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NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 12:23 PM

Good Day,

I'm working on a project (Home Hobby) that require Stepper motors.

Some of my requirements:

  • Torque: 1000 oz/in minimum
  • bipolar parallel
  • Motors rated for minimum of 72 Volts

I looked and found that this falls in the NEMA 34. And begin looking for a motor that fits my requirements. Of which I found it. It was a KL34-8N-1000 See below. I began designing for NEMA 34 mounting brackets.

NEMA34 Hybrid Servo Motor,

  • KL34-8N-1000,
  • 1/2" Shaft
    Rated Torque 1128 oz-in,
  • 8 N-m
  • with Encoder 1000 line

Now what I found is, there is a dimensional discrepancy. I contacted the supplier and they sent me a link that they said should help, but it reflected the same.

The question that I have is a dimension on the frame size shown below.

This is (NEMA 34) KL34-8N-1000 That actually says 60mm (in red). The link to it is above.

All other dimensions are the same for NEMA 34, is there something I'm missing here. I contacted the supplier, he responded this morning, and gave me another link that should help, but its the same. And I thought I'd poised this here, is there something, I'm missing, frame size or something. I thought NEMA 34 should have the same mounting configuration.

And this is what I thought was a standard for NEMA 34. I circled in red the discrepancy

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#1

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 12:44 PM

I think you have NEMA 24 and 34 mixed up....

http://www.osmtec.com/nema_34_stepper_motor_34_hr.htm

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#2
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:14 PM

You can see from the scale that the hole to hole is 69,6 the circle is slightly larger, it couldn't possibly be 60...

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#3
In reply to #1

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:15 PM

Actually the KL34-8N-1000 doesn't match NEMA 24 all together, it is listed as a NEMA 34. and on a KL34-8N-1000 The bolt holes, shaft and body match NEMA 34, but, the center 60 mm disc should be 73 mm. Which I use for centering on the mount.

That is the only difference this motor KL34-8N-1000 has from the NEMA 34. Is that circle. It show clearer on the spec. link spec's of KL34-8N-1000 .

I never saw this before, and I'm just hoping, that I'm missing something. (All because this past week, someone shared a head cold with everyone at work)

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#8
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:51 PM

This seems like a one-off motor, special purpose....so it's a modified NEMA 34...

I don't see any listing for it on the website...

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#9
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 2:07 PM

That's what I was thinking, and that's what I asked Automation Tech....

I like it and will probably go with plan 'B' by making a spacer washer on my mount... in case the motor doesn't preform where I'd have to change it out.

I do have time, I may even look for another motor that falls in the standard.

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#16
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/14/2016 12:02 AM

For what it's worth, I have 2 different NEMA-34s on hand, and they both check out at 73.03mm (2.875").

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#19
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/14/2016 10:09 AM

That's what I that all NEMA 34 were. And for larger NEMA 34 motors, it just was longer.

I only caught the difference is I sketched it up and inserted in cad it to my mount. Just to see how it fitted and extruded from the machine.

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#4

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:29 PM

Your torque requirement should be in oz x in and not oz / in.

1000 oz-in = about 7.06 N-m

http://www.convertunits.com/from/oz-in/to/N-m

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#5
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:32 PM

gotcha 1000 oz-in.... Thanks,.... anything else?

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#14
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 4:59 PM

Nope, no more nits to pick...

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#15
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 6:09 PM

Give me some time... I have plenty of material to dispense for you.

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#20
In reply to #14

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/14/2016 3:02 PM

Excuse me for joining in the nit-picking fest, but it should be ounces times inches, not ounces minus inches

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#6

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:42 PM

Can you fabricate (or order) a 60 i.d. x 73 o.d. x 2 thick washer?

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#7
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 1:47 PM

Yes, I can fabricate one, that was my plan 'B' I just hate to have extra parts for what I thought was a standard. I was just wondering if anyone saw or experienced this before.

I'll be contacting my supplier again on Monday about this.

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#10

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 3:54 PM

It would be prudent to wait for the motors to arrive before fabricating mounts.

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#12
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 4:26 PM

That's what I'm doing.

The project I'm doing is converting a (New) manual milling machine X, Y, Z to CNC.

How I'm doing it, I have the mill drawn up in Cad, so I can get the ball screw lengths, and bearings mounted which I'm just working on.

After I spec'd out the motor, I then spec'd the power supply, drivers and breakout board spec'd out. Actually, then I started the cad on the motors....

After my mounts are design before I start making them, I'll order the parts. But when I was fitting things up, it wasn't wasn't fitting right.

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#17
In reply to #12

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/14/2016 12:24 AM

Had a look at the data sheet. Do you know about Pull out and Pull in toque figures for the motors for the project you are doing?

Something what data you are looking at for a stepper motor I think it involves acceleration and since you are using on a milling machine I would oversize the motors to avoid having the cutting tools slowly coming to a stop. Here

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#18
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/14/2016 10:05 AM

That is a good point, I don't have the pull out and pull in torques on this motor. And I should have that documented.

how I sized the motor torque was I question what others had and was satisfied. Even though my mill is slightly bigger, I felt that they were just borderline big enough at under 800 oz-in. So when in doubt.... I put it at 1000 to 1200 oz - in for torque.

I also didn't like the open loop system, and went with the closed loop. This should deal with the synchronized slippage.

For now, I wouldn't go into the error handling on the closed loop system. It of course isn't a high end machine $$$$. But one has to draw a line, and I felt I was pretty gra¢ious.

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#11

Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 4:05 PM

I would go with the vendor's published spec of 60 mm. If you receive the motor and find out the spec is in error you can always re-bore the mount to the larger 73mm diameter. Yes this is more work, but easier than fabricating an adapter.

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#13
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Re: NEMA 34 Stepper Motor Dimensional Size Question

08/13/2016 4:29 PM

The vendors spec's on the their other NEMA 34 stepper motors, one that is 1200 oz-in, are the standard 73 mm. I may go with that.

my original question really was, has anyone come across this before?

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