[liudongxjtu]

Hi guys,

Some question about manual feedrate override need to acquire you.
In our lab, we have an Excello Machine Tool with a Fanuc15-MA CNC system that is a big PCB board CNC system, and it has a feedrate override function implemented by former colleagues, now I can't understand, so I guess you experts can remove my confusion.
The first part is related to the AUTO feedrate Override, the ladder in PMC is shown as below,

The AUTO Feedrate Override table is defined by the CODE function, shown as below:
000 00255 00245 00235
003 00225 00215 00205
006 00195 00185 00175
009 00165 00155 00145
012 00135 00125 00105
015 00105

I can understand the AUTO Feedrate Override by the data table, it is that the G12 address can be overridden by the R400 input index, and the all value in the table is from 105% to 255%,
it makes sense.


But for the Manual Feedrate Override function in ladder, I totally can’t understand, it use a similar table to determine the value in address G14, but the data table is
000 00000 -01001 -02001
003 -03001 -04001 -05001
006 -06001 -07001 -08001
009 -09001 -10001 -11001
012 -12001 -13001 -14001
015 -15001

I don’t know why they use a negative number, for example -8001 here, and I know that the G0014 address only have two bits can be override for the feedrate, I attached the explanation about address G14 as below.
I don’t know why need to use a negative number and why it is those number.
G14.bmp
Look forward to your reply.
Thanks a lot.