CNC Laser cutters come with an onboard security feature such that a cut in the water flow results in a Water Error. This stops the laser beam from firing as the machine would not have registered the availability of water cooling so as to safeguard the laser tube. Without this feature there is danger of the tube overheating and cracking.
The first step would be to check for any loose connections according to the following wiring diagram:
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The Test button on the power supply can also be used to try and fire the laser beam whilst eliminating the control panel button. Also check the water supply from the chiller since the water flow sensor will not pick it up if reversed. The water should flow from positive (thick red wired side) to negative across the laser tube at all times.
To confirm that the flow sensor is indeed faulty one can bridge G(Ground) and WP(Water Protection) on the laser power supply green connector. The feature would be unsafe to use over long periods of running but if the laser beam does fire that confirms the sensor as faulty.
Open the back panel to access the flow sensor which is a white device mounted onto the body with inlet and outlet water pipes. Cut the 2 wires from the sensor so as to test for continuity from a multimeter with the water running. For a working sensor the meter should beep indicating that a signal is being sent out as the water flows across it. That is how the machine is alerted on the availability of cooling and in turn enables the laser beam.
When replacing the sensor please take note of the water flow direction in the case that the replacement sensor is different in structure. This is usually indicated by an arrow originating from the water input side and pointing towards the water output side.
For testing purposes, you do not need to mount the sensor onto the machine but can just hang it somewhere safely so as to avoid the wiring from touching and short circuiting. Proceed and repeat the continuity test. If successful fire the laser from the control panel to confirm. The new flow sensor can then be mounted onto the machine whilst carefully soldering and insulating the wiring. At this point the laser cutter will be ready to work in a safe manner.