Do I Have the Right Sized Motor?

This is a rendering of my 2 axis plankton feeder. I has another wheel, like to white one shown here, at the other end of the 8 foot rail.

I have a stepper motor that was given to me but I don’t think that it is working at its best. It is not running as well as the last time that I tested it. When I take the wire off and turn it manually, the drag is not constant as it makes a full rotation.

The motor was being tested in the assembly without having to move the carriage. It just has to drive wire around the two wheels that are 8 feet apart. There is very little drag on the system. The other wheel spins freely, even under a side load.

That being said, when I run the assembly, it does not running well. It is slow and chatters. Given the same amount of power from the driver, should I go with a motor that is bigger or smaller?

The motor that I now have is a 57BYG084/1.8 Step Angle/12V/4 phase/0.6A per/100ohm(500VDC)/20ohm per/Class B/25mH Inductance per/Rotor inertia 38g.cm2/holding torque

It is powered by an Arduino Mega 2560 with a Rugged Stepper Motor Driver. It does not have a micro-step mode.The spec.(s) on the driver say that it has a Peak DC current per phase of 2.8A. I am running it at 30V from a printer adapter. It supplies 0.83A which could be part of the problem as well. ? Would a 30V 5A adapter improve the situation and be safe to use?

I am wondering if I should buy the same motor or go with a different size, either bigger or smaller?

I use this code for MaxRPM:
int maxRPM = 150; // Top running speed of main stepper

instead of 300

and it still chatters and can barely turns the cable. Besides the potentially ailing motor, do you think that a bigger or smaller motor would perform better, powered by the Rugged Stepper Motor Driver, should I just buy the same thing new?

I have to say that a 2-axis plankton feeder sounds amazing, every home should have one(!)

I'm wondering if you have resonance problems - mechanical oscillation can cause a stepper to mis-step, and its common to need to damp-down oscillations to control this (micro stepping helps prevent oscillations starting when the step frequency is close to the resonant frequency). Your large system probably has some low-frequency resonances? Could these be damped (more friction?). Of course this then means you might need more torque.

LOL I didn't want to take up peoples time explaining what it was. This won't help much but I am making a small plankton farm that will fit in my garage. For What? To feed my corals and fish in a sale water reef tank.

Tank you for another thing to considerate. It sounds like that might have a lot to do with it.

Now back to the questions. Would a 5A adapter help things. And should I buy the same sized motor, go bigger or go smaller?

If your motor wants 0.6A per winding, and your power supply is rated at 0.8A, then you will get significant power sag when you step more than one winding at a time (which you will.) I would try with a stronger power supply first. If that doesn't solve it, then try to adjust acceleration parameters of the stepper motion -- start and stop slower, run faster in the middle. If that still doesn't work, I'd try for a bigger motor. Bigger is always better! (OK, I lived in Texas for a few years, I'm irreparably damaged :-)