Stepper Motor High Torque Low Amp

Hi all,
Was thinking of maybe moving up to a servo motor system for higher torque with a gecko drive. Then I looked around for some motors and saw that some of the new stepper motors have low amp ratings and very high torque. I have a Xylotex board, so 2 amps would work just perfect, and the motor is 7 volts or so so that would work aswell. But then I see other motors on the same page with amps around 4 and voltage a little less with the same torque. Is there any advantage or disadvantage with these motors? There has to be a catch somewhere because I think that in the torque curves it shows big declines after about 110 rpm or so. Is this why they can put out soo much torque. Would they not be very good for CNC use. How many IPM could one expect with a 12TPI Screw?
Thank you soo much for the help.
I really appreciate it. :) :wee:

All steppers have a much lower torque at higher rpms than at standstill. The best performing motors are generally those with a high current and low voltage rating. If you want to use your xylotex controller, then you should select a motor that don't need more than about 2 amps.

The 7v 2amp motor is not perfect for the xylotex. The motor voltage is too high. Because the xylo's supply can be no higher than about 32v, you won't get much speed out of the motors.

The other motor is a poor match also since it needs almost twice the current as the xylo can deliver.

So, I could only run the motors at 3x the normal voltage with the Xylotex board right? How fast could I expect to get IPM with a 5 TPI Leadscrew at 300 rpm? Is it 60IPM?
Thanks. :)

Your calc's are correct, but take a careful look at the torque curve to make sure they specified the values using a 7v supply.

Also keep in mind that your actual speed depends on how much force you need to generate. What is the motor's rated holding torque?

Here is the website, it is a bit of an expensive motor, but I have seen similar at lower costs this one has more info ex. torque curve etc. :

http://www.orientalmotor.co.jp/cgi-b...K&frameSize=85

Thank you very much for the help.
I really appreciate it. :)

Also, when it says 2 amps per phase and this is a 2 phase motor, does this mean 4 Amps total?
Thanks. :) :wee:

automationdirect.com has some nice steppers, their biggest nema 23 motor has a very nice curve, they also have a larger nema 34 frame stepper that has an incredible amount of torque for the amount of current, although the problem with that motor is that it will have a hard time pushing 500rpm, my motors on my mill typically run around 1000rpm and on my lathe, (nema 23 272oz-in from automationdirect) they will be running 1500-2000rpm
It all depends on the motor, some cant handle the high rpm.

Jon

Ya, those are some nice motors. The smaller ones look similar to homeshopcnc.com and xylotex.com ones. Are they the same? Surestep ones? So how many IPM could one expect from a stepper system with the xylotex using a 5TPI ballscrew?

If you can pump the voltage and the pulses into them, you could push 200ipm+ with the 272oz-in motors on 5tpi ballscrews depending on the load.
Im not sure about the xylotex drives, I had my geckos at 50v pushing close to 2000rpm or more without any load at all(not hoked up to the screw)

Jon

So half of that 25 Volts you could expect 1000 rpm with no load. 200 IPM is a lot, but as the speed goes up the torque goes down, so it may not be able to push the ballscrews at only 50oz in because of the speed-torque ratio, is this correct?
Thanks. :)

you are correct, after its up to speed, it doesnt always need too much to keep it going, although you want plenty there so you dont randomly miss any steps and mess stuff up.

Jon

Do you know roughly how much torque you need to turn a 5TPI ballscrew or a 16TPI screw? I know that it is very easy to turn a screw, but with less TPI it takes more to turn it. So, I'm wondering how much it takes so that I can figure out how many rpm I can rapid at approximately. I know the other considerations are also there, gantry weight, friction, etc.
Thanks. :)

Do you know what the voltage is on those Automationdirect motors, they look real nice.
Thanks. :)

The automationdirect motors are aproximately 3v nominal, they run great on 50vdc, I thought about running 70v and decided to keep it on the safe side, I still can anytime I want too though.

Jon