A spindle motor
They turn a tool at very high speeds
The Spindle is the main effector on your CNC Mill/Router. It holds the end mill or drill bit, makes it turn and remove material.
While manual control is sometimes fine ( turn it on before starting your G-code, off when you are done ), it is so much neater to have G-codes to control it automatically : simply put an ON G-code at the beginning of your G-code file, and a off G-code at the end of your G-code file, and you don't have to think about it any-more.
First thing you need to do is choose which component on the Smoothieboard is going to choose to control your Spindle.
Controlling using a VFD
AÂ VFD, or Variable Frequency Drive, is a box that takes mains power, transforms it into the voltage your spindle needs, and varies the frequency to control the speed of rotation of the spindle.
If you are using a VFD to power your spindle, you can use your Smoothieboard to control the VFD, start the spindle and control it's speed.
There are two methods, using Modbus, or using an analog signal.
For information on doing so, see the Spindle Module
This is the recommended method.
Controlling using mosfets
If you are not using a VFD, an alternative is to use one of the mosfets on the Smoothieboard to control the spindle.
If you want to learn about this technique, go to controlling a spindle with a mosfet.