Prohibit to plug or unplug the USB cable in an energized state! Otherwise it'll cause to burn electronic components.
Correct steps:
Step 1, plug the USB cable;

Step 2, open the software (to establish communication connection);
Step 3, turn on the laser power;
Step 4, start working.
Step 5, after working, turn off the laser power first, then quit the software;
If you want to unplug the USB, you must turn off the power and quit the software.