Sound From the Robot when motors are activated

  • Good Morning to all,

    Here I am again with another problem with my D Series:

    I have came accross this a few weeks back. I could solve with after a "System Inicialization" of it (from the operation manual Section 17.3) and a download from the back up I had done before.

    I noticed the problem was back yesterday noon after the robot being unplugged for almost a week.

    Going back to the first time I had the problem it also happened after sometime being off.

    In advance, the robot is something around 10 years old, it had been sitting in the previous company for almost a year also not being turned on and we have no confirmation that its battery has been changed (which was one of our first idea for a cause).

    Following I am uploading a video that show the problem as it is. In addition: when the problem first happened and also a few times yesterday, the error i was being returned on the screen was Amp Overcurrent (mainly on the Jt3 but it also happened in the others).

    thank you all for the help!!


    • Video1.mp4

      (5.06 MB, downloaded 17 times, last: )
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  • Doesn't sound healthy at all, could be bad gear or physical brake not releasing.


    You should try and locate where this sound is resonating from by using screwdriver or metal bar resting on cast and 'listening' at the end of the screwdriver/metal bar (old school method).


    Try and get robot in a different posture, by testing using manual brake release.

    - Remember safety first as with manual brake release each joint will react to gravity direction for freefall.

    - It could be physical brake(s) is not releasing.

  • It comes from the motor on the JT2 (apparently) which made me think: why would it cause an overcurrent on other joints as 3 and 4?

    Also, as I had this proble before, it was just a Lucky shot that it came back to normal with the things i have done?

    is it even possible that my board is somehow damaged and having some assynchrony between the hardwares (board, encoder) and the software? (this is just a thought).

    I have read a few about the break releasing before, and it is advised on the manual that I should have the robot arms held to avoid the to free fall, and also, wouldnt it affect in any way the configuration on the encoder or some other feature?

    Thank you!!

  • okay, I a quite impressed: the MCB F4 is returning +/- 20V~ while F3 and F5 is returning e 220V~.

    unless this was expected, what the F4 MCB Connects? and where the power for it comes from?

    thanks for the help.

    Ps.: I didnt do everything you said, in fact i was doing something else and came to check on any answer and decided to do the easy thing and measure it.

    if you still want me to do so, i will do it once i have finished with the other stuff.

  • Yes i know, just mentioned it because I measured them as well to compare, didnt do anything besides it.

    just did the other steps you asked me to and yet no good news afterwards. Although the sound has decreased slightly, which doesnt make much difference as the problems still come up and the arms are still trembling when i try to move the robot in any direction.

    and here my doubt is still the same: do the breaks operate with 20V AC?

  • It seems like you are intent on measuring things so:

    1. Measure the incoming supply.

    - Are all 3 phases present.

    - Are all 3 phases balanced.

    2. How are you measuring the output F4 with respect to.

    - It is usual for brake AC to be approx 26VAC, so it could be a little low.

    - Depending on the incoming supply, if low, then the brake AC supply maybe low.

    - This AC is converted to DC inside the MC Unit to provide ALL motors the same DC brake voltage.

    - But if motor brake is mechanical failure (ie not releasing), then this can cause motor deviation issues.

    - To fully check, you must use manual brake release and see if each joint can moved during release.

    - For this, you should have someone else to assist safely and/or way to arrest joint fall during test.

    - if ALL motors not releasing, then problem is supply or MC Unit issue.

    - If only 1 motor is not releasing, then problem is on that motor or harness issue.

    - If ALL motors are releasing then issue is more likely gear box with specific joint.

  • So, I have done the measurements you asked, I also tried and changed the socket i was using (just in case) and repeated them: i noticed one of the phases was 15~20V under the other which i dont think would do much difference, but anyway...

    I also saw in the troubleshooting manual Section 1.2.4 that 21VAC is actually the normal voltage the MC system would operate, which means that this just might be alright...

    I didnt try to release the brakes manually once i have no one to help me at the moment (at least for the JT1,2 and 3) but what should i do afterwards: will i be able to move them with my own strenght or can i operate it normally with the TP?

    I am asking because i was thinking that i could do it at least for the JT4 as it has no chance to move in Z from the position i have the robot.

  • JT1, JT4,JT5 and JT6 should be no problem for some one to move on their own.

    But you do require someone to assist with the manual brake release switches.

    If no-one is available to help, it would be foolish of me to advise further regarding manual brake release functions.

    It may not be your brake release that is causing the issue, but considering the age of the robot arm, the symptoms I hear are the sounds I have heard in previous instances when a brake is failing to release.

    Alternatively it could be a gear box issue.

    You could try isolating the problem by using Joint Mode in Teach.

    - Jog each individual joint and see if you receive any errors during each joint test.

    - As gravity is acting on a joint (not currently being jogged), if there is a problem, then an error may occur.


    say you just jog JT1, whilst jogging JT1, you get an error relating to JT2 or JT3.

    Then try as you can jogging that joint to a different posture instead where gravity is not acting on it.

    Then repeat the test.

    This will isolate your error possibly and prove which joint is the problem.

    Then you can ascertain if brake is not being released or possible gearbox problem.

  • First, we just tried here releasing the brakes for JT4 and JT5 and we could actually rotate the robot tool on these joints.

    second and responding to your request: the video I made I was actually jogging the joint 1 and just now i tried it again and the problem always come on the joint 3 (which is actually joint more liekly to being affected by gravitational force at the moment).

    while trying to move the robot it is trembling quite a lot and even when static i can see the variation on the enconder for JT1 and JT3 (mainly).

  • What about JT1 and can do that also on brake release and test.

    Which leaves JT2 and JT3 with question marks.........

    Any juddering occurring will be reflected on the encoder, and if this value goes outside of it's following error, then you will usually receive speed or positional deviation errors as the robot always looks at current position

    Get JT2 and JT3 down to the floor (to minimise) gravity acting on them.....but do it safely.

    Then use a long bar, and during brake release, try and move joint using bar but with no too much pressure applied and see if there is resistance.

  • I think i have also tested with them for the JT6 but i wasnt really sure about JT1.

    Also they are a bit crancky and they are reluctant to believe the brakes are the problem so i will ask someone else's help doing that.

    probably will have it tested tomorrow anyways and will let you know of any result i get...

    for now we are also testing the battery as they asked me to once this problems showed up after the robot being off for a while.

    thank you so much for everything i have tried so far.

  • Also they are a bit crancky and they are reluctant to believe the brakes are the problem so i will ask someone else's help doing that.

    probably will have it tested tomorrow anyways and will let you know of any result i get...

    for now we are also testing the battery as they asked me to once this problems showed up after the robot being off for a while.

    In that case, I am out of ideas...............except for a couple of options:

    1. Get them to pay for troubleshooting and mechanical training so you can diagnose and service the equipment you intend to supply your customers.

    2. Pay for a Kawasaki engineer to come out and diagnose the problem directly.

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