Hybrid calculator + report
Run the load-life screen first, then use the report to judge package fit, evidence, and limits for 1.5 mm inverted micro-actuators.
Decision summary
These conclusions keep the tool and report aligned: the calculator is a triage screen, while the report explains why a warning or resize result should not be overridden without engineering data.
The 1.5 mm inverted format is strongest when the nut must become part of the actuator package. If length is not the limiting factor, a standard planetary roller screw is usually lower risk.
Evidence: Architecture choice, manufacturing complexity, and internal Micro-RV packaging data.
Treat 100 N as the conservative continuous-duty screen. Loads above 100 N can be investigated, but need duty-cycle, lubrication, preload, and thermal review before quoting.
Evidence: Internal Micro-RV preliminary load table plus L10 screening assumptions.
Peak or theoretical capacity is not a published continuous catalog limit for this package. The calculator now blocks combinations above the conservative 1.5 mm review envelope.
Evidence: Public size-specific empirical data remains limited; use project validation.
A 1.5 mm screw cannot be responsible for side load, moment load, or actuator alignment. The application must include rails, bushings, or a guided carriage.
Evidence: Roller screw selection practice and micro-scale package constraints.
Fig 1. Conceptual inverted roller screw cross-section, not a manufacturing drawing. Actual roller count, thread form, preload, and housing interface are project-specific.
Specifications
Values below are screening inputs for this page. Final use requires project drawings, inspection plans, lubricant selection, and life-test criteria.
| Parameter | Screening Value | Boundary / Limitation | Source |
|---|---|---|---|
| Nominal screw diameter | 1.5 mm | Axial load only; radial and moment loads require external guides. | Internal Micro-RV preliminary specification. |
| Nut outer diameter | From 5.5 mm | Quote-specific wall thickness, preload, recirculation clearance, and housing interface must be confirmed from drawings. | Internal package concept, not a public guaranteed catalog value. |
| Lead used by calculator | 0.5 mm | Other leads change linear speed, efficiency, self-locking behavior, and calculated life. | Internal Micro-RV preliminary specification. |
| Preliminary dynamic capacity | C_a 0.8 kN | Used only for RFQ triage under clean axial loading; not a warranty or final catalog rating. | Internal Micro-RV preliminary specification. |
| Continuous axial load screen | <=100 N | 100-300 N requires load-spectrum review. Above 300 N should resize or move to a larger RVi package. | Conservative engineering screen from internal data. |
| Stroke screen | <=30 mm | Longer travel increases nut length, buckling sensitivity, critical-speed risk, and alignment sensitivity. | Micro package design rule; verify by application geometry. |
| Speed screen | <=1,500 RPM | Higher speed needs heat, lubricant shear, preload torque, and motor integration review. | Conservative calculator boundary for this page. |
| Positioning target | Drawing-specific, often <5 um backlash target | Preload improves backlash but increases friction and temperature. Absolute zero backlash should not be specified unless needed. | Application-specific metrology requirement. |
Evidence
Public manufacturer pages support the general roller screw selection logic. Size-specific values for this 1.5 mm inverted package are internal preliminary data and must be confirmed per project.
| Source | Supports | Confidence |
|---|---|---|
| SKF planetary roller screw product guidance | General roller screw architecture, load-life selection practice, and the need to validate application conditions. | High for general roller screw principles; not size-specific to this 1.5 mm inverted custom package. |
| Schaeffler linear motion product guidance | Public manufacturer context for linear motion components and application-level selection. | High for category context; use internal drawings for the 1.5 mm inverted geometry. |
| Internal Micro-RV preliminary specification | 1.5 mm nominal diameter, 0.5 mm lead, preliminary C_a 0.8 kN, C_0a 1.2 kN, and G3/G5 accuracy options. | Medium until confirmed against project drawings, heat treatment, lubrication, and inspection records. |
| Public data gap | There is not enough public empirical data to claim >600 N continuous operation at this 1.5 mm inverted package size. | High as a limitation. Treat high-load claims as engineering-review territory, not self-serve catalog selection. |
| Option | Best For | Tradeoff |
|---|---|---|
| 1.5 mm inverted roller screw | Shortest actuator stack, integrated nut/rotor concepts, medical or optical micro-actuation. | Highest manufacturing risk and narrowest validation window. Use only when the short package pays for the complexity. |
| 1.5 mm standard planetary roller screw | Small diameter with less packaging pressure and easier inspection access. | Longer actuator body than inverted architecture, but usually simpler and less costly. |
| 2-3 mm inverted RVi package | Loads above the 1.5 mm conservative envelope or strokes beyond 30 mm. | Larger envelope, but better margin for preload, heat, buckling, and manufacturability. |
| Micro ball screw | Lower load, lower cost, and smoother sourcing when life margin is modest. | Lower load density than a roller screw and may need a longer nut for the same force margin. |
Assumptions: 60-90 N intermittent axial load, <=10 mm stroke, guided jaw.
