NMB PG, GT and GS Hybrid Stepping Motors with Gearboxes Review: Specs, Price and Applications
Updated: 4 days ago
NMB and MinebeaMitsumi’s geared hybrid stepping range combines a two-phase hybrid motor with a reduction gearbox. PG20, PG25, GT42, GT56 and GS42 are distinct families with different ratios, torque limits, electrical connections and backlash. Their smaller nominal output-step angles are useful command scales, but the gearhead’s mechanical limits remain essential to positioning and load selection.
Quick Verdict
Consider these assemblies for an OEM adjustment, pump, valve or indexing mechanism where reduction and compact stepper control fit the load cycle. Select the exact gearhead and winding from current manufacturer data. Check output torque, speed and backlash together; do not multiply motor holding torque by ratio and assume the gearbox can transmit that result indefinitely.
NMB PG, GT and GS Hybrid Stepping Motors with Gearboxes at a Glance
Specification | Details |
Current PG20 ratios | 4.3 / 16 / 27 / 79 / 99; full output-step entries 0.419 / 0.113 / 0.067 / 0.023 / 0.018° |
PG20 rated / instantaneous torque | PG0043: 0.300 / 0.450 Nm; PG0160 and PG0270: 0.550 / 0.825 Nm; PG0790 and PG0990: 1.500 / 2.250 Nm |
Current PG25 rated / instantaneous torque | PG0043-10M100: 0.750 / 1.100 Nm; PG0160/0270: 3.000 / 4.500 Nm; PG0790/1000: 5.000 / 7.500 Nm |
PG electrical configuration | PG20: bipolar, 0.50 A, 8.50 Ω; PG25: bipolar, 1.00 A, 3.00 Ω in current tables |
GT42 ratio / permissible torque | 3.6 / 7.2 / 10 / 20 / 30 ratios; corresponding 0.35 / 0.70 / 1.00 / 1.50 / 1.50 Nm |
GT56 ratio / permissible torque | 3.6 / 7.2 / 10 / 20 / 30 ratios; corresponding 1.25 / 2.50 / 3.00 / 3.50 / 4.00 Nm |
GT electrical configurations | GT42: unipolar, 1.00 A, 3.10 Ω; GT56: unipolar, 0.90 A, 5.80 Ω |
GS42 ratio / permissible torque | 3.6 / 7.2 / 9 / 10 / 18 / 36 / 50 / 100; 0.20 / 0.40 / 0.50 / 0.56 / 0.80 / 0.80 / 0.80 / 0.80 Nm |
GS42 electrical and backlash | Unipolar, 0.85 A, 4.20 Ω; listed backlash 2° or less; nominal output steps down to 0.018° |
Control scope | External driver and controller; shaft feedback or load sensing is a separate system choice |
Price | Request a quote for exact motor, ratio, winding, shaft and operating duty |
Design and Engineering Assessment
Reduction changes both output speed and the mechanical load seen by the motor. It can raise usable output torque and reduce nominal angular movement per motor step, but gearbox efficiency, tooth loading and bearing limits constrain the result. The permissible gearhead torque must be checked independently of the motor’s available torque at speed.
The current PG tables specify torque in mN m, while the GT and GS tables use N m. For example, PG0043-08M000 is rated at 300 mN m, which is 0.300 N m. Keeping those units explicit prevents a thousandfold error. Current PG model codes and limits should also remain separate from older gearhead revisions rather than inheriting an old family-wide table.
Backlash can be larger than a nominal output increment. GS42 at ratio 100 has a 0.018 degree step entry, but its listed backlash is up to 2 degrees. A fine command scale therefore does not guarantee equal bidirectional positioning accuracy. A mechanism that reverses frequently must account for the clearance, compliance and load direction at its actual output.
The GT torque tables also show why increasing ratio is not an unlimited torque multiplier. GT42 ratio 20 and ratio 30 both have a 1.50 N m permissible-torque entry, despite their different speeds and output-step angles. A designer must select from the gearhead limit and the motor curve together, rather than extrapolating from one ratio.
PG20 and PG25: preserve the current model and torque units
PG20 current examples range from PG0043-08M000 at ratio 4.3 to PG0990-08M000 at ratio 99. The corresponding gearhead-length entries are 20, 26 or 32 mm depending on reduction. These are gearhead lengths, not the complete motor-and-gearbox envelope.
PG25 uses its own -10M100 references and rated limits, reaching 5.0 N m for the listed ratio 79 and 100 models. Its 1.00 A bipolar winding differs from the 0.50 A PG20 configuration. Specify the full model, output shaft and drawing before comparing electrical settings or replacement fit.
GT42 versus GT56: torque, speed and backlash
The GT42 family lists a permissible output-speed range ending at 500 rpm for ratio 3.6, 250 rpm for 7.2, 180 rpm for 10, 90 rpm for 20 and 60 rpm for 30. These are permissible speed entries, not proof that maximum torque is available at every point with any drive supply.
GT56 uses the same listed ratio progression with higher permissible torque. Its backlash entries are 35 arcmin at ratio 3.6, 15 arcmin at 7.2 and 10, and 10 arcmin at 20 and 30. GT42 instead lists 45 arcmin for ratio 3.6 and 25 arcmin for the other compared ratios. Compare the actual reversal requirement rather than choosing solely by frame size.
GS42: reduction range and mechanical error budget
GS42 provides ratios through 100 with output-step entries down to 0.018 degrees. Its permissible torque reaches 0.80 N m at ratio 18 and remains at that value through the higher ratios listed here. Higher reduction continues to change speed and command scale without increasing the listed torque ceiling.
