Posts by tmuthesius


    some time ago, we did our first wood milling :

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    Hi, sorry for my late replay.

    I my case, the component that caught fire was a varistance (mounted in // after the rectifier) intended to catch high voltage spikes from the main (if I understood this well).

    I read somewhere that this components have a limited lifetime because of the stress caused by high voltages and often end in short circuit failure.

    In my case (and regarding your picture, I would say that it's also your case), I am assuming this failure caused the one or two thermistances mounted in series just between the rectifier and the varistance to blow up because of over current.

    I changed all 3 components and everything worked again.

    Not sure if I am allowed to send direct links to Farnell here, but I the case you are't able to read the components values, this are the one I ordered :…57213?CMP=i-bf9f-00001000…13006?CMP=i-bf9f-00001000

    Hope this can help.

    By the way, here at the workshop, we managed to interface the robot with rhino + grasshopper + kukaPRC and to make him draw something.

    Here is a little video of this :

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    At the moment I am doubtful about precision, but I will write a more detailed message about this ASAP.

    Have all a nice day.

    Hi, thanks for this explanations.

    As you said, with programmed mouvements the acceleration ramps are really smooth and I don't notice any jerk.

    I will see how it works when I'll get a spindle attached...

    BTW : I had another issue last week : the cabinet suddenly stoped working and the breaker had tripped. When rearmed I just got a huge spark in the PM6 power supply...:fearful_face:

    Luckily it was only the over-voltage protection varistance just after the rectifier who caught fire and probably got shorted. Apparently this components get aged.

    I took advantage that the PM6 was open for 5th time to change to 2 big capacitors of the power supply. Not sure if this had any sense ?

    Everything is back to normal for the moment.

    Have a nice day. Tobias.

    Hi, The Robot is bolted on ground. Although the concret thickness doesn't meet the kuka recommandations...

    Nothing is attached to the robot yet.

    It's seems to be related to the stiffness of the robot, but since I don't have any previous experience with robots, I can't judge if this is just normal.

    Perhaps I should move on with programmed movement tests.

    I let you know.

    Hi !

    I received and mounted a new (but used) IGBT (ordered on RGB Elektronika) and ....

    the robot works again ! Hiiiiihaaa !

    So I could terminate the mastering and make the first manual "linear" movements. Already impressing me a lot... :face_with_open_mouth:

    I am a bit confused about the spring effect the arm does when a movement stops suddenly (about some millimeters). Is this normal ? Or a problem of play in the gears or in the counterbalancing ? Anyway, I will make some tests when I will gets hands in programming and perhaps start another thread for this.

    Thanks again for your help.


    So, some days ago I changed the faulty current transducers and tested again and....... same error :loudly_crying_face::tired_face:.

    Yesterday, I studied the PM6 schematics and found out that there is a IUBER fault signal not coming from the current measuring circuit but from the IGBT driver boards. This signal is generated form the IGBT driver chip by measuring the desatauration voltage. I did not exactly understand how this work (data sheet of the driver chip -> BUT I just measured the IGBT the way they tell in this video (

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    ) and found out that 1/6 of the output is shorted.

    Seems that I have to change this component... but I still have a lot of questions :

    - Can this fault damage the current transducer ? The faulty IGBT is on the middle line, the one that do not pass through a transducer...

    - Can this fault have damaged other components ? Or is the design of this PM6 unit robust enough ?

    - If it's the same problem that enleth described why is this frequently affecting axis 4 ? Because of it's position on the heatsink ? :thinking_face:

    - And last but not least : where will I find this IGBT (6MBI25LB-120) since they seem to be no more produced. Would someone have spare or salvaged ones and be willing to sell one or two ?

    Wish you all a good Sunday !


    thanks for the confirmation about torque and current. I didn't mention it yesterday, but the transducers indeed have internal electronics. I opened the doubtful one and measured the coils (there are two in series) and one seems open. Why did this happen ? I don't know and I hope it's not another problem that triggered this failure. BTW, it's the most bottom transducer that is involved, I did't see any label for it on the PCB.

    Now waiting for the new transducers. I'll let you know if I reach something.

    Elia_ : about schematics, would you accept me to contact you in MP for that ?


    this afternoon I measured resistance on the current transducers legs and found out that one of the axis 4 ones had open circuit between + and - and between M and -.

