pic: CNC Router Project

[Molten]

Originally Posted by Formerly Famous

It's my understanding that it is the step (Do I have that name right? ) motors that cause the sound. It happens on all CNC machines.

But how do they make the noise? I want to understand the physics.

[Eugene Fang]

Originally Posted by Molten

But how do they make the noise? I want to understand the physics.

I'm not 100% sure, but this is what I think:

Are you familiar with how stepper motors work? When electricity is applied to them, they go one "step," so in order to get them to move a full rotation, electricity has to be turned on and off and back on multiple (or actually hundreds/thousands) times (depending how many "steps" per rotation the motor has).

To get the motor to go at different speeds, you turn the power on and off at different rates. Pulsing something at hundreds of times a second creates different notes. For example, when you hit a tuning fork for the note "A," it vibrates at 440 Hz.

Thus, moving a motor faster means faster pulses, resulting in a higher note. And slower gives you a lower note.

[Cjmovie]

Using this as a reference point:
http://en.wikipedia.org/wiki/Stepper_motor

Basically, stepper motors differ from normal motors in that they move to certain, pre-defined rotations instead of just rotating at an RPM approximated by voltage. So you send a signal to a stepper motor, it moves one step (usually 1/200th of a revolution or so), and you send another and it moves another step, etc. (slightly more complicated, but the wikipedia article can tell you that).

Since it's not a constant motion (it's stop start stop start to at least a small degree, even when "smoothly" rotating) there's a vibration created. The frequency of this vibration is the rate at which you're sending pulses to it, since this is the speed that it's stop-starting. Kind of like turning a voltage on and off to produce a square wave sound. In our case they're mounted to metal plates, which amplifies this in a way similar to a drum. So if you control the rate at which pulses are sent, you can change the note/frequency they produce.

All based on intuition, though, so if someone has a more accurate answer please feel free to pop in.

[techtiger1]

Think of a stepper motor as a servo motor that can spin 360 in increments at a time. D5 nice little unit and good thought of using that to prototype cnc parts. .

-Drew

[RoboMaster]

This is fairly related to stepper motor sounds, or at least the theory behind it and how you can purposefully create them. Although, it's interesting, but not actually from normal use.

Stepper motors playing Mario Theme

Music Theory and control behind it

[Molten]

Thanks all, I was sure someone could explain it terms I'd understand. I'm not so good with tool knowledge, so anytime something can be explained without the assumption that I know a tool...it is most appreciated.