MITSUBISHI RH-3CRH4018-D , CR800 ONTROLLER

    • New

    Hello EveryOne,

    I want help regarding an Screwing Torque application.

    As I mentioned I am using an Mitsubishi RH-3CRH4018-D Robot with a CR800 Controller and I want to Measure Live Torque when the robot reaches to one of the taught Position.

    At The moment i have been successful to read out the torque but the issue here is when the robot is at speed of 20 the torque measurement is almost right but when I speed up the Robot the Torque read is wrong.

    I tried Setting a Bit once the Robot Reaches the Position or Completes the cycle (I will compare with the Torque if it reaches 0.4nm the screw process is completed, but at the moment it is trial phase)

    How can I do that?? Did any one has done some thing like this before.

    • New
    • Best Answer

    hi,
    I've never done direct screwdriving with a robot, but from my experience with servo driven screwdrivers, you measure the load on the servo, not the torque directly, and that depends on the speed of the servo.
    In the screwdriving applications I have done, the speed was fixed, so I was able to calculate the torque from the load.
    You can make calculation from measured load and torque at different loads (you need some external torquemeter) to put some math function into robot, but it's almost never worth it because once you are on expected time of application, there is no need to change it.
    Depending on the screw, you can make the first X% of the screw go faster, but the last few revolutions are better to slow down (we use 50rpm to final tightening).

    If you are interested, the mathematical discussion is here.
    https://www.plctalk.net/threads/polynomial-fitting-on-mitsubishi-fx5u.139783/
    It is not directly about Mitsu robots, but it should be similar in principle.

  • SSRIKAKOLUM January 9, 2025 at 9:15 AM

    Selected a post as the best answer.
    • New

    Thank you So much,

    That is a really good option I can go with and surely the last bit of tightening I will slow down

    Also I would Like to add the torque I am calculating is from the ARMS(RMS ampere) which is the current and as because it is RMS I multiply by root2 (1.414). but the problem here is Speed the cycle time of the machine is 3seconds from Pick - Screw - Drop .


    So i was thinking of Slowing down during the last few revolution to slowdown Set a bit to trigger to read current Load.


    Thank You Again that was really Helpfull.

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