Verify the rating basis
Use C and lead from the same configuration. Keep the example state if the values are illustrative; unknown methods produce no life estimate.
Load spectrum & fatigue
Screw life calculator: L10, travel and hours
Estimate cubic fatigue life from a resolved load profile and rating. Compare configurations, travel and hours, then prepare an engineering review.
Example inputs loaded · cubic / 1 million rev basis only · no automatic model approval
Evaluate a repeating load profile
Example inputs · cubic method
Cubic mean effective load
165.096 N
Candidate A · example
222.222 M rev
Candidate A · hypothetical estimate
- L10 (million rev)
- 222.222
- Total travel (m)
- 222,222.222
- Profile repeats
- 2,777,777.778
- Moving time (h)
- 3,086.42
- Elapsed cycle time (h)
- 7,716.049
- Cycle / max phase-mean rpm
- 480 / 1,200
Conditional cubic fatigue arithmetic for this repeating profile. Elapsed hours include holds; static holding and complete-actuator life remain unassessed.
Candidate B · hypothetical estimate
- L10 (million rev)
- 750
- Total travel (m)
- 750,000
- Profile repeats
- 9,375,000
- Moving time (h)
- 10,416.667
- Elapsed cycle time (h)
- 26,041.667
- Cycle / max phase-mean rpm
- 480 / 1,200
Conditional cubic fatigue arithmetic for this repeating profile. Elapsed hours include holds; static holding and complete-actuator life remain unassessed.
One profile: 80 mm absolute travel; 4 s moving / 10 s elapsed. Peak entered load 300 N. Holds are excluded from the rolling-fatigue sum, not from static or thermal review.
Take the profile into engineering review
Copy/download locally or choose an inquiry channel. The RFQ accepts a one-time brief within ten minutes and clears it when read; closing the tab clears remaining session storage. Internal navigation carries only the source path.
Mini Linear Actuators — screw L10 fatigue review Source: https://minilinearactuators.com/engineering-tools-and-cad/screw-life-calculator Method: cubic load-life; C based on 1,000,000 revolutions; p=3. Effective load path: resolved. Forces must already account for supplier-specific preload/direction treatment. Phase 1: F=200 N; absolute travel=40 mm; duration=2 s. Phase 2: F=100 N; absolute travel=40 mm; duration=2 s. Phase 3: F=300 N; absolute travel=0 mm; duration=6 s. Profile: 80 mm; 10 s elapsed; 4 s moving; peak 300 N. Cubic mean load: 165.0963624 N. Candidate A: C=1000 N; lead=1 mm/rev; basis=example; reference=hypothetical / unconfirmed. L10=222222222.2 rev; travel=222222.2222 m; profile repeats=2777777.778. Moving=3086.419753 h; elapsed cycle=7716.049383 h; mean=480 rpm; max phase mean=1200 rpm. Candidate B: C=1500 N; lead=1 mm/rev; basis=example; reference=hypothetical / unconfirmed. L10=750000000 rev; travel=750000 m; profile repeats=9375000. Moving=10416.66667 h; elapsed cycle=26041.66667 h; mean=480 rpm; max phase mean=1200 rpm. Boundaries: illustrative or supplier-entered arithmetic, not a verified model selection, warranty or complete-actuator service life. Dwell adds elapsed time, not rolling fatigue capacity. Static/peak loads, preload, reversals, short strokes, lubrication, contamination, buckling, speed, thermal limits and actual supply need separate review. Please confirm the rating source, configuration/lead, resolved load path, duty conditions and applicable drawing/CAD revision.
Read the result
Three decisions before using an estimate
Resolve the load path
Obtain effective nut-load magnitudes after preload and direction treatment. Do not cancel signed forces or substitute a simple time average.
Keep the clocks separate
Travel and profile repeats follow from screw turns. Holds change elapsed hours while static holding and temperature still require review.
Calculation method and rating basis
The tool implements the cubic subset documented in Schaeffler TPI 291, page 27 and the ball-screw calculations in Thomson, page 68. Check the selected supplier method before entering C; the tool does not infer a rating definition from a screw type.
| Quantity | Equation / units | Interpretation |
|---|---|---|
| Equivalent effective load | Fm = [Σ(Fi³ × di) / Σdi]^(1/3), N | Fi is already-resolved axial magnitude. di is absolute rolling travel in mm. |
| L10 revolutions | 1,000,000 × (C / Fm)³, rev | C must use the cubic, one-million-revolution reference. |
| Travel and profile repeats | Travel = L10 × lead / 1000, m; repeats = L10 × lead / Σdi | Lead is mm per screw revolution; total profile travel includes all return motion. |
| Moving / elapsed hours | Repeats × moving seconds / 3600; repeats × total seconds / 3600 | Different clocks for the same predicted fatigue travel. |
| Cycle / phase-mean speed | Mean rpm = 60 × Σdi / (lead × Σti); max phase mean = max[60di / (lead × ti)] | Cycle and phase-average kinematics only; actual peak speed needs the motion curve. No speed-limit approval. |
For a constant lead, di = speedi × timei makes distance weighting consistent with speed/time weighting. All motion is counted as positive path length. The implementation normalizes loads before forming the cubic sum; it does not round a small positive load to zero.