The 2 degree-or-less backlash entry is important for reversal and load changes. If the process needs a smaller output error, evaluate a different gearbox, a one-direction approach strategy or direct load feedback as appropriate to the mechanism. Motor-side pulse counts alone do not measure the output shaft through gear clearance.
Electrical connections and duty
Current PG examples are bipolar, while the reviewed GT and GS tables list unipolar drive sequences. Those are different electrical arrangements, so a shared stepper label does not establish driver compatibility. Match the winding connection, phase current and excitation sequence to the purchased reference.
Evaluate acceleration, running and holding portions of the cycle. A stationary energized motor still produces heat, and repetitive starts can create a different thermal duty from steady running. Check the exact motor curve, supply and installation conditions alongside the gearhead’s permissible torque and speed.
Mechanical installation and load support
Use the full assembly drawing for pilot, mounting pattern, shaft projection and cable clearance. A quoted frame or gearhead length does not establish the complete envelope or permissible overhung load. Support the driven mechanism appropriately and avoid forcing a misaligned coupling onto the output shaft.
A reduction gearbox should not be assumed to prevent backdriving or safely hold a gravity-loaded mechanism. Define the required holding, braking and isolation arrangements from the actual machine loads. Neither energized motor torque nor gear reduction is a universal substitute for those functions.
Commissioning and alternative selection
At low limits, verify the actual output direction, ratio and travel per pulse. Test loaded reversals and reference repeatability, then qualify the representative warm motion cycle. Include a jam, power interruption and any required load-holding response in the machine’s acceptance plan.
Compare PG, GT and GS at the same permissible output torque, speed, reversal error and life requirement. A PM geared motor is a separate product class, while a closed-loop servo gearmotor changes feedback and control scope. Request a complete configuration quotation and retain the motor, gearhead and drive settings together for service.
Applications and Selection
The manufacturer identifies optical equipment, pumps and analyzers, flow-control valves and related OEM mechanisms for geared hybrid selections. Choose the exact family by its output duty, mechanical error budget, electrical architecture and environmental requirements; a component application example does not qualify a finished medical or safety-related device.
For NMB PG, GT and GS Hybrid Stepping Motors with Gearboxes, define the actual machine duty before selecting an ordering configuration. Include the required operating point, available installation space, environment and control interfaces. The specification table describes the product or family; the surrounding machine determines which of those features matters for the intended job.
Price and Value
Price: Request a quote for the exact configuration. Compare the product, compatible control equipment, required mechanical parts, cabling and commissioning as one installed system. A component price alone does not represent the cost of a working automation axis.
Evaluate an alternative against the same duty and acceptance criteria. Match the continuous operating requirement first, then compare transient capability, feedback, mechanical fit and support. This avoids choosing between superficially similar products whose ratings describe different operating conditions.
Pros and Cons
Advantages
Several gearbox families offer distinct torque and reduction choices
Current tables distinguish rated or permissible torque from instantaneous limits
GT provides documented backlash entries for an explicit selection
Motor and reduction gearbox arrive as a matched mechanical assembly
Limitations
Gear backlash can dominate nominal step resolution
Higher ratio does not necessarily raise permissible output torque
Bipolar and unipolar configurations require different electrical matching
External control, position assurance and machine holding provisions remain necessary
Who Should Consider NMB PG, GT and GS Hybrid Stepping Motors with Gearboxes?
Consider these geared hybrid families when a compact OEM mechanism needs a defined reduction ratio and stepper drive architecture. Specify permissible torque and speed, backlash, load support and power-loss behavior together, then validate the selected assembly under the actual load cycle.
NMB PG, GT and GS Hybrid Stepping Motors with Gearboxes FAQ
Are PG, GT and GS the same geared motor?
No. They are distinct geared hybrid families with different ratios, torque limits, electrical arrangements and backlash. Keep the exact full model and current manufacturer table with the machine specification.
Is 300 mN m equal to 300 N m?
No. 300 mN m equals 0.300 N m. The current PG tables use mN m, while the reviewed GT and GS permissible-torque columns use N m. Preserve units before comparing values.
Does the highest ratio always provide more output torque?
No. For example, GT42 ratios 20 and 30 both list 1.50 N m permissible torque, and GS42 higher ratios remain capped at 0.80 N m. Check the actual gearhead limit.
Does a 0.018 degree output step guarantee that positioning accuracy?
No. It is a nominal command increment. Gear backlash, compliance, mounting and load behavior affect the result; GS42 lists up to 2 degrees backlash despite its finest step entry.
Can one driver be used for all these families?
Not automatically. The current PG examples are bipolar, while the reviewed GT and GS tables specify unipolar sequences with different phase ratings. Match the purchased winding and connection arrangement.
Will the gearbox safely hold a load when power is lost?
Do not assume it will. Backdriving and holding depend on the exact assembly and external load. Specify an appropriate brake or other holding provision if the machine requires it.
What should be checked during commissioning?
Verify output direction, ratio, travel scale, loaded reversals, reference behavior and temperatures. Test the required responses to obstruction, power loss and external forces with the actual mechanism.
What is the price?
Request a quote for the exact motor, gear ratio, shaft, winding and required duty. Include the compatible drive, controller, load support and any feedback or holding provisions needed for the complete axis.
Prices are indicative and may change. Confirm the final configuration, commercial terms and delivery schedule before ordering.
