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Error 50056 and 50021

  • Hello, I have a IRB6400 M97, its throwing mainly 2 errors but the joints change. I cannot get any of the joints to move as they throw these errors. I cannot manually move them either via the brake buttons. There is no click at all.

    Error 50056 - Actual torque on Joint IRB_4 is higher than ordered while at low or zero speed

    Error 50021 - Actual position of joint IRB_3 is too far away from ordered position

    I have tried to look at previous threads about checking the KM3 contactor. I don't see this anywhere I assume I have a different year/model.

    Any help on this is greatly appreciated.

  • The contactors are at the top/front/center of the controller under the metal panels.

    There is information in the product manual that has the location and the circuit diagrams for tracing out the 24V Brake circuit.

    Normally the brake release buttons will operate a few seconds after the disconnect is turned on. To avoid unexpected movement of the robot, PLEASE be careful when pressing the brake release buttons.

    Also note there is approx. 265VAC at contactor K1 when power is turned on. Please be careful.


    Some of my favorite possibilities are:

    A loose wire at the contactors or someone has miswired the contactors.

    Bent pins at the motor power connector at the base of the robot.

    Loose connector on the Brake Release board in the robot

  • Thank you Scooter for you help on this.

    I had an electrician come in and check the contactors he took them out and performed tests to re certify them. They are working. I was curious and I removed the small round communication cable from the cabinet to the back of the robot and swapped it with another robot. Weirdly enough both robots worked for about an hour the same robot that was having the issues started acting up again. throwing the same errors plus a new one 39211(High temperature on transistors on drive unit joint 3.

    Where would the brake release board be located?

    Thank you for the warnings, I am aware of those and am very careful. I really do appreciate these warnings as I do want to go home safe when the day is done.

  • I had similar problems to this with a 6400, especially the temperature warning. turned out to be bad connection at the large connector motor cable into the base of the robot. it wasn't obvious as all the pins looked ok.

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    Regarding the contactors: A weak contactor may test good but can occasionally drop out. I like to test them at 18-20VDC and make sure they have a solid "thunk". Sometimes the aux contacts can be dirty - they may "beep" on a continuity test but the resistance may still be several hundred ohms.


    Regarding the Brake Unit location for your 6400: It is in the robot on the axis 3 motor side. Remove the (4) T30 screws holding the cover for the manual brake switches. Those switches are part of the Brake Unit. The function of the Brake Unit is to route the 24VDC for the brakes in each motor and to provide manual brake release for each motor.


    Regarding the 39211 error: Assuming the drive unit is good, the overheat may be coming from the excessive power being used or the lack of cooling due to the fins of the servo amp clogged and/or the servo fans not working. The error should also tell you which joint(s) are giving the overheat. If the error is consistent on a specific axis, try swapping two of the drive units and see if the problem moves.

  • Thank you FriendlySteak. I swapped this cord out with another robot. I also swapped the cabinets and have isolated the problem to be within the cabinet somewhere. I can move axis 1,2 and 3 but axis 4, 5 and 6 will not move. they throw the same errors as before

    Error 50056 - Actual torque on Joint IRB_4 is higher than ordered while at low or zero speed

    Error 50021 - Actual position of joint IRB_3 is too far away from ordered position


    Thank you Skooter,

    I have isolated the issue being in the cabinet itself. Consistently i can always move 1,2 and 3 now but never 4, 5 and 6. Would this eliminate the problem to be the K1,2 and 3 contactors?

    I am no longer getting the overheat error either. In hooking up another cabinet to this arm I can freely move all axis.

    Its strange.

    Where is the brake release board located? A82 ?

    Edited once, last by Brokenenvy ().

  • Regarding the Brake Unit location for your 6400: It is in the robot on the axis 3 motor side. Remove the (4) T30 screws holding the cover for the manual brake switches. Those switches are part of the Brake Unit. The function of the Brake Unit is to route the 24VDC for the brakes in each motor and to provide manual brake release for each motor.

    Since the robot is not the problem, the Brake Unit is no longer a consideration.


    I still suspect a lack of brake voltage to the robot. The large axes can power through the brakes on an older 6400 with many hours.

    Make sure contactor K3 pulls in when you enable the deadman and slightly move the joystick. Measure for +24VDC at contactor K3 terminal 8 with the K3 contactor pulled in. Also verify that wires 364 & 365 are connected to K3-8 and wires 313 & 314 are connected to K3-7.

  • Thank you Scooter. I had an electrician come in and he fully tested all 3 of those contactors to the point of recertification. they are all in perfect working order. any chance it could be the A81 or A82 boards? anything to test those? or even rule anything else out?

    Your help on this has been fantastic so thank you again.

  • We had the motor on lamp short out to the extent that the brakes would not release. Maybe if you are having a minor short intermittently, it could cause this issue. I had never even thought that the brake release power runs that lamp also.

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