Screen: Usually within the continuous envelope if thermal duty is low and the jaw carries side load.
Next action: Send CAD section, cycle target, and gripping duty profile.
Assumptions: Short insertion stroke, sterilization-compatible lubricant, low backlash target.
Screen: Technically plausible, but validation must include lubricant, preload torque, and regulatory material constraints.
Next action: Start with prototype risk review before locking preload or material.
Assumptions: Low force, fine motion, high repeatability, and compact motor integration.
Screen: Strong fit when the inverted nut shortens the mechanism and load stays well below 100 N.
Next action: Request lead accuracy, backlash, and cleanliness requirements.
Assumptions: >30 mm stroke or sustained load above 100 N.
Screen: Not the default 1.5 mm use case; buckling, critical speed, and heat margin dominate.
Next action: Compare against the 2-3 mm inverted RVi family.
Related paths
Use these pages to compare the 1.5 mm inverted roller screw against larger RVi packages, product families, engineering review, and manufacturing constraints.
| Risk | Impact | Control |
|---|---|---|
| Peak load mistaken for continuous capacity | Overheated preload, rapid wear, and misleading life estimates during qualification. | Use <=100 N for self-serve screening; require engineering review above 100 N and block above 300 N. |
| Side load or misalignment carried by the screw | Uneven roller contact, backlash drift, and early surface fatigue. | Use external guides and specify allowable radial/moment load separately from axial force. |
| Over-specified zero backlash | Unnecessary preload raises torque and heat in a package with little thermal mass. | Specify the real repeatability target first, then choose preload and inspection method. |
| Cleanroom or medical lubricant mismatch | Viscous drag, particle risk, or failed sterilization validation. | Qualify lubricant and material stack before final life testing. |
| Long stroke at 1.5 mm diameter | Lower critical-speed margin and a longer nut that defeats the package advantage. | Resize to a larger inverted RVi package when stroke exceeds 30 mm. |
No. Treat this page as a technical screening page for a custom 1.5 mm inverted roller screw. Final dimensions and ratings require drawings and inspection records.
The package is extremely small, so preload heat, lubrication, and alignment can dominate the theoretical load rating. The calculator is built for RFQ triage, not final design release.
Possibly, but not as a self-serve continuous-duty assumption. Above 100 N needs duty-cycle and thermal review; above 300 N should usually resize or move to a larger package.
The page uses a simplified L10-style life screen from preliminary dynamic capacity, axial load, speed, lead, and stroke. It excludes shock, contamination, side load, and preload heat.
No. The screw should be treated as an axial transmission element. Rails, bushings, or a guided carriage must carry radial and moment loads.
Choose the larger family when load exceeds the conservative 1.5 mm envelope, stroke is longer than 30 mm, or the actuator needs more thermal and preload margin.
It can be investigated with preload and precision grinding, but the right target depends on repeatability, torque budget, lubricant, and inspection method.
Send axial load, stroke, speed, duty cycle, life target, packaging envelope, backlash or repeatability target, lubricant constraints, and any sterilization or cleanliness requirements.
No. It is a preliminary package target. Final outer diameter depends on thread form, roller count, preload, material, heat treatment, and how the nut interfaces with the actuator.
Only after project-specific material, cleanliness, sterilization, biocompatibility, and regulatory validation. This page does not claim medical approval.
A custom micro inverted roller screw commonly needs a drawing review, process setup, grinding, inspection, and life test planning. Exact timing should be quoted after specs are confirmed.
Keep the result as a prototype-review signal. Send the load spectrum and CAD package so the design can be checked for heat, preload, stroke, and alignment risks.
Include axial load, stroke, speed, duty cycle, life target, packaging envelope, backlash or repeatability target, guide structure, lubricant restrictions, and any cleanroom, sterilization, or material constraints.
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