What is "NEMA"?

[O'Seanski]

I did a "define:" on Google, and it told me that NEMA means "The National Electrical Manufacturers Association". However, I see "Nema 17", "Nema 23", etc steppers listed on websites. Is "NEMA" a generic term, or the name of a manufacturer, or what? What does it mean?

Secondly, how fast can I expect a NEMA 17 to reliable move a moderate load? e.g. - A 1/4" router bit plunging into solid wood.

[mcphill]

NEMA is a standards orgainzation, and the codes you reference (NEMA 17, 23, etc) are standard motor frame sizes. This lets manufacturer make different motors that will fit the same application, instead of every one being designed uniquely.

References:

http://www.numberfactory.com/NEMA%20...Dimensions.htm

[Al_The_Man]

Although NEMA size gives the frame size, it does not reflect the torque value of the motor, which is often a misconception.
Al.

[martinw]

Dear O'Seanski,

All above advice is accurate. My understanding is that NEMA ratings are just the standardised mechanical fixing points at the shaft end of the motor. Motors with the same standardised fixing centres can have hugely different electrical/torque/etc etc performance. Also, the motor bodies can vary in dimensions, although they may share the same mounting dimensions for the same NEMA rating.

I hope this does not confuse..

Best wishes,

Martin

[O'Seanski]

OK, so I suppose my question was like asking if a laptop computer was faster than a tower computer. The "NEMA" numeric designation only describes the bolt hole pattern, shaft diameter, etc. Correct?

I have read that a CNC router requires at least 100 oz/in steppers. How accurate is this assessment?

[ger21]

Originally Posted by O'Seanski I have read that a CNC router requires at least 100 oz/in steppers. How accurate is this assessment?

Depends. It is accurate, but still tells you nothing. Some routers may need 300 oz steppers, some may need 1000 oz steppers. Basically, you need to know how much weight you have to move, how fast do you want to accelerate and move it, and what method you are going to use to move it. Also, how much force do you want to have at those speeds? Not a simple yes or no answer.

[martinw]

Originally Posted by O'Seanski OK, so I suppose my question was like asking if a laptop computer was faster than a tower computer. The "NEMA" numeric designation only describes the bolt hole pattern, shaft diameter, etc. Correct? I have read that a CNC router requires at least 100 oz/in steppers. How accurate is this assessment?

Dear O'Seanski,

I think the mounting centres and shaft diameters are standard for a given NEMA rating . Certainly the length of the motor body can vary within the same rating. The electrical and mechanical performance can vary hugely.

Could I hand over to better men than me? Oh, and Good Luck.

Best wishes,

Martin

[mcphill]

Originally Posted by O'Seanski OK, so I suppose my question was like asking if a laptop computer was faster than a tower computer. The "NEMA" numeric designation only describes the bolt hole pattern, shaft diameter, etc. Correct? I have read that a CNC router requires at least 100 oz/in steppers. How accurate is this assessment?

To use your computer analogy, that's like asking what speed processor you need to run your software - without telling us what software...

Well, if all you do is e-mail, not much. If you want to be a render farm for some movie computer graphics, you'll need a bit more... You are still way short on the information needed to give you the answer it seems you are looking for. Post some specs or some ideas of what you want to do, and this may move along faster. 100 in-oz motors are pretty small...

[O'Seanski]

Post some specs or some ideas of what you want to do, and this may move along faster.

Sorry, I guess that's a no-brainer. I should have done that in the first place.

I'm somewhat flexible as to what I want to end up with. I will be cutting with 1/4" and 1/8" bits - probably smaller as I find them. I will be doing plunge-roughing, but mostly light cuts on ornamental work. If I can work out a flying gantry, I would like to have at least a 36" wide bed with at least 2.5" depth. I'm wondering if a torsion box, like the Joe 2006, is the way to go. I'm not really ready for metal yet, as my budget isn't extravagant.

I've got a machine almost done, but I'm having some alignment issues that I'm really not comfortable with. It's also DC motors with quadrature feedback, and I don't have the knowledge to handle all the current moving around - I've popped half a dozen chips so far. I had decided against steppers for fear of losing steps, but getting this machine up and running has proven to be much more difficult that I originally anticipated. Steppers might be an order of magnitude simpler.