Independent arithmetic
Three hypothetical checks
These values are worked examples, not offered products, sample tests or customer results. Use the matching preset above to reproduce each case.
| Case | Entered profile and rating | Hand-checkable result |
|---|---|---|
| Constant load | C = 1000 N; lead = 1 mm/rev; 200 N over 50 mm in 5 s | Fm = 200 N; (1000/200)³ × 1e6 = 125,000,000 rev; 125,000 m; 2,500,000 profile repeats. |
| Stepped cycle | 200 N over 40 mm in 2 s; 100 N over 40 mm in 2 s; 300 N held for 6 s | Fm³ = (200³ × 40 + 100³ × 40) / 80 = 4,500,000 N³. Fm = 165.096 N. At C = 1000 N, L10 = 222.222 million rev. |
| Stationary holding | 200 N; 0 mm travel; 10 s | No rolling-travel denominator. No finite or infinite fatigue-life result; review holding/static limits. |
In the stepped case, the first moving phase contributes 8/9 of the modeled cubic sum, the second 1/9 and the hold zero. Raising only the illustrative C from 1000 to 1500 N gives (1.5)³ = 3.375 times the modeled revolutions. It does not establish a ball-versus-roller advantage.
Distance weighting and the two clocks
For the 80 mm stepped profile at 1 mm/rev, one repeat is 80 revolutions. Dividing the example's L10 by 80 gives 2,777,777.778 profile repeats. Those repeats contain 3,086.42 moving hours and 7,716.049 elapsed-cycle hours.
If the hold becomes longer, the same number of rolling revolutions takes more clock time. That conversion does not assess stationary damage, brake capability or heating. A holding-only requirement belongs in a separate review.
Supplier selection distinguishes fatigue from other service-life limits; see Schaeffler TPI 291, pages 13–14.
| Change, same C and lead | Rolling-fatigue result | Clock / review effect |
|---|---|---|
| Increase a stationary hold | Fm, L10 rev, travel and profile repeats unchanged | Elapsed hours rise; moving hours unchanged. Holding/static/thermal checks remain. |
| Increase duration of a moving phase at unchanged distance/load | Cubic load and fatigue revolutions unchanged | Lower phase rpm and more elapsed/moving hours for the same travel. |
| Add loaded return travel | Recalculate the full distance-weighted load | Return path must be included in each repeat; resolve its effective load direction first. |
| Increase loaded travel at unchanged force | Constant-load L10 rev unchanged; repeat count changes | More turns per repeat consumes the modeled life in fewer repeats. |
Why load-definition errors matter
The cubic relationship magnifies a force-estimate error. The following is normalized arithmetic with all other assumptions fixed; it is not a change you can make to a real screw's rating independently of its configuration.
| Effective-load multiplier | Life multiplier at fixed C | Use in review |
|---|---|---|
| 0.5× | 8× | Revisit the load model rather than treating this as measured life. |
| 0.75× | 2.37× | Revisit the load model rather than treating this as measured life. |
| 1× | 1× | Revisit the load model rather than treating this as measured life. |
| 1.25× | 0.512× | Revisit the load model rather than treating this as measured life. |
| 1.5× | 0.296× | Revisit the load model rather than treating this as measured life. |
| 2× | 0.125× | Revisit the load model rather than treating this as measured life. |
Compare configurations on a common basis
| Compare | What must match or be known | What remains unproven |
|---|---|---|
| C and method | Each candidate source identifies its own cubic, 1e6-rev C | A matching numerical C does not prove identical design or test conditions. |
| Lead and nut configuration | Use the documented C for that lead, nut and preload | Lead is not an independent life-upgrade control in a real catalogue. |
| Profile and operating point | Same resolved application profile; check the required rpm for each lead | Motor torque, critical speed, peak force and heat are not selected here. |
| Commercial and package fit | Request drawings, quotation, availability and validation scope | No price, stock, size, MOQ or cost saving follows from a life ratio. |
Discuss the required evidence before accepting the cost of a larger or more complex axis. A source-aware calculation brief helps define that review; a high calculated number alone cannot choose a supplier.
