Coolant supply system for laser processing head and method for supplying coolant to laser processing head

A coolant supply system for supplying coolant to a laser processing head, the system comprising:

• a capacitance type distance sensor for measuring a distance between the laser processing head and a workpiece;
• a coolant tank for accumulating coolant generated by using deionized water;
• a coolant supply passage for supplying the coolant that accumulates in the coolant tank to the laser processing head, wherein the coolant is to be injected from the laser processing head toward the workpiece;
• an electric conductivity meter for measuring an electric conductivity of the coolant to be supplied to the laser processing head;
• a first drainage passage having an electromagnetic-first-drainage-passage valve and capable of draining the coolant to an outside of the coolant tank;
• and
• a controller configured to control open and close operations of the electromagnetic-first-drainage-passage valve,
• wherein the controller is configured to turn the electromagnetic-first-drainage-passage valve from a closed state into an open state to drain the coolant accumulated in the coolant tank through the first drainage passage when a measured value of the electric conductivity meter exceeds over a preset upper limit value;
• and
• an electromagnetic-coolant-supply valve that is provided on the coolant supply passage to open and close the coolant supply passage, wherein
• the first drainage passage is branched from the coolant supply passage between the electromagnetic-coolant-supply valve and the coolant tank,
• the controller is configured to control open and close operations of the electromagnetic-coolant-supply valve in addition to the open and close operations of the electromagnetic-first-drainage-passage valve, and
• when the measured value of the electric conductivity meter exceeds over the preset upper limit value, the controller turns the electromagnetic-coolant-supply valve from an open state into a closed state to stop supplying of the coolant to the laser processing head and turns the electromagnetic-first-drainage-passage valve from the closed state into the open state to drain the coolant accumulated in the coolant tank through the first drainage passage.