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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 Answer 1

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 kg • 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 (62oz·in, 4.5kg·cm) or more holding torque
  • 1.8 or 0.9 degrees 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 Steeper 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 Mendal 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.