Hey Sean,
in my spindle datasheet, it says “max. 35 °C”. I own a 2.2 kW 80 mm water-cooled spindle.
In my spindle manual, the manufacturer recommends in its Safety Warnings …
automatic monitoring and automatic disconnecting power if the coolant flow rate falls below 1 liter/min, or the temperature after the motor spindle exits motor spindle exceeds 40 °C.
My cooling station has sensors for this, and triggers alarms when that occurs, through a three-pin circular connector which I can connect to the VFD, the system’s Safety relay, or to the CNC controller.
Furthermore, my spindle manual says:
Water-cooled motor spindles:
When dimensioning the cooling system, it must be ensured that the temperature of the cooling liquid leaving the motor spindle does not exceed the permissible value of 30 °C in normal operation.
At least one flow indicator and one temperature sensor with temperature display must be installed in the cooling circuit so that they can be easily seen by the operator and used to monitor the cooling system. Temperature monitoring must take place after the motor spindle has left and before it enters the heat exchanger. If the cooling system is monitored manually, check every 15 minutes during operation whether the coolant is within the permissible temperature range and whether there is coolant circulation. If the coolant does not circulate, or if the temperature exceeds the permissible limit, stop operation immediately and correct the problem.
Use special coolant that ensures corrosion protection of non-ferrous metals, does not attack rubber seals and has the lowest possible electrical conductivity. Use only coolant offered by the manufacturer.
My spindle is this, my water chiller is this. My coolant liquid is this.