Deviation in position between RoboGuide and real robot

    Hello Everyone,

    Good and Healthy 2021 I wish you.

    FANUC Arc Mate 100iC 12L

    The first welds that were programmed via TP were OK, however when I started using welding programming from WELDPRO I came to a situation where the tool was loaded into the model. This was especially pronounced when the tool needed to be rotated along the J6 axis. Then we discovered that the JOG robot on the Y axis is not good, ie. that the whole plane is rotated by +Z for 0.6 degrees, at a distance of 1100 mm deviation is 15 mm. Afterwards, I added some more points for checking, the readings in ROBOGUIDE and TEACHPENDANT are with an error on the 3rd decimal, however in reality the deviations are from 15 to even 25 mm !!!.

    MASTERISATION and CALIBRATION were done first, according to data and information from experts from FANUC but that was't solution, I am still waiting for a solution.

    At picture you can see deviation in position reading, index 1 is from RoboGuide, index 2 is from TeachPendant when Tool was Joged to desired control point.

    Any idea?


    Quote from gpunkt

    When jogging, are you using a user frame, the world frame or the tool frame?
    Are you sure that the robot is mounted level (using a machine level)?
    Are you sure that the tool frame is correctly set up?

    To remove any suspicion I use only World frame.

    The robot is mounted on a desk and all dimensions in reality and in roboguide are with an error of no more than 1 mm.

    TCP is certain specified, at picture is visible position of tool relative to peak of TorchMate,

    when rotated with by -/+X and -/+Y

    Hi,

    at real robot:

    Create a program.

    Teach one point at the left side(table surface) in front of the robot.

    --> P[1]

    Move(instruction) the robot with an offset of 500mm(1000mm) to Y-, measure.(WORLD COORD)

    !PR[1]= 0,0,0,0,0,0

    !PR[1,Y]= -500

    J P[1] 25% fine;

    L P[1] 100mm/sec fine Offset PR[1];

    Is your measurment result ~500mm ?

    No? --> Mastering,Calibration is not correct.

    By the way , why did you master the robot?

    Best regards

    PnsStarter

    Your problems are the reason why 'real robot programmers' use user frames.

    You will never ever be able to mount a real robot absolute precise in position and angle.

    So always create a user frame on your working place, then measure it in real and virtual robot. Measuring on virtual one can be done by using values from CAD.

    Quote from hermann

    Your problems are the reason why 'real robot programmers' use user frames.

    You will never ever be able to mount a real robot absolute precise in position and angle.

    So always create a user frame on your working place, then measure it in real and virtual robot. Measuring on virtual one can be done by using values from CAD.

    Have an error by one axis - problem but solvable,

    Have an error by two axis - big problem but solvable,

    Have an error by three axis - nightmare and daymare.

    I didn’t imagine having to do a tens of pages calculation to correct a error

    We are talking about accuracy / repeatability of +/- 0.08 or even 0.04 mm (for this kind od robot), so I have an error accurately 24 mm +/- 0.04 mm!? :loudly_crying_face:

    I have a distorted and twisted situation

    ~500 mm by reading on TP.

    We had little misalignment on markers J3 and J6, recommendation was to make Mastering and Calibration, new parameter was given from Fanuc

    Edited once, last by fmiroslav (January 12, 2021 at 9:34 PM).

    Accuracy and repeatability are two different pair of shoes.

    Repeatability is much better than accuracy. Most robot manufacturers don't give values vor accuracy.

    Seems that You don't understand my concerns about accuracy of mounting the real robot and other devices on your table. If there is only a deviation of 0.5 degree in one direction on the robot mounting you will get an absolute difference of 8 mm when robot is 1000mm away from socket.

    Your table is not really straight and even. You have mounted 800mm 'candle holder' I don't believe that they are that exact like in the CAD.

    In my eyes it doesn't make sense what you are trying to evaluate. You only can evaluate a mixture of mounting / machining precision and robot precision.

    A second and last time: use user frames on both sides. And make your measurements in respect to that user frame.

    There are many publications about robot calibration, have a look to them.

    Quote

    Rock4xfab

    https://www.robot-forum.com/robotforum/thread/30564-discrepancy-between-picked-actual-points-and-measured-virtual-in-olp/?postID=128323#post128323

    Rock4xfab What is Your story, did You solve that discrepancy between OLP and real robot?

    My steps are similar,

    * Mastering - Data for Mastering were obtained from Fanuc, all markers were aligned very well, with no Tool I read out XYZ data for J6 which correspond from technical data.

    * determination TCP - when swing Tool around +/- X and +/- Y axis top of wire stay in place near the tip.

    * Step 3* -

    * I determinate UF of table (this UF is linked with step 3 :winking_face: , UF for work place 1 and UF for work place 2

    * Definition of welding line in RG and creating TP program - After all this steps I get that welding line is correct (Two horizontal weld line with gap 8 mm, from one and another side of vertical plate) but only problem was I must hunt zero position different from programed in RG. When I use UF of table welding model in Real Robot World I must to move by X, Y (8,5 and 4 mm) and turn (by -Z). With UF for work place 1, I must to correct UF by Z for 3 mm (lift them), correction for model was 2 and 2,5 mm by X, Y and turn by +Z.

    So conclusion, I get better welding lines in RRW but position of welding model must be hunted on working table.

    * Step 6* -

    * I would like Step 3 and Step 6 I get from Fanuc but it wasn't case, Documentation is obtained on a small kinder ice-cream spoon as Top Secret, for step 6 I make preparation and after repeating steps 4 and 5 I can post my experience.

    Think you will not get any answer from Rock4xfab, even if you ask for one in every single thread. His last activity is nearly 2 years ago.

    But he already stated that the factory mastering of Fanuc is BS (think this should be bullshit:frowning_face:).

    And he told us that he corrected the mastering, but didn't explain how exactly he did.

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