Cycloidal gearbox
Sumitomo Drive Technologies Fine Cyclo UA-Series cycloidal gearbox
Double-stage high-torque-density cycloidal reducer with concentric shafts, allowable peak torques from 625 to 30,000 Nm, ratios 60:1 to 283:1 and lost motion under 0.5 arcmin.
Key specifications
| Peak torque (max) | 30,000 Nm |
|---|---|
| Ratio | 60–283:1 |
| Lost motion | <0.5 arcmin |
Summarised in our own words from Sumitomo Heavy Industries, Ltd.'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Notes on this data
Fine Cyclo is a cycloidal reducer; recorded as type planetary because the allowed gearbox types have no cycloidal option.
Specify Motion is not affiliated with Sumitomo Heavy Industries, Ltd.. Sumitomo Drive Technologies and Fine Cyclo UA-Series are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Sumitomo Drive Technologies part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Cup-type strain-wave gear component sets for building your own joint; the LCSG high-torque version lifts capacity by around 30% over the standard LCS.
| Published maximum | Fine Cyclo UA-Series | LCS / LCSG |
|---|---|---|
| Peak torque | 30,000 Nm | — |
| Ratio (max) | 283:1 | 500:1 meets or exceeds |
Hollow-shaft strain-wave gear units with a large central bore for routing cables and services; LHSG is the high-torque version (over 30% more torque).
| Published maximum | Fine Cyclo UA-Series | LHS / LHSG |
|---|---|---|
| Peak torque | 30,000 Nm | — |
| Ratio (max) | 283:1 | 500:1 meets or exceeds |
Ultra-flat cup-type strain-wave gear with a very short axial length, light weight and high stiffness for its size.
| Published maximum | Fine Cyclo UA-Series | LCD |
|---|---|---|
| Peak torque | 30,000 Nm | — |
| Ratio (max) | 283:1 | 500:1 meets or exceeds |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a cycloidal gearbox is
A cycloidal gearbox reduces speed with one or more lobed cycloid discs driven by an eccentric input shaft, rolling inside a ring of pins. Each input revolution moves the disc by one lobe, so high ratios are achieved in a compact stage. Many pins share the load, giving high torque capacity, stiffness and shock resistance. Precision robot types, often called RV reducers, add a planetary input stage and support the output with large integrated bearings. Backlash is typically very low.
When engineers choose a cycloidal gearbox
Choose a cycloidal reducer for heavy, stiff, shock-resistant joints such as robot bases, shoulders, positioners, turntables and machine tool axes. It handles high moment loads and impact better than strain-wave gears. The trade-offs are weight, size and cost compared with planetary units, and some ripple at the output. For compact light joints, a strain-wave gear is lighter. For general servo axes, planetary units are cheaper.
How to specify the Sumitomo Drive Technologies Fine Cyclo UA-Series
Send these with your enquiry and an engineer can confirm the right Fine Cyclo UA-Series variant or an equivalent:
- Ratio (:1)
- Rated and peak output torque (Nm)
- Emergency stop torque (Nm)
- Moment and axial load on output bearing (Nm, N)
- Torsional stiffness (Nm/arcmin)
- Backlash and lost motion (arcmin)
- Input arrangement and motor interface
Common mistakes to avoid
- Ignoring tilting moment from offset payloads on the output bearing
- Not checking emergency stop torque
- Skipping the recommended grease change interval
- Sizing on average torque only
Sumitomo Drive Technologies Fine Cyclo UA-Series: frequently asked questions
What is the Sumitomo Drive Technologies Fine Cyclo UA-Series?
Double-stage high-torque-density cycloidal reducer with concentric shafts, allowable peak torques from 625 to 30,000 Nm, ratios 60:1 to 283:1 and lost motion under 0.5 arcmin. Published series figures include peak torque 30,000 Nm, ratio 60:1, ratio 283:1. It is made by Sumitomo Heavy Industries, Ltd.; Specify Motion can help source it or propose an equivalent.
Who makes the Sumitomo Drive Technologies Fine Cyclo UA-Series?
The Sumitomo Drive Technologies Fine Cyclo UA-Series is made by Sumitomo Drive Technologies (Sumitomo Heavy Industries, Ltd.) and is listed here for engineers comparing options. Specify Motion is not affiliated with Sumitomo Heavy Industries, Ltd.; brand names are used only to identify the product.
What is the peak torque of the Sumitomo Drive Technologies Fine Cyclo UA-Series?
The published series maximum peak torque is 30,000 Nm. Individual models and sizes in the Fine Cyclo UA-Series range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Sumitomo Drive Technologies Fine Cyclo UA-Series?
Yes. On published figures, LeaderDrive LCS / LCSG and LeaderDrive LHS / LHSG are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
What is the difference between a cycloidal and a strain-wave gear?
A cycloidal gear uses rigid lobed discs rolling on pins, giving high stiffness and shock resistance. A strain-wave gear uses a flexible spline, giving compact high ratios and near-zero backlash at lower weight. Cycloidal suits heavy base joints; strain-wave suits lighter, compact joints.
What is an RV reducer?
An RV reducer is a precision cycloidal gearbox with a planetary input stage feeding two or more cycloid discs, plus a large integrated output bearing. The design gives high torque, stiffness and moment capacity in a compact package, which is why it is common in industrial robot joints.
Further reading: Harmonic vs planetary vs cycloidal · How to select a gearbox · Gearboxes and harmonic drives
Other cycloidal gearbox series
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