Stepper innards detached?

[amishx64]

Hey guys. I'm new to the zone. Looks like a great place.

I recently have decided to build my own CNC for various purposes, including PCB milling. Having built 70% of my machine thus far, I have started setting up my controller board with mach 3 and my stepper motors.

I have a few questions about how my stepper is behaving.

In mach 3, when ever I set the velocity above 3, the stepper starts spinning for half a second, then the motor's axis stops, but still sounds like the coils are still spinning internally. After a few seconds the pitch becomes very high.

Does anyone else have this problem or is this normal?

Also when my stepper is on but not doing anything, I can still hear a slight buzzing internally.

My last question: What are the Step and Dir pulse values in Mach 3 for? Why would I want anything but 1 and zero? any advantages to changing this? It dosn't seem to make a difference.

400oz/in steppers
12v (I know *sigh*)
8 wire in bipolar series

Edit: I'm going to try the other two I have. The motor seems easy to stop when using pliers.

[amishx64]

Update: other motors behave same way. After left on for a while, motors get pretty warm.

[H500]

With 12v, you won't get much speed out of the motors. The sound you hear is when the rotor loses sync with the rotating magnetic field.

Try lowering your acceleration.

[amishx64]

Oh. I know I should be using a higher voltage but I didn't know that was the reason.

Awesome. Thank You.

[johnmac]

Sounds like the motors are stalling. Using 12V motors will add a challenge. You didn't say what voltage you are running the steppers at. Done correctly, you can run them at a higher voltage and get better top speed. The controller you are using will determine the maximum voltage and how the current will be limited.

John

[amishx64]

Originally Posted by johnmac Using 12V motors will add a challenge. You didn't say what voltage you are running the steppers at.

Sorry. I meant to say that I am running the steppers at 12v while they are rated at 4.2v, 3A. My controller can accept a higher voltage, but I am using an ATX PSU from a PC.

Thanks for posting.