Some of our stepper motors are equipped with PG series gearboxes, such as the 17HS15-1684S-PG27. PG series gearboxes differ from the conventional EG series gearboxes we sell separately and are not interchangeable with them.
Key Differences Between PG Series and Conventional Gearboxes
1. Input Shaft Design
Unlike conventional gearboxes that connect to the motor shaft via a coupling, PG series gearboxes require the motor shaft to be specially machined—for example, as a gear shaft or splined shaft.
Because of this specialized shaft machining, motors used in PG series gearbox assemblies are not compatible with conventional gearboxes. Conversely, standard motors have unmodified shafts that are not compatible with PG series gearboxes.
Important: Due to the compact size of NEMA 8 PG series gearbox motors, reassembly after disassembly is extremely difficult. Do not attempt to disassemble the gearbox, as it may not be possible to reassemble it properly.
2. Gearbox Size
Because the PG series gearbox connects directly to the internal gears without requiring a coupling, its overall length is shorter than that of the conventional EG series.
3. Reduction Ratios
The internal structure of PG series gearboxes differs from that of EG series gearboxes. The tooth counts of the planetary gears and sun gear result in reduction ratios that are generally non-integer values. For example, the 23HS22-2804S-PG15 has an actual reduction ratio of 15.3. If your application requires an integer reduction ratio, please select a different gearbox series.
4. Backlash and Accuracy
As a cost-effective product in our lineup, the PG series gearbox motor is designed with a trade-off in precision compared to our premium gearbox lines. The backlash of EG series gearboxes sold separately is generally ≤20 arcmin, while the backlash of PG series gearboxes is generally ≤3 degrees (≤180 arcmin). Although the precision is lower than that of other gearbox series, PG series gearbox motors remain a good choice for applications where high accuracy is not critical.
