Spindle Interlocks

What is the usual method of interlocking the spindle to be sure that there
is no way that the spindle can start while I'm changing tools?

Background: The machine is a B-port series I with the Boss-6 controller
replaced by an Ahha RC-500. Spindle is Kwik-Switch 200. There is a
pneumatically actuated (via solenoid) spindle brake. I am running Ahha
Artisan as the control software. The spindle is run via a VFD.

I want to be sure that, even if someone presses enter on the keyboard to
terminate a 'pause for tool change', the spindle will not start until I have
physically enabled the spindle again.

My thought is to:

1) Have my tool change macro:

a) wait for 0 spindle RPM (signal from the inverter) - (waiting for the
spindle to stop would cause less strain on things),

b) raise an I/O signal that will disable the inverter drive and apply the
brake,

c) wait for an acknowledge signal from the operator panel (old 'spindle
enable' switch on the front of the head),

d) release the brake and exit the macro.

2) The wiring of the brake and inverter disable would be through a latching
relay that must be latched to start the spindle (via the 'spindle enable').
The 'disable' signal from the controller (and the e-stop circuit) would drop
out this relay disabling the spindle and immediately applying the brake.

3) I will also need to use the latching circuit to light the 'Spindle
Enabled' light to let me know that the spindle may go active.

Am I missing something?

Cheers,

Chuck Hackett
Omaha, Nebraska, USA