Major lack of torque with steppers

[curtisturner]

I am having trouble with a new setup I am using the following:
2 680oz Torque Bipolar Steppers
Belt driven axis
36 Volt / 2.5 Amp Power / Controller (1 for each axis)
Mach 3

Everthing works OK, however with a 1 finger I can easily stop either axis.
Even with a low feed rate and low speed I could easily stall either axis.

HELP, this cant be right I know 680oz means holding torque, but when moving a meager 30 rpm it should have more than a couple oz of torque right ?

Thanks in advance.
Curtis-

[jerber]

What drivers are you using ?
Torque is related to the current, maybe the current is limited some way.
Is there a way to adjust it ?

Is the 2.5 Amp for one phase of the stepper or is it for both phases ?
If it's for both phases then I think it's to small for a 680oz/in stepper.

At 30 rpm you should have plenty of power.

Jeroen

[ger21]

What is the voltage and current ratings of the motors, and what drives are you using?

[curtisturner]

The drivers are built into the power supply (JTENG)
I am not sure if it is per phase or not, there is an adjustment that goes from 0 to 2.5A
I turned it the whole way to 2.5.

I did want to add 1 more thing, when it is not turning I can turn the pulley by hand with only a mild ammount of resistence not 680 oz by any means.

I also wanted to ask because I read it in one of the forums could it be a bad parallel port? That does not add up in my mind but what do I know!

Thanks
Curtis-

[ger21]

Do you have a link to the drive manufacturer? Or specs on it?

It's not likely the parallel port. A drive should lock the motors when powered up whether or not it's connected to the parallel port.

[pminmo]

Unless the 680oz motors are rated for a much higher current?

[curtisturner]

The motors are rated at 2.8 amps / PH , I could not find t he voltage rating
These were mated by the manufacturer, and were bought a month ago brand new.

Thanks
Curtis-

[pminmo]

At 2.5A on a 2.8A motor you shouuld have gobs of power. Still need info on the motor driver. i.e. electronics that hooks up to the motor. Maybe a picture?

[curtisturner]

OK, I dug up some more info

http://www.j-teng.com/STP-DRV-35025.pdf
Picture
http://www.j-teng.com/images/27_1_b_150x145.jpeg

More Motor Info
2 Phase
DEG/STEP 1.8
Volts 5
Amps / PH 2.8
Ohms 1.8
mH 18
Oz Torque 680


Thanks
Curtis

[pminmo]

measure your DC voltage on each driver to see what it is, I suspect you may not have you AC transformer wiring configured correctly and are getting a low DC motor supply voltage, thus no power.

Out of curiosity, why can't your driver supplier support you?

[mcpltd]

Also 2.5A rating for the driver is 1.76A RMS so if your motors are rated in RMS you will only get just over half the torque.
(Motors are normally rated RMS)
Also are the you connecting in series or Parallel?

[pminmo]

[QUOTE=mcpltd]Also 2.5A rating for the driver is 1.76A RMS so if your motors are rated in RMS you will only get just over half the torque.
(Motors are normally rated RMS)
[QUOTE]

In full step mode true, but that will be the case for many, many microstepping drivers. (BUT NOT ALL )
Still should have more power than described.