I have a dual shaft stepper motor I am trying to replace.
It is dual shaft and is marked as:
STEPPING MOTOR
TYPE 23hd450y-28s
fh230911
I have tried everywhere from Google to Aliexpress to no avail. Does anyone have any ideas please?
What has gone wrong with the poor thing to need a replacement?
Stepper motors generally outlast everything else in the machine, because the rotor is the only moving part and it rides on good bearings. Disassembling a motor will kill it by demagnetizing the rotor, but, barring mechanical damage, it should last forever.
Several mishaps can kill the motor driver stone cold dead, causing “motor problems” that cannot be cured by a new motor.
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I moved the gantry by hand and after that it just stopped working.
Stepper motors become generators (more exactly, alternators) as their shafts turn, so shoving the gantry forces current back into the stepper driver circuitry. Depending on a host of unknowns, this can destroy the driver output transistors or the circuitry behind them.
If only the Y axis is dead, you can verify that the motor is OK by connecting the Y axis motor to the X axis driver, then jogging the X axis:
- If the gantry moves, then the Y axis motor is in fine shape and it needs a new driver.
- If the gantry doesn’t move, then there are other problems.
Searching for the “Top Laser” mentioned in your profile produces a pile of chaff showing “Top” is a terrible brand name, so a link to the machine description will help us explore what might be wrong.
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I changed the controller to a Rudia and all was going well. I will swap the drivers and check that. Good advice…
They are generators not alternators.
An alternator takes some power to create a magnetic field so some power needs to be supplied to the alternator for it to work.
Generators use permanent magnets, so they will work with no other power supplied.
I’d suggest measuring the flat side of your motor. These are NEMA motors and a NEMA 23 is 2.3” on a side.
Likewise for generators: you gotta spin the shaft (as in “moved the gantry by hand”) to get power out of the wires. The (admittedly pedantic) difference being generators produce DC and alternators produce AC.
Going even further down the rabbit hole, I’m misusing “generator” for the machine properly known as a “dynamo”.
Sheesh & similar remarks. 
The main difference, dealing with car alternators, there is no magnetic field to make the interaction work if you don’t have power available.
If your cars battery is dead, then an alternator won’t work, you can spin it, but it can’t generate power since there is no magnetic field.
On the laser, you can unplug it from power and make energy from the PM of the stepper, if it was an alternator, you couldn’t do that.
Both an alternator and a dynamo require field windings, energized to create the magnetic field within the device.
A pm generator has this magnetic field and requires no external power.