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Stepper motor has no torque

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raynerd:
Hi guys, it's been over a year now since I wired up a stepper and over the last few nights I've been pulling my hair out.

I've wired my stepper up, 4 wire, and my controller turns it nicely, but even when I hold it by hand it just judders and stops...never mind putting any cutting strains on it! I'm using one of kwackers divider controllers to run it although the motor is actually turning a linear table axis. It has worked in the past but I'm sure it is wired correctly and I'm sure the divider setup is correct! Likewise, if my wiring was wrong, would it still turn smoothly with no load?

Could the stepper have died? - only I'd have presumed it would have totally blown if this was the case but as it is, I get perfect smooth motion when under no load. Yet virtually no torque both driving or holding.

Any thoughts, help or advice appreciated.

raynerd:
Not the motor, tried two with the same results but they have no markings on them. so not sure what motors they actually are. With steppers can you read into the length of the as an idea of their rating? - only these two are pretty long. Can't imagine the torque of them being so low they can be stopped with a finger!

rleete:
What kind of power supply is feeding them?  Sounds like low voltage/current to me.

vtsteam:
Yup, need specifics. Motor model and number, power supply specs. etc.

Heat and over-current can demagnetize a motor, but I bet it's something else relatively minor and fixable. Or hope so.

awemawson:
Chris said in his second post :

"Not the motor, tried two with the same results but they have no markings on them. so not sure what motors they actually are"

So we're not going to get specifics on the motors, but as he's eliminated the motor by substitution we're left with the driver / psu combination.

Chris, do you have an oscilloscope to watch the outputs? Possibly one of the power stage drivers has gone either short or open circuit.

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