The FANUC IO board has been allocated according to the board model when we wrote the ladder diagram. If three IO boards are connected in series, then when the machine is running, the FANUC system detects that the number of IO boards is less than three, and it will alarm ALM197 (OID, 31IB, OIF system), 972 (18, OIA, OIB, OIC system):

 

 

 

 

 

The reasons for this alarm are as follows (the order is based on the probability of occurrence):

1 Short circuit of external IO point;

2 The external IO fuse is broken;

3 An external IO board is broken;

4 JD1A-JD1B IO link cable is damaged

5 The FANUC system motherboard is broken.

6 The switching power supply for IO is broken.

Case analysis:

          There is a horizontal machining center with FANUC 18-MC system. During operation, 972 alarms occur sporadically, as follows: