There are reference recall procedures connected to the machines’ control units. For instance, a machine equipped with Fanuc control requests a reference reminder first with the “306 Battery voltage low” alarm to indicate battery voltage is low, and then it displays the “300 APC Need ZRN” error to indicate taking a reference reminder action is necessary. The following corrective steps should be taken:

Change the battery, before anything else,
– Bring the relevant axis to reference position manually (note the sign with double arrow pointing opposite directions, depending on the model)
– Press the Off-Set key on the keyboard
– Press the Setting key under the display
– Type 1 in the blank “Parameter Write : ….”, and press the Input key
– Press the SYSTEM key (the parameters page appears)
– Type 1815, and press the No SRH key under the display
– Bring the cursor on the relevant axis line and set both the APC and APZ columns to 1, then switch off, and start the machine again.

This varies depending on the control unit used in the machine. The below given steps are for a Fanuc 0i-MF control unit:
– Set the Program Protect switch to Auto
– Set the mode switch to RMT (DNC)
– Press the right arrow key under the display
– Press the software key: [DIR] (under the display)
– Press the software key: [OPRT] (under the display)
– Press the right arrow key under the display
– Press the software key: [REFRESH] (under the display)
– Program list will be displayed. Type the line number of the program you want to run.
– Press the software key: [DNC SET] (under the display)

NOTE: TO CANCEL DNC SET, press the software key: [DNC CLR]

This alarm is due to the Emergency Stop key -used to stop the machine in case of emergency- left depressed.

This may due to a depressed EMG switch on the axis, used to stop the machine in case of limit excess, depending on the model. The problem can be solved by moving the axis to the opposite direction with the switch save key that enables the axis to move.

The AC motors that drive swarf conveyor and water pump in CNC machines are fed over a thermic and contactor system and in such overload (excess load) errors are generally due to thermic shut-down. Press the reset button on the respective thermic of the motor to solve the problem.

There is a level sensor to check the lubricant level in the lubricator tank used to lubricate skids and ball bearings in CNC systems. This alarm is displayed when the lubricant level is low to zero. Fill the lubricant tank with the appropriate lubricant to solve this problem.

The level sensor may be broken, or stuck due to contamination, if the alarm is displayed when the tank is full.