Thing-O-Matic: New X Axis Stepper Motor

New X axis 34 mm NEMA 17 motor in place
New X axis 34 mm NEMA 17 motor in place

A group of 34 mm NEMA 17 steppers arrived from the usual eBay seller, I wired one up, and popped it in place under the original cork sheet. The bolts sit on steel washers riding atop compliant bushings from the batch of 43 mm NEMA 17 steppers that drive the extruder and Y axis.

[Update: Not that you’ll ever find another one, but here’s the straight dope directly from the motor label…

  • Astrosyn P/N FH5-1043 02
  • Minebea 17PM-J034-P2VS
  • No. T6Z01-03


Putting a cork sheet under each motor was a nice idea, but  it didn’t work as intended: the bolts quite effectively couple the vibration to those resonant acrylic and plywood sheets. I had to cut the two front bushings in half to ease the bolt heads under the X axis stage at that end of its travel, but the motor is now isolated from the Y stage. I’m sure the bolts touch the slots, but even I am unwilling to fit compliant bushings around the bolts.

Lashing the cable to the side of the box should suffice for strain relief, as the jacket forces it to flex in a large upward loop with no sharp bends.

X axis motor wire strain relief
X axis motor wire strain relief

That picture’s inverted so the flash lights up the stuff sticking out of the bottom of the box. The thin silvery arch is a cable tie around the motor connector holding it securely against the motor frame, but the Y axis follower bearing just to its right actually sticks out slightly more.

This motor has six active terminals and could run in either unipolar or bipolar mode. The wiring harness has four leads and that’s why I bought it: the MBI driver board expects a bipolar motor.

The winding resistance is a mere 2 Ω, compared to the MBI motor’s 35 Ω. Of course, I don’t have any specs for this motor, but similar Minebea 17PM-J0xx motors run around an amp with 130-180 mN·m of pull-in torque, compared to the MBI motor’s 14-ish mN·m. I expect to run it around 500-750 mA at half the rated torque, where it’ll dissipate maybe a watt, tops, with no overheating.

19 thoughts on “Thing-O-Matic: New X Axis Stepper Motor

  1. How is it possible that the Minebea motors have an order of magnitude more pull-in torque than the MBI motors for similar size and wattage?

    1. That’s a very good question for which I don’t have an answer. It’s possible Kysan just dropped a zero from the numbers along the Y axis of the graph, but I’ve never heard anybody suggest that’s the case.

      What I know: using motors with more torque produces a major win!

    2. Awe, Ed,

      Just give us the number. Let us muck around looking for the motor which you have the only one in the WORLD! of…. (smile).

      1. Who knows? The usual eBay supplier(s) might unearth another stack…

        X axis

        • 34 mm case
        • Astrosyn FH5-1043
        • Minebea 17PM-J034-P2VS
        • No T6Z01-03

        Y axis and geared extruder

        • 38 mm case
        • Minebea-Matsushita 17PM-K150-P1V
        • No T6824-02

        I’ll stick those in the original posts, just so other folks need not go a-digging in the comments…

  2. Are these Kysan motors your using? Iv been on the hunt for some replacement motors myself, just curious of the specific motors you used? Sounds very promising.

    1. Are these Kysan motors

      Nope, they’re not-quite-random Minebea motors from eBay.

      I picked ’em based the usual inadequate product descriptions. Pretty much any bipolar motor with a winding resistance in the 2-to-5 ohm range should work; it’s hard to find anything with a pull-in torque as low as those Kysans.

      The only trick for the X axis motor is finding a 34 mm housing that will fit inside the Y stage; that took a while. I used a 38 mm motor for the Y axis and stepper extruder, but I think you could get away with 34 mm motors everywhere.

      The post for today (5 May 2011) summarizes what I’ve figured out about the original motors…

      1. So you also replaced the stock extruder stepper? I was just going to pickup the Y axis motor from automation direct. But have been unsure about the X axis one.

        1. replaced the stock extruder stepper

          I printed out a geared extruder that works wonderfully well.

          Recent reports of the MK6 direct drive extruder “missing steps” under what seem to be ordinary circumstances suggests that the hulking MBI motor suffers from exactly the problems described here; the puny-by-comparison stepper I’m using has no such troubles.

          1. Ya wouldn’t happen to have a model number for the X axis stepper you used would ya? =)

            1. It’s a Minebea custom motor that doesn’t appear in their datasheets, so the number really doesn’t make much difference: you’ll never find another one like it!

              With that said, though, the X stepper is from their 17PM-J0xx series… which simply means it has a 34 mm case length.

              However, the Y axis stepper is another custom motor, with a sticker saying 17PM-K1xx. The datasheet says it should have a 42 mm case, but in actual fact, it’s 38 mm long. That is why you must start from the fundamentals, rather than depend on a model number!

              Now, if I were buying retail steppers from an authorized outlet, the numbers would be useful… but remember that I’m not getting paid for any of this, so I tend to be a bottom feeder. [grin]

  3. Hi Ed,

    I am in the process of building a RepRap with the same Minebea FH5-1043 motors (I got my hands on five of them)
    and cannot for the life of me get them to turn on my Pololu drivers.

    Did you do anything special to the wiring?

    1. Did you do anything special to the wiring?

      Nope, plugged it in and away it went…

      The obvious question, based on some experience [grin]: did you pull down the -Enable input and pull up the -Reset input?

  4. I may be a little late, but for anyone else who is looking for information on these motors, you wont find datasheets for them just by throwing the name into google.
    I got a set of five of these motors from a seller who seems to be pulling these out of old machinery by the dozen. Mine have the following part number:


    This is what it means:
    17 – is a nema 17 motor
    P – type – has something to do with the lamination
    M- Step angle – Z = 0.9 deg, M = 1.8, U = 3.75

    J – Type of laminated stator – J= Better Performance at high speed
    0 – Motor Length – 0 = 1.5″
    34 – Electrical Variation

    P – Gear or pulley, assuming G would mean gear
    2 – Mechanical variation
    VS – flange type

    (the last section is specific to custom made steppers)

    There is all the information you need here –>

    Hope this helps anyone who is wondering :)

    1. Some of the motors in my heap don’t match anything in their catalog, but just browsing the catalog can show a “close enough” motor that gives you an idea of what’s inside.

      Thanks for the update!

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