Manual Operation After Cnc Conversion

[grepper]

Looking at motor specs, most just say 2 phase and give a torque rating. Some however, such as this
http://www.omc-stepperonline.com/ne...per-motor-31nm439-ozin-24hs343008d-p-275.html have 8 wires and can be configured however you want.

I take it most motors are bipolar parallel? I understand the difference, just don't know what is standard when it is not stated.

Rated Current(Bipolar Serial) 2.1A
Rated Current(Bipolar Parallel) 4.2A

 

[JimDawson]

The bi-polar parallel is the most common. Normally it is clearly stated if a motor is an 8 wire.

 

[grepper]

.
I thought I was good to go and had run out of questions! But if you can stand it, I have a couple more. (I'm almost there).

Stepper Online has this 3.5A, 425 oz, dual shaft motor. Just what I want:

http://us.stepperonline.com/3pcs-of...motor-35a-31nm439-ozin-24hs343504d-p-398.html

But it has an ~8 mm shaft? 3/8" = ~9.5 mm. I thought in general shaft sizes were either 1/4” or 3/8". Are this slightly smaller size shaft going to be an issue? Am I going to run into mounting issues?

Also, how much real world difference will a 3.0A motor be compared to a 3.5A draw motor? Both have about the same OZ holding torque, but I’m not seeing curve charts.

 

[JimDawson]

The shaft sizes seem to be a moving target and each manufacturer seems to have their own ideas about it. They don't all use the NEMA standard regarding shaft sizes. The good news is that couplings come in a range of shaft sizes to adapt almost any shaft size to your leadscrew size.

Also, how much real world difference will a 3.0A motor be compared to a 3.5A draw motor? Both have about the same OZ holding torque, but I’m not seeing curve charts.

I'm not sure why the same holding torque rating would have two different current ratings. I going to guess that the motor performance is going to be slightly less at the higher RPM ranges on the lower current motor. Without realistic performance curves, it's hard to tell.

 

[Jim_Hbar]

4 Lead Bipolar connection = 8 Lead Bipolar Series Connection.

8 Leads gives you the option to wire the coils parallel - so you can achieve higher speeds than you will ever need on your small mill.

I admit it is a totally personal bias, but I don't like the beam couplings that Jim has shown above. When a $10 part puts down a multi-million dollar production line for an hour or so, you do something different next time! They do seem to work in this hobby application however. Make sure to buy a spare.
Couplings that clamp onto the shafts are what you want - the ones that just use grub screws are to be avoided.

PS. - Do you realize that that 439 oz-in motor produces about a 1000 lbs of thrust when it stalls out driving a .2" pitch ball screw???

 

[JimDawson]

Couplings that clamp onto the shafts are what you want - the ones that just use grub screws are to be avoided.

:+1:

 

[grepper]

Thanks. I’m finally getting close to finalizing my setup! This has been a real trip. I'm so glad to see the endless research and having to ask questions coming to an end!

The higher amp motor did have more torque. (My bad)

I guess my motor choice is #1:

Nema 24 Dual Shaft 3.5A 3.1Nm(439 oz.in) 24HS34-3504D, inductance 5.6 mH
http://us.stepperonline.com/3pcs-of...motor-35a-31nm439-ozin-24hs343504d-p-398.html

I was also looking at:

Longs Motor 23HS9430B, 3A, Nema23, 425oz.in, 3A, inductance 6.8 mH
http://tinyurl.com/hm9vtoh

 

[grepper]

Jim H.- You responded while I was typing.
"PS. - Do you realize that that 439 oz-in motor produces about a 1000 lbs of thrust when it stalls out driving a .2" pitch ball screw???"

What are you trying to tell me? Is there a problem choosing that motor?

 

[Jim_Hbar]

Pick one, you'll be fine..

The service qualities of the Vendor is the most important thing - not a 3% difference in a theoretical torque number.

 

[grepper]

Last question before I finalize my order.

Because I want to add handles for manual operation, (and be able to quickly remove them), I was thinking of ordering the motor shafts D cut to facilitate a set screw in the handle.

Any problems with that as far as ball screw mounting? I'm guessing not, but I thought I'd ask.