Hey Stuart,
if you run a spindle you forcibly run a VFD. And a spindle coolant pump is always controlled by the VFD, not by the CNC controller. Every VFD has control outputs for a coolant pump. Often they even have a relay integrated so you can connect the pump directly, both DC and AC pumps. See the specification of the control outputs in your VFD manual. It is important for the spindle’s longevity that the spindle coolant pump runs when the spindle runs. And it’s the VFD that knows when the spindle runs. Should the spindle cooling rely on the CNC controller, and the latter would fail, possibly the spindle would run without cooling and be destroyed. That’s why the spindle cooling is always controlled by the VFD. A good VFD can even be programmend to continue to cool the spindle for a while after the spindle was stopped.
The VFD’s control ouputs are programmable so you program the relay output to be active when spindle runs, so spindle coolant pump runs at the same time.
Although I have no personal experience with the spindle/VFD kits from PwnCNC, I’m sure that Daniel @PwnCNC intended for the coolant pump to be connected to the VFD.
A CNC controller usually only controls workpiece coolant (workpiece mist coolant (M7)) and workpiece flood coolant (M8)), not spindle coolant.
And unlike a CNC controller like the Masso G3, the VFD also always knows at which speed the spindle runs. You may also order a spindle with a thermal sensor and make spindle coolant flow depending on the real heat.
Also the dust collection is often switched on and off by the CNC controller (usually at the same time when VFD is sent the “spindle RUN” command (M3)), but of course you can also let the dust collection be controlled by a programmable output of the VFD, just like the spindle coolant pump. The VFD knows the best when the spindle runs. But more often dust collection is controlled by the CNC controller, because if you mill wood, you need dust collection but not workpiece coolant, while when you switch to milling aluminium or soft metals like brass, usually the dust collection is of no great use, but you may want to spray cutting fluid or isopropanol on the workpiece with M7/M8. That’s why on the Onefinity Elite Series, the dust collection connected to the ‘vac’ power supply output is switched on with M8.
Welcome to the forum!