Spindle cooling system

I am nearly finished with my Portable MPCNC build. The last couple of days, I built a system for keeping the 1.5kW water-cooled spindle cool. It came with a submersible pump. I got some nice nylon tubing that is more flexible than the polypro tubing it came with, and clear so I can see inside it. Quick-release no-drip couplings will make set up and tear down easy. I put the pump in a clear bucket (for bird food balls), sealed up the tubing and wire inlets with Sugru, and built a stand to hold it and the CPU-cooler radiator. (no, I didn’t use a CNC to make it). I programmed an ESP32 board with a small screen to indicate the temperatures of the coolant, pre- and post-cooling. It will beep an alarm if the spindle gets too hot. What do you guys think is a temperature that might damage a spindle? I was thinking of setting the alarm at 50C.
Here are a few photos. If anyone wants more details, just ask.

The control cabinet is the grey toolbox in the background, still a work in progress. I will post more about that when it is finished.

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Doesn’t the spindle documentation provide a safe temperature range?

Have you considered a temp safety interlock that sends a pause or cancel command to the CNC if the spindle starts running too hot?

Nothing about temperature in the sparse documentation that I can see. I have an inquiry out to the seller.

Yes! I plan to have all sorts of safety interlock things in the final version. And I also plan to push alarms to my phone from the ESP32s that will be monitoring various systems. I have done this before with a device that I made for monitoring my heating oil tank. You can read about that on Instructables.

I want the emergency stop button to trigger a pause, not a shutdown, with the spindle braking in 1 second, raising, and keeping the Z stepper (and other steppers) powered, so that the job can be resumed accurately in the right spot after the problem has been resolved. I read in another post here about one attempt to make a pause feature, but it does not slow down any ongoing movement gracefully, or start gracefully. If anyone has implemented a graceful pause capability, please point me to the details!

I think pause functionality depends largely on the firmware. Marlin has a command buffer that makes pausing challenging. Grbl supports a pause button that does what you describe and which can be linked to an enclosure interlock so the machine will pause if the door is opened.

I’ve stated before my personal distinction between a convenient pause and an emergency stop. On my machine the e-stop removes all power from all systems. It is intended as the last-ditch, no kidding, make it all stop right now and sacrifice the workpiece to prevent worsening of fire or injury measure.

Thanks for that info, Tom. That is good news as I plan to migrate to a grblHAL board in the next 6 months, once I have become familiar with the limitations of the RAMPS/Marlin setup. For the power-cut emergency stop function, my control box is fitted with an inline RCD (GFCI in the US) whose “test” button is easy to get to and serves as both the Main Power switch and Emergency Cut switch. This device is built to trip every time it is unplugged, so plugging it in, you have to hit Reset (thus testing its RCD functionality each time, too). This is what made me decide to just use that as my main power switch.