Hey Mike,
Yet I’m waiting for my Onefinity CNC including the Onefinity Controller (which is a variant of buildbotics.com Controller), so I can only be of limited help, but in Buildbotics Controller Manual it says:
4.1.3. Emergency Stop Button
A yellow and red “emergency stop” button is present in the upper right part of the screen on all pages. Clicking this button puts the controller in the ‘ESTOPPED’ state. When in the ‘ESTOPPED’ state, all motors and the spindle are disabled, all position and homing information is lost, and the yellow ring blinks between orange and yellow.
I’ve already thought about what this Emergency Stop Button does, but it is clear that electrically, this it is not a “real” Emergency switch:
The National Fire Protection Agency (NFPA 79) requires that the class of emergency stop button be determined through a risk assessment. The soft “emergency stop” button on these web pages and the estop pin (pin 23 on the DB25 I/O connector) are both software controlled, and cannot be used for safety. If your risk assessment requires an emergency stop button to be installed for safety purposes or mission critical applications, then Buildbotics LLC recommends installing a “listed“ hardware Emergency Stop button in line with system power.
I’m about to wire my control cabinet too. Usually you connect an Emergency Stop Switch to a safety relay such as the Omron G9SE (datasheet), which will then interrupt the power to the spindle in the most direct way possible (by hardware-triggering a Safety Input on the VFD, instead of the CNC Controller Software sending a command via RS-485/ModBus network).
Still, if buildbotics claims the that the spindle should be switched off when pressing the emergency switch, I believe it should send such a spindle stop command. Did you connect your VFD via PWM method or via RS-485?