Use the tool first to get an immediate fit decision, then use the report layers to verify assumptions, understand risk boundaries, and choose the next engineering action.
Input your torque, ratio, duty, and backlash target to get a first-pass fit decision.
No result yet.
Run the checker to see stage recommendation, estimated efficiency, and next action.
Published stage windows consistently place 3-10 in one stage, 10-100 in two stages, and 100+ in three stages. Start sizing from ratio architecture before micro-optimizing backlash.
Public catalog ranges show approximate baselines near 97% (1-stage), 94% (2-stage), and 91% (3-stage), so ratio splitting impacts thermal and motor margin.
Vendor baseline classes often widen from roughly 6-8 arcmin to 10-12 arcmin as stage count rises. Tight positioning projects need reduced-backlash classes or topology changes.
Duty hours, load profile, and starts/hour can move service factor from below 1.0 toward 2.0+, dramatically changing the rated torque requirement.
When ratio, backlash, or torque demand crosses tool boundaries, the best next step is engineering review with dimensional, stiffness, and thermal confirmation.
Numbers below are used as screening anchors. They are not universal guarantees and must be confirmed against target frame/model.
| Metric | Published Range / Example | Why It Matters | Source Family |
|---|---|---|---|
| Typical stage ratio windows | 1-stage: 3-10 | 2-stage: 10-100 | 3-stage: 100+ | Primary architecture split for quick sizing | Neugart Wiki + APEX PGII |
| Published efficiency baseline | 97% / 94% / 91% (1/2/3-stage) | Higher stages increase thermal and motor margin pressure | APEX PGII |
| Typical backlash baseline | 6-8 | 8-10 | 10-12 arcmin | Precision target can invalidate stage choice | APEX PGII backlash classes |
| Linear error intuition | 1 arcmin ≈ 2.91 mm at 10 m radius | Small arcmin numbers can still create visible endpoint drift | APEX backlash article |
| Service factor baseline examples | 0.8 to 2.25+ by duty/load class | Rated torque checkpoint can more than double | Von Ruden duty class table |
| Scenario | Good Fit Signal | Not-Fit Warning | Decision Note |
|---|---|---|---|
| Servo indexing, moderate ratio, medium precision | Planetary usually fits quickly | If ultra-tight repeatability is <1-2 arcmin without upgrade budget | Start with 1-2 stage screening and reduced-backlash options. |
| High ratio with compact envelope constraints | Planetary works if thermal margin is controlled | If duty and starts force oversized frames beyond envelope | Check stage split and derating before locking flange geometry. |
| Continuous heavy shock load | Possible with high service factor allowance | If procurement assumes nominal torque without load class margin | Service factor and torsional stiffness verification become mandatory. |
| Extreme zero-backlash positioning | Possible only with premium reduced-backlash classes | If project budget only supports standard backlash classes | Compare planetary premium classes vs harmonic/cycloidal alternatives. |
The tool combines boundary validation, stage architecture rules, duty-based service factor, and backlash class screening.
Boundary states intentionally stop overconfidence and route you to manual engineering review.
| Step | Logic | Output |
|---|---|---|
| Input normalization | Validate torque, ratio, duty, starts/hour, and backlash target; reject non-physical boundaries (e.g., >24 duty hours/day). | Clean numeric input with explicit fail-fast errors |
| Stage architecture selection | Auto-map ratio to 1/2/3-stage unless the user explicitly overrides stage mode. | Candidate stage count and baseline ratio corridor |
| Torque and service-factor checkpoint | Estimate output torque from motor torque × ratio × stage efficiency; scale with peak factor and duty-derived service factor. | Rated torque checkpoint for shortlist filtering |
| Backlash boundary screening | Compare target backlash to stage baseline bands; flag review/no-go when target is tighter than baseline class. | Go / review / boundary status with explicit next action |
This comparison is decision-oriented. Unknown/partial values are explicitly marked instead of guessed.
| Option | Strength | Tradeoff | Data Confidence | Typical Fit |
|---|---|---|---|---|
| Planetary gearbox | Balanced torque density and industrial availability | Backlash usually not the absolute minimum without premium class | Strong public data availability | General automation axes and OEM machines |
| Harmonic drive | Very low backlash potential in precision robotics | Cost and lifecycle sensitivity under shock can be constraints | Comparable public data often vendor-specific (partial) | Ultra-precision compact joints |
| Cycloidal reducer | High shock resistance and torsional stiffness potential | Integration envelope and sourcing complexity can increase | Public comparables vary by vendor and frame | High-load robotic or indexing systems |
| Worm gearbox | Simple architecture and cost accessibility | Efficiency and backlash are usually weaker for precision servo use | Broad but less precision-focused comparables | Cost-sensitive, lower precision duties |
Risks are grouped by misuse, cost, and scenario mismatch so each has an executable mitigation.