    This wasn't the case on the other transducers. So I suppose I do have a track.

    I will replace this unit and let you know.

    Have a nice day. Tobias.

    Hi and thanks a lot for your quick and detailed responses.

    I really appreciate your testing advices and safety warnings. I don't think I will make any measures with disassembled and powered PM. I hope I can find the problem juste by measuring components offline ?:thinking_face:

    I really suppose the PM600 is in cause since the test I made by swapping axis 4 and 5 connectors on it immediately triggered the over current fault still on axis 4. To be sure I juste made the unconnected axis 4 cable (but shorted cable position pins) test and still same fault.

    I also measured the resistances of the motor coils directly at the PM connector (disconnected from the PM of course) and it seems consistent between axis 4 and 5 (about 2.1 ohm on each coil).

    So it sounds similar to enleth's problem and I also suspect the current measurement circuit. What I find interesting is the way the problem became gradually badder : over torque faults sometimes to over current every time. I am very curious to know how the torque is measured. Because if it is with the same current sensing circuit, this errors would be consistent and there progressive graduation would perhaps indicate a slowly blasting component. A capacitor ?

    Do you think there is some possibility to find detailed schematics of the PM-600 ?

    Thanks again for your help. Tobias.

    Hello everyone !

    I am french so excuse my not perfect english.

    First of all, thank you all for this amazing community, it already helped me a lot in rescuing my new (old) robot.

    As introduction : I work with wood and am passionate by technology (programming, electronics, mechanics...) but I don't have any experience with industrial robotics.

    I have the project to use a robot to do some wood carving/milling for making some carpentry assemblies and other stuff involving a spindle attached to the robot.

    So, 2 weeks ago I bought an old kr150L150/2SP with a KRC1 controller and KCP. The robot was not used the 10 last years.

    What I all already did on it:

    - backup the original HDD (clonezilla with IDE to USB adapter)

    - change the big capacitors of the motherboard so it POST again

    - install a new (old) HDD, the original one made annoying sounds during backup

    - partitioning, formatting and clean install of Windows 95 and KSS 4.1.7 following the Kuka manual (more or less, I did't use a CD but copied the install stuff on the D partition)

    - get the right MADA folder to use by asking Kuka with the serial number of the robot (they answered within 2 hours! nice)

    - get the 6 axis to move in manual mode

    - get the robot down the pallet and bolt on floor

    - turn an aluminium dial gauge adaptor to make the mastering

    - mastered axis 1 - 2 - 3

    And now I am stuck.

    In fact the next day a made the first movements, as I wanted to try again, I got an "over torque on axis 4" error just after pressing a movement button (axis 1 if I remember) and having bad sounds in the robot. I checked the hardware stops (not in cause) and after 2 or 3 trials it worked again correctly.

    Some days after : same thing.

    And yesterday I got an "overcurrent on axis 4" error and this time I got to restart the whole krc1 to reset that (if someone have a faster solution to reset it...).

    After that, it restarted to work correctly so I could master axis 1 to 3 and as I wanted to move 4: "overcurrent"...

    What I did yesterday :

    - made a try with motor 4 powercable disconnected -> "got over torque error" / can this damage the PM ??? I hope no :loudly_crying_face:

    - swaped cables of motor 4 and 6 -> error still on axis 4

    - measured resistance of motor coils and brake in the connection box -> seems OK (similar to the other motors)

    - took out and opened PM6-600 and checked the output short relay opened correctly -> seems OK / not understanding for what purpose this relay is, if someone have an explanation...

    - swaped axis 4 and 5 connectors on PM6-600 -> error still on axis 4

    - reprogrammed the current limiting EEPOT according the kuka manual (with swap of the programming jumper) -> not sure something happened since the UI tells nothing...

    Now, whatever axis I try to move, I directly get the "overcurrent on axis 4" error without any sad sound in the robot.

    I now decided to ask for help since I feel stuck with this problem.

    So everyone is informed : I don't have any access to Kuka spare parts to make swap tests. I am equipped with some electronic tools : oscilloscope, protocol analyser. I am ready to put hands in the PM6-600 since I don't want to spend the price I have bought the whole robot to replace this unit.

    Thanks to everyone that read until here and that could give me some tips to move on.

    Wish you a good day. Tobias.

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