Stepper Motor

As no-one else in this forum can see the <...stepper motor...> it is going to be difficult for anyone else to know, or even to investigate, from this distance. All that one can ask is:

1. What investigation activities have been carried out so far?
2. What was the outcome of those activities?
3. Why has this information been withheld from the forum?

Thank you sir.

There is only one reason why any motor does not turn as far as expected. That motor is not developing enough torque to overcome all opposing forces. Conversely, the only reason a motor moves farther than expected is that the opposing forces (including motor braking) are insufficient to stop motion.

Now why and how your motor stage is acting the way it is can only be identified by first examining the kinematics (is the stage sticking in places, does gravity help in only part of the travel, etc.) and then seeing if your motor and/or computer program is expecting too much.

Thank you sir.

Possibly there could be noise in the logic driving your motor controller. Bypass caps on the supply might help. (Just a guess...)

Thank you sir.

The fault may be in:

1. the driver program

2. the electrical connections

3. the motor itself

4. the load on the motor

none of which we know anything about. Start by removing the load, to eliminate the possibility of #4. Then try another motor, to eliminate the possibility of #3. As for #2, the electrical connections include the stepper driver circuit and its power supply. If the stepper driver is a ready-built module it is very unlikely to be a problem, otherwise you will need to examine the output pulses with a digital storage oscilloscope as well as using a multimeter to check the power supply.

TBH, I think that #1, the program, is far and away the most likely source of your problem.

Thank you sir.

Thank you sir .

One reason would be that the motor is being run open loop. Without any position indication you have no idea where it has settled.

It is also possible that there are programming errors resulting in control pulses are improperly formed; i.e., not wide enough, too wide, improperly timed, asymmetric/unbalanced, etc., etc.

Since OP has provided no feedback to any of the forum's questions, the best advice is for him/her to start using his favorite search engine to do his own homework/research.

I have seen a case where there was a mechanical resonance in the mechanical load driven by a stepping motor. The stepping motor was acting erratically because the stepping rate was close to the mechanical resonance frequency. If it is possible, you might try a different stepping rate to see if that solves your problem.

https://phidgets.wordpress.com/2014/07/28/how-to-avoid-resonance-issues-in-stepper-motors/

Actually what induces midband resonances is when the drive switches from being effectively a current source to a voltage source. This becomes a problem because the available torque in a motor is proportional to the current. The phase shift of this transition induces the instability. Geckodrive has a nice white paper on this. Now where this corner happens is affected by the mechanical load kinematics. An inertial damper can smooth this out but at the cost of less torque being available to move the rest of the load.