supplier’s product-form and temper certificate, then compare strength, thermal behavior, corrosion, joining, and machinability for the actual design. |
| Other alloys or polymers | No universal material ranking is established by the sources listed here. | Use supplier data and part-level tests for load, temperature, environment, process, and lifecycle requirements. |
The cited 6061 sheet is revision 2019/01 (2/2019). Confirm current supplier data for the purchased product form and temper before releasing a drawing. See the Hydro datasheet for its test context and thickness-specific properties.
Retention and Sealing Trade-offs
Set the Ingress Target
State the required ingress protection, contaminant, and exposure conditions. Compare candidate seals against that target and measure their effect on output drag; this page does not establish a universally best seal type.
Stator Retention
Frameless motor makers document different retention options. Celera Motion describes bolting, press fit, shrink fit, adhesive bonding, and axial clamping, with warnings specific to its motor kits. Follow the selected motor’s interface drawing, load limits, temperature range, and adhesive instructions; do not treat any method or compound as universal. Read the guide.
Methodology and Applicability Boundaries
- Prefer a standard module when:Its interfaces and rated operating conditions meet the joint requirements, and custom integration has no measured benefit large enough to justify NRE and qualification.
- Evaluate a custom design when:A documented envelope, mass, thermal, load, sealing, or service requirement cannot be met with a standard option, and the benefit can be verified in a prototype or production-intent test.
Risks and Trade-offs
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| Risk | Trigger / consequence | Practical safeguard |
|---|---|---|
| Fit and alignment error | A tolerance stack or assembly process outside the selected motor or bearing requirements can cause interference, runout, or inconsistent assembly. | Use supplier interface drawings, functional datums, inspection records, and an assembly trial before pilot release. |
| Retention over temperature and load | Retention performance can change with thermal expansion, torque, vibration, material pairing, and bond-line or fit design. | Select the method with the motor maker for the full temperature and load range; validate it on representative assemblies. |
| Ingress and output drag | A seal change can affect protection, service, and output drag; an assumed rating does not verify the assembled joint. | Define the exposure and test target, then record ingress and drag results on the same production-intent assembly. |
| Prototype-to-production variation | Supplier, process, material-form, or drawing revisions can change fit and performance. | Agree revision control, critical inspection points, and pilot acceptance criteria before repeat orders. |
See the Celera Motion installation guide for one motor family’s product-specific retention guidance.
Decision Questions for Sourcing
Choose the architecture
Does every humanoid actuator need a custom housing?
No. Keep a standard housing or module when its envelope, interfaces, duty rating, thermal limits, and environmental protection meet the joint requirements. Consider custom work when a measured integration constraint justifies the added design and qualification effort.
When does custom housing justify its non-recurring cost?
When the current assembly misses a documented envelope, mass, thermal, structural, sealing, or service target and a prototype shows the custom design closes that gap. Compare engineering, tooling, validation, and unit costs at the expected production quantity.
How should torque density be compared?
Use the same torque definition and mass boundary for both candidates. Record peak and continuous or RMS torque separately, along with speed, duty cycle, cooling, and test conditions. A housing label alone does not establish actuator performance.
Thermal and mechanical integration
Can a custom housing improve cooling?
It can provide a designed conduction path into a larger structure, but the result depends on contact, geometry, materials, airflow, nearby heat-sensitive parts, and duty. Validate winding and component temperatures on the assembled joint under the intended motion profile. Source note
Is an interference or shrink fit always best for a frameless stator?
No. Retention methods and limits vary by motor design. Celera Motion lists several approaches and warns against press fits for its kits; it also does not recommend shrink fit as the sole retention method. Follow the selected motor maker’s drawing and installation guidance. Source note
Does using a custom housing automatically improve backdrivability?
No. Backdrivability depends on the full transmission, bearings, seals, preload, alignment, and control. Measure output breakaway and running torque on the assembled unit against the application requirement.
How tight should the housing and bearing tolerances be?
