Stepper Motor for Prusa i3

Question

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)

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 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:

• NEMA 17 stepper motor, and;
• Stepper motor

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.

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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.

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