HELP! OVC Alarms 7th Axis Fanuc

  • :wallbash:
    Fellow Robot Wranglers
    I am working with a Fanuc R30a R-2000ib. The robot is used in casting to pour melted aluminium into molds (a die casting robot) The robot eoat is a ceramic ladle with a 7th axis motor. The 7th axis rotates one direction to fill the ladle in furnace and rotates opposite direction to pour the aluminum in mold. This 7th axis get alot of OVC alarms. The alarms used to occur whenever the robot ran a certain dumping program. I found the 7th axis was rotating to slow and caused it to fault and OVC. Once i sped the trajectories up this fixed that ovc problem. THE ISSUE I HAVE NOW: If the robot is told to stop once after it has filled the ladle-(from bad machine signal) The 7th axis completely relaxes and then causes OVC alarms! How do i get rid of the OVC alarms on a ladle full of aluminum? Also moving the robot in manual, if ladle is full and the dead man is released an OVC will occur. Some how 2nd shift always finds a way to fault the robot and cause OVC when it is nowhere near a collision. Thanks

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  • Sorry ^ There are not any payload schedules set up. Since none are set this means that the default payload is set to max capacity? Which in this case is 125kg. With Collision guard enabled @ 100%.

  • Has it always ran this way? If so the motor is probably overloaded, I've experienced this before when the gear ratio was half of what it should have been.

    I would guess for your application, the gear ratio could be increased, which would reduce the load on the motor.

  • Yea Im sure it has always run at these settings cause the fella who set it up 6 years ago hasn't been back since,,,,, the ovc alarm started occurring after adding a application that calls for heavier load to the 7th axis. Increasing the gear ratio is done on controlled start?
    I was going to try to increase the allowed amp to for that axis to see if that would effect the over currents...but that axis disturbance torque cannot be adjusted, J7 it is (****) with the alarm message Collision Detect Disabled.
    Would Setting payload even affect the rotation of this axis?
    E1. J7 it is in SubGroup 1 and not a separate group 2.

  • When was the last time the 7th axis grease/oil changed? Since it's subject to heat, it could be now be a stinky, black, watery substance that has little value as a lubricant. Check for metal content in the grease/oil, you may have a bearing going bad. Motor could also be the fault if it weak or has a dragging brake. Even the servo amp could cause this.

    Not sure what you mean by 'relaxes' but it sounds like a bad brake.

    Upping the load and stretching out the accel time as Racermike said would be where I would start if all mechanical/electrical is good.

  • If the load was increased you should make changes to cope with the new load
    What kind of mechanisms is used? If it uses a gear reducer then you can start with that
    Some ladle mechanisms use a 4 bar linkage mechanisms
    You can make one linkage longer to increase the pull ratio
    Or can you add a counter-weight to balance the weight of the ladle???
    Counter-wieght is the simplest solution
    if notting works you shoud use a bigger motor

  • You may want to make some changes to the load ratio, max speed, and accel times in the setup for the extended axis.
    I would start with increasing the load ratio if it isn't maxed out. Then the max speed, and then the accel times.

    I have read up on this, Thank you everyone for the knowledge. How/Where do i Adjust the Load ratio? and Gear Ratio?

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