We have stepper motors with these specs:

  • 1200 mA
  • 4 V
  • 3.2 kg • cm

Are these enough for building a Prusa i3 3D printer?

(I live in Turkey and these are the specs of the NEMA 17 they sell in here)

  • 1
    $\begingroup$ Pet peeve: Torque is measured in kg·cm, not kg/cm. $\endgroup$ – Tom van der Zanden Jan 30 '17 at 22:50
  • $\begingroup$ Hi TuanSSM. This question is too vague. I can link you 3d printers that work off Lego kits. Or ones made from DC motors from HP printers. If there was an electronics you were looking to use or so on.. we could help. $\endgroup$ – StarWind0 Jan 30 '17 at 23:00
  • $\begingroup$ Are they really 32 kg•cm, and not 3.2 kg•cm (or 32 N•m)? That seems either awfully high, or I am reading it wrong..? $\endgroup$ – Greenonline Jan 31 '17 at 3:55

Awful answer, I know, but it depends... on where you are going to employ them:

  • are they are all, or just some, of the axes, or;
  • just for the extruder?

If they are for use in translating movement of the axes, then the weights of:

  • the y-axis plate;
  • the x-axis carriage, and;
  • the print head,

will all come into play - amongst many other things.

With a torque of just 32 N • cm1, they seem, at first glance, to be a little underpowered - a torque of 44 N • cm (4.5 kg·cm) is the recommended minimum. Also, the current, of 1.2 A, seems to be a tad on the low side, 1.5 - 1.8 A is recommended.

There are some great resources on the RepRapWiki. See:

The minimum (recommended) specifications, for a Nema 17 stepper motor, are:

  • 1.5 A to 1.8 A current per phase
  • 1 to 4 V
  • 3 to 8 mH inductance per phase
  • 44 N·cm (62 oz·in, 4.5 kg·cm) or more holding torque
  • 1.8° or 0.9° per step (200/400 steps/rev respectively)

You may be able to get yours to work, but is it worth the hassle, just to save a few quid? Best to get the recommended, and most popular steppers, which are:

  • Kysan 1124090/42BYGH4803;
  • Rattm 17HS8401, and;
  • Wantai 42BYGHW609

Obviously, you don't have to use one of these three motors - other stepper motors can be used. On the Nema 17 Stepper motor link, above, there is a table of a number of stepper motors, of various makes and models, that have been proven to work.

Further Reading

Motors, a thread on the RepRap forums - specifically for the Prusa Mendel v2, so not entirely related to the i3, as the steppers for the z-axis are less than those for the x and y axes, but it is a good informative read nevertheless.

1 I assume that you actually mean either 32 N • cm, or 3.2 kg • cm.


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