Serious problem with axis A2

    Hello guys,

    i have a big problem on my KUKA KR16 robot.

    We called a technician that help us to install the robot, and he made a big error.

    The phisical endstop of axis A2 was installed in a wrong position. As you can see in the photo attached, in moving the robot, the calibration part of the axis A2 hit the arm of the robot because the endstop is not reached before the calibration part hit the arm.

    So i have tried to move in the right direction the arm of the axis A2 with the + button but the arm try to move in the opposite direction and the controller told me that the gear torque exceed on axis A2. So i'm not able to move the arm in the right direction to change the position of the phisical endstops and calibrate the axis.

    How can i solve this problem?


    The technician don't know how to fix the problem ... :pouting_face:


    Thank you very much in advance for you help.

    there is something you are not telling.... what was he doing exactly (or trying to do, what kind of work)?

    what was the reason to move hard stop? was he taking arm apart? looks like link arm was removed and not put back correctly. perhaps wrong gear was installed? more pics?

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    I’ll try to explain better...

    Three months ago we bought a used robot.

    The robot arrived by courier in our company disassembled (only the axes were mounted).

    then we called a company that helped us to robot positioning and starting.

    After some test on the motors all was good and the technician going to calibrate all the 6 robot axes.

    Unfortunately the technician doesn’t saw that the physical endstops are not mounted well ... and yesterday when we try to teach some point for a program test... we manually moved the axis a2 back to “compact” the robot.

    We receive the message “gear torque exceed on axis A2” ... so we checked the robot and we saw that the calibration point hit the arm below and after that we are not able to move the axis A2 and A1...

    All others axis work perfectly...


    now my question is: how can I solve this issue?

    Ps. When I try to move the A2 axis to + direction the arm try to go in the - direction and the error above appears.


    Waiting your feedback ... any help is very appreciated...


    bye :smiling_face:

    "When I try to move the A2 axis to + direction the arm try to go in the - direction and the error above appears"


    so don't try to move it in the + direction. there should never be collision with pin. if you got robot in parts, chances are you got ... mix of parts.... maybe they are not all from the same robot.


    if the gearbox is different it can be different dimensions (thinner) and turning the wrong way. this could explain why the link arm got so close to rotating column that it interferes and why the axis moves wrong way. btw gearboxes are expensive. this is why so many chop-shops are refurbishing and selling used robots. big mistake was to get something in parts. now you will find out if it was worth it.


    moving in wrong direction could also be due wrong MADA. to verify that you need to compare what robot thinks with what is on the robot nameplate.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    the robot was bought assembled ... not in parts ... only cables and cabinet were not connected...
    Just to be clear, this is a new problem ... the day before yesterday I used the robot without any problem and I made also 3 little programs and the directions was right ...

    yesterday when I’m programming I put the robot in a position that the calibration pin hit the arm below... this happens because the robot reseller mount in a wrong position the physical end stops of a2 axis ... but I know how to fix that but for do that I need to move the a2 in + direction ...

    how can I move the axis a2 in the + direction?

    Do you think that restoring a backup can help?


    let me know


    thanks

    We are still missing something here, a normal robot never hits his physical endstops. There are software limits before it. if you where able to move past it someone must have changed them or they where wrong from the start.


    Depending on which it is restoring back-up could help or it could not.


    As a last resort you should be able to move the arm by hand if you can access the motor of A2 (I have never worked with a KR16 so i dont exactly know how they are put together but i assume it is similar as the bigger models). In this case you have 2 options:


    1. Secure the arm and remove the motor. I can not recommend this because you dont seem to have a lot of experience with robots. But after a motor is pulled from the gearbox it should be pretty easy move the arm and place the motor back. in case you go for this option please be mindfull that without an motor installed there is nothing to keep the arm in stationary.

    2. Hand crank the motor, by far the easiest way the only drawback is you will damage the brake in the engine.


    Before you attempt either make sure that there isn't something else you or your technician missed. any setting you changed or anything you might have been experimenting with.

    Every problem has a solution, that isn't the problem. The problem is the solution.

    I'm sure that there is something wrong in the robot from the start but now this is not the matter.

    I need to move the A2 axis in the + direction and also the A1 axis that is not moving too... i don't know why.

    I tried to restore the backup but the problem is still here.

    A robot without right mastering can hit the physical endstop so i think that when the robot was mastered is not mastered right and so the arm can hit the other arm in the calibration point.

    As you can see in the photo of the first post.

    Attached you can find also a photo of the entire robot, there is nothing that block the A2 axis in + direction... but there is the calibration point that hit the other arm in the - direction... i don't know why the motor can't move in + direction...


    Is there a way to deactivate the gear torque control on that axis... in this way i can try to move the robot in + direction with the controller...

    Waiting your reply ... i'm becoming crazy ... i have to solve this problem...

    There is now way to just turn of "gear torque control" as you put it. In this case and judging by the foto's i think the arm could also be stuck on the calibration point, so your best option is probably to move the arm by hand. And if it is truly stuck that might also be a problem.

    Every problem has a solution, that isn't the problem. The problem is the solution.

    If you remove the small circular cap on the back of the A2 motor, this should expose a 12mm hexagonal fitting. This is the end of the motor drive shaft. A socket with a long lever can be used to forcibly rotate the motor without releasing the brakes. Power should be off while this is done, obviously.


    Using this method will damage the motor brakes, so only use it to the minimum degree necessary to un-bind the joint.


    After this it will be necessary to re-master A2. Given the damage to the A2 mastering gauge, this may present a real problem.


    However, I must agree with the other posters -- under any normal circumstances, it is not physically possible to cause the kind of collision shown in your original photo. The fact that this was able to happen at all makes me suspect your robot is modified, or non-standard in some other way. Can you post a wider-FOV photo showing the entirely of A2 and the collision area in a larger context?

    Hello at all, i have news.

    For some strange reason i was be able to move a little the a2 axis in + direction with help of an hand, a little bit to unblock the arm.

    So i checked what happens when i push + button to move the a2 axis... and then the surprise... seams that the motor don't turn when the brake was released... and with the weight of the upside part of the robot, the a2 axis go down ... to - direction...

    So in my opinion the connection works good because the brakes released... but the motor don't turn...

    Is that possible? How can i check if there is some motor or driver problem?


    ps. the mastering gauge was not demaged... only the arm has a little demage but is not important i think... see photos attached...

    what is the exact controller type?


    brake needs 24V and about 1A to release. if there is no current through brake, it will not release. you may not realise that since all brakes are working at the same time so click you hear is the other brakes.

    reason brake may not release is open circuit (loose connection for example) and this needs troubleshooting.


    so measure brake resistance (or at least check continuity) directly and with cables until you find the problem, may be bent or pushed out or oxidised contact, bad motor, etc.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    Ok panic mode, the model of the controller is VRK C2.

    how can i check the continuity of the motor brake? where i have to put the multimeter? There are many and many cables inside any connector and i don't know which is the brake motor cable... Can you help me?

    the first one is just a table of fuses, not a electrical schematics.

    second one is cabinet label. Based on this KUKA support can provide you with copy of the original schematics.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    Ok I’ll ask kuka the schematics ...

    Is there a test for the motor?
    If I put the motor away and I connect it without the arm ... free to move ... can I check if the shaft rotates?
    that can be a good test for checking the motor??? Let me know and thanks

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