Programs freeze on M08 command

[Noizemaker31]

I'm having an issue with an MTI dicing saw (with Fanuc 18-M) that won't read code beyond an m8 command. When an M8 (coolant pump on) command is initiated, the coolant does come on, but the program siezes at this point. The flow meter on the front of the machine shows that there is in fact flow. When I run an M8 in M.D.I. the coolant comes on and the M8 command remains on the screen. When I shut coolant of with an M9 command, the coolant switches off and the command disappears (as with every other command that has finished executing).

It seems to me that something in the saw is waiting for feedback that the coolant has been turned on, and everything freezes because this feedback never comes. M32, 33 and 34 commands (left coolant, right, or both) create errors, as they are not "installed options." It looks as though M8 is the only coolant-related functiuon that it will recognize.

Does anyone have any ideas as to what is going on here? Any input would be much appreciated...

[Dan Fritz]

All M-codes require a "Finish" signal to let the control proceed to the next block. When the relay comes on for the coolant pump, there must be a set of contacts in the relay (or maybe a pressure switch) that will confirm that the coolant is on. That switch or relay will generate an "MFIN" (M funtion finish) signal to the control.

I would guess that your control has some "Ladder" logic in the programmable controller that will show the status of all these signals. See if you can find the "Ladder" display, or (better yet), some Ladder documentation from the machine tool builder.

[Noizemaker31]

Thank you for this advice Dan. I (as well as some of my genius colleagues) are going to get out the manual and dig in search of anything regarding "Ladder Logic" that we can find.

When we get this squared away I will post a reply with whatever ends up being the answer to our problem.

Thanks again!

[neilw20]

Dan Fritz will be right about the MFIN signal.
Can you examine the internal PROGRAM CYCLE CODE for M8.
It will probably give you a good clue to what's hanging.
Most likely this CYCLE is never returning.
If the code looks OK and is not currupted or weird, look for a broken wire from the pressure switch or coolant contactor auxiliary contacts.