| Risk | Trigger | Impact | Mitigation |
|---|---|---|---|
| Precision misfit risk | Backlash target defined late or ignored during ratio selection | Positioning error and rework after pilot | Freeze backlash budget at concept stage and validate class before PO. |
| Thermal/rated torque risk | Nominal torque used without duty and service-factor uplift | Overheating or premature wear under real cycle load | Apply duty/load-class factor and run conservative scenario before shortlist. |
| Layout interface risk | Inline vs right-angle chosen by packaging only | Mounting, stiffness, and maintenance tradeoffs discovered too late | Review interface, stiffness, and access constraints together in pre-RFQ checklist. |
| Procurement expectation risk | Tool result interpreted as final model release | Commercial commitment before engineering closure | Treat quick screen as gate-0 only; require engineering sign-off for final BOM. |
| Scenario | Premise | Process | Outcome |
|---|---|---|---|
| Pick-and-place axis retrofit | Need 10:1 ratio, moderate duty, <=8 arcmin target, compact inline envelope | Tool yields 1-stage or 2-stage candidate depending on torque margin. Team runs conservative mode to test thermal headroom. | Shortlist narrowed to two frame sizes; engineering review requested for flange fit before sample PO. |
| High-cycle packaging line | Starts/hour spikes during indexing; procurement initially used nominal torque only | Service-factor uplift in tool changes rated torque checkpoint and pushes one frame size up. | Avoided undersized selection and reduced pilot failure risk at commissioning. |
| Ultra-tight motion budget project | Backlash target below standard class while ratio requirement stays high | Tool flags review/no-go boundary and recommends reduced-backlash class or alternative topology review. | Project avoids false certainty and starts topology comparison earlier. |
Is this tool a final model selector?
No. It is a fast screening layer for architecture and risk gating. Final selection still requires engineering confirmation.
Why does stage count matter so much?
Stage count shifts both efficiency and backlash baseline. It changes thermal margin and achievable precision class at the same time.
Can I force stage count manually?
Yes. Manual stage mode is useful for what-if checks, but forced settings can violate ratio/backlash feasibility.
What if my ratio is outside 3 to 1000?
The checker enters boundary mode and asks for manual engineering sizing to avoid false confidence.
How should I interpret backlash numbers?
Use backlash as a motion-budget input, not a marketing label. Arcmin values must be tied to endpoint displacement tolerance.
Why can a low backlash target trigger review even when torque is feasible?
Because standard stage classes may not meet the target. Precision class upgrades or topology alternatives can be required.
Why do balanced and conservative modes differ?
Conservative mode increases service-factor pressure and lowers efficiency assumptions to expose risk earlier.
What is the most common sizing mistake?
Locking frame size on nominal torque without duty-cycle and starts-per-hour uplift.
What should be included in RFQ after using the checker?
Include torque profile, ratio, backlash target, duty hours/day, starts/hour, motor model, and layout constraints.
When should we compare against harmonic or cycloidal?
When target backlash is significantly tighter than standard planetary classes or when stiffness/shock priorities dominate.
Can right-angle and inline be treated as interchangeable?
Not safely. They often differ in envelope, interface behavior, and torque packaging constraints.
How do we reduce project risk after a go result?
Run conservative-mode confirmation, complete interface checks, and require engineering sign-off before purchase release.
Source-backed fields are listed below with checkpoint date. Any non-source value is explicitly treated as heuristic.
| Source | Checkpoint Date | Data Used | Link |
|---|---|---|---|
| APEX Dynamics PGII product page | Snapshot checked: 2026-05-06 | Stage ratio sets, efficiency values, backlash ranges | https://www.apexdyna.nl/en/products/industrial-planetary-gearboxes/pgii-series |
| APEX Dynamics backlash explainer | Snapshot checked: 2026-05-06 | Arcmin-to-linear deviation example and backlash context | https://www.apexdyna.nl/en/gearboxes/backlash-planetary-gearbox |
| Neugart PSFN product page | Snapshot checked: 2026-05-06 | Efficiency and reduced backlash class examples | https://www.neugart.com/en-us/products/planetary-gearboxes/psfn |
| Neugart technical wiki | Snapshot checked: 2026-05-06 | General stage ratio windows and selection context | https://www.neugart.com/en-us/wiki |
| Von Ruden planetary gearbox guide | Snapshot checked: 2026-05-06 | Duty/load-class service factor table concept | https://www.vonruden.com/planetary-gearbox/ |
After screening on this page, continue with adjacent decision modules based on your project stage.
Inquiry Email