Set them from the selected bearing and motor interfaces, operating temperature range, load cases, and complete tolerance stack. Put functional datums and inspection requirements on the drawing; do not copy a generic H6/H7 or stack-up value without analysis. Source note
Materials, sourcing, and verification
Is 6061-T6 always the best housing material?
No. Select material and product form against structural loads, thermal path, corrosion, joining, machining, and supply requirements. Hydro’s 2019 extrusion datasheet reports a typical 6061-T6/T6511 conductivity value at 25°C; that datum alone cannot choose a finished housing or establish a comparison with 7075. Source note
When is a 3D-printed housing useful?
It can help test packaging and low-cost research prototypes if the material and process meet the loads and temperatures. Berkeley Humanoid Lite documents a 3D-printed modular gearbox; that example is not proof of production life or a substitute for validating your own design. Source note
What should an RFQ say about sealing?
State the required ingress target, contaminants, exposure, temperature, service interval, and acceptance test. Ask suppliers to identify the seal arrangement and measure its effect on output drag for the assembled joint.
What should we test before approving a custom housing?
Check fit and alignment, stator retention, peak and continuous duty, winding and gearbox temperatures, output drag, ingress protection, service access, and repeatability across representative pilot units. Agree limits and test conditions before the RFQ is released.
How long will a custom housing take to source?
There is no reliable universal lead time. Ask each supplier to quote drawing review, prototype, inspection, qualification, and repeat-order timing separately, with assumptions for material availability, quantity, and revision changes.
Next Steps: Compare Candidates in an RFQ
Ask suppliers to return the same evidence for each candidate so a custom design can be compared against a standard module.
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| RFQ input | Specify or disclose | Acceptance evidence |
|---|---|---|
| Duty and thermal boundary | Peak and continuous torque, speed profile, duty cycle, ambient, cooling, and nearby component limits. | Agreed test profile with winding, housing, and gearbox temperatures recorded. |
| Mass and interfaces | Define what is included in mass; provide envelope, mounting, cable, and service-clearance constraints. | Released CAD and drawing review, then measured mass and interface fit on a representative unit. |
| Alignment and retention | Identify motor and bearing part numbers, supplier interface drawings, datums, temperature range, and proposed retention process. | Inspection results and retention/assembly checks agreed with the selected component manufacturers. |
| Ingress and lifecycle | Describe contaminants, exposure, service interval, forecast quantity, and expected revisions. | Ingress and output-drag results, pilot repeatability, and quoted prototype-to-production schedule. |
Inquiry Email
Include target torque/speed, quantity, and delivery location.
Application Engineer
+8618857971991
Talk directly about drawings, torque-speed targets, and RFQ data gaps.
Sources and Reference Verification
Sources include a motor manufacturer installation guide, an aluminum alloy datasheet, and an original research paper. The statements above are limited to those sources and the stated design assumptions. Source check completed on .
- How to Install a Frameless Motor: Installation & Design Guide (opens in a new tab)
Manufacturer installation guide · Celera Motion / Novanta · published 2026-05-18 · Accessed 2026-10-10
Describes several stator-retention methods and explains product-specific limits for press fits, shrink fits, adhesive bonding, and axial clamping.
Limit: Recommendations apply to Celera Motion motor kits. They are not a universal design rule for other motors or assemblies.
- Hydro Alloy 6061: Extruded Mechanical and Physical Property Limits (opens in a new tab)
Manufacturer material datasheet · Revision 2019/01 (2/2019) · Accessed 2026-10-10
Reports typical 6061-T6/T6511 extrusion thermal conductivity of 167 W/m·K at 25°C and minimum mechanical properties by section thickness.
Limit: The value is typical, specific to the listed extrusion data and temperature, and is not a guaranteed property for every product form or finished housing.
- Demonstrating Berkeley Humanoid Lite: An Open-source Humanoid (opens in a new tab)
arXiv preprint · submitted 2025-04-24 · accepted at RSS 2025 · Accessed 2026-10-10
Documents a contrasting low-cost research platform using a modular, 3D-printed actuator gearbox and widely available components.
Limit: This is one research build, not a controlled comparison of custom and standard housings or evidence of production suitability.