We have a Fanuc R-30iA controller that we use with a M-900iA 350 manipulator (<6 months old). The problem is that OVC is generated only when the robot is run at low speed and at only one point in its path. There is no problem when the robot runs during production i.e., 100%.
The OVC alarm is generated in the 5th axis (only) and at only 1 point in the cycle where the current in the J5 axis (-21.8 A) is almost close to the minimum current limit (-21.9 A). Physically, the manipulator is carrying downwards a payload of almost 285 Kg (145 Kg Hand + 140 Kg Underbody) and J5 is at an angle of ~-100° (I hope you can visualize the robot position). When I bring down the speed to 30-40%, the current at that point shoots up to almost 25 A and the OVC is issued. I find this very strange.
If it was any other robot, I would have done the payload estimation for the robot with Hand + Body (currently payload estimation of Hand + Underbody is present. I think it was determined from OLP itself) again. But here it is not possible because (A) the underbody is huge and (B) the robot just carries the underbody down from point a to point b and does not grip/clamp it in any way.
What could be the reason and any ideas how I can resolve the issue?