Hey all, cartoner on line 3, 1756-L72, PanelView Plus 7 running the recipe screen. Operator loaded the new 250ml recipe this morning and the controller went straight to major fault. Cleared it, loaded the recipe again, and it faulted again the moment the load button was pressed.
Major Faults says Type 04 Code 34 and points at a TON in P_Cartoner, R_Glue, rung 8, Glue_Dwell_TON, and that timer's been there since 2019. The 250ml recipe went in last week, our packaging engineer added it on the HMI only. I deleted the TON and put it back in with no change, and the old 500ml recipe still runs fine.
Can a TON corrupt itself, or any ideas what's going on?
Not a firmware bug. A T04:C34 is the controller telling you the .PRE or .ACC of a timer went negative, which only happens if something upstream is writing a value into the preset that it should never be allowed to write. What does the recipe write into Glue_Dwell_TON.PRE? Go online, load the 250ml recipe, and read the .PRE before it faults, or trend it. Firmware on the L72?
What's the difference between .PRE and .ACC on the TON? Is .ACC the one counting up?
31.011. Caught it in the watch window. Glue_Dwell_TON.PRE goes to -1600 the moment the recipe lands, then the fault. The other recipes put 800, 1000, 1500 in there and this one was entered as 800 on the screen too. joeb, .PRE is the preset, .ACC is the running count. Not sure why it's negative, but that's what the watch window shows.
HMI tag or direct reference on that numeric entry?
HMI tag. Opened Tags in the panel project, Glue_Dwell_ms has Scale 1 and Offset 2400. The 500ml tag next to it has Offset 0. Engineer says he copied the tag and thought Offset was a range limit. It isn't. The panel takes the offset off before it writes, so 800 typed on the screen lands as -1600 in the PLC.
There it is, and it's not just one fix. Both sides need doing. Panel: Tags editor, Offset back to 0, then Minimum 100 and Maximum 5000 on the numeric entry. PLC: land the HMI value in Glue_Dwell_Req, LIM 0 to 5000 in front of a MOV into .PRE. Plus a program fault routine in P_Cartoner so a T04:C34 logs and clears.
Done both. Offset back to 0 on the panel tag, min and max on the entry, and the LIM in front of the MOV. Loaded the 250ml recipe twelve times this morning, dwell lands at 800ms every time, no fault.
So an HMI tag offset of 2400 pushing the preset negative, and T04:C34 is what a TON does with a negative .PRE. Offset back to 0, plus the LIM in the PLC so it can never happen from the panel again.
Program fault routine isn't in yet. Our change control wants a review for that, so next shutdown.
Thanks rsdave and hannah.
Learned that one the same way, on a filler. Not fun. That offset field has bitten more than one of us.