Kevink18 wrote:it would be very easy to use a relay plugged into controller to start spindle when you start G-Code.
I've been using just that setup with the controller-enabled coolant for a while, and I can tell you from experience that having
the automatic-enable be at that point in "the system" is the exact wrong place to put it.
When you have the CNC controller turn on the coolant pump, that means that the coolant is only flowing when a program is
running. Not a good idea when you've just finished a multi-hour long run, the coolant is hot, the spindle is hot, and the program just
ends. Because the spindle RPM isn't being controlled by that same controller, the spindle will keep running, leading to bearing burnout.
Stepping away for even just a few minutes at the end could lead to catastrophe with overheated bearings if the coolant pump gets
turned off by the controller, but the speed isn't cut.
No, it needs to be that the coolant pump turns on automatically whenever it's possible for the spindle to move under power at all.
That way, after that hot run finishes, you turn the spindle speed down to zero (never turn it OFF before turning it down and letting it stop; takes
WAY longer if you turn it off first, and the VFD is made to brake the motor to the degree it can) and then leave the "Run" mode enabled.
That way the coolant will keep circulating, even though the spindle has stopped.
But, to do this requires multiple configuration changes (or at least verified) inside the VFD itself, and it requires adding a relay between
a specific pull-up voltage output from the VFD to one of it's Open-Collector outputs (configured to output the signal, under the right
condition).
The relay Normally-Open contacts are then wired in parallel with any pump-enable switch you might already have added. In
my case, it's a lot safer because it's a 12VDC RV lavatory pump, not a 120VAC aquarium pump, so I can use normal low-voltage wiring
to that relay. Depending on the pump, the relay needs to be able to handle that AC and inductive load (use 0.7x the rated DC load).
That way, you can use the original switch, or just let it turn itself on and off. But, one way's for sure, if that spindle is turning,
the pump WILL be on. That's a level of failsafe you'll NEVER get from any NWA controller-driven solution.
When you're moving into more-advanced uses, you find that being able to spin the spindle at low RPMs, say <1K, is needed to warm
the spindle up on a cold morning (a few minutes of warm up will save you many hours of lifetime), or to use an edge-finder
(electronic or mechanical, they all expect to be spinning), or to measure bit runout. My point is, in all those cases, you still
want coolant to flow, even if you're not running a program.
Hope that clarifies the real-use needs a bit.
Cheers!
Thom