A CNC Laser machine comes with a non-contact proximity sensor used for motorised auto focus distance setup. This sensor or sensor wiring, although rarely, can become faulty leaving the user no choice but to manually set the focal length. In that case the malfunctioning entity would have to be changed.
Any metal piece can be used to test if the sensor is working. When the metal piece is brought into close proximity the sensor should light up red. The wiring can also be tested by checking for continuity from end to end making use of a multimeter.
Please refer to the manual in the link provided for the wiring diagram: (Via CNCU.CO.ZA)
Start by removing the wiring in between the sensor and the CNC controller from the trunking. If the sensor is initially not lighting up connect it directly to the controller to eliminate the wiring and test again. In this case the sensor worked perfectly when connected directly to the controller indicating that the wiring was faulty. The right-hand side panel on the laser cutter can be removed to make the wiring replacement easier. Approximately 4m of 3 core electrical wiring is required as the replacement.
Tape one end of the new wiring with insulation tape and feed it through the trunking and X Axis gantry. Connect one end to the controller and the other to the sensor whilst properly soldering and insulating the connections. Securely reconnect the sensor onto the nozzle. After placing the ruler provided directly below the sensor auto-focus the machine by pressing the Z-0 button on the control panel.
The focal length can be adjusted from the TruCut software. To do this the machine should have a direct USB connection to the computer where the TruCut software is installed.
Start by Reading the machine settings so as to access the onboard settings:
File -> TruCut machine config -> Read Machine Config
To rectify the onboard settings:
File -> TruCut machine config -> Axis Config -> Z Axis Home Offset
Increasing the home offset increases nozzle to material clearance and vice versa. After altering the home offset click OK followed by Write Config to Machine and proceed to test the focal length until the desired clearance has been achieved. It is advisable to get the focal length as accurate as possible as it affects the maximum cutting thickness and also how fine the detailing will be.