Planetary gearbox
maxon GPX planetary gearbox
Configurable planetary gearheads from 4 mm to 70 mm diameter, with ceramic and ultra-performance versions for higher torque and life.
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What are you specifying?
Select everything you need. A motor, drive and gearbox can be specified together as one axis.
Key specifications
| Outer diameter | 4–70 mm |
|---|---|
| Rated torque (max) | 70 Nm |
| Peak torque (max) | 87.5 Nm |
| Ratio | 3.9–1,526:1 |
| Backlash (max) | 81 arcmin |
Summarised in our own words from maxon group (maxon motor ag)'s published data; series maxima, individual models vary. Last checked 2026-10-29. Source 1 · Source 2 · Source 3
Notes on this data
GPX 70 UP 2-stage: 70 Nm continuous, 87.5 Nm intermittent; GPX 22 ratios 3.9-1526 (4 stages). Other sizes may extend ratio range; not read. Backlash given in degrees: 0.5 deg (GPX 70) to 1.35 deg (GPX 22 4-stage) = 30-81 arcmin; 81 stored (converted). Sizes 4, 6, 8, 10, 12, 13, 14, 16, 19, 22, 26, 32, 37, 42, 52, 70 mm.
Specify Motion is not affiliated with maxon group (maxon motor ag). maxon and GPX are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
maxon GPX replacement and alternative options
Use these supply-network options as a starting point for an engineering check. We can also help source the original maxon part. Published series figures do not establish an exact-model or drop-in replacement: confirm ratings, fit, interfaces and approvals for your application.
Apex Dynamics high-precision helical planetary with a one-piece stainless planet cage and very short length; ADS adds a keyed input shaft for belt pulley or coupling drive.
| Published maximum | GPX | AD / ADR / ADS |
|---|---|---|
| Rated torque | 70 Nm | — |
| Peak torque | 87.5 Nm | — |
| Ratio (max) | 1,526:1 | — |
| Backlash (lower is better) | 81 arcmin | 1 arcmin meets or exceeds |
High-precision round-flange planetary with high input speed capability and near-zero backlash, aimed at robotics and CNC.
| Published maximum | GPX | WAE |
|---|---|---|
| Rated torque | 70 Nm | — |
| Peak torque | 87.5 Nm | — |
| Ratio (max) | 1,526:1 | — |
| Backlash (lower is better) | 81 arcmin | 2 arcmin meets or exceeds |
Hollow-shaft rotary platform reducer with helical gears and crossed roller bearing for low-backlash, high-load indexing.
| Published maximum | GPX | WTN |
|---|---|---|
| Rated torque | 70 Nm | — |
| Peak torque | 87.5 Nm | — |
| Ratio (max) | 1,526:1 | — |
| Backlash (lower is better) | 81 arcmin | 0.5 arcmin 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.
Typical applications
What a planetary gearbox is
A planetary gearbox reduces speed and multiplies torque using a central sun gear driven by the motor, several planet gears on a carrier, and an outer ring gear. Load is shared between the planets, so the gearbox is compact, coaxial and torque-dense. A single stage typically gives ratios of about 3:1 to 10:1, and stages are combined for higher ratios. Precision servo planetaries use ground helical or spur gears, preloaded output bearings and a motor adapter flange, with backlash typically a few arcminutes or less.
When engineers choose a planetary gearbox
Choose a planetary gearbox for most servo and stepper axes that need more torque, lower reflected inertia or a better inertia match. It is efficient, typically above 95% per stage, stiff and widely available in standard frames. The trade-offs are backlash, which is low but not zero, and limited single-stage ratio. For zero backlash in a compact joint, a strain-wave gear suits better. For very high shock loads, a cycloidal reducer may be more robust.
How to specify the maxon GPX
Send these with your enquiry and an engineer can confirm the right GPX variant or an equivalent:
- Ratio and output speed (:1, rpm)
- Nominal and peak output torque (Nm)
- Emergency stop torque (Nm)
- Backlash (arcmin) and torsional stiffness (Nm/arcmin)
- Radial and axial output loads (N)
- Motor flange, shaft diameter and length (mm)
- Duty cycle, mounting orientation and lubrication
Common mistakes to avoid
- Sizing on motor torque times ratio without checking acceleration torque and service factors
- Ignoring the input speed limit at high motor speeds
- Mounting a pulley or pinion that overloads the output bearing
- Forgetting the gearbox efficiency and heat in continuous duty
maxon GPX: frequently asked questions
Can you help replace maxon GPX or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including supply-network options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the maxon GPX?
Configurable planetary gearheads from 4 mm to 70 mm diameter, with ceramic and ultra-performance versions for higher torque and life. Published series figures include outer diameter 4 mm, outer diameter 70 mm, rated torque 70 Nm, peak torque 87.5 Nm. It is made by maxon group (maxon motor ag); Specify Motion can help source it or propose an equivalent.
Who makes the maxon GPX?
The maxon GPX is made by maxon (maxon group (maxon motor ag)) and is listed here for engineers comparing options. Specify Motion is not affiliated with maxon group (maxon motor ag); brand names are used only to identify the product.
What is the outer diameter of the maxon GPX?
The published series minimum outer diameter is 4 mm. Individual models and sizes in the GPX 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 maxon GPX?
We can assess suitable replacement options. On published figures, APEX Dynamics AD / ADR / ADS and Wanshsin WAE are options to assess from our supply network. An engineer confirms the fit against your application before recommending anything.
How do I choose a planetary gearbox ratio?
Start from the load speed and motor speed range, then check inertia matching and torque. A ratio that brings the reflected load inertia close to the motor inertia improves dynamics. Then confirm peak output torque during acceleration is within the gearbox rating and that input speed stays under the limit.
What backlash does a precision planetary gearbox have?
Precision servo planetary gearboxes typically have backlash from below one arcminute to several arcminutes, depending on grade and stages. Lower backlash costs more. For most positioning axes, a few arcminutes is fine; for robot joints or optics, strain-wave or zero-backlash designs are used.
Further reading: How to select a planetary gearbox · Harmonic vs planetary vs cycloidal · Gearboxes and harmonic drives
Other planetary gearbox series
Engineer support
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