Running Fanuc OiMD in MDI Mode while in Alarm State

[yaji63]

Hi,

I have a machine with Fanuc OiMD controller. This is with incremental encoder. At times after a Power ON the machine does not get to HOME position in any one of the axis and gives an overtravel alarm if i try to HOME it with the homing switch on the control panel of the machine. The axis will not be anywhere near limits during this time and the alarm happens only because of the machine being an incremental encoder and it forgets the present machine position during a power OFF or power failure.

Below are the steps which i take to solve the problem.

1. Enable parameter write function on setting screen.
2. Manually change the travel limit to -9999 in the respective axis in system variable #1321.
3. HOME the axis by pressing the button on control panel for homing the particular axis (dog referencing happens and machine reaches home position)
4. Change the limit back to original values in #1321.

I want to do this through a programmed M code if possible so that the operator intervention is taken out of the whole scenario to avoid mistakes by operators while changing the parameters. The problem here is that the machine does not permit running any NC code while in overtravel alarm state (or probably any alarm state). Is there a way to run a program or M code while in this state wherein i can program an M code where the system variable values for #1321 are changed by G10 L52 command and then change it back to original values after homing. Below is the program example:

%
O9090 (THIS PROGRAM NUMBER IS ONLY AN EXAMPLE AND CAN BE ANYTHING)
G10L52
N1321 P1 R-9999.0
N1321 P2 R9999.0
N1321 P3 R9999.0
G91G28X0
G91G28Y0
G91G28Z0
N1321 P1 R-3.0
N1321 P2 R560.0
N1321 P3 R550.0
G11
M30
%
(THE VALUES GIVEN FOR INDIVIDUAL AXIS IS ONLY AN EXAMPLE)

Like i have already stated, no program can be run in MDI mode while in alarm state in the present condition on the machine. Is there a system parameter which i can enable which in turn permits running a program in MDI mode ?
I do recall from somewhere that this can be done by parameter setting but i dont know whether this is on Fanuc OiMD or another controller.

Thanks a ton to everyone who can chip in with a solution to the above problem.


PS : I do understand the hazards of permitting the machine to run NC codes in alarm state Also made a detailed post so that the issue is properly explained.

[fordav11]

you can't run or do anything in a program or MDI if there is an alarm on the machine.

why not just power-on while holding P an CAN and it won't check any soft limits.
Then just zero return all axis.

[yaji63]

Thanks for the suggestion. I did try this once when the alarm was generated and it has worked.

Will try it a couple of times and if it works then i will lock the system screen to avoid system variable editing.