Applicability and unresolved conditions
THK's selection guidance defines the nominal fatigue population basis and treats preload and sign-changing loads separately. Here, those questions must be resolved before calculation; the unresolved option keeps the profile available for an RFQ while withholding life.
| Condition | Tool behavior / boundary | Next engineering input |
|---|---|---|
| C basis or formula unknown | Candidate life unavailable | Supplier/model/revision, reference revolutions and calculation method. |
| Preload or reversing load unresolved | No effective mean load or life estimate | Supplier-specific effective nut-load treatment, with direction and internal preload. |
| No rolling travel / no loaded travel | No infinite physical-life claim | Static holding, brake, lubrication and failure-mode review. |
| Short stroke, contamination, alignment or lubrication concern | Not resolved by cubic arithmetic | Manufacturer application conditions and validation plan. |
| Peak, buckling, support, radial load or rpm concern | Kinematic speed and entered force do not approve operation | Static/peak limits, end supports, guides and speed checks. |
| Complete actuator or sliding-thread life | Outside this rolling-fatigue method | Motor/gear/seal/electronics data or the applicable wear model. |
L10 describes a specified fatigue model, not average failure time or guaranteed minimum life. A real miniature axis also needs evidence that the required motion can be repeated under its actual environment and maintenance conditions.
Prepare the next engineering decision
Bring the rating document, model/lead/nut configuration, resolved phase loads, absolute travel, cycle timing and application conditions. Use the live brief above for the current values.
Screw life calculation questions
Method and inputs
What does L10 mean in this screw life calculator?
L10 is the nominal rolling-fatigue basis associated with 90% of a population of identical assemblies under the stated model conditions. It is not an individual actuator warranty, a reliability certificate or a prediction of every failure mechanism.
Can I use the same formula for ball and roller screws?
Use this calculator only where the screw supplier specifies the cubic relationship with C referenced to one million revolutions. Schaeffler TPI 291 page 27 documents that method for its roller screws. A screw name alone does not confirm the rating definition; another basis requires the supplier method.
Why is effective load weighted by distance rather than time alone?
Each entered phase contributes load cubed multiplied by its rolling travel. A long stationary hold adds no travel in this model. Speed and time can supply the same weighting through their product, provided the same lead and effective load definition apply.
Can I enter negative push or pull forces?
Enter nonnegative effective load magnitudes after resolving the applicable load path with the supplier. This tool does not cancel signs or solve separate contact paths. Choose the unresolved state when reversal or preload treatment is not yet established.
How should preload and shock factors be included?
Ask the supplier to define the effective nut loads and any applicable modification. No universal preload or shock factor is added here. Enter only the resolved loads consistent with the chosen rating method, or request review without a life estimate.
What is one profile repeat?
It is one repetition of every phase you entered. Include all outbound and return travel and holds. The calculator does not assume that one row is a complete out-and-back cycle; total path is the sum of absolute travel in the profile.
Interpretation and selection
Does a stationary hold increase fatigue life?
It does not increase the calculated revolutions, travel or number of profile repeats. It increases elapsed hours for the same number of repeats. Holding load, static damage, brake behavior and heating need separate checks.
Why is there no result for zero travel or unloaded movement?
A profile without rolling travel cannot define rolling-fatigue life. If all moving phases have zero effective load, this model has no loaded travel to evaluate. Neither state is converted into an infinite physical lifetime.
Why do two candidates with the same C have different travel or hours?
Lead converts revolutions into linear path. At the same entered linear profile, a different lead changes screw turns per profile and rpm. In a real design, C, lead, nut and preload belong to one configuration and must be supplied together.
Is dynamic C the maximum permitted operating force?
No. C is a reference used by the fatigue method. Supplier peak-load conditions, static rating, support, speed and other limits remain independent. A numerical life result does not approve operation at the entered peak force.
Can I use the result for an Acme screw or the whole actuator?
This method covers an eligible rolling screw fatigue calculation. It does not predict sliding-thread wear, motor or gearbox life, seals, feedback, electronics, lubrication intervals or the reliability of a complete actuator.
How can I send the calculation for engineering review?
Use Review this life calculation to carry a one-time brief into the RFQ within ten minutes; it is removed when read and closing the tab clears the remainder. Copy, text download, email and WhatsApp use the same input/result record. If storage is blocked, copy it manually or choose a direct channel.
Sources, verification and ownership
- THK: studying the service life — fatigue definition, reference conditions, preload and direction treatment.
- Thomson: Precision Metric Ball Screws, page 68 — cubic life, speed/time weighting and hours.
- Schaeffler: Roller Screws, TPI 291, page 27 — cubic roller-screw calculation and distance weighting; pages 13–14 discuss further operating/service-life conditions.
Reviewed 22 October 2026 · Published by Mini Linear Actuators. Formula implementation, scenarios, figures and software checks are reproducible calculation evidence. They are not tests of a supplied actuator or customer results. Document references entered by visitors are not independently verified by the calculator.
Review the load spectrum before selecting a model
Use the current result's review action to include its exact record. For an unresolved method or application, send the available rating document and the missing conditions for clarification.
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