Stepper Motors

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Revision as of 20:37, 27 May 2010 by Stephen George (talk | contribs) (Added a number of rules of thumb to help with purchases)
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This page has been flagged as containing duplicate material that StepperMotor also attempts to cover.
These pages should be merged such that both pages do not attempt to cover the duplicate topics.

Holding Torque

It is recommended that you get approximately 13.7 N-cm (that is 1400 g-cm or 19.4 oz-in) of Holding Torque (or more) to avoid issues, although one stepper with less has been used successfully (see below). If in doubt, higher is better. If you need to convert between different units for the torque you can use the torque unit converter here.

Stepping Angle

Most stepper motors used for a Mendel have a step angle of 1.8 Degrees. It is sometimes possible to use motors with larger step angles, however for printing to be accurate, they will need to be geared down to reduce the angle moved per step, which may lead to a slower maximum speed.


If going for the smaller NEMA 14 motors, aim for the high torque option. NEMA 14s are neater, lighter and smaller, but can be hard to get hold of with the appropriate holding torque. NEMA 17s are quite easy to get in the specification that Mendel needs, but are bulkier and less neat. NEMA 14s are running near the edge of their envelope: they will get warm. NEMA 17s are well inside what they can do, and will run much cooler.

Note that any Mendel part that goes on to a Stepper Motor shaft expects the shaft to be roughly 5mm. If the shaft is a different size, you will need to make allowances for this in the parts you obtain/make.


Steppers motors come in several wiring configurations. 4,6, and 8 wires are all fairly common. 5-wire version have been reported to exist. 5 wire versions won't work, the others will. See stepper wiring for more details.


Below is a list of possible suppliers and motors. Please add to it. If you have built a Mendel successfully with a given motor, remember to put true in the tested field.

Stepper Motors - Nema 14 (Smaller, neater and used on the Mendel prototype)
Vendor (with link) Shipping location Manufacturer Model # Datasheet NEMA (Size) Holding Torque Shaft Tested Additional notes
Motion Control Products  ? Fulling Motor FL35ST36-1004B FL35ST36-1004B Datasheet 14 ~13.7 N-cm Dual true Used in mendel prototype
Active Robots UK Wantai 35BYHG04 35BYHG04 Datasheet 14 ~12.3 N-cm 4.9mm true Less Holding Torque than recommended, but has apparently been used successfully
Pololu US SOYO SY35ST36-1004A  ? 14 ~13.7 N-cm 5mm ? Note: Pololu list this motor as 1400 g-cm AND as 20 oz-in (converts to 19.44 oz-in). According to supplier information, the metric value is correct.

Stepper Motors - Nema 17 (larger and generally heavier but with more room to put a higher torque than a Nema 14)
Vendor (with link) Shipping location Manufacturer Model # Datasheet NEMA (Size) Holding Torque Shaft Tested Additional notes
Zapp Automation UK SOYO SY42STH47-1206A SY42STH47-1206A Datasheet 17 ~31.1 N-cm Single true None
Zapp Automation UK SOYO SY42STH47-1684B SY42STH47-1684B Datasheet 17 ~43.1 N-cm Dual true Round Ø5mm Shafts
Zapp Automation UK SOYO SY42STH47-1684A SY42STH47-1684A Datasheet 17 ~43.1 N-cm Single ? D-Shape 5mm shaft with 4.5mm flat
Cool Components UK Mercury Motor SM-42BYGH011-25 SM-42BYG011 Datasheet 17 23 N-cm 5mm  ? None
Interinar Electronics, LLC US Oriental Motors Vexta PX243M-01AA PX243M-01AA Datasheet 17 15 N-cm Single ? Not strong enough for direct drive extruder, Uses Imperial #4-40 TPI mounting holes instead of M3 metric US Lin Engineering 4218L-01-10 4218L-01-10 Datasheet 17 ~53 N-cm 3/16 inch = 4.7625 mm (Round) true None US Lin Engineering 4218L-01-11 4218L-01-11 Datasheet 17 (?) ~53 N-cm ~5 mm = 0.1968 inches (D-Shape) true None US Wantai 42BYGHW811 42BYGHW811 Datasheet 17 ~47.1 N-cm 4.9mm ? None
SparkFun US Mercury Motor SM-42BYG011 SM-42BYG011 Datasheet 17 23 N-cm 5mm true None
Robot Gear AU Mercury Motor SM-42BYG011-25 SM-42BYG011 Datasheet 17 23 N-cm 5mm true None
Mindkits NZ Mercury Motor SM-42BYG011 SM-42BYG011 Datasheet 17 23 N-cm 5mm true None
AusXMods AU Rugao Xinhe 17H185H-04A  ? 17 ~43.8 N-cm  ? ? None
Kysan China Kysan 42BYGH4803 Datasheet 17 49 N-cm 5mm true Successfully tested with Wade's Geared Nema 17 extruder - high flow rates.

Unscientific rules of thumb for motor purchases

1) The longer the motor body generally the more torque the motor has. 2) If a motor is rated 2.5A and your stepper driver produces only 2A your motor may not produce the manufactures rated torque. 3) If a motor is rated 35 volts and your stepper produces only 12 volts your motor may not produce the manufactures rated torque. 4) A motor can exceed it's rated voltage but will produce more heat. This may not be a problem in Bath/England but may be a problem in warmer climes. 5) Stepper Motors should not exceed 65c. 6) ABS melts at 120C but softens at 80C. 7) Power is measured in Watts and is calculated at Volts X Current. 8) Power made available to a motor will be turned into heat and motion. 9) The more power made available to the motor the higher the amount of heat and motion. 10) Power and torque are related. The more power the more torque.