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.
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.
|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.|
|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|
|Alltronics.com||US||Lin Engineering||4218L-01-10||4218L-01-10 Datasheet||17||~53 N-cm||3/16 inch = 4.7625 mm (Round)||true||None|
|Alltronics.com||US||Lin Engineering||4218L-01-11||4218L-01-11 Datasheet||17 (?)||~53 N-cm||~5 mm = 0.1968 inches (D-Shape)||true||None|
|Phidgets.com||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.|