Stepper Motors
Holding Torque
It is recommended that you need 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.
Stepping Angle
Most stepper motors used for a Mendel have a step angle of 1.8 Degrees. It is something 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.
Size
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.
Suppliers
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 | Unknown | Unknown | FL35ST36-1004B | FL35ST36-1004B Datasheet | 14 | ~13.7 N-cm | Dual | true | Used in mendel prototype |
| Active Robots | UK | Wantai/Phidget (?) | Phidget 3301 | 3301 Datasheet | 14 | ~12.3 N-cm | 4.9mm | true | Less Holding Torque than recommended, but has apparently been used successfully |
| Zapp Automation | UK | Unknown | SY42STH47-1206A | SY42STH47-1206A Datasheet | 17 | ~31.1 N-cm | Single | true | None |
| Zapp Automation | UK | Unknown | SY42STH47-1684B | SY42STH47-1684B Datasheet | 17 | ~43.1 N-cm | Dual | true | 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) | ? | 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/Phidgets(?) | Wantai 42BYGHW811 | 3303 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 | Unknown | 17 | ~43.8 N-cm | ? | ? | None |
